MikeCAdministrator
(Admin)
Sat Aug 18 2007 12:15 AM
Hurricane Dean Reaches Category 4 Strength

8:30 AM 18 Aug 2007 Update
The latest recon shows about the same windspeed as in the advisory, and the pressure down to 926mb, and since the next two or three days are going to be critical for the ultimate mainland landfall location, I'm sure there is a lot of "no it's moving more north-- no it's moving more west" type of observations, which are always interesting...

Intense Hurricanes with eyes like Dean tend to wobble around like a spinning top, and it's hard to gauge if something is a trend, or a wobble. The SSD satellites with the forecast track overlays are helpful here, but I think bare minimum is a 4 frame change to really see if something is a wobble or a true movement.

Track is not the only variable, forward speed is as well, so it's important to watch the changes in forward speed as it affects the eventual movement of the system. It appears the latest model runs initialized the Upper Level Low over Florida too weak, so what this means for the track is uncertain at this time.


This shows the official forecast track from 5AM, vs the actual position of Hurricane Dean at 8:30AM. Click the image to go to the latest animation (Check the "Trop Pts" Box to see the track overlay)

7:30AM EDT 18 August 2007 Update
Dean has strenghtened a bit overnight to just shy of Category 5 strength, with 150MPH winds.

Dean is at a high enough intensity to start being affected by hard to time eyewall replacement cycles and other less understood elements of very extreme hurricanes. However that said, it still hasn't reached the warmest waters of the Caribbean yet, and may strengthen further. It is likely to weaken and strengthen some in cycles as it maintains this intensity for a bit.



The National Hurricane Center hasn't really changed the forecast track at all in the past two days, and continues it on the generally just slightly north of west motion into the Yucatan and eventually into Northern Mexico, however there is still some wildcards in the future track, especially as it approaches 85west, but the NHC's track makes the most sense at this time.

Jamaica will have until tonight before effects from dean start showing up, and the worst of it on Sunday.

9:35PM EDT 17 August 2007 Update
Recon has found 145 MPH winds, making Dean now a stronger Category 4 hurricane. Minimum pressure is now 936 mb. Dean is still strengthening.

Jamaica... For comparison, hurricane gilbert in 1988 had135MPH winds when it hit Jamaica.


Original Update
Recon Aircraft found a pressure of 946 mb and flight level winds of 146 knots, which estimated down to the surface represents about a 135MPH Hurricane, crossing into Category 4 terrirtory.

Dean has strengthened very rapidly today from a category 2 in the morning, to a category 3 in the afternoon, to a
category 4 at 8PM. Jamaica is the next target, dean would likely make its closest approach to Jamaica Sunday afternoon. Please take this one seriously Jamaica, it may not brush by like Emily did a few years ago. and very well may be stronger when it does.

After that, the Caymans may have to deal with this system. Then the Yucatan is now looking like a target, models have shifted back again (Well the GFDL did), it is still far enough out that it's worth watching for anyone in the Gulf and Caribbean though. Dean may have more surprises to come.

See Clark's blog below this article for more on the future of Hurricane Dean.



Event Related Links:

Jamaican Radio (106 Power)
Go Jamaica Hurricane Dean Watch
Jamaica Gleaner (Jamaican Newspaper)
Jamaican StormCarib Reports
Jamaican Meteorological Service
{{Radarlink|jua|San Juan, Puerto Rico}}
Guantanamo Bay, Cuba Radar
Martinique Radar Animation Recording
{{StormCarib}}
{{StormLinks|Dean|04|4|2007|1|Hurricane Dean (Far Eastern Atlantic)}}


allan
(Weather Master)
Sat Aug 18 2007 12:29 AM
Re: Dean Reaches Category 4 Strength

I will not be surprised if Dean is a category 5 tommorrow morning with a pressure of 900 or below.. Nort saying it will happen but a hurricane that intesifies in the "Hurricane Graveyard" is rare.. Anyways much more comparision to Allen back in 1980, the question that lies beneath and will be answered tommorrow is "will the ULL be west enough for the track to stay on course?"
If that ULL is'nt in FL or in teh GOM by tommorrow, expect a big change in course!


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 12:53 AM
Re: Dean Reaches Category 4 Strength

NRL site now shows Dean at 120kts, which is 138mph. Of course the NHC only forecasts in 5kt/5mph increments, so that might not represent any strengthening at all.

Random Chaos
(Weather Analyst)
Sat Aug 18 2007 01:09 AM
Re: Dean Reaches Category 4 Strength

Impressive microwave overpass just in:

http://tinyurl.com/3xlv4r

Clearly visible eye and feeder bands.


Lee-Delray
(Weather Master)
Sat Aug 18 2007 01:21 AM
Re: Dean Reaches Category 4 Strength

Is it me or did Dean jist squeek under Herbert's Box? Hard to tell.

DougBaker
(Verified CFHC User)
Sat Aug 18 2007 01:21 AM
Re: Dean Reaches Category 4 Strength

It would seem beyond the atmospheric conditions, that the interaction with land that will have a great impact on the future of Dean.

How big of a piece of land does it take to zap the strength of this size hurricane? Is Jamaica big enough? or if this storms moves across the Mexican Yucatan, could it die in the gulf or for certain regain strength.


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 01:22 AM
Re: Dean Reaches Category 4 Strength

Quote:

It'll probably be 145 mph by 11 PM




Or higher...
the next recon isn't until the morning I don't think, but whenever it is, unless there is an intervening eyewall replacement cycle, I think they'll find a cat 5.


dem05
(User)
Sat Aug 18 2007 01:32 AM
Re: Dean Reaches Category 4 Strength

The number 15 express has departed...I'm trying to be a bit humorous here on a Friday Night

Dean reached 15 north and has rode along that same latitude like along freight train on rails. Earlier today, everyone was concerned that Dean seemed alittle north of path, and he may be going elsewhere. Bottom line is this, if you trimline everything, Dean remains on the "Here to Jamaica" path. Don not get overly concerned about a little north of path, and little west of path for thenext 36 hours. This will happen and it means little.

Later on, and beyond Jamaica, the Riddler would have a field day. Being in SW Florida, I still think a visit from Dean is a wildcard. However, to phrase the ever and always confident and and straigh forward NHC Hurricane Specialist Avila at the the 5PMdiscussion, he offerred a blanket statement. Coming from him,this is a more significant message and he posted it at the end of the discussion.

"THE BOTTOM LINE IS THAT DEAN IS EXPECTED TO BE A DANGEROUS HURRICANE
THROUGH THE NEXT SEVERAL DAYS...AND ALL INTERESTS IN THE CARIBBEAN
SEA AND THE GULF OF MEXICO SHOULD CLOSELY MONITOR THE PROGRESS OF
DEAN."

I only mention this becuase a lot of folks are stating Alabama westward and etc. Florida Folks, it is not very likely that we will see something from this one, but keep in mind that it is out there and there are some atmospheric dynamics that could create a surprise change in course. If those changes in the forecast philospophy occur, you may need to take action...Just something to keep in mind in case of a surprise...With that said, I do not expect any major surprises at this time, but Saturday night into Sunday may be a day of truth along the Gulf...Everyone will have a much better idea of the upper ridge/trough/ULL interaction by then.

Otherwise, nothing much new to report in my thinking that hasn't already been said.


ltpat228
(Storm Tracker)
Sat Aug 18 2007 01:37 AM
Herbert's Box

Quote:

Is it me or did Dean jist squeek under Herbert's Box? Hard to tell.





I had NO clue what you are referring to, so I looked it up and below is an explanation:

http://www.hurricanecity.com/hebertbox.htm


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 01:38 AM
Re: Dean Reaches Category 4 Strength

Quote:

Is it me or did Dean jist squeek under Herbert's Box? Hard to tell.




Hebert's Box, according to this site: http://www.accessmylibrary.com/coms2/summary_0286-6748972_ITM

Covers between 15 N and 20 N and 60 W and 65 W.
Dean's location of 15N 64.5W, was WITHIN the box, at 5pm.

UPDATE FROM NHC... Dean now with winds of 145mph as of 9:30pm ET.


MikeCAdministrator
(Admin)
Sat Aug 18 2007 01:42 AM
Re: Dean Reaches Category 4 Strength

Wow, I can't remember this strong a storm in this part of the Caribbean, Jamaica better hope for some sort of weakening trend, dry air, shear, or something along those lines. 145MPH winds and 936mb pressure is unlike anything recent.

Random Chaos
(Weather Analyst)
Sat Aug 18 2007 01:42 AM
Re: Dean Reaches Category 4 Strength

New recon in

Wind speed is down slightly, but pressure is also down.

Summary:
936mb pressure
111 kt winds
15 nm circular eye.

