MikeC
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| (Admin) |
| Fri Aug 31 2007 01:13 PM |
Tropical Depression #6 Forms East of Caribbean
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4:00PM EDT 31 August 2007 Update
Call has been made, Tropical Depression #6 forms East of the Caribbean. Advisories to begin at 5PM.
1:58PM EDT 31 August 2007 Update
Recon found a surface circulation, TD may have already formed.
1:50PM EDT 31 August 2007 Update
Tropical Cyclone Formation Alert issued for 94L, recon is very near/in the system now and is checking it out.
Original Update
94L, which was persisting, but not really developing all week, has come together and looks to be forming into a tropical depression. Aircraft recon will be out there later today to make the determination as well.
Things may change rapidly, and it is likely we will have a depression at 11AM to track, or if not later this afternoon. It is moving westward into the Caribbean.
The current early model trends keep it in the Caribbean moving westward. As it develops a better model picture should be available. It is important to note that the strong ridging that kept Dean moving westward past Jamaica does not seem to be there this time, but a upper level high will likely fill the gap to keep it more westward. As of now, it seems most likely to be a straightforward westward moving track, there isn't much out there to suggest otherwise at the moment. -- also the system is located further south than dean was at the same longitude.
Central America/Nicaragua is the most likely westward position at this time, but it could change.
The extreme southeastern Caribbean is not all that conductive for Tropical Systems, as land interaction with South America tends to bring in dry air from the south. So this system has some rough times ahead if it does form.
Tropical Storm Watches or Warnings may be up very soon for the Windward Islands.
More to come soon.
{{StormCarib}}
{{StormLinks|TD#6|06|6|2007|1|Tropical Depression Six}}
{{StormLinks|96L|96|8|2007|3|96L (Disturbance Southeast of New Jersey))}}
| CoconutCandy |
| (User) |
| Fri Aug 31 2007 01:18 PM |
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Tropical Depression / Felix On The Way
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Well, it certainly is beginning to *look* like the Hurricane Hunters will find a closed off low, with steadily lowering surface pressures. This one has TD and Storm written all over it, just judging by its steadily improving appearance.
It seems likely, IMHO, that there is no turning back now. Felix is in the hopper. While you've all slept overnight, I've been watching this little invest mushroom into something more than just a 'little invest'. (Remember, I am 6 hours behind Florida time)
Judging from the greatly increased aerial coverage and the intensity of convection, I'd hazard that surface pressures are beginning to lower, and banding features are blossoming out everywhere, indicating a steady increase in organization, when all the convection works together to lower surface pressures, which in turn steadily increases the wind speeds.
But of course, you all know this already. It's just always interesting, from a weather hobbyist perspective, to see it happening right before your eyes, time and again. Let's hear it for the animated time-lapse satellite loops!
Additionally, the disturbance is beginning to exhibit a greatly improved upper-level outflow pattern, with good outflow to the NE, and recently, beginning towards the S and SW, as well. Good ventilation will only support intensification.
94L is quite likely to become TS Felix in the not-too-distant future. The TCFA has been out for some time now, the thermodynamic environment is becoming increasingly favorable and the 'negative' factors seem to be dwindling.
It'll be interesting to see what the Recon mission will reveal with regard to thermodynamic structure and wind fields.
And it'll be interesting, too, to see what becomes of the 'alleged' FAMCG (Far Atlantic Monsoon Cyclonic Gyre
), currently cycling within a large area SW of the Cape Verde Islands, in the coming days as it seems that the gyre might be setting up shop there for a'while.The latest tropical weather discussion (2am EDT, as I write) indicates " ... BROAD ELONGATED LOW / MID LEVEL
CYCLONIC ROTATION COVERING THE AREA FROM 12N-19N BETWEEN 28W-37W WITH SEVERAL POSSIBLE ILL-DEFINED LOW LEVEL CIRCULATIONS.", which would be entirely consistent with the behavior of a monsoon cyclonic gyre, as discussed in the "Hurricane Ask/Tell" Forum. Pretty interesting stuff. Well worth a look.
Hold onto your hats and batten down the hatches, as it appears that "Ferocious Felix" will be the start to a quick succession of storms in the coming weeks, in a still yet predicted 'above average' season.
-----------------------
Flash: NHC has just issued a 'SPECIAL TROPICAL DISTURBANCE STATEMENT'.
http://www.nhc.noaa.gov/text/refresh/MIADSAAT+shtml/311310.shtml?
Apparently, they're impressed with its steadily improving satellite signature, as well.
| native |
| (Weather Guru) |
| Fri Aug 31 2007 02:27 PM |
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Re: Tropical Depression Developing East of Caribbean
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I'd be interested to know from the Mets here (or others more in the know than I) if 94L keeps heading in a fairly straight forward westerly direction, what, if any, impact could the northern coast of Venezula have on this developing system?
| weatherguy08 |
| (Weather Hobbyist) |
| Fri Aug 31 2007 02:36 PM |
Re: Tropical Depression Developing East of Caribbean
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The post on the home page as well as some of the model runs are saying that 94L/TD6/Felix is to continue a generally westwards track. I have to disagree with this somewhat after looking at the 700 - 850 MB Steering Layer Map from CIMSS. The map shows a strong ridge in place, centered east of Bermuda, extending as far west as midway between Bermuda and the East Coast. Also, the southwestern corner of the high has very fast steering currents which lie just ahead of the system. Should it enter this area, we could see a brief, but rapid and significant northward jog of the system. If this occurs, the two major scenarios I could see would be for the system to go out to sea or possibly affect Florida and The Bahamas. Also, the Gulf Coast may have to watch this system in the future as the National Weather Services offices in Houston, Lake Charles, Slidell, and Mobile are all forecasting a retrograding trough over the northern GOM to spawn an upper-level low over central Texas which would move northeastwards causing a breakdown of the high pressure over the area.
