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MikeCAdministrator
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Erika Falls Apart
      #86829 - Thu Sep 03 2009 07:12 AM

2PM EDT 4 September 2009 Update
95L is now being tracked in the Eastern Atlantic, 30-50% chance of development in the next 48 hours, but there doesn't seem to be that great of model initialization on it yet.
6:30AM 4 September 2009 Update
At 11PM last night the National Hurricane Center discontinued advisories on Erika, as it has weakened to an open wave.

It will continue to be monitored for any signs of reorganization, as there is still some convection associated with it, it fact a good area near the old center formed overnight.

Another wave in the east Atlantic is being monitored as well, it has no investigation number as of yet, and has a <30% chance of formation in the next 48 hours.


6:30PM Update
Erika has weakened to a depression, the main low level circulation racing away from the convection. The NHC forecasts it to dissipate as it nears Hispaniola now, bringing heavy rainfall to the area.

Even though it is most likely to fall apart, much of the convection to the east remains. We'll continue to watch for any signs of re-organization.

Original Update
Tropical Storm Erika remains in the northeastern Caribbean, moving slowly toward the west northwest. The current forecast track now takes it right over Puerto Rico, but it will mostly be a rain event for the island. It may be downgraded before it gets to Puerto Rico.

After that it is expected to slide into the Bahamas, but also run into heavy shear, which the National Hurricane Center is forecasting to weaken it further into an open wave. The remnants of the wave may wind up in Florida, bringing us rain mid next week.



There are still some uncertainties with the storm, so it will have to be monitored, particularly if it slows down even more.

There is quite a bit of convection across the Leewards right now, I'm sure a few places will see flash floods, places like Montserrat are a bit vulnerable to that. But overall Erika seems to be on the weakening trend. It would be foolish to take attention off of it now, however, at least until the main convection dies down. Especially since some modes still insist on intensification and the still general slow westward motion.

It's really down to which factors are more important, dry air, shear, vs steering and massive convection, computer models against old fashioned forecasting. Erika is still very interesting, and even though the dissipation scenario is most likely, it is by no means definite.

Martinique Radar
Flhurricane Recording of Martinique Radar/Erika Approach
San Juan, Puerto Rico Radar Loop (Latest Static)
StormCarib Reports from the Caribbean Islands

Caribbean Weather Observations

Barbados Brohav Weather Fax

Full Caribbean Radar Composite

Caribbean Broadcast Corporation (TV/Radio from Antilles)

San Juan, PR NWS Page

Various Caribbean Radio Stations

DR1 Dominican Republic Hurricanes

Invest 95L Event Related Links


float7latest.gif stormplotthumb_7.gif

SFWMD Model Plot (Animated Model Plot) SFWMD Hurricane Page

[https://flhurricane.com/floatanimator.php?year=2009&storm=7 Flhurricane Satellite Floater Animation of Invest 95L
GOES Floater
Animated Skeetobite Model Plot of Invest 95L


Clark Evans Track Model Plot of Invest 95L (Animated!) Model Plots in Google Earth - In Google Maps
Clark Evans Intensity Model Plot of Invest 95L (Animated!)

Clark Evans Track Plot of Invest 95L

Other Model Charts from Clark

Clark Evans Top 10 Analog Storms for Invest 95L
More model runs on from RAL/Jonathan Vigh's page
NRL Info on Invest 95L -- RAMMB Info
COD Atlantic Satellite View



Edited by Ed Dunham (Fri Sep 04 2009 08:43 PM)


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craigm
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: MikeC]
      #86830 - Thu Sep 03 2009 07:45 AM Attachment (642 downloads)

What a mess. We have a couple microwave passes that just looking at overall symmetry would put what looks to be the most dominant circulation just NE of Antigua/ Barbuda. (see attached) I'm not buying into initial point for the models. I wish they would put this instrument on a geostationary sat. At this point moving W to WNW even moving through the islands there is not much to get ripped apart. I see Erika, even if she is downgraded continuing to spin off vortices in different directions until conditions become more favorable if they ever do. We still have two intensity camps -- remmnant low on one side -- storm to hurricane on the other -- all heading in the general direction of the Bahamas. Like I said what a mess.