------

646
URNT12 KNHC 180136
VORTEX DATA MESSAGE AL042007
A. 18/01:15:40Z
B. 14 deg 51 min N
065 deg 29 min W
C. NA mb 2579 m
D. 111 kt
E. 044 deg 011 nm
F. 136 deg 138 kt
G. 044 deg 011 nm
H. 936 mb
I. 10 C/ 3056 m
J. 20 C/ 3047 m
K. 008 C/ NA
L. CLOSED
M. 15
N. 12345/7
O. 0.02 / 2 nm
P. AF302 0504A DEAN OB 09
MAX FL WIND 138 KT NE QUAD 01:12:20 Z


weatherguy08
(Weather Hobbyist)
Sat Aug 18 2007 01:45 AM
Re: Dean Reaches Category 4 Strength

Quote:

If that ULL isn't in FL or in the GOM by tomorrow, expect a big change in course!




Allan, you mentioned this about the upper-level low. What changes did you exactly mean?

Anyway, I am very interested to see what the 10:00 PM CDT forecast is going to show. The GFDL appears to have come back towards the consensus, if there is one. GFDL now put Dean near Galveston.


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 01:47 AM
Re: Dean Reaches Category 4 Strength

Hate to say it Random Chaos, but that recon report was the one where they got the 145mph winds.
138kts at flight level, times 90% = 124.2kts at surface, which is 142.83mph.

Line D is an unofficial estimate of the winds based upon what they see from the aircraft, as I understand it, it's not the official wind speed reported, which is based upon an extrapolation of 90% of flight level (at the level they are currently flying).


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 01:49 AM
Re: Dean Reaches Category 4 Strength

Quote:

Wow, I can't remember this strong a storm in this part of the Caribbean, Jamaica better hope for some sort of weakening trend, dry air, shear, or something along those lines. 145MPH winds and 936mb pressure is unlike anything recent.




Mike... I started to ask y'all if anyone ever remembered a hurricane this intense in this part of the Caribbean. This is, traditionally, considered the Graveyard. Events have seemingly conspired to create the monster that is Dean, though.

WU recon report indicates pressure down to 935. NHC vortex message shows 937.


MikeCAdministrator
(Admin)
Sat Aug 18 2007 01:54 AM
Re: Dean Reaches Category 4 Strength

Yep, check out the "Recon Info" link on the left which has a "Hurricane Hunter" to English translation program there.

I want to trash the GFDL model right now. The latest run... don't even joke with me putting a 170MPH hurricane nearing Galveston/Houston. If you follow these models they will stress you out, this one is beginning to. If it shoots the gap as a strong storm into the hot central Guif, it's possible but probably overdone.

But like I said, I'm ready to trash it, and go with the westward trend, 15N, and that idea now. But still, this system has a ways to go, it hasn't reached Jamaica, still in the Eastern Caribbean and wouldn't be anywhere near the Gulf until Tuesday-Wednesday. So it helps to keep perspective.

edit: corrections made, initial reaction to the surprise was a little over the top.


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 01:55 AM
Re: Dean Reaches Category 4 Strength

Hugh, yeah, I assumed the surface speed estimate was good - usually it is.

The vortex recon was updated. Pressure was increased by 1 mb to 937mb.


Beach
(Weather Guru)
Sat Aug 18 2007 01:57 AM
Re: Dean Reaches Category 4 Strength

http://www.ndbc.noaa.gov/station_page.php?station=42059

The center of Dean is about 80-100 miles away, and winds are picking up at our bouy.

Wind Direction (WDIR): NNE ( 30 deg true )
Wind Speed (WSPD): 25.3 kts
Wind Gust (GST): 33.0 kts
Wave Height (WVHT): 11.2 ft
Dominant Wave Period (DPD): 8 sec
Average Period (APD): 6.1 sec
Atmospheric Pressure (PRES): 29.75 in
Pressure Tendency (PTDY): -0.02 in ( Falling )
Air Temperature (ATMP): 84.2 °F
Water Temperature (WTMP): 83.8 °F
Dew Point (DEWP): 72.9 °F
Heat Index (HEAT): 90.5 °F


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 02:00 AM
Re: Dean Reaches Category 4 Strength

Quote:

Yep, check out the "Recon Info" link on the left which has a "Hurricane Hunter" to English translation program there.





I've looked at that page in years past and it was Greek to me, but maybe I should give it another shot.

Quote:

But like I said, I'm ready to trash it, and go with the westward trend, 15N, and that idea now.




I really do not buy the westward trend *across* the Yucatan, but I'm not ready to rule it out either, partly because the shear thought of a 190mph superstorm entering the bathwater of the eastern/central Gulf... and THEN potentially going through the Loop Current? Impossible to comprehend. So, for me, it's much easier to accept that Dean will strike the Yucatan and then go on over to Texas.


wxman007
(Meteorologist)
Sat Aug 18 2007 02:10 AM
Re: Dean Reaches Category 4 Strength

The GFDL is NOT forecasting a 190 mph hurricane...it's forecasting 190 mph 35 meter winds....there would be quite a bit of reduction down to sfc from 35 meters...probably down to about 170 mph..which is STILL not good to ponder, but not 190. Just clearing things up. (BTW, I think the GFDL is WAY overdone)

Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 02:12 AM
Re: Dean Reaches Category 4 Strength

alright back online.. wow... go away for a bit.... and come back.... one vortex drop to another... it drops... what almost 10mb in less than two hours? Almost certain an eyewall replacement cycle will be happening tonight....

Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 02:21 AM
Re: Dean Reaches Category 4 Strength

Quote:

alright back online.. wow... go away for a bit.... and come back.... one vortex drop to another... it drops... what almost 10mb in less than two hours? Almost certain an eyewall replacement cycle will be happening tonight....




Looking at the AVN loop, it's hard to say, but one COULD be underway right now. Or it could just be regrouping in preparation for the move up the Cat 5. The cloud tops around the eye have warmed a bit though over the last hour or two.


Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 02:28 AM
Re: Dean Reaches Category 4 Strength

hmm... trying to catch back up.. looks like they may move the official track to the left some in the 11pm... As for the Eyewall Replacement cycle... was trying to look at recon data and see if the eyewall is closing in... between drops... looks so, so slightly.. I expect that we may see the Cat 5 of Dean in the next 12-24 hrs. Wow... rapid intensification today! and not even near the warmest waters of the Carb.

Random Chaos
(Weather Analyst)
Sat Aug 18 2007 02:33 AM
Re: Dean Reaches Category 4 Strength

Looking at the AVN IR loop at SSD, the storm is shedding it's long feeder bands and starting to take on the classical pinwheel shape.

I would expect continued intensification.


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 02:34 AM
Re: Dean Reaches Category 4 Strength

Quote:

Wow... rapid intensification today! and not even near the warmest waters of the Carb.




Yeah... I've been wondering about that. This area is supposed to be the Hurricane Graveyard. So why is Dean proving to be the obstinent (pick your expletive)? Why can't it cooperate and fall apart like good hurricanes are supposed to do in the Graveyard? Seriously, this could get really REALLY ugly for Jamaica unless an eyewall replacement cycle intervenes, and does so at the right time. Now, one could come but then Dean could restrengthen even more after it ends, but before nearing Jamaica.


Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 02:36 AM
Re: Dean Reaches Category 4 Strength

Did notice that the Dewpoint inside the eye, dropped about from 13c to 8c... (from 23:32:00z to 01:15:40z.) and strongest winds were measured on the NE quad of storm... roughly about 12 miles from the center. Plane last i saw was flying on an east route.. well south of storm...

Clark
(Meteorologist)
Sat Aug 18 2007 02:39 AM
Re: Dean Reaches Category 4 Strength

Given this appearance on MW imagery, I don't think an eyewall replacement cycle is likely for at least another 12-18 hours:



It has some of the makings of an outer eyewall, but lacks the closed structure to one, suggesting that a significant eyewall replacement isn't likely in the short term. Plus, Dean is moving toward a region even more favorable from a heat potential standpoint:



If it stays far enough south of Hispaniola, things could get pretty interesting as it nears that warm eddy. Of course, by then, it might be in the midst of an eyewall replacement cycle...only time will tell.


neospaceblue
(Weather Watcher)
Sat Aug 18 2007 02:46 AM
Re: Dean Reaches Category 4 Strength

NHC has landfall over the Yucatan as a Cat 5

Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 02:48 AM
Re: Dean Reaches Category 4 Strength

hmm... i didn't think anything was goin on right now... what gave it away is recon didn't report to two eyewalls.... but...i am curious to see what NASA images are up tomorrow... were there any HOT towers this afternoon that helped Dean to get a goin?

weather999
(Weather Watcher)
Sat Aug 18 2007 03:07 AM
Re: Dean Reaches Category 4 Strength

Just a couple questions about hurricanes and warm eddy's that would be greatly appreciated to be answered.

