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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He needs to have a chill pill lol.Relax!!
Member Since: December 31, 1969 Posts: Comments:
Dmin can do some pretty shocking things to systems, we could just say wait and out and see what happens before we chastise the NHC

but whatever
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Quoting VAbeachhurricanes:


They didn't even wait for another pass, which an hour later through the very same section showed 20 mph winds


Saw that. First impressions !
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Quoting STXHurricanes2012:
Have you heard of DMIN??? lol!! This is the case here!


No, whats that?
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‎20 years ago today on 8/17/92, a tropical storm formed in the central Atlantic and was given the name Andrew.
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Quoting Hurricanes101:


no, but disagree in the right way

you sound like you are whining


Because I am astonished they are keeping a swirl with no thunderstorms at all, a TS I am not whining. It is 11pm and I am still at work on a friday, so maybe yes a little whining hahaha
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Quoting kmanislander:


Those winds were produced in large part by proximity to the SW terrain of the Bay. Still, they named it but no surprise the shelf life is less than a mayonnaise sandwich.
lol
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VABH'S I think Helene was a tropical storm before the HH got into it.
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Have you heard of DMIN??? lol!! This is the case here!
Member Since: December 31, 1969 Posts: Comments:
Quoting kmanislander:


Those winds were produced in large part by proximity to the SW terrain of the Bay. Still, they named it but no surprise the shelf life is less than a mayonnaise sandwich.


They didn't even wait for another pass, which an hour later through the very same section showed 20 mph winds
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Quoting VAbeachhurricanes:


Totally forgot we always have to agree with everything they say, my b


no, but disagree in the right way

you sound like you are whining
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Quoting scott39:
I remember Opal. Is there a strong enough trough to do that with Helene? Opal was late Sept early Oct.


I dont think so.
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Quoting Hurricanes101:


then send them an email


Totally forgot we always have to agree with everything they say, my b
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Quoting VAbeachhurricanes:
The only reason the NHC is keeping it a name is so they don't look like idiots for naming it when they found 5 minutes of 40 mph winds...


Those winds were produced in large part by proximity to the SW terrain of the Bay. Still, they named it but no surprise the shelf life is less than a mayonnaise sandwich.
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Quoting redwagon:

Let's try another approach. If Helene was inland, the HHS would never know as they aren't allowed to fly over MX. So you think they fabricated a fake center to save face?


I've seen them be off by 50 or even 100 miles before, and a few hours later issue a re-position, even though the official direction of movement was quite the different direction.

It has happened before a few times.
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A tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has a closed low-level circulation. Tropical cyclones rotate counterclockwise in the Northern Hemisphere. They are classified as follows:

They just totally forgetting this part?
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Quoting kmanislander:


Opal was close to that. Became a TD just East of the Yucatan then crossed over to the BOC. Tracked N then NE as a major


I remember Opal. Is there a strong enough trough to do that with Helene? Opal was late Sept early Oct.
Member Since: December 31, 1969 Posts: Comments:
Quoting ncstorm:


I told ya he was going to have a field day with that run..NY is doomed and he wants to be the first to say he told us so..
Lol.Not only N.Y.But all the east coast is doomed.We here in D.C depending on how large the storm is are going to at least get 50+mph winds.We did with Irene as well.Your going to catch it first if that track comes true as N.C get's whacked.
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Quoting pottery:
Post 577, Good One.

Thor Hyerdahl, Jaques Custeau and others had lots to say about Sahara Dust in the 50's & 60's too.
very good post. long range effects. wonder when the studies will come out about japan radio activity effecting the west coast of the US
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Quoting VAbeachhurricanes:


Have you seen it? Pretty sure in their description of a TC sustained convection must be present. Where is it?


then send them an email
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Quoting RTSplayer:
The CoC is obviously near 20.5N 97.5W, which is inland.

The center is not overland!
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Quoting Hurricanes101:


wow never seen anyone outright attack the NHC like this in awhile

cool your jets and see how this plays out


Have you seen it? Pretty sure in their description of a TC sustained convection must be present. Where is it?
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The CoC is obviously near 20.5N 97.5W, which is inland.
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Quoting VAbeachhurricanes:


The only reason the NHC is keeping it a name is so they don't look like idiots for naming it when they found 5 minutes of 40 mph winds...


wow never seen anyone outright attack the NHC like this in awhile

cool your jets and see how this plays out
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The only reason the NHC is keeping it a name is so they don't look like idiots for naming it when they found 5 minutes of 40 mph winds...
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Quoting VAbeachhurricanes:
This is a joke right?