In summary, everyone along the United States coast should watch this storm (check daily updates for now). As for the models, I do not put a whole lot of stock in them at this point as it is early and the storm has not become established yet. Also, Recon data that is inserted into the models can cause a massive impact on model guidance as we saw with Hurricane Dean.
Link to Steering Layer Map: http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8dlm1.html
Edit:
Almost forgot! This map from the HPC shows a low pressure and trough over the north-central United States which is forecast to help the breakdown in the ridge over the eastern half of the CONUS late next week.
Link: http://www.hpc.ncep.noaa.gov/medr/9mh.gif
| LoisCane |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 02:44 PM |
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Re: Tropical Depression Developing East of Caribbean
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I see your point. But, the models don't see it so... have to see if any of the next few model runs show any variation other than westward bound.
late next week might be too late for THIS system.. but any following might feel the weakness and have a different track from Dean2
| weatherguy08 |
| (Weather Hobbyist) |
| Fri Aug 31 2007 02:52 PM |
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Re: Tropical Depression Developing East of Caribbean
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That's one thing I am wondering about. About how fast will this thing move. Because again, if you look on the CIMSS map, there is a potential for a northward jog during the next 24 hours. In my opinion, I do not think this will move it very far to the north but it could delay its westward movement. In other words, it could buy the system some time before hurrying off to the west. But I agree, we should for sure continue to watch trends from the models and of course like I said earlier, if the NHC decides to insert the Recon data into the models, we could see a shift in the guidance. Also, the breakdown of the high over the eastern CONUS is forecast to occur on Day 7 (next Friday) which is a very long way off. My point being that it may not be too late for our storm to "enter" the weakness as it will take 5 - 7 days to traverse the Caribbean. Remember that Dean which was cruising across the Caribbean, if my memory is right, it took it four days to go from the Windwards to the Yucatan. So if the system takes that northward jog, which if it does I would predict it to last 12 - 24 hours, it could delay the system an extra day in moving across the Caribbean.
| LoisCane |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 03:27 PM |
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Re: Tropical Depression Developing East of Caribbean
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slower than Dean..so true
but that weakness also has shear doesn't it?
i noticed a few models "lost" Felix after it gets into the carib
good link tho to hold onto... because if felix doesn't stay low could gain a bit in lat...
time will tell
pretty little system today
| CoconutCandy |
| (User) |
| Fri Aug 31 2007 03:46 PM |
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Tropical Depression 6 / Felix Determination
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Hmmm. No 11am advisory on a "newly formed TD6", as some of us were expecting.
I suppose that, with the good folks with 53rd Weather Reconnaissance Squadron heading for the disturbance, NHC decided to avail themselves of all that great technology, and let the Recon Data decide what the status of the disturbance should be. I can understand their call.
And, as just noted, the recon data will be inserted into the global models, providing a much better and more accurate picture of what will evolve over the coming days. So they're hedging their bet with that Special Statement, and letting the awesome power of technology have the actual honors of making that crucial determination.
And maybe the 'Special Tropical Weather Statement' was issued because they thought it'd catch more attention from 'casual' visitors to their home page (and the media) if they FLASH it up there, whereas not everyone 'digs down' and reads the nitty-gritty TWO on a routine basis, like many of us.
All I can say, IMHO, it sure looks like and could very well be a Depression already. And NRL has just increased the winds to 30 Kts. Felix is ready to pop out of the oven.
| doug |
| (Weather Analyst) |
| Fri Aug 31 2007 03:46 PM |
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Re: Tropical Depression Developing East of Caribbean
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Everything is moving west, including that current, which is clearly seen in the Sat pics... However, the ULL and trough in the West Carribean is not moving too fast so I do tend to agree that a more NW track is in the future, just not too sure as to when or for how long as the flow returns to westerly around the Greater Antilles.
In general this is a very confusing pattern effecting what this system will do, in contrast to Dean which was on a fast track all the way. I have never seen so tight track agreement throughout as that system (Dean) generated. The models will differ greatly on this one.
| LoisCane |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 04:24 PM |
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Re: Tropical Depression 6 / Felix Determination... no go
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Well I guess they wanted to wait to be SURE... or they want to prove the value of Recon.. I mean why bother to send a plane in to determine what is going on in the system if you can make the call from Sat obs and Quikscat? And... really, nothing like recon so ..
I'd imagine an upgrade around 2.. 2:30... official advisories maybe at 5.
Maybe they want to be sure it's a Tropical Depression and not a Tropical Storm?
We'll see but either way a headsup is basically a press release to the media to get your act together because we will probably have film at 11. News media and other weather sources..
| LoisCane |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 04:33 PM |
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flora 63 came in that low too but went out to sea
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different year and different time of year.. different steering currents but you can't just assume a storm that comes through at that low level will keep going west as weather is fluid..
don't see anything in models to show other than west but its still early
and after the planes get more info the models will be more accurate
http://weather.unisys.com/hurricane/atlantic/1963/FLORA/track.gif
| audienceofone |
| (Verified CFHC User) |
| Fri Aug 31 2007 04:43 PM |
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Re: Tropical Depression Developing East of Caribbean
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Have I majorly missed something or are people using "Felix" just assuming that this system will be upgraded to a storm? Just a little confused as I've been away for a couple days and don't remember hearing about another storm yet. Thanks!
| doug |
| (Weather Analyst) |
| Fri Aug 31 2007 04:59 PM |
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Re: Tropical Depression Developing East of Caribbean
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" Felix" should not be used...this system is unclassified and the historical data for storms in the proximity this may have to the continent indicate it may not develop at all beyond what is now there.