Does the actual eye/eyewall of the hurricane need to pass OVER the eddy to intensify the hurricane?

Because in Dean's scenario, according to latest track, the centre would pass just north of the eddy.. another question--can eddy's move/intensify/weaken in 24-48 hours?

Thanks!


nc_tropical_wx79
(Weather Guru)
Sat Aug 18 2007 03:12 AM
Re: Dean Reaches Category 4 Strength

ok Dean slowed down some is this due to the ULL everyone has been going on about? And could the ULL start effecting Dean in the next 48 hrs and on? Lastly, when and/or if the ULL effected Dean what would be the effect and what time frame could we see it in?

GENIE
(Registered User)
Sat Aug 18 2007 03:27 AM
Re: Dean Reaches Category 4 Strength

If you have not checked it out lately. There is a good view of the eye on the long range Puerto Rico long range radar.

Clark
(Meteorologist)
Sat Aug 18 2007 03:29 AM
Re: Dean Reaches Category 4 Strength

No, not necessarily; some thing that passing over gradients of heat potential associated with those eddies is sufficient. Just part of the circulation passing over such an eddy would likely provide a minor boost to the outer circulation, so while it may not be the direct positive punch to the inner core, it would still be significant.

Eddys do move and change in intensity, but not over time spans of 1-2 days unless something like a major hurricane passes over them (generally causing substantial weakening). The time scale of significant oceanic change is generally at least a week.


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 03:31 AM
Re: Dean Reaches Category 4 Strength

New vortex recon. Little change from the last:

491
URNT12 KNHC 180328
VORTEX DATA MESSAGE AL042007
A. 18/02:58:10Z
B. 14 deg 53 min N
065 deg 55 min W
C. 700 mb 2547 m
D. 126 kt
E. 148 deg 007 nm
F. 245 deg 117 kt
G. 141 deg 005 nm
H. 935 mb
I. 11 C/ 3049 m
J. 20 C/ 3028 m
K. 10 C/ NA
L. CLOSED
M. C15
N. 12345/ 7
O. 0.02 / 2 nm
P. AF302 0504A DEAN OB 17
MAX FL WIND 138 KT NE QUAD 01:12:20 Z
MAX FL WND OUTBOUND FROM CNTR 129KT @ 03:00:50Z


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 03:36 AM
Re: Dean Reaches Category 4 Strength

WU recon report shows minimum pressure of 932 (not in a vortex message, though). Regardless, it's not going UP any, and may be continuing to plummet.

jbmusic
(Weather Watcher)
Sat Aug 18 2007 03:43 AM
Re: Dean Reaches Category 4 Strength

In reading the lastest advisory it says tropical force winds extend out 205 miles. If this storm goes across the tip of the Yucatan or between it and Cuba. Wouldn't the Florida Keys feel tropical force winds?

Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 03:47 AM
Re: Dean Reaches Category 4 Strength

Quote:

In reading the lastest advisory it says tropical force winds extend out 205 miles. If this storm goes across the tip of the Yucatan or between it and Cuba. Wouldn't the Florida Keys feel tropical force winds?




If it goes across thetip of Cuba, or through the Yucatan Channel, it will be a close call, but on the current forecast track, the closest T.S. force winds would get is the centerline across Cuba longwise.


EMS
(Weather Hobbyist)
Sat Aug 18 2007 03:48 AM
Re: Dean Reaches Category 4 Strength

Staring at Water Vapor Loop imagery - it seems the ULL east of Florida is nudging towards the west ever so slowly and also seems to be even dropping a little south. Could this feature already be having an impact on the storm? Could this be why Dean is slowing down? I always tell folks (rightly or wrongly) it's simple physics - it's harder for storms to turn the faster they are moving. Not saying the storm will turn, just trying (like everyone else) to understand the dynamics of the ULL and how it might interact with Dean.

Mike N
(Verified CFHC User)
Sat Aug 18 2007 03:48 AM
Re: Dean Reaches Category 4 Strength

First, thanks to all pros, semi-pros and all the others with insightful comments. This is the most informative hurricane site on the net! (That I've found at least) I am a 3 year lurker with little comments - just enjoy the reading. A few thoughts I've had that never seem to be answered.

Few Things: Dem05 posted yesterday about watching the ULL over the Bahamas and it's obvious consequences in determining Dean's ultimate track. The ULL hasn't moved that much - maybe roughly 100 mi WSW to just off West Palm. This pace is slow. If Dean was to get to a position due S of the ULL which direction would he want to be pulled. Wasn't it supposed to have been moving faster already? Also, NHC mentioned that it should weaken as it progresses westward. I know they were probably talking about as it traverses the GOM but looking at WV - how does one tell if it is weakening? Does the spin pace slow and it starts to open up if you will? Also, there is a lot of talk about the ridge...what's the best way to see this ridge? WV? Again, what am I looking for? On WV now, between the ULL over the Bahamas and the ULL roughly located at 27N 52W there is a line where black starts to meet brown situated from 29N 70W running SE to 23N 55W...is this the ridge? I know there are not exact answers to all of these questions, if there were, we'd all know where Dean is going. Any insight on some of the basic questions I'm sure would help everyone.

Dem05 - what is your day by day analysis tongiht? I was looking forward to your follow up thoughts from how things progressed from last night as you saw them.

Thanks and God Bless to all wherever this thing ends up.


StrmTrckrMiami
(Weather Guru)
Sat Aug 18 2007 03:58 AM
Re: Dean Reaches Category 4 Strength

It looks as though the arms of this storm are very big. I was looking at the pictures with my fiancee and he says that the strength that Dean has defies all odds. He thinks that Dean has strenghtened over the past few days immensly because of the span of the Arms is very large. He thinks that it is a possibility that this storm is going to weaken and then gain strength again because of the warm waters. He also thinks that Florida should atleast prepare for the aftermath, because he said that he remembers Floyd when the armbands hit them, they got severe thunderstorms. We are getting some storms, whether this is occuring because of Dean or not, we dont know.

danielwAdministrator
(Moderator)
Sat Aug 18 2007 03:59 AM
Re: Dean Reaches Category 4 Strength

Quote:

In reading the lastest advisory it says tropical force winds extend out 205 miles. If this storm goes across the tip of the Yucatan or between it and Cuba. Wouldn't the Florida Keys feel tropical force winds?




This link will update, (I think), with the probabilities of an area/ location receiving Tropical Storm force winds.
Hurricane Dean-Tropical Storm force wind swath


danielwAdministrator
(Moderator)
Sat Aug 18 2007 04:05 AM
Dean

Using a mapping program that I have.

For Tropical Storm force winds to occur in Key West, with a radius of 205nm.
Dean would have to pass over the Isla de Juvidad-Isle of Youth, or just to it's west.

Something strange is going on with Dean...

A Major Hurricane with 145mph winds should be more symmetrical than Dean is.
The latest IR loop from GHCC shows some strange Vortice swirls spinning off of the Eye.
http://wwwghcc.msfc.nasa.gov/GOES/goeseastconusir.html

And the latest Dvorak enhancement shows that Dean has lost nearly 70% of his higher cloud tops over the last few hours.
http://www.ssd.noaa.gov/goes/flt/t1/bd-l.jpg


Allison
(Weather Guru)
Sat Aug 18 2007 04:25 AM
Re: Dean

Quote:

Something strange is going on with Dean...

A Major Hurricane with 145mph winds should be more symmetrical than Dean is.
The latest IR loop from GHCC shows some strange Vortice swirls spinning off of the Eye.
http://wwwghcc.msfc.nasa.gov/GOES/goeseastconusir.html

And the latest Dvorak enhancement shows that Dean has lost nearly 70% of his higher cloud tops over the last few hours.
http://www.ssd.noaa.gov/goes/flt/t1/bd-l.jpg





That's odd... as best I can tell, it doesn't appear to be an issue of cooler SST's, shear or dry air.... And I'm naturally going to defer to Clark that an ERC is still several hours away....

Perhaps a diurnal fluctuation?


ltpat228
(Storm Tracker)
Sat Aug 18 2007 04:25 AM
Re: Dean

Quote:


Something strange is going on with Dean...





Yes, I saw the same thing!
It almost appears as if Dean is beginning to separate at the top.
Can hurricanes actually tear apart or spin off another system?

Even though I rarely post, they always seem to end up in the Graveyard and I'm just praying this one will last long enough so I can see an answer.

Thank you CFHC as this is one heck of an exciting and addicting night!!!