--------------------
Why I'm here:
Weather hobbyist

Edited by craigm (Thu Sep 03 2009 07:53 AM)


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weathernet
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: craigm]
      #86831 - Thu Sep 03 2009 09:19 AM

I have to agree with Craig regarding an odd, yet seemingly apparent mid level rotation trailing to the NE quad. of the "blob known as Erika". Given so much uncertainty with multiple vorticity aside from a "mean" tracked broad and diffuse low level circulation, I think that model insight for the moment is useless. Bigger question for the moment would seem to be, where might Erika ( or remnants of ) be in approx. 48-60 hours from now. Perhaps depending on where the greatest convection remains, along with any persistent vorticity, then here where things could once again get interesting. The 0600. GFS 200/250mb runs would indicate differing upper air hostility depending on whether one is looking at the higher 200mb flow, or the slightly lower 250mb flow. Equally critical would be where in the world Erika, or any remaining pulse of Erika might be at such a time.

At some point however, it would appear that the 250mb flow becomes less of a separate unidirectional flow, and the upper level flow in general would seem to be more or less anticyclonic. This "general anticyclonic flow" could still remain hostile, or simply be an extension of a broadening upper level high over the area and extending over a once again deepening storm. Here though, is where the question might arise as to whether or not, and where might a re-deepening of the depression or open wave formerly known as Erika ( almost wanted to say musician formerly known as Prince ) occur. Overnight NOGAPS ( typically conservative on development ) starts to spin up Erika in about 36-48 hrs., just east of the Southeastern most Bahamas. Oddly, upper air conditions would still appear to be fairly hostile in that place and time. Along with the NAM, NOGAPS would then pretty much carry the deepening system mostly NNW'ward, and thus not threatening the S.E. CONUS. Meanwhile, the GFS model would seem to show a distinct, albeit week , ridge starting to show up at 72-78 hours a few degrees east of W. Palm Beach. This ridge would appear to be an extension of the recently building 594 high which will be building westward over the next couple days. With the overall mid term pattern over the E. CONUS being mostly zonal and with no appearant mid/upper level perturbations at that time, then a very week west/WNW flow could carry any system just north of E. Cuba toward Florida.

Whether due to evolving El Nino conditions, or other things at play, we are at minimum dealing with a very
vigerous tropical wave, in what could be an overall week steering flow in the days to come. And such as the models bare out, there could be a hurricane impacting land within a week, or a diffuse wave producing scattered showers somewhere. Though the later is more likely to occur, the potential threat that lies here is greater due to the potential suddenness of re-intensification and lack of anticipation and preparation by the general public should this occur.

After posting this, just took a look at Martinique radar and talk about this system being "fluid" and constantly changing...... Notice how what would appear to be a tight center shooting off to the WSW, only to become diffuse, and then one could make an argument that a newer center may be forming underneath the western edge of the convection. Either multiple vortices's, or a constant effort to "re-invent" itself. Link to Martinique radar http://flhurricane.com/imageanimator.php?69
( at bottom of radar, click play then increase animation speed )

Edited by weathernet (Thu Sep 03 2009 09:43 AM)


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berrywr
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: weathernet]
      #86832 - Thu Sep 03 2009 11:00 AM

03/1430Z - Good morning everybody! Awaiting the update from NHC shortly. Satellite imagery once again as it has been for the past few days has been somewhat impressive during the early morning and today is no exception. Within the larger circulation envelope there appears to be within the convection two possible centers and visible satellite imagery is indicating a LLC or near surface center to the NW of the convection about 180 miles E of Puerto Rico.