It is gradually building the strength and organization to become classified. What may be holding it back now is the LLC is still large and it may have to tightnen down some. I have not seen any recon data, if they even went in, the last Quicscat I saw was 25-30 mph and that's not good enough.
| Unregistered User |
| (Unregistered) |
| Fri Aug 31 2007 05:06 PM |
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Re: Tropical Depression Developing East of Caribbean
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16:54:00 14.00N 60.45W 410.4 mb 7,422 m - From 69° (ENE) at 23 kts (26.4 mph) 23 kts (~ 26.4 mph) - -
that is the latest and isnt near the center yet
| cieldumort |
| (Moderator) |
| Fri Aug 31 2007 05:18 PM |
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Re: Tropical Depression Developing East of Caribbean
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recon is indeed already in and investigating 94L's environment.
Here's one of the latest messages, decoded
Fri Aug 31 2007
1642 GMT
Latitude 14.7 N
Longitude 61.1 W
No turbulence
Currently flying in the clear
Flight altitude 22999 feet (7010 meters)
Flight level winds 80 degrees at 16 knots (18 mph)
Temperature -14 C Dewpoint -48 C
Remarks: AF305 01FFA INVEST OB 03
Thought I would start to highlight something else -
Honorable mention to the quasi-tropical cyclone up around 42N. Hopefully we see an Invest tag slapped on it soon, such that model runs and microwave images become more available. Some tropical cyclogenesis is occurring within a deeply-stacked, non-tropical low... embedded within the parent large, cyclonic gyre, ESE of Newfoundland.
Here's what the latest TWO has to say about it
A NEARLY STATIONARY AND RATHER STRONG NON-TROPICAL LOW HAS DEVELOPED
ABOUT 700 MILES EAST-SOUTHEAST OF CAPE RACE NEWFOUNDLAND. THIS
SYSTEM HAS BEGUN TO ACQUIRE SOME TROPICAL CHARACTERISTICS AND WILL
BE CLOSELY MONITORED FOR SIGNS OF ADDITIONAL DEVELOPMENT.
| Rich B |
| (British Meteorologist) |
| Fri Aug 31 2007 05:19 PM |
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Re: Tropical Depression Developing East of Caribbean
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Satellite imagery would support classification, but NHC are holding off on doing so until RECON gets in. If it was 1000 miles further east then it would probably have been classified on imagery alone. The advantage is they will have a sure answer in the next hour or two. Given the motion it looks likely that northern Venezuela will get at least some wet and windy weather, but it is also possible the centre will track pretty near the coast. This interaction will probably limit its intensification during the time period too.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 05:29 PM |
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Re: Tropical Depression Developing East of Caribbean
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last check on recon... they were directly south of Barbados... dropping in alt. down to about 16,000ft.
At 17:14:00Z (last observation), the observation was 36 miles (57 km) to the S (182°) from Bridgetown, Barbados... i expect will have atleast a TD.... maybe a TS... but again looking at the models... this looks to keep heading west... another central american system?
| Climate Aficionado |
| (Registered User) |
| Fri Aug 31 2007 05:33 PM |
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Re: Tropical Depression Developing East of Caribbean
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That is some sight off of Newfie...
ESE NF
| Storm Hunter |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 06:07 PM |
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Re: Tropical Depression Developing East of Caribbean
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looks like we may have a TD. on HDOB the winds shifted, like there was a center... possible closed? more coming.. they went through a center.. winds at ft. lv. went down to 2kts.. (17:47:00Z at11.52N 58.52W at an alt. of (~ 28.54 inHg) 392 meters(~ 1,286 feet).... Flt. level winds From 94° at 2 knots
(From the E at ~ 2.3 mph) ).. more coming
**haven't seen any winds that would indicate a TS, yet... flt. lvl. winds around 15-25mph at 1,286ft***
| Storm Hunter |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 06:19 PM |
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Re: Tropical Depression Developing East of Caribbean
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Recon just went back through the center..... winds did shift... looks like we have a TD... haven't seen a vortex drop... winds went from ENE to WSW... flight level temp didn't change that much... which i would think its not closed?
| Thunderbird12 |
| (Meteorologist) |
| Fri Aug 31 2007 06:41 PM |
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Re: Tropical Depression Developing East of Caribbean
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Recon data seems to indicate a relatively weak and broad surface circulation in 94L. Max flight-level winds so far (that I have seen) are 28 kts. It'll probably be classified at the next advisory time, even if the plane doesn't find anything tight enough to merit a vortex message. The satellite signature of the storm is impressive, but the available data so far indicates that the surface reflection is still getting its act together.
I also noticed that some convection has flared up around 15N/35W, in the vicinity of the tropical wave/broad low pressure that was getting a brief mention in the TWO for the last couple of days before being dropped. If that persists, it may start getting mentioned again, but nothing is imminent.
| typhoon_tip |
| (Meteorologist) |
| Fri Aug 31 2007 06:50 PM |
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Re: Tropical Depression Developing East of Caribbean
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I will be quite surprised if this is not a depression in the 5pm and it may develop substantially overnight tonight.
The last 3 frames here: http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html Clearly show an accelerating cyclonic torque centered very close to 11.5N/58W -- of course this may vary from official.
Rapid improvement in sat presentation has commenced.
Deep layer wind analysis shows very little shear. As the convection potency has increased the transfer of mass to the upper levels, that injection enhances the outlfow in an already fairly favorable 200mb to begin with.. This means that the system has an above average evacuation being established. (There is also a thermodynamic process involved in the latent heat release of convection but that may be over folk's heads).
Oceanic heat content is quite high where 94L is and will only increase along its extrapolated path. There was some question of turbulent overturning left in the wake of Dean, but given to the depthy thermoclines of the Caribbean, and observing SSTs, this does not seem to be a problem.