Beach
(Weather Guru)
Sat Aug 18 2007 04:26 AM
Re: Dean

5-day plot - Wind Direction Wind Direction (WDIR): NNE ( 20 deg true )
Wind Speed (WSPD): 29.1 kts
Wind Gust (GST): 38.9 kts
Wave Height (WVHT): 20.3 ft
Dominant Wave Period (DPD): 13 sec
Average Period (APD): 8.1 sec
Atmospheric Pressure (PRES): 29.67 in
Pressure Tendency (PTDY): -0.08 in ( Falling )
Air Temperature (ATMP): 82.0 °F
Water Temperature (WTMP): 83.8 °F
Dew Point Dew Point (DEWP): 73.4 °F
Heat Index Heat Index (HEAT): 87.6 °F

http://www.ndbc.noaa.gov/station_page.php?station=42059&unit=E&tz=EST


Miss Christine
(Registered User)
Sat Aug 18 2007 04:28 AM
Re: Dean Reaches Category 4 Strength

Hi all, long time fan of this site. This is only my second time posting since 1998. Ignore me if you wish (or delete me). With the ridge pushing south, the way I "think" I see it, it's going to miss (South) Jamacia and the U.S. It has moved South and more westerly. I think the ridge will keep it well south of the U.S. Anywhoo, I know you don't like these kinds of posters so I'll mossey along. Link to my claims:

Miss Christine

http://www.goes.noaa.gov/HURRLOOPS/huwvloop.html


charlottefl
(Weather Hobbyist)
Sat Aug 18 2007 04:31 AM
Re: Dean

It appears Dean is getting close to an eyewall replacement cycle. The eye appears to be contracting on IR
satellite imagery. It should be interesting to see how an eyewall replacement cycle will affect short term track
changes. It also appears Dean is getting ever closer to interacting with the ULL in the Bahamas. Should be an
interesting night for model output.


StrmTrckrMiami
(Weather Guru)
Sat Aug 18 2007 04:35 AM
Re: Dean

That does look strangly odd. I am not too sure about if it can form a new storm or not, but I do know that according to
http://www.eurekalert.org/multimedia/pub/3299.php?from=91170
that outer rainbands can form a new eye wall around the existing one. Maybe that is what Dean is doing? But the sataline images do seem something out of the ordinary than what I have ever seen.

Here is the link for the hurricane eyewall replacement cycle

http://www.eurekalert.org/pub_releases/2007-03/uow-hcf022307.php


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 04:49 AM
Re: Dean

Looking at past hurricanes (only have visible, not IR), looks like there are swirls coming off the eye in intense hurricanes. I wish I had more resolution on the IR.

Reference:
Isabel's eye: http://rsd.gsfc.nasa.gov/goes/pub/goes/QTmovies/030912.isabel.mov
Katrina's eye: http://www.esl.lsu.edu/quicklinks/hurricanes/2005/KATRINA/images/Katrina-eye-closeup.gif


wxman007
(Meteorologist)
Sat Aug 18 2007 04:55 AM
Re: Dean

After studying the aforementioned sat loops I can say with some assurance that Dean is not doing anything unusual, nor is it separating or becoming two storms. The fluctuations you see in the Dvorak loop are entirely reasonable...hurricanes pulse in intensity and the CDO will reflect this, and is reflecting this. The GHCC IR loop is showing mesovortices rotating around the center...again, entirely normal and seen in strong hurricanes. Dean is extremely impressive on IR this evening, and is doing nothing unusual or rare....it is behaving just as a Category 4 storm should.

I don't see any eyewall contraction yet, and there has been no indication from Quikscat or recon of an outer eyewall forming, so I would say we are a bit away from an ERC...it certainly does not appear to be imminent.


Just watching
(Registered User)
Sat Aug 18 2007 04:55 AM
Re: Dean

Dean almost looks like elongated like it is trying to turn. Is this temporary?

StrmTrckrMiami
(Weather Guru)
Sat Aug 18 2007 04:56 AM
Re: Dean

what do you mean elongated and trying to turn??!

What website are you using to look at the images of Dean??


Just watching
(Registered User)
Sat Aug 18 2007 05:00 AM
Re: Dean

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?wv_east_enhanced+12

Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 05:01 AM
Re: Dean

Well.. looking at the sats.. it appears to me that the rapid intensification is over... notice in this image loop of cloud tops IR that it seems the system has vented all it can for the short time... notice how the cloud tops are warming and the eye appears to be shrinking on sats.. now that may be that high cirus is covering it up some, but usually i think its a sign of a contracting eyewall...

Clark, was the 85hz image was from 6pm cdt this evening?
I thought i noticed from one vortex to another after that... in little over an hour that the eyewall contracted about a mile... that seems like pretty big to me...in just an hour... (i may have read the data wrong)... but also noticed that the dewpoint dropped pretty good there for a few hrs inside the eye... I do think we will see a Cat 5 some time on Saturday... with another good run of intensification late saturday...

**Just looked at the hrd 1930Z surface wind analyses from todays data/invest...*** storm is a classic... Strongest wind region on the north to east side wrapping around.. **a decent region of the 100mph winds on that side too***

this is off the FTP... may not be able to view it? 1930Z


scottsvb
(Weather Master)
Sat Aug 18 2007 05:08 AM
Re: Dean

wxman said it in a well inform paragraph that this is typical for a Cat 4 system. Christine I saw your post, you could be right about going south of Jamaica but even if it doesnt....cant go away from the models that still say Mexico landfall. Still watching the upper low near FreePort Bahamas... I still wonder if it will move as fast as the models say. Btw dean should turn more wnw tomorrow as it gets past the ridge lying 65-68W.

Random Chaos
(Weather Analyst)
Sat Aug 18 2007 05:09 AM
Re: Dean

We don't have the vortex data message yet, but we do have a near vortex read showing 113 30-sec FL winds and 106 surface winds. Looks like it is weakened slightly.

From URNT15:
045830 1449N 06629W 6958 02768 9525 +175 +105 296101 108 097 033 00
045900 1451N 06628W 6976 02659 9480 +128 +128 289113 117 106 035 03
045930 1452N 06626W 6930 02635 9380 +144 +142 279079 095 079 024 03


wxman007
(Meteorologist)
Sat Aug 18 2007 05:13 AM
Re: Dean

For those of you who are new to storm tracking....use water vapor with EXTREME caution. Water vapor is a poor choice for looking at storm structure...it only images a relatively thin slice of the atmosphere centered around 600 mb. If you are trying to look at mid and upper level features (such as ULL, etc) WV is a fine choice...for discerning storm features is it a very poor choice. As far as sats are concerned, Vis is king, but at night use IR instead of WV.

Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 05:16 AM
Re: Dean

agree, they made the last pass i think for the night.... *inbound*
at 04:59:00Z they were at 14.85N 66.47W at an alt. of (~ 20.60 inHg) 2,659 meters (~ 8,724 feet)
(~ 27.99 inHg) The highest winds were - From 289° at 113 knots (From the WNW at ~ 129.9 mph)... (a 10 sec fl. lvl wind of 117kts)

**air temp at 65F at 8,500ft.*** last data i got has them inside the eye... SFMR has a surface measure of 106 knots*

Looks like the pressure may have went down some more... ? (around 931mb?) will no soon when vortex is out


wxman007
(Meteorologist)
Sat Aug 18 2007 05:17 AM
Re: Dean

Quote:

We don't have the vortex data message yet, but we do have a near vortex read showing 113 30-sec FL winds and 106 surface winds. Looks like it is weakened slightly.



From URNT15:
045830 1449N 06629W 6958 02768 9525 +175 +105 296101 108 097 033 00
045900 1451N 06628W 6976 02659 9480 +128 +128 289113 117 106 035 03
045930 1452N 06626W 6930 02635 9380 +144 +142 279079 095 079 024 03




Can't say that for sure...that is only a point sample of one side of the storm, not the entire storm itself...there very well could be (and will be) higher wind speeds elsewhere...the wind field around a hurricane (especially those with mesovortexes like this one) is NOT symmetric.


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 05:21 AM
Re: Dean

Looks like I was premature. Definate strenthening!

150 kt (@89 degrees) FL winds; 121 kt surface.

But with reduction from FL, 155 mph (135 kt) surface winds. Borderline Category 5!

----


050330 1506N 06627W 6944 02705 9478 +103 +103 096136 148 999 999 05
050400 1507N 06627W 6971 02758 9990 +082 +999 089150 154 121 034 05
050430 1508N 06627W 6991 02795 9990 +075 +999 086143 146 112 040 01
050500 1510N 06627W 6963 02862 9749 +071 +071 090134 138 104 034 00
050530 1511N 06627W 6964 02897 9791 +069 +069 092122 123 095 038 03
050600 1511N 06627W 6964 02897 9802 +072 +072 094120 123 095 033 03


Storm Hunter
(Veteran Storm Chaser)
Sat Aug 18 2007 05:24 AM
Re: Dean

there flying through from SW to the NE... no doubt there is stronger winds coming... kinda weird... that in a 1min in 30sec... flt. levl winds went from 130mph... to 30 mph.. ... there out of the NE part of the eye and climbing... vortex coming soon! I think i saw a 929mb reading... will see?

