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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Quoting pearlandaggie:
422. i've always used Firefox and i've never seen "blog stretched"...i guess that's an Internet Exploder thing!


FF automatically sizes images to fit
Member Since: October 1, 2007 Posts: 81 Comments: 26511
422. i've always used Firefox and i've never seen "blog stretched"...i guess that's an Internet Exploder thing!
Member Since: September 14, 2007 Posts: 3 Comments: 3963
OMG, I think I blinded myself
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting jeffs713:

Windows XP Pro / IE6 here @ work.

Vista Ultimate and FF3.5 at home. To say the least, the blog gets super-stretched here at work, and no problems at home.


Ditto actually. lol
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Member Since: October 1, 2007 Posts: 81 Comments: 26511
Looking at visible, looks like it spit out a weaker llc than yesterday just se of the 2 islands se of puerto rico. I think she is done the shower base behind seems to be shrinking. Last chance for a low to form there.
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421. or, it's just someone referencing something beyond their means! LOL
Member Since: September 14, 2007 Posts: 3 Comments: 3963
Quoting Orcasystems:


I agree.. but we have people on here from work.. and you would think they are still using Windows 3.1 and IE 5

Windows XP Pro / IE6 here @ work.

Vista Ultimate and FF3.5 at home. To say the least, the blog gets super-stretched here at work, and no problems at home.
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Quoting pearlandaggie:
414. doh! LOL


The state of education these days is appalling...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Quoting watchingnva:
looking at some of the loops and observations, this is what my amateur eyes are seeing...i think shes trying to have the coc in the islands work down to the surface...but if she doesn't continue to fire convection over and around it...she just might be gone by tomorrow...

img src="Image Hosted by ImageShack.us
" alt="" />

I like the way you have done this, let's all see what you see. Good job, is it right, I am not knowledgeable enough to comment.
Member Since: July 20, 2007 Posts: 0 Comments: 107
Quoting pearlandaggie:


you're assuming I'm not at 'work'? LOL


Its also why I made the reflector site.. a lot of members cannot access the blog from work.. but since the reflector is a legit webpage, not a blog, they can view it :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
414. doh! LOL
Member Since: September 14, 2007 Posts: 3 Comments: 3963
Quoting LUCARIO:
Erika is looking strong
i bet its a hurricane now


lmao
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i find it funny that recon found a 1009.4mb and 30mph surface wind as they just passed to the north of the little vortex thats racing off to the west...

Link
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Quoting Chavalito:
Requiem in pacem Erika


Christ, if you're going to use Latin, use it right:

Requiascat in pace (rest in peace)
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Quoting Vortex95:


My dad had 3.1 on his office computer until a full year after windows 95 came out.


I still have the disks at home in my office... 3.5 and 5.25
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting masonsnana:

Pls post what you can about Recon..I see the so called coc, good job all, want to see if plane picks this up...


You won't have to wait long if Recon finds another LLC it will be posted multiple times with pressure, winds, SFMR etc......
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Quoting Orcasystems:


I agree.. but we have people on here from work.. and you would think they are still using Windows 3.1 and IE 5


you're assuming I'm not at 'work'? LOL
Member Since: September 14, 2007 Posts: 3 Comments: 3963
Quoting Cotillion:
Models are a tool.

If you're a carpenter, or a mechanic, you wouldn't completely disregard a tool because it isn't needed for one job.

Sometimes they are right, sometimes they are wrong.

But no manner of mathematical improvements and refinement can take away from what they are; a forecaster's tool.
I believe in them being a tool also,i am thankful for them when they work most of the time. Im just wondering if we should be following them right now?
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400.
"Essentially, all models are wrong, but some are useful."

George Box
Member Since: September 14, 2007 Posts: 3 Comments: 3963
Quoting jeffs713:

There are others younger than you on here. I'm 29, and one of the bloggers that contributes very regularly here on WU is a few years younger than I am.


And some of us just graduated college...and there's HS students as well. :-)
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405. Relix
If there is a new COC being formed then the system should go sightly south of PR and go through the mona passage.
Member Since: August 3, 2006 Posts: 0 Comments: 2659
Quoting Grothar:


Thanks Orca. Got to try it. Remember when I asked where you got all those great graphics? Now I know. You are giving away your secrets. Thanks for sharing.


I can cheat also.. I have a webpage I post them onto.. makes it easier.. no size limitations.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting pearlandaggie:
388. if you're running Firefox, you can just right-click on the image and select "View Image". this will open the original image in the browser window.


I agree.. but we have people on here from work.. and you would think they are still using Windows 3.1 and IE 5
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting nrtiwlnvragn:
Recon on its way, not far to go.

Pls post what you can about Recon..I see the so called coc, good job all, want to see if plane picks this up...
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Quoting Orcasystems:
For people who post good high definition pictures..

After you have used the image button to insert the picture... high lite the HTMl coding... and then click link..

In the link box, insert the original HTML coding you used in the image box... this will allow people to see the original picture to its full quality.

I do that with all of my graphics..as people have asked (with old systems) that the graphics be sized to fit the page (usually 500 X 300 for my graphics)




Thanks Orca. Got to try it. Remember when I asked where you got all those great graphics? Now I know. You are giving away your secrets. Thanks for sharing.
Member Since: Posts: Comments:
Models are a tool.

If you're a carpenter, or a mechanic, you wouldn't completely disregard a tool because it isn't needed for one job.

Sometimes they are right, sometimes they are wrong.

But no manner of mathematical improvements and refinement can take away from what they are; a forecaster's tool. Nothing more.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Requiem in pacem Erika
Member Since: Posts: Comments:
Quoting IKE:


I don't believe them.