The dry air that was likely contributory in preventing more robust development heretofore is still prevalent. However, belated but not denied is the key here... The dry air can be overcome given time via storm-centric production of increasing theta-e (moisture in atmosphere). In other words, the developing TC is producing a bit of its own core from which to fester within.
The reason there is only a vague presentation in the models may have to do with the models trying to initialize for a pressure perturbation that is all of 2mb lower than standard sea-level; and also relative to the ambient observed pressures in that area. As the system develops further, however, eventually the models will sniff out its presents more clearly and we will likely see some different solutions emanating rather abruptly. Fwiw, the ECM's 12z solution is a bit more robust now after having lost it for several runs, so perhaps we are beginning this process now.
John
| Rabbit |
| (Weather Master) |
| Fri Aug 31 2007 07:25 PM |
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Re: Tropical Depression Developing East of Caribbean
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very doubtful now that it will be upgraded at 5--NRL still has it as 94L and the winds have been lowered back to 30 mph
| HCW |
| (Storm Tracker) |
| Fri Aug 31 2007 08:25 PM |
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Re: Tropical Depression Developing East of Caribbean
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Quote:
very doubtful now that it will be upgraded at 5--NRL still has it as 94L and the winds have been lowered back to 30 mph
I am going to have to disagree with that since it's listed as noname06 now on the navy site
Is there any chance that this could affect the US with this pattern that we are stuck in ?
| LoisCane |
| (Veteran Storm Chaser) |
| Fri Aug 31 2007 08:29 PM |
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Re: Tropical Depression Developing East of Caribbean
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It was upgraded on will be officially at 5. See the home page.
Next run of models will have the recon data and will be interesting to see what it can do.
Not moving all that fast.
| hurricaneguy |
| (Weather Hobbyist) |
| Fri Aug 31 2007 08:30 PM |
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Re: Tropical Depression Developing East of Caribbean
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Quote:
Is there any chance that this could affect the US with this pattern that we are stuck in ?
Not really. This storm has a Dean path written all over it. It will be just a little further south. The ridge breaking down theory has just as good of chance as that ULL had of sending Dean to the GOM, and we all know how that turned out. This will be a Central America threat.
| StrmTrckrMiami |
| (Weather Guru) |
| Fri Aug 31 2007 11:49 PM |
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Re: Tropical Depression Developing East of Caribbean
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It seems that the majority of the depressions and storm systems are on the path twords Mexico this year. Looks like another Dean for Mexico and Jamaica (poor jamaica) What do you guys predict the hurricanes will do? Will they follow this track or some end up in Florida?
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 12:03 AM |
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Re: Tropical Depression Developing East of Caribbean
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right there at sunset on TD 6 a good development of storms flared up....looks to still be expanding in lastest IR sats and on the AVN loop. It should be right over where the center should be... Still a little curious about the ridge off the SE of US in 4-5 days... if it holds, this appears to be another system being pushed right along into central america.
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 01:16 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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This may be interesting to some...
Barbados is located at 13N/59.3W
As of the 8:05, TD6 is located at 12N/59.3W.
So, the TD is currently passing due S of the Isle of Barbados at a distance of 60 nautical miles.
Now...why that is particularly interesting for me is because they are reporting 2 consecutive hours of sustained 30+mph winds from the E. For a system of mere TD ranking, 60N miles is heck of a lot of distance to be effecting that kind of wind speed.
There could be other explanations, of course, but could it be that we have TS already?
Stay tuned!
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 01:28 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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been reading that too with Obs. from Barbados.. was wondering with the NICE CDO we have now with TD6, could it be a TS now? or was the winds a thing of TD and strong westerlies coming together, to give some good winds to the island?... Some of the 00Z runs are coming out... nice little shift showing up?
One thing i have noticed, seems to me that this time the center of the high will be forming off the New England area, instead of more to the south where the last one was with Dean? Anyone else seeing this... I KNOW its way down the road, but looking at the globals... seems like this may be a little different setup then Dean? On time will tell, but with the shift showing up in a 00z runs... (ones i have seen so far)... this might be something we need to watch closely.... **I know the models will jump around a lot until we they get a good handle on the system and the surrounding enviroment***
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 01:44 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Quote:
been reading that too with Obs. from Barbados.. was wondering with the NICE CDO we have now with TD6, could it be a TS now? or was the winds a thing of TD and strong westerlies coming together, to give some good winds to the island?... Some of the 00Z runs are coming out... nice little shift showing up?
Actually, I am not really inclined to think it is all that different than Dean's set-up at this time; though like snowflakes, no two patterns are "identical" either.
The -GLAAM (Global Atmospheric Angular Momentum) is very powerfully locked in an anomalous state at this time...
Moreover, the graphical presentation of where the crux of that anomaly distribution is situated is along and beneath 30N, and N of 30S... What that means is, -GLAAMs are correlated with longitudinal biases in the field and therefore, there is less likelihood that a wayward opening in the ridge will suddenly emerge and draw this system up; the meridional incursion (or in other words, increased troughing) into sufficiently south latitudes becomes anticorrelary and thus doubtful, given to this background overwhelming signal to maintain a stronger subtropical ridge axis.
That is far from absolute, of course! The GLAAM is a scalar value that is a calculation of integrated torque via several sources, throughout the atmosphere as a whole. It is not a prognostic tool, it is a measurement.
That being said, until this deeply negative anomalous state starts to show a positive modality, it is just the lesser of likelihoods at this time that meridional avenues will open up. It is the best way to use this observable teleconnector "responsibly", as possible correction scheme for forecast models. In this case, however, the models are pretty clearly persistent with the ridge and therefore, we have little room to doubt their veracity -- even at this extended lead; highly unusual but this is probably directly the cause in why the Global models did so terrifyingly beautiful predicting the path of Dean. They were locked into a persistence pattern where subtropical ridging was anomalously strong along 30 to 35N.