**opps missed it by a mb


URNT12 KNHC 180522
VORTEX DATA MESSAGE AL042007
A. 18/05:00:30Z
B. 14 deg 55 min N
066 deg 26 min W
C. 700 mb 2498 m
D. 105 kt
E. 193 deg 004 nm
F. 291 deg 117 kt
G. 197 deg 005 nm
H. 930 mb
I. 12 C/ 3044 m
J. 20 C/ 3055 m
K. 9 C/ NA
L. CLOSED
M. C13
N. 12345/ 7
O. 0.03 / 2 nm
P. AF302 0504A DEAN OB 24
MAX FL WIND 138 KT NE QUAD 01:12:20 Z
MAX FL WIND OUTBOUND 154KT AT 05:04:00 Z


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 05:26 AM
Re: Dean

[delete - storm hunter beat me to the Recon data]

danielwAdministrator
(Moderator)
Sat Aug 18 2007 05:28 AM
HDOBs and Vortex Messages

For those using the HDOBs to track Recon.

The last message was sent just prior to the SW Eyewall penetration. Hence, the weaker windspeeds.

The next message should be more indicative of the current NE Quadrant strength.

Check the lat/ longs.. They are going North and East.
Flying from the SW Quadrant TO the NE Quadrant.

THe NE Quadrant is normally where the highest wind speeds will be found.

Also new to 2007. The Max Flight Level WInd Speed on the inbound leg- into the EYE.
Is amended as necessary on line "P". IF the outbound Max Flight Level Wind Speeds are higher than they were when the vortex message was transmitted.

This can be done using a "Corrected " Vortex Data Message.

www.ofcm.gov/nhop/07/nhop07.htm


PA101
(Registered User)
Sat Aug 18 2007 06:37 AM
GFDL

Long time lurker (at least three years) and finally have something to add to the discussion.

Those of us wondering if the GFDL is out to lunch this week may not have long to wait. Until now the GFDL has been an outlier beginning at 48-72 hours but has been within the model consensus during at least the first 24-36 hours of each run.

As of the 00Z run the GFDL is predicting significant northward movement Real Soon Now and forecasts the COC will pass over extreme southwestern Hispanola early Sunday morning. If it sees something (maybe up around 300mb given the power of the storm) that all the other models are missing it should start to verify during the day Saturday.


Rabbit
(Weather Master)
Sat Aug 18 2007 07:04 AM
Re: HDOBs and Vortex Messages

i just noticed that NHC is actually FORECASTING Dean to hit Cat V intensity--they dont do this very often

Lake Toho - Kissimmee
(Storm Tracker)
Sat Aug 18 2007 07:26 AM
00Z Models

I know Dean is the most immediate threat, but looks like all the models are showing something developing in the next few days that may effect Florida.

Doombot!
(Weather Guru)
Sat Aug 18 2007 07:38 AM
Re: 00Z Models

Quote:

I know Dean is the most immediate threat, but looks like all the models are showing something developing in the next few days that may effect Florida.




Can you aim me to where you're looking? According to http://moe.met.fsu.edu/tcgengifs/ the CMC is the only 00Z run (of 6) that spins anything up.


cieldumort
(Moderator)
Sat Aug 18 2007 07:53 AM
Re: 00Z Models

Re: other systems

There is an abundance of tropical cyclogenesis potential in the Atlantic, and a few model runs want to spin one or more of the most conducive areas up. Currently, the entire stretch from just east of Dean all the way back to the Cape Verde islands is a veritable breeding ground.

Getting back to Dean,

Dean has been flirting with a pinhole eye all evening/night. No signs of an ERC, as some have suggested. The appearance of one is merely the eye tightening up a bit.. normal fluctuations. However, given the occasional foray into a pinhole eye-like scene, it is worth nothing that the TCHP in the western Caribbean is running potentially even higher now than around this time in 2005. Dean may be able to pull off an all-out Wilma while in the western Caribbean. The current forecast out of NHC for a Cat 5 before crossing over the Yucatan, while not a certainty, more than likely did not cost them one single bead of worry sweat that they were stretching a bit. Six more mph and Dean's there.

With respect to the models which have consistently forced Dean's future track to the southernmost ends of the guidance envelope, all of these have initialized him poorly. While one doesn't want to completely throw them out, you just about can, again, because they are not tracking Dean. They have been tracking and creating forecasts based on a weak Cat 1 or Tropical Storm.. and some have even initialized Dean as a neutral core. Nuts. This is garbage in - garbage out forecasting. Stick with the GFDL , HWRF, and certainly NHC, for now.


Rich B
(British Meteorologist)
Sat Aug 18 2007 09:19 AM
Re: 00Z Models

Looks like Dean could make it to Cat 5 at anytime. The 154kt flight level wind measured by RECON earlier would support it, but evidently these winds havent made it to the surfasce enough to warrant the upgrade. Looking at the latest IR imagery, there are no current indications of an ERC, but these are likely as Dean strengthens further. With the high heat content, the low shear, and the track far enough to the south of Hispaniola, he has little to hinder him. Jamaica looks set to get a pounding, as do the low-lying Caymans. Could be pretty catastrophic for these islands. Interesting how models continue to diverge on where Dean will go once past the Caymans, and just goes to show how predictable these things are, and how much everyonhe around the Gulf, Yucatan, and Cuba really need to watch closely, and prepare just in case.

GuppieGrouper
(Weather Master)
Sat Aug 18 2007 09:30 AM
Re: 00Z Models

I am generally not a model watcher because of cynicism towards technology being a person designed entity and therefore intrinsically flawed. But, I have been running water vapor loops in the last two hours showing the past 12 or more hours of hurricane and atmospheric changes. To summarize, all the key elements for steering are changing rapidly. I have noticed a big high pressure coming down from the northwest which seems to be moving slightly faster to the east than any of the ULLs are moving to the west. I will make a small prediction that this pressure system will change everything 180 degrees in the next 12 hours or so. I am not sure whether that will take Texas and points west totally out of the loop or not, but the hurricane's rapid progress forward has already dropped by 7 mph reported . I am watching closely due to a sick family member in the Panhandle. I will have to know when to leave Central Florida if the 180 turn should occur so that I can avoid the evacuation traffic from Key West. I am watching closely and intelligently. I would recommend others do the same. I believe the time for model watching has come to an end and we should be preparing for the worst and hoping for the best.

WeatherNLU
(Meteorologist)
Sat Aug 18 2007 10:03 AM
Re: 00Z Models

Just getting home from work and looking at everything. As some mentioned, it's getting close to showdown time with the models re: a more northward movement or the continued westward track. I think it's still up in the air, but I have noticed since I got home and threw up a sat loop that Dean finally got off of ROUTE 15 and decided to take a jump poleward. The 6Z models take Dean to near 70W at 16N and the GFDL takes it to 70W at 17N. We shall see.

Frank P
(Veteran Storm Chaser)
Sat Aug 18 2007 10:11 AM
Re: 00Z Models

Definitely has the north component in the track this am... its running just a tad north of the projected forecast track but not by any thing significant (a few miles at best)... certainly got that stair step effect in motion... lord I would NOT want this monster approaching or anywhere near me...

http://www.ssd.noaa.gov/goes/east/pr/loop-ir2.html


WeatherNLU
(Meteorologist)
Sat Aug 18 2007 10:21 AM
Re: 00Z Models

I hear ya Frank. Not that I didn't know before, but August 29, 2005 gave me a whole different outlook on things. I wish it could be where no one was going to have to deal with Dean, but someone has to. If that someone is New Orleans, this city is done. I can only hope and pray that it's not us again and that whoever does have to deal with this will get more help than we did. That's all I can do now.

Frank P
(Veteran Storm Chaser)
Sat Aug 18 2007 10:29 AM
Re: 00Z Models

I feel your pain NLU.... we've done better over here in Biloxi but it has been oh so slow... what gets me is I've tracked storms for many years but I can't ever recall so many monster storms that have developed since 2004... now we have another super storm, and its our first hurricane of the year.. If this storm were to come anywhere near the SE LA or MS coast you could practically write off these areas for decades.. when you get hit by a super storm it changes your way of life for years... Dean is going to do just that to whomever it hits... it just CAN'T be us... not for a long time

WeatherNLU
(Meteorologist)
Sat Aug 18 2007 10:36 AM
Re: 00Z Models

Amen Frank! Hey, are my eyes getting tired or is Dean really taking a jump more north than I even realized at first. I just stopped the loop at 15.0 and 66.8 and that was at 0715. The last frame at 0945 looks like 15.3 and 67.4. Defintely more WNW in the last three hours or so. Trend??????