Analyzing the NCEP 03/06Z GFS package this morning a hostile environment for the foreseeable future. At 200mb and 250mb the persistent upper low continues to be near Cuba and HIspanola for the foreseeable future and the longwave trough over the Eastern US remains throughout the forecast period though in pieces, but nevertheless deep enough today that it extends well into the Gulf of Mexico.

It is not beyond the realm of possibility that Erika's structure may reveal itself as a subtropical or hybrid storm with what now appears to be the upper low over the top of Erika H+120 hour position between Cuba and the southern Bahamas.

I see no approach to the United States in whatever form Erika takes. If Erika is to remain tropical it must stay within a very small area between its current location and the coast of South America and remain virtually stationary for the next 5 to 7 days; a tall order.

Wind Shear Analysis out of SSEC states the obvious; it's hostile west, northwest, north, northeast and east of Erika and more hostile along any part of the Gulf and Atlantic coasts of the US.

The thunderstorm complex which has been most impressive for the last few mornings does reflect some outflow but below 250mbs and possibly below 300 mbs. Once again closer examination of thunderstorm tops reveals that any tops approaching 30,000 feet are being sheared away. It looks pretty, but for Erika to strengthen we're talking thunderstorm tops in negative 60C to negative 75C and 30,000 feet is not high enough.

New update just released, no change in reasoning or track.

I'm not willing to write off Erika as a subtropical system, but as the surface ridge makes its presence known, Erika is progged to increase forward speed towards the Bahamas which then it will interact directly with the progged upper low to its west by being under it and the atypical position of the trough over the E US at H+120 and beyond.

I'm not surprised at the frustration Erika has presented to all of us here, but the upper pattern this season has been atypical to the norm and to look out there right now, you'd think it was much later in the season than what the calendar implies. I'm not an expert on El Nino and the Southern Ocillation and frankly it's all above my head anyway. It's interaction with the ITCZ and TUTTs is not what I call interesting reading and even for us who do or did this for a living; for example my specialty with the Air Force is Aviation and Severe Weather; not Tropcial.

We old school guys use to actually plot the data when we were observers, analyze like kids with color pencils and screen mesh and in the tropics, instead of isobars we drew what are called streamers or streamlines. Atmospheric pressure is very minute and a millibar could be big distances. It doesn't take much to get a really good thunderstorm complex going and while it looks downright impressive on satellite where Erika is currenly located is an area of low shear relative to what exists around her.

Erika's convection is an area of confluence (streamlines that converge or come together) at the surface and difluence (streamlines that diverge or move away from each other). At the surface you want confluence and aloft you want difluence...a steam engine! It works small scale too!

Everybody, all have a wonderful day and take care!

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"


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OrlandoDan
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: berrywr]
      #86834 - Thu Sep 03 2009 11:11 AM Attachment (642 downloads)

I think I see one of the low level centers exposed again in the latest RGB IR image.

It is at about 17.25N 64W.

--------------------
Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008), Mathew (2016), Irma (2017), Dorian (2019)

Personal Weather Station: https://www.wunderground.com/dashboard/pws/KFLLONGW67


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hogrunr
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: OrlandoDan]
      #86836 - Thu Sep 03 2009 12:00 PM

Quote:

I think I see one of the low level centers exposed again in the latest RGB IR image.

It is at about 17.25N 64W.




Yes you can, and by turning on the Trop Fcst Points on that map, you can see that LLC is again south and about to be west of the Fcst point.


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MikeCAdministrator
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: OrlandoDan]
      #86837 - Thu Sep 03 2009 12:00 PM

There is quite a bit of convection across the Leewards right now, I'm sure a few places will see flash floods, places like Montserrat are a bit vulnerable to that. But overall Erika seems to be on the weakening trend. It would be foolish to take attention off of it now, however, at least until the main convection dies down. Especially since some modes still insist on intensification and the still general slow westward motion.