I was going over the 300mb, 500mb, and 700mb loops of the tropical Atlantic for the next week's worth of hours and across several runs of the GFS, there is indications of deep layer brick migrating W through the SW Atlantic Basin, across the Bahamas and west through the Gulf, in perfect tandem with "Felix's" probable forced S path.
John
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Ed Dunham
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| (Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)) |
| Sat Sep 01 2007 02:04 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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"but could it be that we have TS already?"
No, not at all. The normal wind at Barbados at this time of year is out of the east at about 15mph (think "Trade Winds"). At 9pm the wind at Barbados was out of the east at 32mph (at 8pm they reported a gust to 49mph). The island is currently experiencing the northern edge of the CDO. Because the normal wind flow is being enhanced by the TD to the tune of about 17mph does not mean that the winds near the center of the system are at TS strength - at least not yet. Same thing at St Lucia - normal wind is ENE at 16mph, but currently NE at 29mph. Grenada, where the normal tradewind flow is blocked by the TD circulation, has NNE winds at 7mph - and Grenada is just a little farther away from the TD center than Barbados is. (I guess thats why they call them the Windward Islands
). This is a case where data on the edge of the system has to be weighed with other known meteorological and climatological factors.ED
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 02:13 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Quote:
"but could it be that we have TS already?"
No, not at all. The normal wind at Barbados at this time of year is out of the east at about 15mph (think "Trade Winds"). At 9pm the wind at Barbados was out of the east at 32mph (at 8pm they reported a gust to 49mph). The island is currently experiencing the northern edge of the CDO. Because the normal wind flow is being enhanced by the TD to the tune of about 17mph does not mean that the winds near the center of the system are at TS strength - at least not yet. Same thing at St Lucia - normal wind is ENE at 16mph, but currently NE at 29mph. Grenada, where the normal tradewind flow is blocked by the TD circulation, has NNE winds at 7mph - and Grenada is just a little farther away from the TD center than Barbados is. (I guess thats why they call them the Windward Islands
ED
I thought of this, Ed. However, I'm considering the 60nautical miles from the central axis of the circulation center, and that is a pretty far distance...even when considering the background factors, to be registering that kind of velocity.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 02:42 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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i may already know the answer to this question, but wanted to check with someone is knows for sure... Does the UCF damage impact model plot (Experimental).... run off the GFDL, or is it a serious out models together? I think i read some where online it was a few other things combined and weighed some on the GFDL... Anyone know for sure?
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 02:45 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Rather than speculating, let's do the Meteorology:
At 8:00pm, Barbados was reporting a sea-level pressure of 1010.7mbs
At 8:05pm, NHC reported a TD depth of 1008mbs, at about precisely 60 nautical miles due south of Barbados at that time.
Since NHC does not include decimal values in their depth assessments, I will go ahead and round the 1010.7mb to 1011mb for consistent units.
Ed wants to give 15mph-worth of the 32mph, back to background trade wind phenomenon, which actually is an assumption because even though trades consistently blow, they do not do so at the same velocity relative to pressure patterns. In reality, we don't know what the trade forcing into the system was as of 8pm, but for sake of discussion, we'll just assume it was 15mph-worth. That means that 17mph-worth of velocity is hypothetically storm generated.
Now, the pressure differential between Barbados and TD6 as of 8pm was ~ 4mbs. There is a general rule that works to a very close approximation: 1mb nearly = 1kt. 4mbs thus equates to 4kts.
So, immediately there is a discrepancy here. If 4mb = 4kts, 4kts certaindly does NOT atone for 17mph, considering that 1mile is 0.864 knots. That means the 4.62mph...or essentially 5mph, sticks us with an unexplained 12mph using this method. Something is adding into this to cause the +12mph
One possible explanation for this disparity is that the trade wind forcing at this time is actually stronger than usual, and thus, Ed has a very strong point: The correction may go the other way and we may yet still have a depression. In other words, even though climate argues for 15mph of trades, we may in fact have (15mph-trade) + (12mph-trade-anonamaly) to consider.
The other possible explanation is that they are wrong about the 1008mb of pressure. They do not directly specify in the 8:05 discussion whether that is based on the last RECON trip or not.
Either way, the available evidence does tend to support Ed's point of view on this.
The other thing to remember is to look at ALL the data, not just these pretty colored sat videos. Seeing as this is about to cross the axis of the Islands, we should know in a hurry if one of these islands happens through an inflow jet that is 40mph or not.
John
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 02:57 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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hmm... just noticed this... with miss piggy and kermit (NOAA2 and NOAA3) being in the islands tomorrow... looks like from 01/2100Z to 02/1430Z there will be an aircraft flying the system (TD 6) [minus about 3 hrs].. along with AF recon... so looks like the HRD will be getting some good research data from this system, if all goes planned! Looks like as of tonight, the next recon will not be out there til, about 01/0930Z?
|
Ed Dunham
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| (Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)) |
| Sat Sep 01 2007 03:08 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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You're right - the 15mph was sort of an educated guess. I used the winds at Barbados at this time last night and figured that the Atlantic ridge probably hadn't changed much in the past 24 hours. We'll all know soon enough since the TD center should pass over (or very close to) Grenada at about 0500AST and Grenada is a 24hour station, i.e., they take weather observations all night.
Grenada Weather Observations
Cheers,
ED
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 03:18 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Quote:
You're right - the 15mph was sort of an educated guess. I used the winds at Barbados at this time last night and figured that the Atlantic ridge probably hadn't changed much in the past 24 hours. We'll all know soon enough since the TD center should pass over (or very close to) Grenada at about 0500AST and Grenada is a 24hour station, i.e., they take weather observations all night.
Grenada Weather Observations
Cheers,
ED
Excellent inclusion!