I am going to get some zzzzz's just incase it's my eyeballs.


charlottefl
(Weather Hobbyist)
Sat Aug 18 2007 10:44 AM
Re: 00Z Models

Dean has been at 15.0 all night and yes it did move more nw erly in the last few frames. The question is
trend or wobble. Only time will tell.


Hurric
(Weather Guru)
Sat Aug 18 2007 11:48 AM
Re: 00Z Models

Dean does appear to be continuing a more wnw track for last four hours. Maybe the ULL is beginning to exert an influence, or could be just a big wobble.
Look at this Link:
http://www.ssd.noaa.gov/goes/flt/t1/loop-rgb.html


VolusiaMike
(Weather Hobbyist)
Sat Aug 18 2007 12:14 PM
Re: 00Z Models

Based on the 08:00 position compared to the 5:00 am forecast track, it is only about 12 - 13 north of anticipated location.

Random Chaos
(Weather Analyst)
Sat Aug 18 2007 12:21 PM
Re: 00Z Models

New recon.

139
URNT12 KNHC 181212
VORTEX DATA MESSAGE AL042007
A. 18/11:51:20Z
B. 15 deg 23 min N
067 deg 52 min W
C. 700 mb 2437 m
D. 121 kt
E. 5 deg 008 nm
F. 137 deg 145 kt
G. 050 deg 008 nm
H. 926 mb
I. 11 C/ 3049 m
J. 23 C/ 3041 m
K. 11 C/ NA
L. CLOSED
M. C12
N. 12345/ 7
O. 0.02 / 2 nm
P. AF304 0604A DEAN OB 03
MAX FL WIND 145 KT NE QUAD 11:48:40 Z
SMALL HAIL INBOUND NE QUAD
RADAR PRESENTATION EXCELLENT


CaneTrackerInSoFl
(Storm Tracker)
Sat Aug 18 2007 12:22 PM
Re: 00Z Models

That does not look like a wobble at all. That's a definitely poleward movement as you can see on the visible imagery.

(Time Sensitive) http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html


MikeCAdministrator
(Admin)
Sat Aug 18 2007 12:32 PM
Re: 00Z Models

The latest recon shows about the same windspeed as in the advisory, and the pressure down to 926mb, and since the next two or three days are going to be critical for the ultimate mainland landfall location, I'm sure there is a lot of "no it's moving more north-- no it's moving more west" type of observations, which are always interesting...

Intense Hurricanes with eyes like Dean tend to wobble around like a spinning top, and it's hard to gauge if something is a trend, or a wobble. The SSD satellites with the forecast track overlays are helpful here, but I think bare minimum is a 4 frame change to really see if something is a wobble or a true movement.



dem05
(User)
Sat Aug 18 2007 12:34 PM
Re: Dean

Good morning everyone, I got a few messages from folks that were kind of hoping that I would have put some more meat and potatoes into my post last night, so I will try and do that this morning. Sorry 'bout that guys!

First, NLU is certainly correct...I also agree with this mornings post that we may be getting closer to "moments of truth" on the interaction of the ULL. Dean has broken free of Route 15 as I am sure that most of you have noticed this already morning. There are one of two thoughts toward this mornings motion. The first one is more straightforward and in line with my thinking last night. Second one will be many hours away from any confirmation.
- Thought 1: As Dean had done yesterday, he is moving a little north of track. Later this evening we may se him bend more to the west again like he did last night, when at 15 degrees north. If so, the overall average motion would basically be in line with the forecast track.
-Thought 2: Dean may be getting close enough to the "Bahamas ULL" (Which I will now refer to as the FL ULL), to feel some of the effects. I am giving option 2 a little more weight this morning than I would have when I posted last night. However, my reasoning for this is not due to the Satellite motion, which is depicting a more northward component. If there is any hint that this wobble may be indicative of some interaction with the ULL, the indication is in Dean’s forward speed. In this mornings 5AM NHC Discussion, the NHC has stated that the forward speed of Dean has decreased again. It would be expected that if Dean was going to feel some of the effects of the ULL, then Dean would have to get close enough to the ULL that it would approach the edge of the ridge...Hence, the forward speed would decrease. While Dean has closed the gap on the ULL over the last few days, I don't think it has closed the gap enough to feel any big influence...However, this may be a sign of things to come. So forward speed will be something to watch today and I imagine there will be some more ground truth as to whether or not this maybe what is going on in about 24 hours or so.

I'd like to take some time to review this morning’s satellite loops and data in a little more detail, but I'll be back in a bit with another post this morning.


madmumbler
(Storm Tracker)
Sat Aug 18 2007 12:42 PM
Re: Dean

Quote:


<<snipped>>While Dean has closed the gap on the ULL over the last few days, I don't think it has closed the gap enough to feel any big influence...However, this may be a sign of things to come. So forward speed will be something to watch today and I imagine there will be some more ground truth as to whether or not this maybe what is going on in about 24 hours or so.




So are we rooting for Dean to speed up or slow down? *LOL*

What is our "best case" scenario that we want to look for to see Dean doing in relation to the ULL? And what is the "worst case?" (Considering I'm in FL, best case means not making a hard turn *LOL* -- sorry everyone in the west!)

I'm NOT panicking or worrying. I know that everything is still up in the air. But i heard TWC talking about the ULL this morning and last night, and I'm still not sure what is "good" and what is "bad" in terms of Dean's movement and forward speed. (Obviously, it's all "bad" in the long run because wherever this hits is going to get whomped.)

Thanks,


mp3reed
(Verified CFHC User)
Sat Aug 18 2007 12:43 PM
West Texas update

My rain gauge this morning is at 5 1/2 inches. Last 24 hours.
Erin is still making it's mark here in Abilene and west Texas.
If Dean heads this way, it can't be good.
Lot's of flooding this morning.
Lakes are above spillway.
So much for hot dry west Texas.


craigm
(Storm Tracker)
Sat Aug 18 2007 12:58 PM
Re: West Texas update

Dean is almost on top of this bouy located at 15.01N 67.5

http://www.ndbc.noaa.gov/station_page.php?station=42059&unit=E&tz=EST

Actually, looking at the wind speed, direction and pressure it looks like Dean passed just to the north about 4 hrs ago


CaneTrackerInSoFl
(Storm Tracker)
Sat Aug 18 2007 01:06 PM
Re: West Texas update

By the way, NRL has Dean's pressure down to 924 mbs.

MikeCAdministrator
(Admin)
Sat Aug 18 2007 01:12 PM
Re: West Texas update

Some interesting signs to watch to see if they hold. Seems like the GFS (and thusly a lot of models based on it) initialized the Upper Level Low over Florida much much too weak, and are downplaying it too much. Also the slight jog north of Dean is a bit troubling. Not saying it really means much now, bu the potential is there for changes to happen. So it may be a good idea to keep close watch on these two things and see if they persist over the next several hours or not.

It will be very interesting to see what newer model runs do with all this, it's very important.



charlottefl
(Weather Hobbyist)
Sat Aug 18 2007 01:18 PM
Re: West Texas update

Everyone has been paying attention to the ULL in the Bahamas, which is obviously important to the track of Dean.
I'm curious though. The hurricane has slowed it's forward motion. There is a 2nd ULL to the NE of Dean gaining ground
on Dean. Will this ULL have any impact on the future track of Dean? Lots of variables in the track of these storms.


flanewscameraman
(Weather Watcher)
Sat Aug 18 2007 01:19 PM
Re: West Texas update

A question for those of us not versed in the sciences. Would the effect of the ULL over Florida be to erode somewhat the ridge that is keeping Dean on a Westward heading, and thus allow it to take more of a WNW or NW jog.

Thunderbird12
(Meteorologist)
Sat Aug 18 2007 01:29 PM
Re: West Texas update

Dean has resumed its WNW after moving due west for much of the evening last night, but overall it appears to be right on track (unfortunately) for Jamaica. While it is slightly north of the projected path at its current position, keep in mind that the last forecast had a more westerly motion early in the period before more of a turn to the WNW towards Jamaica. Dean will end up right on the forecast track again around Jamaica if it keeps its present bearing long enough.

The 06Z GFDL came in a lot further south. It is still on the northern fringe of guidance, but brings Dean through the Yucatan for the first time before heading into the Gulf and making landfall in south Texas.


danielwAdministrator
(Moderator)
Sat Aug 18 2007 01:31 PM
Hail

Quote:


139
URNT12 KNHC 181212
VORTEX DATA MESSAGE AL042007
A. 18/11:51:20Z

P. AF304 0604A DEAN OB 03
MAX FL WIND 145 KT NE QUAD 11:48:40 Z
SMALL HAIL INBOUND NE QUAD
RADAR PRESENTATION EXCELLENT




Small hail is usually indicative of a storm trying to gain More intensity. Also unnerves the flight crew to some degree.
Imagine hail hitting your car while traveling at 300 mph instead of 60mph.


Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 01:42 PM
Re: Hail

Quote:


Small hail is usually indicative of a storm trrying to gain More intensity. Also unnerves the flight crew to some degree.
Imagine hail hitting your car while traveling at 300 mph instead of 60mph.




The 8am advisory mentioned that the satellite presentation of Dean over the last several hours hinted at some weakening, yet all signs I have read from the recon - small hail, and pressure now down to 920mb according to one report I saw - indicate that Dean is on the verge of the Cat 5 threshhold, if not already on the other side of it. Why did the NHC mention the possibility of weakening based upon satellite images?

Edit: Read latest vortex message which shows pressure actually UP to 929mb, so go figure


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 01:44 PM
Re: Hail

New recon:

090
URNT12 KNHC 181340
VORTEX DATA MESSAGE AL042007
A. 18/13:23:30Z
B. 15 deg 28 min N
068 deg 14 min W
C. NA mb 2475 m
D. 102 kt
E. 122 deg 006 nm
F. 220 deg 117 kt
G. 125 deg 007 nm
H. 929 mb
I. 11 C/ 3046 m
J. 18 C/ 3045 m
K. 12 C/ NA
L. CLOSED
M. C12
N. 12345/7
O. 0.02 / 2 nm
P. AF304 0604A DEAN OB 09
MAX FL WIND 145 KT NE QUAD 11:48:40 Z
RADAR PRESENTATION EXCELLENT


Random Chaos
(Weather Analyst)
Sat Aug 18 2007 01:47 PM
Re: Hail

Looking at satellite, it appears that there was some disruption in the western portions of the system. This disruption appears to have closed up and the storm looks beautiful on IR now. In fact, the storm looks to be growing in size.

Latest recon recorded a drop in wind speeds and rise in pressure, so we can assume that is the weakening that NHC mentioned might occur. Based on radar, I suspect next recon will show the system re-strengthened.

Also, the strongest winds seem to have been in the NW quad, where the recon plane didn't pass through this time.


tekkrite
(Registered User)
Sat Aug 18 2007 01:48 PM
Re: 00Z Models

The wave at about 10N 35W looks more formidable than Dean did at that point, and is starting to form up. Any observations from the mets here?

danielwAdministrator
(Moderator)
Sat Aug 18 2007 01:51 PM
Weakening?

Probably because the "weakening flag" has been turned on as of 0845Z per the Dvorak AODT page.

http://cimss.ssec.wisc.edu/tropic/adt/04L-list.txt

And Dean looks rather weak here:
Dean


Thunderbird12
(Meteorologist)
Sat Aug 18 2007 01:51 PM
Re: Hail

The satellite indicated the possibility of some weakening because the cloud tops had warmed somewhat and the CDO was somewhat asymmetric. Based on the latest recon (pressure back up to 929 mb), it seems to have peaked momentarily in intensity. Cloud tops around the center have begun to cool again on the last few frames, so it may attempt to begin another intensification cycle soon.

The warmest waters of the Caribbean are still further west, so it may be about as strong as the environment will allow right now.


h2ocean
(Weather Hobbyist)
Sat Aug 18 2007 01:58 PM
Re: 00Z Models

tekkrite, yeah, I have been watching to the east of Dean. Models are picking up on one or two features out there. Here is an exceprt from the Melbourne, FL NWS discussion early this morning:

EXTENDED...STRONG TROPICAL WAVE OR POSSIBLY CLOSED LOW INDICATED BY
GFS APPROACHING BAHAMAS IN EASTERLIES LATE WED/EARLY THU WITH
MOVEMENT TOWARD S FL ON THU AND THERE IS SOME REFLECTION OF THIS
WAVE AS WELL IN ECMWF. SYSTEM IS SHOWN INTERACTING WITH AN EAST
COAST TROUGH AND PULLING NWD ALONG THE FL EAST COAST SLOWLY ON FRI
AND INTO SAT. HAVE INCREASED POPS AND OTHER FORECAST ELEMENTS TO
REFLECT THIS BUT HAVE DECREASED WINDS OVER THE MARINE AREA AT THIS
EARLY JUNCTURE DUE TO UNCERTAINTIES.


HanKFranK
(User)
Sat Aug 18 2007 02:12 PM
dean and waves to follow

i'm still not sure what to make of dean's jogs. don't suspect that the relationships for steering that existed yesterday have changed all that much, as dean has bled some speed and is making up for the due westward motion in the evening. model guidance is more to the left (though some of the upper initializations are called into question for the gfs) overall... same basic camps persist. i don't think we'll see much aside from the nhc official today or tomorrow, with the only interesting side notes being how the hurricane interacts with the caribbean islands. be interesting to see if hispaniola and then maybe cuba do the windfield-warp thing and tug the hurricane north of jamaica.
back behind dean it's hard to make any sense of the wave jumble. the one behind dean slowed down so that it's follower is catching it... with most of its energy shunting ahead off to the north, and the leader tucking up underneath closer to the itcz. it's hard to resolve how this complex mess will initiate another system. the part going by to the north is progged to get north of the islands and interact with the upper trough off the east coast, split some, and have a bit of its energy drift towards the bahamas. cmc makes a storm out of this (has for days), while the other globals see just an inverted trough. none of the models buy much into the leader wave east of the islands, with outflow from dean washing over it. the itcz bump further east from the trailer wave seems to spawn another system on the gfs suite, though, and that creates another storm on it by next weekend. hard to trust exactly what the gfs is thinking from there.. it moves nw towards a then large trough near the east coast, and ends up in the gulf by labor day weekend. of course these individual features can't be trusted right now, only watched for persistence. the niggardly way the gfs has suggested tropical activity this season and it's seeming enthusiasm for sending more to the table has me thinking that there will be something there regardless of whether the details are close to right.
HF 1412z18august


OUSHAWN
(Weather Guru)
Sat Aug 18 2007 02:14 PM
Re: Hail

Well, looks likw this will be a Mexico storm. The models are starting to all agree on that...even the GFDL is really coming south to almost the Mex/Tex. border. Looks like the US really dodged a huge bullet on this one. Looks like there won't be anymore back and forth with the models now. Man I feel alot better now.

Shawn


jbmusic
(Weather Watcher)
Sat Aug 18 2007 02:18 PM
Re: Hail

Quote:

Well, looks likw this will be a Mexico storm. The models are starting to all agree on that...even the GFDL is really coming south to almost the Mex/Tex. border. Looks like the US really dodged a huge bullet on this one. Looks like there won't be anymore back and forth with the models now. Man I feel alot better now.

Shawn




Shawn don't let your guard down yet it is far from over. Everyone along the gulf needs to still keep an eye on this system. THis morning slight north movement shows that.

I know this should have been a PM but I wanted to state this here because if there are new people in here and read his post they make think it is over and stop monitoring the storm


allan
(Weather Master)
Sat Aug 18 2007 02:20 PM
Re: Hail

the forecast models still cannot be trusted.. the ULL is still in FL and if it does'nt make a move before Dean does all bets are all off! Still the models do not have the strength and speed of this ULL Dean is actually moving north of his track, and it's not a wobble either.
I expect if things don't change that Dean will do more of an Ivan and make more of a northward approach towards the Central Gulf.


OUSHAWN
(Weather Guru)
Sat Aug 18 2007 02:22 PM
Re: Hail

You're right. I know this post as well as the last one need to go to the other part on the site. I will keep that in mind for the future. I also know that the models can change at any time...just got a little to excited first thing this morning. I will watch that from now on and start posting in the right areas.

Thanks,
Shawn


OUSHAWN
(Weather Guru)
Sat Aug 18 2007 02:30 PM
Re: Hail

I found this on Accuweather's site. I've been looking at it over the last couple of days and I do have to say that it's a mess of models but at first there were not really any of these models that had it making a turn towards Texas but now there are quite a few. I just noticed this a second ago. Very interesting.

http://hurricane.accuweather.com/hurrica...&stormNum=3

Shawn


MikeCAdministrator
(Admin)
Sat Aug 18 2007 02:33 PM
Re: Hail

This is just observation and no indication of how I think right now, I'm still thinking the NHC is generally correct, but I mentioned watching the trends, here's an updated satellite image with the track plotted and the current movement extrapolated.



Mostly interested to see how things are tonight.


