Tropical Storm Helene arrives; 94L a potential threat to the Lesser Antilles

By: Dr. Jeff Masters , 10:41 PM GMT on August 17, 2012

After a long path across the Atlantic that mirrored the track of Hurricane Ernesto, Tropical Depression Seven finally got its act together enough over the Bay of Campeche tropical storm breeding grounds to earn the name Helene. Helene's formation on August 17 ties 2012 with 1933 for the 2nd earliest appearance of the Atlantic's eighth tropical storm. Only 2005 had an earlier formation date of the season's eighth storm. Most of this year's storms have been weak, though, so the total Accumulated Cyclone Energy (ACE) of 21 is not that much higher than the normal year-to-date ACE of 15, based on a 1981 - 2010 ACE climatology. The normal yearly ACE for the Atlantic is 104. Helene doesn't have much room to work with before landfall, but has the potential to be a prodigious rainmaker for Mexico, with NHC predicting 5 - 10 inches for portions of Northeast Mexico. This part of the coast is not in drought, so will be prone to heavy flooding. Fortunately, Ernesto's main rains fell to the south of where Helene's rains are falling. Helene's rains should remain south of Texas, though we can't rule out a few thunderstorms bringing 1 - 2 inches of rain to extreme South Texas on Saturday and Sunday.


Figure 1. Afternoon satellite image of Helene.

94L a potential threat to the Lesser Antilles
A large tropical wave emerged from the coast of Africa Thursday night, and was designated Invest 94L by NHC this Friday morning. The models have been impressed this system, and develop it into a tropical storm by the middle of next week. The latest set of 12Z (8 am EDT) model runs are divided on how far west 94L will make it before curving more to the northwest. The ECMWF model keeps 94L weak for the next 5 - 6 days, and has progressively been bringing the storm closer to the Lesser Antilles Islands with each successive run. The ECMWF predicts 94L will pass very close to the northern Lesser Antilles August 24 - 25 as a weak tropical storm. The 12Z GFS model predicted recurvature of 94L well to the east of the Lesser Antilles and Bermuda, but the latest 18Z run has the storm plowing through the Lesser Antilles on Thursday, August 23, as a strong tropical storm, then becoming a hurricane in the Eastern Caribbean. Given that our two top models for forecasting hurricane tracks are increasingly showing a threat to the Lesser Antilles, residents of the islands should pay close attention to the progress of 94L. The eventual track of 94L will depend on the strength of the storm over the next seven days, which is difficult to forecast, since 94L will have the usual trouble with dry air to the north from the Saharan Air Layer (SAL.) With the models changing their tune drastically from run to run, its tough to say what land areas might be most at risk from the storm in the long term. In their 2 pm EDT Tropical Weather Outlook, NHC gave 94L a 10% chance of developing into a tropical depression by Sunday afternoon.


Figure 2. MODIS satellite image of Invest 94L taken at 8 am EDT August 17, 2012, off the coast of Africa. Image credit: NASA.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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Disregarding the euro run due to lack of model consistency - the previous runs had a major hurricane. the 00z CMC/GGEM have a good handle on the system's track and intensity IMO. There is no reason that 94L shouldn't develop into a powerful tropical cyclone and the Euro model has been showing it for days. Just typical that it would drop it.
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06z GFS looked like it had convective feedback issues, sent it NNW in the middle of the Atlantic again.
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Quoting bigwes6844:
as a cane?


I think so. But I think what's happening with the CMC is they're over estimating the intensity, as usual, and it's moving the storm more north. Could be wrong of course. I'm no expert. :)
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Gordon seems to have an eye forming! should be interesting in a few mins if it is a cane
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thanks i meant Isaac
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Quoting stoormfury:
morning from the windwaad islands, it looks, like 94L/Isidore according to the GFS will slam into the islands thursday next week, the system is so large, that the effects will be felt earlier. to add insult to injury there is 95L/Joyce following the track of 94L. very disturbing scenario and one of tremendous concern.
not isidore. future Isaac
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Quoting AtHomeInTX:


The border looks like.

as a cane?
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morning from the windwaad islands, it looks, like 94L/Isidore according to the GFS will slam into the islands thursday next week, the system is so large, that the effects will be felt earlier. to add insult to injury there is 95L/Joyce following the track of 94L. very disturbing scenario and one of tremendous concern.
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Quoting AtHomeInTX:


Yes. But I've gotta say the GFS is probably right. Still don't like to see this on a model though.



The GFS seems to have it doing a couple of loopty loops before it goes anywhere lol.
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Quoting gustavcane:

That looks a lot like Hurricane Rita's path


Yeah I'd say that's pretty damn close lol.
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Quoting AtHomeInTX:


The border looks like.