It's really down to which factors are more important, dry air, shear, vs steering and massive convection, computer models against old fashioned forecasting. Erika is still very interesting, and even though the dissipation scenario is most likely, it is by no means definite.


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OrlandoDan
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: MikeC]
      #86838 - Thu Sep 03 2009 12:11 PM

As of this writing, the IR AVN loop shows a substanital weekening of convection.

--------------------
Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008), Mathew (2016), Irma (2017), Dorian (2019)

Personal Weather Station: https://www.wunderground.com/dashboard/pws/KFLLONGW67


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Clark
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: MikeC]
      #86840 - Thu Sep 03 2009 01:01 PM

Erika continues to be sheared from the west, with an exposed LLC moving generally just north of due west out ahead of the mass of convection to the east. The shearing is occurring between a trough axis extending from about 27N, 62W to 21N, 73W and an upper level ridge just to the east of Erika (i.e. not far from the deepest convection). Thus, we get a mess of a situation: Erika's LLC is located along the axis of strongest upper level winds, while the convection is situated to the east in the region of strongest upper level divergence (winds spreading apart at upper levels favors rising motion and thus often convection).

Satellite imagery hints at a mid-level vortex located within the convective mass, as it did yesterday, but there haven't really been any signs of the surface center reforming underneath it. As such, the vortex keeps chugging westward, steered by the low level trade winds. If the surface center were to re-form under the deep convection, Erika might have a fighting shot, but it's got Hispaniola and/or Puerto Rico to deal with shortly down the line. Plus, the shear doesn't look to abate all that much over the next few days.

While it's not impossible for Erika to regain strength, there's a lot stacking up against it doing so. Florida should keep an eye on it, of course, but this looks more like another Ana or Danny than anything else right now.

--------------------
Current Tropical Model Output Plots
(or view them on the main page for any active Atlantic storms!)


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doug
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: Clark]
      #86844 - Thu Sep 03 2009 02:09 PM

Goodness! Just looked at the visible images and then read the intermediate advisory. Wow, I could have sworn I heard a loud RIPPING noise as the convection hit the wall of shear while the LLC continued on its merry way. This is the worst looking system all year. I see what Clark is saying about a midlevel rotation, but even that convection is being ripped apart too.

--------------------
doug


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hogrunr
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: doug]
      #86845 - Thu Sep 03 2009 02:42 PM

STORM ERIKA WAS LOCATED BY AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT NEAR LATITUDE 16.6 NORTH...LONGITUDE 64.7 WEST OR ABOUT
80 MILES...130 KM...SOUTH OF ST. CROIX AND ABOUT 155 MILES...
245 KM...SOUTHEAST OF SAN JUAN PUERTO RICO.


I think the most important thing to watch with Erika is it's continued fight against everything that would normally make sense for a tropical system. The NHC continues to be wrong on their track, (not blaming them, just saying this is a hard system to track) and the system still is holding on. 40mph winds still and the pressure dropped 2 mb since the last advisory, and the system is still staying SW of the projected tracks. The intensity models range from TS to Cat 3 at 120 hours, and the track models range from Cat 5 off the carolina coast to a TS/low level Cat 1 doing a U turn in the gulf back into florida.

IN SUMMARY: Just watch because nothing else is going to tell us what this system is going to do! lol


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MikeCAdministrator
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: hogrunr]
      #86846 - Thu Sep 03 2009 02:51 PM

The low level center is racing away now similar to Chris (2006) and Debby (2000), which could indicate the end, but the convection to the east can't be written off yet.

Probably a TD at 5PM, although I'm sure there are some that would argue it was less than that now. If it weren't for the convection I'd be inclined to agree. It is waning currently, though.