Thunderbird12
(Meteorologist)
Sat Aug 18 2007 02:35 PM
Re: Hail

Well, now the cloud tops in the CDO seem to be warming slightly again. Dean may struggle to hold its own for awhile until it gets into the higher oceanic heat content that is further downstream. There may be some shear affecting the system, since it looks like the outflow in the SE quadrant is being impinged a little bit.

Hugh
(Senior Storm Chaser)
Sat Aug 18 2007 02:36 PM
Re: Hail

Quote:

This is just observation and no indication of how I think right now, I'm still thinking the NHC is generally correct, but I mentioned watching the trends, here's an updated satellite image with the track plotted and the current movement extrapolated.
Mostly interested to see how things are tonight.




Excellent graphic, Mike. I believe the NHC will need to make minor adjustments to the track, but that is to be expected with any storm. It looks like Dean is going to move just north of Jamaica, and just south of Haiti, based upon the current movement, which also looks to be in a straight line, rather than a wobble about the forecast line.


charlottefl
(Weather Hobbyist)
Sat Aug 18 2007 02:42 PM
Dean

There is one important factor I would like to point out. If Dean continues on the more Northwesterly track it's going to pass very near
if not over a very large mountain in the SW tip of Hati. This would serve to greatly disrupt the circulation of the storm. Just have to wait
and see if that occurs.


scottsvb
(Weather Master)
Sat Aug 18 2007 02:43 PM
Re: Hail

The NHC will adjust the track if the models adjust. I think they will leave it the same or adjust slightly south. The whole overall picture of this will come into affect over the next 24-36 hrs as Dean approaches Haiti-Cuba. I feel Dean will get close to Haiti then turn west with the models and run just north of Jamaica but it could cross it.. no one really knows forsure about Jamaica. ULL is moving more quickly then yesterday..now over SW Florida. With the Ridge begining to build back east over the souther U.S. today and tonight....I see the upper low continuing a W movement alittle quicker and letting Dean turn back west on Sunday. Its a wait and see.

mikethewreck
(Weather Hobbyist)
Sat Aug 18 2007 02:48 PM
Keeping Quiet

I just want to remind the rest of newbies like me to keep quiet on the main post during this critical time with Dean. I feel like a child listening to an interesting discussion amongst adults. I don't understand everything that is being said, but I feel privileged to look through a window into a bigger world. There are a lot of professional meteorologists on this site. If Dean so much as passes gas noisily, one of them will spot it and alert all of us. I would like those who (like me) lack formal met training to step back and listen. If you have a specific question, message one of the posting met folks and I dare say they would be happy to answer and if the information is relevant for all, they will post it or clear you to post it. Thank you, I hope I have not offended anyone, and I will go back to lurking right now.

NewWatcher
(Storm Tracker)
Sat Aug 18 2007 02:51 PM
Re: Keeping Quiet

NHC changed the movement from 275 to 290 so i guess they believe it is not just a wobble. Doesnt mean it wont go back the other way and even out eventually tho.

seabass
(Registered User)
Sat Aug 18 2007 02:53 PM
Re: Hurricane Dean Reaches Category 4 Strength

Not to be a doomsdayer,but it looks as if a large part of the storm will be over Haiti,and if it goes between Jamacia and cuba more land mass,will hinder strenghting,then if it enters the gulf north of western Cuba,then its really cranks back up.Bad news for gas prices if it gets to the central gulf,so lets hope that the forecast track is right.I am not wishing Dean on anyone ,but the a U.S. strike will be anightmare,still alot of Fema trailors out there.

OUSHAWN
(Weather Guru)
Sat Aug 18 2007 02:58 PM
Re: Hail

Scott, I thought I saw the ULL moving a little quicker this morning. If this continues than this would keep it moving on the more westerly track and not give it a chance to turn toward the north,right? If this is the case, is there anything left out there that would cause Dean to make a more northerly turn?

weather999
(Weather Watcher)
Sat Aug 18 2007 03:05 PM
Re: Hail

Quote:

Scott, I thought I saw the ULL moving a little quicker this morning. If this continues than this would keep it moving on the more westerly track and not give it a chance to turn toward the north,right? If this is the case, is there anything left out there that would cause Dean to make a more northerly turn?



Avila mentioned that Dean was being steered to 290 due to a high in the Western Atlantic as well--it seems that this high has been somewhat overshadowed by the ULL... If the ULL is quickly replaced by a ridge of high pressure that global models say, then Dean will likely be shoved more westerly.


ChessieStorm
(Weather Watcher)
Sat Aug 18 2007 03:07 PM
Re: Hail

According to WV imagry, the ULL is now west of Ft. Myers, Fla in the GOM and seems to be moving pretty quick to the west.

It doesn't look like it is having much of an effect on Dean. The outflow over the storm still looks good and clouds on the west side of the storm are under anti-cyclonic high and not being sheared from the ULL.


dem05
(User)
Sat Aug 18 2007 03:12 PM
Attachment
Dean and the Upper Level Pattern

I’ve attached an image I created that depicts the upper level features over the CONUS and Atlantic Basin. You may want to make a copy to follow along in the discussion. I hope it helps in depicting some of what I am seeing.

I’d also like to repost the Water Vapor Links:

Pacific NW Water Vapor Loop: http://www.goes.noaa.gov/GSSLOOPS/wcwv.html
Atlantic Wide Water Vapor: http://www.ssd.noaa.gov/goes/east/tatl/loop-wv.html
NW Atlantic Water Vapor: http://www.ssd.noaa.gov/goes/east/nwatl/loop-wv.html
CONUS Water Vapor: http://www.goes.noaa.gov/GSSLOOPS/ecwv.html

Well, I have a bag full of wrenches, so I may as well start throwing. Before I do however, I do want to caution that I will not be delving into the models or basing my statements on much of what the models have to say. Traditionally, this is a dangerous game, but with indication that the models are having a tough time in initializing storm intensity, the intensity of the upper level features, and problems with the models racing Dean off probably a bit too fast, I’ve decided not to go much farther in my discussion of them than this. With that said, the models very well may have the correct solution albeit they are not performing as well as one would hope.

The breakdown:
The Florida Upper Level Low is on the move again. From my best estimate, the center is probably right about above my head here in SW FL as I type. It does look like it is now trying to tuck south of the High Pressure Ridge. At some point, I will imagine that the Upper Low will have to either stall or phase out. At this point, it shows no evidence of phasing out, but that may happen in a couple days. Earlier, someone asked about Dean’s forward speed slowdown and how the interaction will affect track. If the Upper Level low had been stationary right now, we would likely expect that Dean would be turning North at some point. However, The Upper Level Low is also moving westward, so I would expect it’s overall influences to resulting a general WNW motion for the next 2-3 days. Dean is probably close enough to feel some of these effects now, but it is also far enough away that I would expect to see subtle fluctuations in forward speed and direction. In other words, Dean slows down a bit, the ULL moves a bit further away, the ridge builds backing a bit and Dean will move slightly faster and a little more westerly…Then Dean will catch up again, slow down and move a bit more WNWerly. In general though, I would not dismiss the Idea that Dean may get closer to Haiti than anticipated. Later on down the road, if the Upper Level low does not phase out and it stalls between 90-95W…I would say that chances for problems in the Eastern Gulf would really increase…Otherwise, the further west it can move before stalling or dissipating will result in problems points west.

Side note/disclaimer: The yellow arrows do not show a forecasted track. They are just there to show the upper air flow ahead of Dean.

Looking at the mid latitude weather systems and the jet stream, there are some other considerations to make. The jet stream over the CONUSis not zonal like it was a few days ago. (The jet stream is identified in the pink, the movement of the jet stream is outlined with Green Arrows). The trough over the Northeast US is moving out and being replaced by a ridge. The ridge is highlighted in Blue and this is the feature that the Florida ULL will sweep under. With that said, the ridge IS moving east, and may continue to do so through this evolution. There is a pretty darn good trough entering the Pacific. This trough is probably starting to move the US weather patterns along. At this time, I know the $64,000 question would be…Will that trough get into the Gulf area. Unfortunately, I don’t have an answer for that or if it would have a direct affect on Dean…But it is something to watch, and I have included a link to the Pacific NW Water Vapor Loop. With that said, it is not impossible to assume that the Florida ULL may stall in a couple days as the High Pressure ridge moves east and the Upper Level Low moves around to the SW Side of the ridge. For an additional quirk that may be another wildcard factor…It does appear that the remnants of Erin may also be evolving into a weak upper level low feature. I really can’t say that this would have any ramifications on the overall upper level pattern, but over time, it will be interesting to see if anything unfolds with that.

So that’s basically the way I see it right now…Unfortunately there are more questions than answers, but it is still to early to Pinpoint specific threats and/or dismiss any Gulf Coast possibilities at this point. Keep on tracking…



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