That looks a lot like Hurricane Rita's path
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Quoting HimacaneBrees:




That is showing next sunday?


Yes. But I've gotta say the GFS is probably right. Still don't like to see this on a model though.
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1164. docrod
Quoting gustavcane:
here is one possible outcome for 94L if that Ridge to the north quickly slams shut in its face.


Good eve WU night crew.
And thus the Cape Verde season appears to be in full swing.

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Quoting AtHomeInTX:


The border looks like.





That is showing next sunday?
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Quoting bigwes6844:
Do they have helene going towards LA?


The border looks like.

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Do they have helene going towards LA?
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here is one possible outcome for 94L if that Ridge to the north quickly slams shut in its face.
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NOGAPS 144 hrs. farther north and east on this run.



Canadian 144 hrs. clips the northern leeward islands and has a system (not sure if it is still Helene at that point) strengthening and heading towards the Gulf Coast.



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Quoting GTcooliebai:
Doesn't look like nothing more then maybe a tropical storm at best.
even if that, that thang could become a major storm because of no shear and warm SSTs in the GOM. Not good at all. Im rolling with the GFS
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Quoting bigwes6844:
i knew they were tryna do it. smh! i hate the euro i really do! is dat a hurricane in that run?
Doesn't look like nothing more then maybe a tropical storm at best.
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Quoting GTcooliebai:
Yep exactly as you said.

i knew they were tryna do it. smh! i hate the euro i really do! is dat a hurricane in that run?
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Quoting gustavcane:

Hello AtHomeInTX, That looks like a bad run that the ECMWF is taking 94L for us in the gulf states.


Yeah I don't want anything in the gulf. But was relieved not to see a hurricane slamming into the islands.
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Quoting AtHomeInTX:


94l lol
no!!!!! wat happens after that! i told u GT they were being slick
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Quoting AtHomeInTX:
Lol. I don't know what to think but I hope this is right.


Hello AtHomeInTX, That looks like a bad run that the ECMWF is taking 94L for us in the gulf states.
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1148. zillaTX
so much 94L focus, panic,worry.. look helene has not even made landfall! wtf?
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Quoting bigwes6844:
yeah euro being slick. because if it stays weak it will trickle into the carribean and then the GOM
Yep exactly as you said.

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Quoting bigwes6844:
uh wat the heck is dat between cuba and the yucatan


94l lol
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Quoting AtHomeInTX:
Lol. I don't know what to think but I hope this is right.

uh wat the heck is dat between cuba and the yucatan
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I think 94L is going to be a big Cape Verde type hurricane like the size of a gilbert or Katrina look at the size of the moisture field. Future 95L getting ready to come off the African coast will not have any dry sal to worry about.
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not good for the islands and PR. GFS has been good on it lately too
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Lol. I don't know what to think but I hope this is right.

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Quoting gustavcane:
1965 Hurricane Betsy
NOOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!
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1140. JLPR2
94L up 5 knots and down one millibar.

AL, 94, 2012081806, , BEST, 0, 121N, 268W, 25, 1008, DB

Helene, winds steady, pressure up one millibar.

AL, 07, 2012081806, , BEST, 0, 213N, 965W, 35, 1007, TS

Gordon, no change.

AL, 08, 2012081806, , BEST, 0, 340N, 415W, 60, 990, TS

Well now, the blog is quietly empty. xD
I'm off then, goodnight!
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1965 Hurricane Betsy
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1138. JLPR2
Next one is ready to emerge.

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Quoting GTcooliebai:
Euro 144 hrs. not showing much.

Quoting GTcooliebai:
Euro 144 hrs. not showing much.



Yes is showing something the strong ridge in the atlantic!!!
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Quoting GTcooliebai:
Euro 144 hrs. not showing much.

yeah euro being slick. because if it stays weak it will trickle into the carribean and then the GOM
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Here is the 1928 Lake Okeechobee Hurricane.
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Euro 144 hrs. not showing much.

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another one. every one of these storms that goes thru the first Hebert Box hits the state of Florida so if 94L passes thru the US Virgin Islands like the GFS runs is doing then anyone in the Virgin Islands to Florida including Cuba need to get your hurricane emergency supplies in order.
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Here comes the train! Its getting mighty active now!Get ready for a long week ahead.
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T EURO is showing the same of GFS when this two models are showing the same we know the history


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See you tomorrow everybody....stay alert
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8 oclock models let see in about couple of mins what they will do
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This update seems somewhat adjusted North...

Hope it keeps adjusting...

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1126. gugi182
Same stores you will find in the United States you will see them also exactly the same here in Puerto Rico we even have a subway also. Looks like the one's in New York City. Going to read a book on my ipad2 later my PR people.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather