Erika dumping heavy rain on the Lesser Antilles

By: Dr. Jeff Masters , 2:12 PM GMT on September 03, 2009

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Tropical Storm Erika is hanging together despite strong wind shear, and is bringing high winds and much-needed heavy rain to the Lesser Antilles Islands. Winds on the south shore of Dominica Island were sustained at 37 mph this morning, and 8.03" of rain have been measured at the airport over the past two days. Winds and rain at nearby islands have been less, according to our wundermap for the region. The Hurricane Hunters are in the storm now, and have generally encountered top winds of 40 - 45 mph at the surface. They did find one spot of 50 - 65 mph winds, but that was likely due to outflow from a strong thunderstorm, and is not representative of Erika's wind field.


Figure 1. Radar image of Tropical Storm Erika at 9:15am EDT 9/3/09. Image credit: Meteo France.

Erika has improved in organization a bit since last night, but remains weak and disorganized, thanks to about 20 knots of shear at the 200 mb level, as seen on last night's Guadeloupe upper air sounding. Radar animations out of Martinique show plenty of heavy rain moving through the Lesser Antilles, but little organization of the echoes. Satellite imagery shows no low-level spiral bands and little upper-level outflow. Long range radar out of Puerto Rico is beginning to show rain echoes from Erika approaching the island.

The forecast for Erika
The computer models have come into better agreement about the track of Erika, taking the storm west-northwest over Puerto Rico and the Dominican Republic. This track will take Erika into a band of significantly higher wind shear of 25 - 35 knots, Friday through Saturday. Considering that Erika is barely maintaining itself as a tropical storm with 20 knots of shear, the combined effects of the higher shear and the encounter with the high mountains of Hispaniola and Puerto Rico should be enough to cause Erika to dissipate by Sunday. Erika's remains will still be capable of dumping very heavy rains of 3 - 5 inches over the Dominican Republic and 1 - 3 inches over Haiti and the Southeast Bahamas, due to the slow motion of the storm. By Monday, when the remains of Erika should be over the Bahamas, the storm will have penetrated through the band of high wind shear over the Greater Antilles, and shear may fall low enough for redevelopment of the storm. This is a scenario offered by the NOGAPS model, which then takes Erika northward towards North Carolina. The other models predict quite a bit more shear in the region than the NOGAPS, and any redevelopment of Erika early next week remains an iffy proposition. The GFDL and HWRF models continue to insist that Erika will brush off the high shear this weekend, avoid Hispaniola, and intensify into a Category 2 hurricane five days from now. These models have not been giving enough emphasis to how the current shear is affecting Erika, and are being discounted at this time.

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A number of wunderground users with the McAfee virus protection software installed were alerted yesterday that a possible Trojan virus existed on our web pages. After an investigation of the issue, we have determined that this is a false alarm. It appears McAfee updated their virus files yesterday, and included in their list of suspected viruses JavaScript web pages that are compressed using the packer compression system used by wunderground. We've changed the compression technique used on our web pages, and hopefully this will eliminate the bogus McAfee alert messages.

Elsewhere in the Atlantic
A large, strong tropical wave with plenty of spin emerged from the coast of Africa this morning. The wave is not yet generating much in the way of heavy thunderstorms, but has the potential to gradually develop into a tropical depression by early next week. NHC is giving this wave a low (less than 30% chance) of developing into a tropical depression by Saturday. The GFS model has been consistently developing this wave in its runs over the past few days.

I'll have an update this afternoon.

Jeff Masters

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Thoughts on what will happen if Erika relocates back near Guadeloupe/Martinique?

Back in a few.
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winds shifting to the west in Dominica is interesting but there is not enough evidence to conclude the development of a closed low yet.
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Quoting cirrocumulus:
Thanks for those images from time to time Patrap.


Helps with the current as anyone can ramble on as to what they THINK is happening,..featured Blogger,or former, period.
Its a good way to Learn,..and well..Kinda cool to see it in almost real time.