Our normal users have the advantage of some spectacular Met on-going...
| Beaumont, TX |
| (Storm Tracker) |
| Sat Sep 01 2007 03:33 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Some of the models are showing a more northern track after four days. Is it possible the high won't build as far as it is supposed to or that
there will be a weakness somewhere? I suppose it is still too early to tell. It looks like it is headed straight for Belize but a lot can
happen in four days so I do not think the Gulf Coast should dismisss the storm just yet.
| HanKFranK |
| (User) |
| Sat Sep 01 2007 03:36 AM |
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down deep
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td 6/felix has a heaping collection of model support taking it wnw on a dean redux path. there don't seem to be any synoptic scale caveats here... looks like a straightforward forecast. dean churned the waters along future felix's path... look for a lesser version of the storm, but a similar path seems perfectly reasonable. the more strengthening the more northerly a path is likely. a weaker storm will likely scuttle in nicaragua, a stronger one might head for the yucatan. the emphasis nhc is placing on 'might be a major hurricane' is probably well-founded.
models starting to snoop on the african waves again. not much support for the elongated monsoon trough near 35w with the wave-enhanced convective blip. it will still have a decent chance if a follow-on wave doesn't overtake it... for slow development like the 6/felix system out in front of it.
following wave train is all developed by the 18z gfs. one shows as a long-track hurricane there, with a dubious refusal to recurve into a weakness in the eastern atlantic. persistent disturbed weather near the southeast coast shows some suspicious activity but no tropical cyclone development, but that will be an area to watch nonetheless. the typhoon poised to hit japan after being blocked by a strong ridge, and the future track of henriette in the eastpac into the baja seem to suggest ridging near the east coast in the upcoming timeframe. have to be vigilant for one of these things to develop further north and also take a westerly track.
HF 0336z01september
| dem05 |
| (User) |
| Sat Sep 01 2007 03:36 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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I found this exerpt of the TWD to be fairly insightful/interesting...
THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
THROUGH 36 HR...THEN SOME SPREAD OCCURS. THE HWRF AND THE SHALLOW
AND MEDIUM MEAN LAYER BAM MODELS FORECAST A MORE NORTHWARD MOTION
TO A 120 HR POSITION NEAR THE YUCATAN CHANNEL...WHILE THE REMAINDER
OF THE GUIDANCE TAKES THE CYCLONE TO BELIZE AND THE SOUTHERN
YUCATAN PENINSULA. THE HWRF SHOWS THE STORM DISSIPATING DURING THE
FORECAST PERIOD...WHICH MAY ACCOUNT FOR ITS MORE NORTHWARD FORECAST
TRACK. THE TRACK FORECAST IS DOWN THE MIDDLE OF THE REMAINDER OF
THE GUIDANCE AND IS SIMILAR TO THE PREVIOUS FORECAST.
Traditionally, I have been used to seeing the models demonstrating a more westward biased when they see the system as weaker (shallower)...and a more northward biased when a stronger storm is forecast. In this case, the models are apparently showing the opposite (Per this NHC discussion blurb). I'd love to hear opinions on this, but my take is that a stronger system in this circumstance will strengthen the low/mid level ridge to the north and result in a more westward course....WIll be interesting to see if the other models move more toward the BAMS, BAMM, and the HWRF (Yucatan Channel)...or to see if the exact opposite will occur. Overall, the pattern does look like Dean revisited...but I'm sure there will be some interesting tracking differences in the coming days.
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 03:39 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Quote:
Some of the models are showing a more northern track after four days. Is it possible the high won't build as far as it is supposed to or that
there will be a weakness somewhere? I suppose it is still too early to tell. It looks like it is headed straight for Belize but a lot can
happen in four days so I do not think the Gulf Coast should dismisss the storm just yet.
Anything is possible, first off...
Much of this HAS to be probabilistically derived.
That being said, I refer you back to post # 77637 of this thread.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 03:54 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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***just a side note... *** Update your bookmarks
Was launched tonight from cira at colostate (RAMSDIS Online)
http://rammb.cira.colostate.edu/ramsdis/online/index.asp
Beta Test of the New RAMSDIS Online
Welcome to the new version of RAMSDIS Online. We're in the process of transferring all the products to the new streamlined version, starting with all the tropical products.
Using new coding for faster access to products on the web site....
| flahurricane |
| (Weather Hobbyist) |
| Sat Sep 01 2007 03:57 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Satellite imagery of the td looks impressive over the last few hours. I wouldn't be surprised if the intermediate advisory upgrades it to a tropical storm.
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 04:04 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Quote:
I found this exerpt of the TWD to be fairly insightful/interesting...
THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
THROUGH 36 HR...THEN SOME SPREAD OCCURS. THE HWRF AND THE SHALLOW
AND MEDIUM MEAN LAYER BAM MODELS FORECAST A MORE NORTHWARD MOTION
TO A 120 HR POSITION NEAR THE YUCATAN CHANNEL...WHILE THE REMAINDER
OF THE GUIDANCE TAKES THE CYCLONE TO BELIZE AND THE SOUTHERN
YUCATAN PENINSULA. THE HWRF SHOWS THE STORM DISSIPATING DURING THE
FORECAST PERIOD...WHICH MAY ACCOUNT FOR ITS MORE NORTHWARD FORECAST
TRACK. THE TRACK FORECAST IS DOWN THE MIDDLE OF THE REMAINDER OF
THE GUIDANCE AND IS SIMILAR TO THE PREVIOUS FORECAST.
Traditionally, I have been used to seeing the models demonstrating a more westward biased when they see the system as weaker (shallower)...and a more northward biased when a stronger storm is forecast. In this case, the models are apparently showing the opposite (Per this NHC discussion blurb). I'd love to hear opinions on this, but my take is that a stronger system in this circumstance will strengthen the low/mid level ridge to the north and result in a more westward course....WIll be interesting to see if the other models move more toward the BAMS, BAMM, and the HWRF (Yucatan Channel)...or to see if the exact opposite will occur. Overall, the pattern does look like Dean revisited...but I'm sure there will be some interesting tracking differences in the coming days.
