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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Member Since: December 31, 1969 Posts: Comments:
Beginning to round itself out.


Member Since: Posts: Comments:
Quoting MississippiWx:


Far from a guarantee. I think some of us are taking the GFS as gospel truth. A storm that strengthens quicker than anticipated goes north of the islands.
George nor Dean didn`t.
Member Since: December 31, 1969 Posts: Comments:
372 hours..
Member Since: December 31, 1969 Posts: Comments:
Meanwhile back to reality....Miss Helene is firing up around the COC.
Member Since: December 31, 1969 Posts: Comments:
Quoting washingtonian115:
Seems Isaac will not peacefully go out to sea without causing some damage(or lots) in the caribbean...
Maybe he will be retire.
Member Since: December 31, 1969 Posts: Comments:
Quoting washingtonian115:
I hope you know we're not taking this totally serious right?.I'm personally looking at it as speculation/entertainment..


Yea i know but...the magnitude of panic in the blog is quite larger than usual with doom-models.
Member Since: December 31, 1969 Posts: Comments:
Quoting ncstorm:
312 hours


That would be a big ouchie for Bermuda if that were to verify!
Member Since: December 31, 1969 Posts: Comments:
Quoting tennisgirl08:


I would tend to agree with you but the GFS has been extremely accurate this season. These runs are not that far out.

Regardless, the islands are going to be hit, just not sure how hard.


Far from a guarantee. I think some of us are taking the GFS as gospel truth. A storm that strengthens quicker than anticipated goes north of the islands.
Member Since: December 31, 1969 Posts: Comments:
300 hrs. and look out for some sort of fujiwhara action since these 2 systems are close together. Could end up something like Dog and Easy.

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Quoting JLPR2:


Depending on what I see tomorrow on the models I'll inform my family and take action.


I did text messages already.... Remember that this local election thing will affect comerce on sunday... I don't think politics are going to announce this or if they are going to use it for their advantage... from them anything can be expected...

But batteries, canned food, Gasoline, water and other supplies should be acquired tomorrow... anyhow something we use everyday....
Member Since: December 31, 1969 Posts: Comments:
Quoting washingtonian115:
Seems Isaac will not peacefully go out to sea without causing some damage(or lots) in the caribbean...


And let's not rule out the US either.
Member Since: December 31, 1969 Posts: Comments:
Quoting ncstorm:
264 hours


Looks a little further east on this run. May save the US from a direct hit. Puerto Rico and that area of the Caribbean, go ahead and get your hurricane plans ready. Looks like a decent bet you all are about to have a bad time...
Member Since: December 31, 1969 Posts: Comments:
Member Since: December 31, 1969 Posts: Comments:
911. JLPR2
Quoting Gearsts:
Please no Isaac! NO! turn back!


He still hasn't formed.
And still it's only the second run that shows us in its path.

I'm cool. :P
Member Since: December 31, 1969 Posts: Comments:
Quoting PalmBeachWeatherBoy:
Omg! PR is gone, OMG! the leewards are gone! lol im sorry but the blog is crying wolf right now. The GFS turns every storm into a monster, I'm not saying that the conditions aren't ripe for a cat 5, but the likelihood of the gfs predicting the exact future is slim.
I hope you know we're not taking this totally serious right?.I'm personally looking at it as speculation/entertainment..
Member Since: December 31, 1969 Posts: Comments:
blockquote class='blogquote'>Quoting Stormchaser2007:
Just north of PR by 204

With the large mid/upr lvl cyclone over the NE Atlantic and the ridge to its west, there is a lot of wavebreaking occurring in the central Atl. This, I believe, makes it more likely that a weakness at the upper levels will prevail in the central Atl and perhaps a more WNW/NW course by the time this system reaches 45-60W.
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Quoting ncstorm:
240 hours
Is Joyce a hurricane?
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Quoting MississippiWx:
A lot of freaking out for a storm that has yet to develop...


I would tend to agree with you but the GFS has been extremely accurate this season. These runs are not that far out.

Regardless, the islands are going to be hit, just not sure how hard.
Member Since: December 31, 1969 Posts: Comments:
Quoting mcluvincane:


Go to bed


Lol. This isn't a surprise coming from you. Saw you put someone on ignore earlier today for saying they thought it would recurve out to sea.
Member Since: December 31, 1969 Posts: Comments:
Quoting washingtonian115:
Seems Isaac will not peacefully go out to sea without causing some damage(or lots) in the caribbean...


Seems he won't go peacefully out to sea at all...
Member Since: Posts: Comments:
312 hours
Member Since: December 31, 1969 Posts: Comments:
Quoting PalmBeachWeatherBoy:
Omg! PR is gone, OMG! the leewards are gone! lol im sorry but the blog is crying wolf right now. The GFS turns every storm into a monster, I'm not saying that the conditions aren't ripe for a cat 5, but the likelihood of the gfs predicting the exact future is slim.


first off, the gfs does not turn every storm into a monster and secondly we are just looking at the forecast runs...does every have to try and crap on the entertainment that is looking at the model runs?
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Quoting 954FtLCane:


204 @992. looks like direct hit on PR is over
and out and on to Bermuda. Man, the gfs run does not like the little islands.
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901. 954FtLCane
4:41 AM GMT on August 18, 2012
Quoting PalmBeachWeatherBoy:
Omg! PR is gone, OMG! the leewards are gone! lol im sorry but the blog is crying wolf right now. The GFS turns every storm into a monster, I'm not saying that the conditions aren't ripe for a cat 5, but the likelihood of the gfs predicting the exact future is slim.