Why does the NHC use them or talk about them in every discussion?

Why do mets look at steering models? Shear models?
Quoting Grothar:


So you see it, too! They must know what they are talking about. After all, they have done a wonderful job in their forecasting on this one, did they not? (Sarcasm) I firmly believe another center is trying to form south of the blob.
I do too. I dont understand why the models are so bias to the N, when this storm proves them wrong over and over and over again!!
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Quoting IKE:


I don't believe them.

Why does the NHC use them or talk about them in every discussion?

Why do mets look at steering models? Shear models?


Because they're the best information available, based on the data at the time of the run (maybe 3 hours prior to posting). The models take a while to calculate and the conditions will change in as little as an hour, especially in a storm that's lived in as complicated an environment as this one
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Recon on its way, not far to go.
Member Since: Posts: Comments:
388. if you're running Firefox, you can just right-click on the image and select "View Image". this will open the original image in the browser window.
Member Since: September 14, 2007 Posts: 3 Comments: 3963
Quoting watchingnva:
looking at some of the loops and observations, this is what my amateur eyes are seeing...i think shes trying to have the coc in the islands work down to the surface...but if she doesn't continue to fire convection over and around it...she just might be gone by tomorrow...


nice -- I was watching the old llc moving NW last night and saw the spinning off to the ENE -- but wasn't sure what it was. It makes sense that Erika shed another mid-level vort. I am glad my eyes are not failing me completely.
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Quoting IKE:
12Z NOGAPS...


12Z CMC...
oh god no thats a fay scenario no. thats not good.
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Quoting stormpetrol:

Good observations, with Erika one never knows.


thanks, who knows with this system...im 6 hours all the convection could be gone and all were left with is a low level swirl and some showers and tstorms...

or...

this new coc could get some decent convection to remain over it and the spiral banding could continue to improve, and we just could have something worth keeping an eye on...

who knows...just right at this very sec, thats what im seeing with my untrained eyes...lol
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Quoting TheDawnAwakening:
Thanks Grothar, the thing was I didn't paste the whole link into the dialogue box.


Oh!
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The avatar matched the posting she will grow up someday.
Member Since: Posts: Comments:
For people who post good high definition pictures..

After you have used the image button to insert the picture... high lite the HTMl coding... and then click link..

In the link box, insert the original HTML coding you used in the image box... this will allow people to see the original picture to its full quality.

I do that with all of my graphics..as people have asked (with old systems) that the graphics be sized to fit the page (usually 500 X 300 for my graphics)


Member Since: October 1, 2007 Posts: 81 Comments: 26511
A weak depression has the chance to produce loss of life, if your living alone a coastline vulnerable to tropical cyclones its your responsibility to know what are you and your families vulnerabilitys are to a hurricane. History teaches that a lack of hurricane awareness and preparation are common threads among all major hurricane disasters. By knowing your vulnerability and what actions you should take, you can reduce the effects of a hurricane disaster.

adrian
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Quoting stormsurge39:
LOL I agree with you with on S jog again. Models refuse to believe it. I dont understand.


So you see it, too! They must know what they are talking about. After all, they have done a wonderful job in their forecasting on this one, did they not? (Sarcasm) I firmly believe another center is trying to form south of the blob.
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It was pretty bad on Dominica last night.

Go AWAY, Erika.
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384. IKE
Quoting stormsurge39:
Why do you believe in these models?


I don't believe them.

Why does the NHC use them or talk about them in every discussion?

Why do mets look at steering models? Shear models?
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Thanks Grothar, the thing was I didn't paste the whole link into the dialogue box.
Member Since: October 21, 2008 Posts: 243 Comments: 3717
Quoting ParanoidAndroid:
Ok enough lurking. Time to post something. Long time weather buff, but I am kind of a "child" here according to many of you (30th birthday coming up next week).

I just discovered this blog recently. The discussions here are addictive! I have no clue what Erika's gonna do, though I can't argue with any of StormW's logic. The NHC seems to keep forecasting a NW bias, and Erika's not listening.

The one and only thing I am wishcasting is that the weather associated with Erika moves away from Haiti. If she crawls across Hispaniola at the speed she's moving now. TC or not, it would be devastating for Haiti :(


There are others younger than you on here. I'm 29, and one of the bloggers that contributes very regularly here on WU is a few years younger than I am.
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Erika continues to show signs that a new surface low is working its way to the surface around 62W and 16N. Convection wanes from the earlier flare up only to have newer convection try and flare up directly around the newer coc. It will interesting to see what the HH find at their 2pm investigation into Erika. I believe they will find this newly formed surface circulation however still poorly defined given the formation has occured so abruptly. As seen in the last visibile image, the old coc is weakeing under shear from the newly forming low. It is also caught into the broad flow of the newly formed coc. NHC 2pm EDT update will probably continue to say what they have been saying about Erika since she weakened from 60mph. They will say she is disorganized and could be downgraded later today with a hurricane hunter aircraft now investigating the storm we will wait until they completed the examination. To some degree I think thats what the 2pm EDT public advisory will say. The 5pm will tell us whether or not she has degenerated into a depression or remnant low. If the current reorganization continues then she will stay as a tropical storm tonight or possibly strengthen, but with signs of increasing wind shear to her west I expect this burst to last only about 12 hours at the latest. The the next 48 hours will determine if she will remain a possible threat to the US as she battles the brunt of land interaction with PR and wind shear of 30-40knots from the west and southwest. We will at this time monitor her progress while the future Fred wave begins to develop. That is what I say will happen in the next 66 hours.
Member Since: October 21, 2008 Posts: 243 Comments: 3717
Quoting IKE:
12Z NOGAPS...


12Z CMC...
Why do you believe in these models?
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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.