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A storm affects to Havana with rain waited for everybody.
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Evening everyone! Appears Erika is still giving everyone fits.
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TO: StormW

I sincerely believe it would be of help on this blog if you were to explain that because a system appears to be waning, that it could regenerate at any time. That the experts have to rely on the information which they receive, at the moment, and must down-grade a system if all of the conditions are not maintained. They really do not speculate to the same degree as would a layman.
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Anyone got a good source that plots wind barbs for every NDBC asset and every airport in the eastern Caribbean?
Cannot seem to find that among Wyoming, COD, rap.ucar, any of our other surface ob sources.
And no, coolwx.com not updating.
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nice little swirl over Kentucky. Could that be Fred? ;)
Member Since: August 3, 2008 Posts: 16 Comments: 5793
Thanks for those images from time to time Patrap.
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StormW,

Can you please help straighten my mind out since Erika has baffled and confused me to the point where I have no clue how to deal with forecasting the system? I'm lost here man.
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Quoting futuremet:


Some spin is quite evident on the Martinique radar


Do you mean more heavy rain may occur?
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918. JLPR
we got west winds in Dominica
Melville Hall, DO (Airport)
Updated: 30 min 52 sec ago
Overcast
81 °F / 27 °C
Overcast
Humidity: 70%
Dew Point: 70 °F / 21 °C
Wind: 7 mph / 11 km/h / 3.1 m/s from the West
Pressure: 29.86 in / 1011 hPa (Falling)

but as you can see they are only 7mph so if there is a LLC under the convection it is a very weak one
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see rainfall in the radar but I don't see it in the conditions on Guadeloupe, Martinique, Antigua...

Granted there is still a heavy band out to sea at the east of Antigua, most likely the one with the winds...

But this is shaping to be another Ana - a non-event

Still, Puerto Rican mayor announcements on TV had them with their yellow rainproof hoodies on, when currently the conditions are ideal for a Margarita and good company under the sun @ the beach.

Good post.
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Quoting Drakoen:
Erika appears to be degenerating. The system failed to make a new center in the convection that was noted last night. There is no evidence that a new center is forming in the convection based on surface observations. The next thing to watch will be a low pressure center off the coast of Africa with a large circulation.


Maybe not in the surface observations, but this appears to be a quite vigorous mid-level circulation.

Look at the thunderstorms moving EAST in the south side of the storm...

RGB Loop
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914. WXHam
Quoting Drakoen:
Erika appears to be degenerating. The system failed to make a new center in the convection that was noted last night. There is no evidence that a new center is forming in the convection based on surface observations. The next thing to watch will be a low pressure center off the coast of Africa with a large circulation.


You figure?
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Quoting StormW:


LOL! maybe more fun..but not professional.

Remember who my main private client is.


I am sure you have read my blogs. I know you have most likely figured out mine. Respond only off blog if you do, please. I shall post a question next in next blog.
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Erika please for heaven's sake dissipate already!!
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LUCARIO.......

??????
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Quoting Drakoen:
The system failed


yup
Member Since: August 22, 2006 Posts: 2 Comments: 1975
>maybe more fun..but not professional.

Actually, it's the other way around. That's why we have NOAA and NASA.

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Quoting atmoaggie:

The ADD TS Erika.

A COC here, a COC there, here a COC, there a COC, everywhere a COC.
e - i - e - i - o


lmao...shes actually making me want to get away for awhile to go baby clothes and furniture shopping with the wife and sister...how scary is that...im getting a headache from all the swirls...lol

*edit* waits for the head-on response...
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905. WXHam
img src="Erika Mission 5" alt="" />

Current Recon Mission 5
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Quoting KarenRei:
Neat -- the satellite view right now shows a great example of multiple layers of shear. Watch the center just SE of PR right now that the HHs just got a fix on. The cloud layer over it dramatically peels back to the southeast, exposing it.. but meanwhile, the convection continues to vent to the northwest.


We have another runaway COC, everybody.
Member Since: August 22, 2006 Posts: 2 Comments: 1975
Some of the issues i see going on is models such as the GFDL/HWRF have had some serious issues handleing the mid level shear currently still impacting the disturbance.
Member Since: May 14, 2006 Posts: 8 Comments: 13597
Erika appears to be degenerating. The system failed to make a new center in the convection that was noted last night. There is no evidence that a new center is forming in the convection based on surface observations. The next thing to watch will be a low pressure center off the coast of Africa with a large circulation.
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Great video for you from NASA.
Link
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Quoting atmoaggie:

The ADD TS Erika.

A COC here, a COC there, here a COC, there a COC, everywhere a COC.
e - i - e - i - o

Ok, thats better than my joke about Erika throwing out shoes.
Member Since: August 3, 2008 Posts: 16 Comments: 5793
Neat -- the satellite view right now shows a great example of multiple layers of shear. Watch the center just SE of PR right now that the HHs just got a fix on. The cloud layer over it dramatically peels back to the southeast, exposing it.. but meanwhile, the convection continues to vent to the northwest.
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Quoting Hurricane009:
?????????????????????????????????????????????????????????????????????????
he forgot to take his medication
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18 Z Dynamic Models (More sophisticated models)

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Quoting KeyWestwx:

great webcam- i need to find one for st. johns. I have friends vacationing there

St. John's
http://www.serendipity.vi/
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Quoting atmoaggie:

Well, the TCHP input data was garbled, so they got THC.


LMAO. So we ought to keep the HWRF away from the fridge then???
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Quoting Prgal:
This is probably a stupid question but, isnt it "normal" for Erika to "die" during the day and "grows" like a beast during the night?

Very Very True!! She loves to "wobble" during the day, party at night!!!
Member Since: February 14, 2004 Posts: 2 Comments: 661
RECON needs to head near Martinique. This would make yet another new ballgame if the center reforms again.
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Quoting cirrocumulus:
>much-needed heavy rain to the Lesser Antilles Islands.

This was a factor in the move toward the islands. Obviously, there were some low level conditions that were influencing the changes in upper level patterns that the models did not pick up. Previous rainfall is a weakness in the models.


I see rainfall in the radar but I don't see it in the conditions on Guadeloupe, Martinique, Antigua...

Granted there is still a heavy band out to sea at the east of Antigua, most likely the one with the winds...

But this is shaping to be another Ana - a non-event

Still, Puerto Rican mayor announcements on TV had them with their yellow rainproof hoodies on, when currently the conditions are ideal for a Margarita and good company under the sun @ the beach.
Member Since: August 22, 2006 Posts: 2 Comments: 1975
887. WXHam
Quoting jeffs713:
I keep on having this visualization with Erika... she is like a woman that can't decide on which shoes to wear for a night out. Each COC that Erika "spits out" is like a pair of shoes she decides not to wear.

I will leave it up to the rest of you to run with that one.


Doh!
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With the LLC just to the SE of Puerto Rico and appearently looking weaker by the hour, it looks like Erika is doomed soon unless the mid-level circulation near Guadeloupe becomes the dominant LLC.
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Definate new center around 62W
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884. WXHam
Quoting fire635:
I cant figure out how to post a picture.. but I have to say Ive never seen a NHC forecast track like the one currently... It shows a forecasted NE track with a swing to the NW. (I know its just because of the coc changing before the next track update... kinda funny to see it though)


You need to find a server on which you post your image then link to the url. I use Photobucket.com. Alternatively, you can link directly to the web page that has the picture and link to that url by simply clicking on "Link" at the top of the comment box. Hope this helps!
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883. Prgal
This is probably a stupid question but, isnt it "normal" for Erika to "die" during the day and "grows" like a beast during the night?
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18 Z Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)

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Erika without a doubt still has a closed LLC
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Quoting watchingnva:
Image Hosted by ImageShack.us


still seeing this...but its my own opinion and based off of current observations only...she could be gone in 6 hours if she doesnt keep a moderate level of convection around the circulation...

who knows...she needs to make her mind up though...lol

The ADD TS Erika.

A COC here, a COC there, here a COC, there a COC, everywhere a COC.
e - i - e - i - o
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.