There is likely some "inside" info they are leaving out. This is a complex question, actually.
In general, your observations are correct for the longer view. There is a tendency for weaker systems to align more westerly...
However, there is also a bit of an on-going anomaly in the respective layers at those time intervals in question; namely, the low-level and mid-level steering fields. The ridge is in the process of migrating west through the Gulf by the time this system reaches the western Caribbean... If "Felix" beats the ridge to those longitudes, there is some prospect that the low level steering would be more NW if it is a weaker system. Why? Because the steering level will tend to turn W at low levels last for retrograding low-latitude ridges.
The modeled steering fields do have a W component nearing the longitudes of the western Caribbean at the time intervals in question; however, the low-level (H850) is pointing NW, and when combined with Beta Drift, and a weaker system, that could easily mean a northerly position.
However, if a stronger system is there, integrating more in the deeper layers where the majority of mass is blowing almost due W, this resumes a westerly course.
You have to look at the actual pattern for each individual circumstance. In this case, the complexities of all are dictating a bit of an anticorrelary correction need.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 04:10 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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well... unless recon is out there tonight, which i don't think they are until the morning... and sats are going into Eclipse from about 400utc to about 600utc... we really want know anything about TD6 for a couple more hours... and last few images from sats, showed the cloud tops were warming a little, so looks like the round of covection has sustained itself for a bit, but will see what it looks like in the morning...
| dem05 |
| (User) |
| Sat Sep 01 2007 04:34 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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I see...Last time (During Hurricane Dean) I payed more attention to the Water Vapor loops...This time, since the overall pattern seems to be "straight forwardly similar to Dean"...I'm gonna be watching each of the models more closely this time...from run to run. Just to see if I learn something new.
Hmmm...Does seem to me that the GFS (9/1 0Z) is maybe having even a bit more trouble in maintaining TD6 than the 18Z run did...With that said, the new run is just a smidge further to the north. Of no significance really though.
The 0Z NAM, which is not one of the reliable models, appears to be pointing toward the Yucatan Channel on this run...Compared to a Nicaragua/Hondoras option that was identified in the 18Z.
Maybe there will be a bit more northward bias in the 00Z model runs...Will have to wait for the reliable models to finish their runs...Let the windshield wiper action begin...
Link to NAM and GFS Models: http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/index_carib.shtml
| typhoon_tip |
| (Meteorologist) |
| Sat Sep 01 2007 04:41 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Also, keep in mind, there are larger scale teleconnectors that suggest the more westerly track; BUT, teleconnectors can change, doing so slower than a point-in-time model output. What that really means is that there are on-going permutation-based possibilities in these matters.
| dem05 |
| (User) |
| Sat Sep 01 2007 06:30 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Hmmm...Well, the 06Z runs of the BAMS, BAMM, BAMD, and the Clipper (Climo and persistance model...not a reliable model) should be out soon. Mean time, I am very interested in seeing the 00Z Nogaps when it comes out. The 00Z GFDL has moved north a fair amount in the last run. Indicating a landfall about 50 miles north of whare Dean came in, but south of Cozumel. General tendancy is toward a subtile recurvature at the end of the track. The UKmet is much faster (probably too fast)...and a bit more concerning if it remains persistent in future runs. It is now showing a recurvature toward the NW and NNW into the central Gulf. With the GFS coming in at 00Z about 50-100 miles north of the NHC at 00Z...if the Nogaps moves northward on the 00Z...Then the NHC 11PM forecast track will be totally outside the guidance envelope (With particular respect to the "reliable models") on the southern end and a track update may be required at 5AM... We should know more about that soon...Like I mentioned earlier...the Windshield wipers are on!
In general, the compromise of the BAMS, BAMM, and BAMD have not bee bad in recent years as far as a consensus track...If they do not shift further north on the 06Z runs...the combination of them, the GFDL, the UKMET, and someothers may place a new track more towards Cozumel (a touch south of there)...with the GFS as a Southern Outlier and the CMC as an extreme southern outlier...But the CMC does not get as much attention for its track as the other big models.
| scottsvb |
| (Weather Master) |
| Sat Sep 01 2007 06:35 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Dem, for the 11pm track, the NHC does the track based on the 18Z runs and which model they prefer compared to the satellite data they review.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 06:42 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Dem05, i think the 00z NOGAPS has been out for a bit... FSU hasn't converted it yet..
but i think this is it below... looks to me it moved just a tad?
https://www.fnmoc.navy.mil/wxmap_cgi/cgi...;dtg=2007090100
*go here, https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxmap_DOD_area.cgi?area=ngp_namer
its not doing to well with the system though... keeps it weak.
| dem05 |
| (User) |
| Sat Sep 01 2007 07:03 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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Yes, that is correct Scott. For the 5AM advisory package, they will be looking at the 00Z information as well as the information for the 06Z on the BAM suite. If the trend persists with the 06Z Nogaps...Everything else is placing the 11PM advisory Forecast on the Southern extent and/or outside of the guidance envelope...as such, we may see a subtle move in the forecast track to the north on days 4 and 5 in the 5AM advisory...