985 is not a monster. Still stinks for whoever is under those conditions. The models are here for entertainment/enlightenment.. thats all..
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900. JLPR2
4:41 AM GMT on August 18, 2012
Quoting Relix:
Don't worry guys, we have no center to latch onto yet, and this is talking in 160+ hours, that's basically a week. Relax, let's see how this unfolds. By Wednesday we'll have a clearer idea.


Yep, but buying some canned food and some new batteries wouldn't be a bad idea. :P
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899. CaribBoy
4:41 AM GMT on August 18, 2012
I'm very anxious and excited lol my heart is beating a bit faster :) Yeah speculation is fun!!!
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898. Gearsts
4:41 AM GMT on August 18, 2012
Please no Isaac! NO! turn back!
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897. 954FtLCane
4:40 AM GMT on August 18, 2012


252 @985
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896. PalmBeachWeatherBoy
4:40 AM GMT on August 18, 2012
Omg! PR is gone, OMG! the leewards are gone! lol im sorry but the blog is crying wolf right now. The GFS turns every storm into a monster, I'm not saying that the conditions aren't ripe for a cat 5, but the likelihood of the gfs predicting the exact future is slim.
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895. ncstorm
4:39 AM GMT on August 18, 2012
264 hours
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894. washingtonian115
4:39 AM GMT on August 18, 2012
Seems Isaac will not peacefully go out to sea without causing some damage(or lots) in the caribbean...
Member Since: December 31, 1969 Posts: Comments:
892. Relix
4:39 AM GMT on August 18, 2012
Don't worry guys, we have no center to latch onto yet, and this is talking in 160+ hours, that's basically a week. Relax, let's see how this unfolds. By Wednesday we'll have a clearer idea.
Member Since: December 31, 1969 Posts: Comments:
891. sunlinepr
4:39 AM GMT on August 18, 2012
Quoting MississippiWx:
A lot of freaking out for a storm that has yet to develop...


True, we should be calm, but observing forecasts....
Anyhow, this is the first time this season that you get consensus on most models on a developing system...

But the real path, is unknown yet...
Member Since: December 31, 1969 Posts: Comments:
890. WxGeekVA
4:38 AM GMT on August 18, 2012
Quoting Relix:
Well Isaac... let's do this. *cracks knuckles*


LEEEEEEROOOOYYYYY JEEENNKINNNSSSSSSSSS!!!!!!!
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889. scott39
4:38 AM GMT on August 18, 2012
All I see is DOOM and fear tactics being used on here for the presidential race of 2012. Lol
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888. 954FtLCane
4:38 AM GMT on August 18, 2012


204 @992. looks like direct hit on PR is over
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887. ncstorm
4:38 AM GMT on August 18, 2012
240 hours
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886. CaribBoy
4:38 AM GMT on August 18, 2012
Quoting sunlinepr:


Posible Double hit....



Well that's 2012 after all lol
Member Since: December 31, 1969 Posts: Comments:
885. Clearwater1
4:37 AM GMT on August 18, 2012
gfs seems to turn it sooner than last run, but not good for the islands, at all. hr 176 to hr 186 really bad news. if it pans out.
Member Since: December 31, 1969 Posts: Comments:
884. stormchaser19
4:37 AM GMT on August 18, 2012
180 hours and this is not good for PR
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883. Gearsts
4:37 AM GMT on August 18, 2012
Quoting sunlinepr:


It will take a while with this local voting, to see DACO take action on freezing prices.... We have the advantage over the Avg. person to act now.... This is serious and looks like we talking about much destruction and posible loss of life....
Omg im scared with this system and GFS showing consistancy per run and PR and DR been a target also the time of the month favors a hit for the islands.
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882. GTcooliebai
4:37 AM GMT on August 18, 2012
204 hrs. trough over Great Lakes:

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881. sunlinepr
4:36 AM GMT on August 18, 2012
Member Since: December 31, 1969 Posts: Comments:
880. JLPR2
4:36 AM GMT on August 18, 2012
Quoting MississippiWx:
A lot of freaking out for a storm that has yet to develop...


Hey! Let us have our moment.LOL! XD
Member Since: December 31, 1969 Posts: Comments:
879. washingtonian115
4:36 AM GMT on August 18, 2012
Quoting MississippiWx:
A lot of freaking out for a storm that has yet to develop...
Speculation is always fun.
Member Since: December 31, 1969 Posts: Comments:
878. STXHurricanes2012
4:36 AM GMT on August 18, 2012
Quoting MississippiWx:
A lot of freaking out for a storm that has yet to develop...

I know lol...take it easy people.Let it first become a TD then you can do whatever u want lol!
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877. 954FtLCane
4:36 AM GMT on August 18, 2012


180, @986..PR..........
Member Since: December 31, 1969 Posts: Comments:
876. KEEPEROFTHEGATE (Mod)
4:36 AM GMT on August 18, 2012
Member Since: December 31, 1969 Posts: Comments:

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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