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.

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A recurve is certainly the likely scenario for 94L. The question is how close it gets before it starts to recurve. A lot of people associate recurve with storms going out to sea, which isn't always the case. Just look at Irene last year. It recurved, but caught a huge chunk of the US in the process. Once they get beyond 70W it's very tough for them to recurve without grabbing a piece of the East Coast.
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I see we have Helene now. Anything else I miss?
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That's an awfully abrupt/northerly track depicted.
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Quoting stormchaser19:

Here we go again everybody questioning GFS?


It just completely flip flopped... so it has to be wrong about one of them.
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Since a run like this is playing out right now let me say..If a bad storm came up the east coast like Irene did no one in De NJ or NY would evacuate at all..They blew up Irene so much and had everyone in south jersey leave(i stayed was in "eye") and nothing happened around here worse then that derencho that happened about 2 months back..so it would end up really bad if a big storm came rolling threw the NE or MidAtlantic
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Quoting Levi32:


Probably. I think you'll see the models in general eventually shift to between 80W and 65W for the recurve though.


I agree, in some point, this should recurve... The question is where and when. A recurve near Bermuda, or possibly a late recurve threatening the East Coast. Just observations for now.
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Quoting Levi32:


Probably. I think you'll see the models in general eventually shift to between 80W and 65W for the recurve though.
Are you gona do a video soon?
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Quoting CybrTeddy:
The only part I'm interested in with the GFS is up to 144 hours, which is generally a more reasonable time to look into this system, and even then I am unsure of it taking that track. I'm somewhat convinced that on the 00z you'll see the GFS shift right back.

Here we go again everybody questioning GFS?
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I've been mentioning for some time now that the pattern does not really favor an easy recurve. We have a stronger ridge then the last few years, weaker troughs.. I figured the GFS was overdoing that trough the last few runs. I don't think the storm moves in the Caribbean though, should be influenced by the trough, maybe spare the islands, and either recurve near Bermuda or possibly threaten the USA. Too early to tell of coarse, but it's always fun predicting stuff like this. Given the forecast heights showing stronger ridging, I can see this next storm possibly making a long trek from Africa to the East Coast. Right now, the Lesser Antilles should be watching 94L the most.

I personally agree with the EURO right now.. It nailed Gordons track first when the GFS had it constantly hitting the USA. EURO shows a weak storm/wave moving north into a ridge and recurving out to sea. I was wrong, the EURO was right.
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Quoting CybrTeddy:
The only part I'm interested in with the GFS is up to 144 hours, which is generally a more reasonable time to look into this system, and even then I am unsure of it taking that track. I'm somewhat convinced that on the 00z you'll see the GFS shift right back.


Probably. I think you'll see the models in general eventually shift to between 80W and 65W for the recurve though.
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the ensembles have been trending west at each run..the operational is just catching up..still plenty of time to watch though
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What happen to Joyce?? and I look that Kirk would potentially be our first storm of September that will be 11 storms.Not bad at all.
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Quoting Felix2007:
Newfoundland's next


Reminds me of Hurricane Bob in 1991. Brushed the Carolina's and made landfall in New England.
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The only part I'm interested in with the GFS is up to 144 hours, which is generally a more reasonable time to look into this system, and even then I am unsure of it taking that track. I'm somewhat convinced that on the 00z you'll see the GFS shift right back.
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El Niño doesn't seem to be making much progress, more like a step forward and another one back, the small anomaly off SA is also expanding and getting colder.

August 2:


August 16:
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we are going too have so marh fun on the blogs the next few weeks
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Quoting CybrTeddy:


At that point in time, 94L would be strong enough to have a very potent anti-cyclone over it to help fend off most of that shear.
Good point. We're doomed.
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Quoting unknowncomic:
Still some shear at 180hrs.


At that point in time, 94L would be strong enough to have a very potent anti-cyclone over it to help fend off most of that shear.
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Quoting STXHurricanes2012:
From Previous Blog:
Quoting RTSplayer:
Yall, calm down.

The models are certainly terrible beyond 7 days on forecasting track, and they even suck within 5 days on intensity.

Needs to be strong enough to classify so they can get a better center fix on it before everyone goes nuts worrying about some northern turn a week from now.

Besides all that, whatever happens in the BoC over the next 5 days is going to screw up the steering anyway...

Agree! You guys need to calm down...we got Helene first!!


Helene will be a rainmaker the only chance it has at becoming anything stronger than a weak TS is if it would head my direction towards the North gulf coast and trust me that wont happen
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Yeah remember anything more than 5 days out on the models is highly unreliable. Hence why Dr. Masters doesn't even bother to mention anything further than that. As usual we just have to watch and wait.
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Quoting pottery:
So, potential Mischief in the Islands on the 23rd???
Not the kind of Birthday present I was looking for.....
Hey Pottery.Just keep a eye to the sky(well africa).
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Still some shear at 180hrs.
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Quoting Felix2007:
Looks like Isaac's gonna be the "once in a blue moon" event.

Cat 5 at least!
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Quoting Grothar:
What I think the models thinking is right now, is they see another area of vorticity to the west of 94L. If 94L becomes stronger and pulls the 2nd are into it, there might be a Fujiwhara effect causing 94L to be moved further North. Not all models are showing this right now. If this 2nd area does not materialize, then 94L could move much further west.


The system is probably to far east for a Fujiwhara effect with 94L, then Isaac as portrayed in the scenario by the 18z GFS. Think of Earl/Fiona in 2010.
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So, potential Mischief in the Islands on the 23rd???
Not the kind of Birthday present I was looking for.....
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The 1821 Norfolk and Long Island Hurricane was one of four known tropical cyclones that have made landfall in New York City. Another, even more intense hurricane struck the region in pre-Columbian times (sometime between 1278 and 1438) and was detected by paleotempestological research.[2] The third was the 1893 New York hurricane and the fourth was Hurricane Irene in 2011.
The first of three recorded tropical cyclones recorded in the 1821 Atlantic hurricane season, it was first observed off the southeast United States coast on September 1, with winds estimated in excess of 135 mph (215 km/h). It moved ashore near Wilmington, North Carolina, and passed near Norfolk, Virginia before moving through the Delmarva Peninsula and New Jersey just inland. The hurricane struck New York City on September 3, approximately near Jamaica Bay, and on September 4 it was observed over New England. The hurricane occurred just 6 years after the destructive Great September Gale of 1815.
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Quoting STXHurricanes2012:
From Previous Blog:
Quoting RTSplayer:
Yall, calm down.

The models are certainly terrible beyond 7 days on forecasting track, and they even suck within 5 days on intensity.

Needs to be strong enough to classify so they can get a better center fix on it before everyone goes nuts worrying about some northern turn a week from now.

Besides all that, whatever happens in the BoC over the next 5 days is going to screw up the steering anyway...

Agree! You guys need to calm down...we got Helene first!!
I'm just stunned at the fact that once again the "I" storm is attempting to cause terror...The models are certainly entertaining to watch though.
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Quoting WxGeekVA:


DOOM!!!
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Quoting Hurricanes4life:

Only difference for us Nova scotians is the SST's are WAY WAY above normal, so the intensity could be much stronger than earl this far north! and yeah, I agree, it is still fantasy land! ;)


Some are saying with GW, Nova Scotia is the new Outer Banks of NC....

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just one run guys. lets see the 0z
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Interesting.

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Quoting Hurricanes101:
does anyone have the latest atcf coordinates for Invest 94L?



AL, 94, 2012081718, , BEST, 0, 112N, 237W, 20, 1009, DB,
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Quoting Hurricanes101:
does anyone have the latest atcf coordinates for Invest 94L?


Heres latest from NOAA

17/1745 UTC 11.1N 24.0W TOO WEAK 94L -- Atlantic
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Quoting Tazmanian:
so far we had 4 name storms in AUG not bad next is the I stormm and that will make 5 name storms for AUGS



but AUGS is close in on the last few weeks how many more you think we can get in AUG be for we turn it too SEP


We'll get Joyce before September.
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Quoting CarolinaHurricanes87:


I was thinking the same thing (from a NC perspective). Man was that a stressful one... hope Isaac doesn't follow suit. Good thing is if the models are predicting it this far in advance, it probably won't happen

Only difference for us Nova scotians is the SST's are WAY WAY above normal, so the intensity could be much stronger than earl this far north! and yeah, I agree, it is still fantasy land! ;)
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Looks like Isaac's gonna be the "once in a blue moon" event.
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From Previous Blog:
Quoting RTSplayer:
Yall, calm down.

The models are certainly terrible beyond 7 days on forecasting track, and they even suck within 5 days on intensity.

Needs to be strong enough to classify so they can get a better center fix on it before everyone goes nuts worrying about some northern turn a week from now.

Besides all that, whatever happens in the BoC over the next 5 days is going to screw up the steering anyway...

Agree! You guys need to calm down...we got Helene first!!
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does anyone have the latest atcf coordinates for Invest 94L?
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so far we had 4 name storms in AUG not bad next is the I stormm and that will make 5 name storms for AUGS



but AUGS is close in on the last few weeks how many more you think we can get in AUG be for we turn it too SEP
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Now then did not we at some ungodly hour a few days ago say that this would happen and it would be an action replay of that,Ernesto thing that got over the isthmus and got another name! Wash was in on it!
Sorry my memory fails me at this time of night and this age of life? Was it an Hector that the last one became.
Anyway action replay. Wheres Wash as she was in on this as well, between avatar switches and Isaac infatuations!
Oh! evening everybody, welcome to a busy night. I'm off outside to look at the stars as there is no moon showing tonight.
Back later no doubt.
Thanks to everybody for all your comments on my photos of our drought.
Now then, flat calm and zero wind 28/C, no moon and nothing to moan about.
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What I think the models thinking is right now, is they see another area of vorticity to the west of 94L. If 94L becomes stronger and pulls the 2nd are into it, there might be a Fujiwhara effect causing 94L to be moved further North. Not all models are showing this right now. If this 2nd area does not materialize, then 94L could move much further west.
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Quoting washingtonian115:
So is the major media networks..they just can't wait...Someone's Labor day plans are going to be ruined.


mmmhmmm..(silently sipping coffee)
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Quoting WxGeekVA:

Holy cow! If these model runs for the Northeast US prove right, or even close, my community will be washed out to sea. It's happened before. I will find the graphics.LOL on Macaulay Culkin!
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33. SLU
Year 2000's Hurricane Isaac and Joyce




GFS proposed Hurricane "Isaac" and TS "Joyce" 2012

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Stormchaser, when you say the 18z the high is stronger, is it accurate or over done?
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Quoting ncstorm:


Im sure one of the ensemble runs has florida in the bullseye..


Maybe Dr. Masters was right about the RNC being in jeopardy after all.... (ducks thrown objects from the anti-politics crowd) :)
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Quoting weatherh98:


JFV is probably crying


Im sure one of the ensemble runs has florida in the bullseye..
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And the next wave comes off the train
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Quoting ncstorm:


TWC is salivating right now..
So is the major media networks..they just can't wait...Someone's Labor day plans are going to be ruined.
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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