Mean time, speaking of satellites, the satellite eclipse is over for tonight. TD6 must have sped up a bit this evening, cuase it is significantly further to the west. That coordinate estimate for 2AM advisory probably should have been further west, but they were flying a bit blind with no recon or satellite. That is, unless TD6 is suffering from easterly shear and the mid level center has been displaced to the west...which I seriously doubt. Not their fualt at the NHC for this though...as I mentined a minute ago, they were flying a bit blind tonight and that was an excellent extrapolation on their part for the 2AM coordinates.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 07:22 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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06z BAMS are all together now in the norther Yucatan... one north of Cancun and others just to the south... but does look like a few more models are well north of the 11pm NHC track, so there may be a SLIGHT adjustment made, or they may hold on it... also just glanced at lastest few sat shots... some weak shear? Looks like it fixing to pass close to that island soon! Also notice now the front/weak low is now just off shore of me (PC, Fl) from that front that is over the SE.
| dem05 |
| (User) |
| Sat Sep 01 2007 07:41 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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I'd been watching for that BAM package to come out...I notice that SFWMD has basically updated all the other models as well. In that I also notice that the GFS ensemble (CONU) is now well north of the NHC 11PM as well...In fact, it is the southern outlier compared to BAM, Nogaps, GFDL, HWRF, and UKMET...but it is also north of where Dean slid on shore and it has a greater northern component than Dean did.
I will not model monger as things will likely windshield wiper a bit over time...but for now, the philosophy for track has changed from a westward mover into Belize to one that may be moving in an almost NW heading on approach to the Yucatan...As such, the models are currently seeming to center around the area south of Cozumel (around the BAMD)...Actually, right about where the CONU is pointing as of 6Z. Coincidently, if TD6 is gonna be a stronger storm (i.e. hurricane), I found it interesting that it moved north once again on this run of the BAMD...closer to the BAMM and the BAMS.
At 5AM, I would suspect that the track change will be subtle due to many changes in the overall appearances of the models. I wouldsay the 5AM will be smack in the middle between the 11PM and the 06Z BAMD track. Justin case the models do windshield wiper back.
Also interesting to note that none of the models have decided to grab the reigns and make TD6 ahurricane...Even though it is forecasted...and quite possible that it will do so. I wouldn't put 100% stockinto the major global models just yet.
| Storm Hunter |
| (Veteran Storm Chaser) |
| Sat Sep 01 2007 08:02 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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hmm.. i think we have a TS now?
Storm Location
Date: Sep. 1, 2007 6Z
Coordinates: 12.2N 61.2W
Wind Speed: 35 knots
MSLP: 1006 mb
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0704 UTC SAT SEP 1 2007
TROPICAL CYCLONE SIX (AL062007) 20070901 0600 UTC
...INITIAL CONDITIONS...
LATCUR = 12.2N LONCUR = 61.2W DIRCUR = 280DEG SPDCUR = 16KT
LATM12 = 11.6N LONM12 = 57.9W DIRM12 = 281DEG SPDM12 = 14KT
LATM24 = 11.3N LONM24 = 55.4W
WNDCUR = 35KT RMAXWD = 30NM WNDM12 = 30KT
CENPRS = 1006MB OUTPRS = 1014MB OUTRAD = 150NM SDEPTH = D
RD34NE = 40NM RD34SE = 0NM RD34SW = 0NM RD34NW = 40NM
| dem05 |
| (User) |
| Sat Sep 01 2007 09:24 AM |
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Re: Tropical Depression #6 Forms East of Caribbean
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5AM NHC Discussion...They must be picking up on the potential for model windshield wiper action with Felix based on their updated forceast path...or, and without meaning this with anegative tone...they are coming off of a high confidence with Dean and they may want to watch that Mother Nature does not chomp some finger tips down there...
For the very first time that I can think of, the NHC has absolutely abandoned the models here. In fact, they went as far to say that they dropped the forecast farther south, even though the whole model group generally moved north. The GFS, which they identify as the southern model package is in fact...north of the 11PM forecast as well as even farther north of the 5AM forecast. I'm pretty surprised, but I also know that they know what they are doing...Unfortunately, the NHC discussion did not mention their reasoning for going southward in any way that really backs the models, or why they are using independant thought...but if you look at the SFWMD site for the 00Z runs and Clark's page of the model plots for 06Z...I am sure you will agree. No knock on them, but they sided against conventional practice here. With that said, they must be really on to something....Therefore, in Belize, please note that they have Felix approaching Category 3 strength before landfall...Something to consider in preparations if the track does hold up. Mean time, further north in the Yucatan...you guys know the Hurricane drill too...
| CoconutCandy |
| (User) |
| Sat Sep 01 2007 10:40 AM |
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Enter Felix, Stage Right
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Good Morning All. TD-6 has been upgraded to Tropical Storm Felix at the 5am advisory.
The convection continues to expand with continuing organization of the feeder bands, several of which are now in evidence in the western semi-circle, with more beginning to take shape in the S and SE quads.
Also, the deep convection has maintained very cold cloud top temps of -70 to -80, all the while continuing to organize better, implying that gradual intensification is underway. And upper level outflow is quite good and only improving.
From NHC's 5am discussion:
"THE CONVECTIVE PATTERN OF THE CYCLONE HAS CONSOLIDATED SOMEWHAT OVERNIGHT...WITH THE COLDEST CLOUD TOPS NOW FOCUSED ON A CLUSTER VERY NEAR THE ESTIMATED LOW-LEVEL CENTER LOCATION ... AND THE ADVISORY INTENSITY IS RAISED TO 35 KT ... SO THE DEPRESSION IS UPGRADED TO TROPICAL STORM FELIX."
Moving a little faster now, it seems that Felix is destined to be, like Dean, a 'Straight Shooter' type system, with high confidence in taking it directly towards Central America, with a possible landfall in Belize nearing Cat 3 strength.
Shear is expected to remain low, so an even stronger hurricane wouldn't be out of the question by the end of the forecast period. Remember that mid and long range *intensity forecasts* have a much greater degree of error than do those regarding location, and all factors appear to be favorable, certainly not inhibitive.
All in all, it would appear that Felix could become a quite 'respectable' Caribbean Hurricane, which fortunately, should not effect US interests.