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scottsvb
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: MikeC]
      #86847 - Thu Sep 03 2009 03:50 PM

I would assume that the LLC will continue to move west and miss Hispaniola to the south due to her going with the LLF.. I dont think she is a TD... just remnent low right now.... The midlevel convection is hitting the shear and diminishing.... I dont see much left of this system. There is a slight chance the LLC can get into a better enviroment in the NW carribean by Sunday into Monday... and I would like to say a new LLC form under the midlevel dying disturbance... but for that to happen..1 shear would have to decrease under 10mph and the original LLC would have to be @ least 8dg west and out of the way!

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hogrunr
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: scottsvb]
      #86849 - Thu Sep 03 2009 03:56 PM

The other thing to watch is, is the LLC that is currently to the west of the convection the only LLC in the system? We've seen how often this system has been spinning off the LLC's and then regenerating multiple more.

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scottsvb
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: hogrunr]
      #86851 - Thu Sep 03 2009 03:59 PM

Erika has had multiple vortecies..but 1 overall elongated LLC....

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hogrunr
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: scottsvb]
      #86852 - Thu Sep 03 2009 04:01 PM

Quote:

Erika has had multiple vortecies..but 1 overall elongated LLC....




Correct, and just taking another look at the latest visible below, it seems there is another vortice still under the convection, well partially under. I just can't tell if it is LL or ML or UL though. (17N, 62.5 W)


http://www.ssd.noaa.gov/goes/flt/t2/loop-vis.html

Edited by hogrunr (Thu Sep 03 2009 04:31 PM)


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berrywr
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03/20Z - Tropical Depression Erika? [Re: hogrunr]
      #86853 - Thu Sep 03 2009 04:27 PM

03/1927Z Vortex Message - Recon did not find winds exceeding 21 knots and I expect NHC will downgrade Erika to a depression with this advisory unless winds measured from satellite found some storm force winds in convection to the southeast. Quikscat found rain contaminated winds to the east of two small vortices along 16.7N and a slightly better defined circulation under the convection near 17.0N 62.5W though difficult to determine if it was all the way closed. Expect course corrections on map with upcoming advisory not reflected in 2 pm intermediate update.

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"


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Ed in Va
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Re: 03/20Z - Tropical Depression Erika? [Re: berrywr]
      #86854 - Thu Sep 03 2009 04:39 PM

How much does historiography play into the models? The history of all early Sep trop storms in the vicinity of Erika is a mixed bag in terms of eventual path http://www.wunderground.com/tropical/tracking/at200906_climo.html#a_topad,
but the track record of those that did becomes canes is impressive. From the graph, Hortense, Ella, Jeanne, Baker, and Enda all became major storms and Gert was a Cat 2. Soooo, if E survives, there is strong potential for intensification.

--------------------
Survived Carol and Edna '54 in Maine. Guess this kind of dates me!


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berrywr
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Re: Weak Erika Slowly Moving Toward Puerto Rico [Re: Clark]
      #86855 - Thu Sep 03 2009 04:41 PM

It appears Erika is spinning down and we'll be paying attention to what happens to its remains in the days ahead and if the upper levels become less hostile as what's left is steered by the low level winds.

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"

Edited by berrywr (Thu Sep 03 2009 04:48 PM)


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berrywr
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Re: 03/20Z - Tropical Depression Erika? [Re: Ed in Va]
      #86856 - Thu Sep 03 2009 04:58 PM

I have no idea. I like to think each storm is its own story; that is when you analyze why one storm is and another storm isn't; it's not as simple as past storms histories, the time of year it is. Yes, there is climatology when we speak in broad strokes, but specific storms; the bottom line here are the upper level winds. As to why the upper level winds are what they are, maybe it does have something to do with the El Nino and Southern Ocillation; if it does, it's beyond my level of expertise. It's been asked whether IF global warming if there would be more hurricanes than normal. I don't think it's a question whether a hurricane is likely to be stronger, but whether global warming and the effects on the upper levels will make it more hostile for hurricanes to develop in the first place. It takes more than hot water to get a storm to spin up. Danny and Erika are proof of what 20 knots of winds at 40,000 feet will do to disrupt a tropical storm.

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"


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