Not really. look at the swirl in the storm and outflow. If Helene can get its energy away from land...it will be worth watching.
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.
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Quoting Hurricanes101:


Opal developed in the BOC but a bit further east


I remember Bret because I watched it...everybody (NHC included) forecasted it to go inland in Mexico and it just kept trucking North. The morning before it made landfall it was a Cat 3 (I think...might have been 2) just to our South and we were suddenly under mandatory evacuations.
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Quoting floridaT:
is there any history of a storm forming there then going north or north east?


Opal was close to that. Became a TD just East of the Yucatan then crossed over to the BOC. Tracked N then NE as a major


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Post 577, Good One.

Thor Hyerdahl, Jaques Custeau and others had lots to say about Sahara Dust in the 50's & 60's too.
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Quoting ncstorm:


I imagine so, you were up with the chickens doing a blog this morning..

Nogaps run


Yes, I wake up very early. This way I can take my naps earlier.
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Quoting RkptMom:


Hurricane Bret 1999. Formed in the BOC, moved North, and went inland just south of Corpus Christi.
just looked that up in the archives, small in size but strong winds of 125 knots
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Here is one that moved all the way across the gulf
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Quoting VAbeachhurricanes:
This is a joke right?

Remember one rule of the tropics..NEVER EVER EVER DECLARE ANYTHING DEAD UNTIL IT HAS FULLY DISSIPATED.BTW I'm not yelling.
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Quoting RTSplayer:
Maybe here will be easier to see


Let's try another approach. If Helene was inland, the HHS would never know as they aren't allowed to fly over MX. So you think they fabricated a fake center to save face?
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Quoting washingtonian115:
Irene wasn't satisfying enough for him?.


I told ya he was going to have a field day with that run..NY is doomed and he wants to be the first to say he told us so..
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Quoting RkptMom:


Hurricane Bret 1999. Formed in the BOC, moved North, and went inland just south of Corpus Christi.


Opal developed in the BOC but a bit further east
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Quoting Tropicalupdate:
The Cone and track for Helene keeps it more along the coast instend of way inland Could it never go in Mexico and stay in gulf?


Some models are indicating it could drift North and be picked up by a very strong ridge building over the US. It will still have to be watched. Never dismiss something because it doesn't look good at the moment. Usually after diurnal max after 2 AM, everything looks good.

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This is a joke right?

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Most of Helenes energy is over land.
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Quoting Tropicalupdate:
The Cone and track for Helene keeps it more along the coast instend of way inland Could it never go in Mexico and stay in gulf?

It's possible. May allow it to strengthen like the GFS is indicating.
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Quoting floridaT:
is there any history of a storm forming there then going north or north east?


Hurricane Bret 1999. Formed in the BOC, moved North, and went inland just south of Corpus Christi.
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Quoting ncstorm:
evidently the GFS has a subscription to Weatherbell..from twitter

Joe Bastardi
Well what have we here. The GFS has shifted west with ideas as per weatherbell discussion for storm threat next week
Irene wasn't satisfying enough for him?.
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Quoting WxGeekVA:


So if I get this right, the NHC is discounting the GFS AND the Euro on the potential regeneration of Helene. WTH?!?

Did you see the new cone? As of 10p eastern, Helene is still offshore. Regardless of what RTS says.
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Look how diluted is the SAL.... Its surrounded by WV...

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This month we've had Ernesto,Florence,Gordon,Helene..Will we add Isaac and Joyce as well?.Stay tuned.September should/could also be busy with activity leveling down in October.Maybe a storm or two between October and November.But you should not let your guard down in October as it has been known to produce significant cyclones.Wilma will Tell you that.
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evidently the GFS has a subscription to Weatherbell..from twitter

Joe Bastardi
Well what have we here. The GFS has shifted west with ideas as per weatherbell discussion for storm threat next week
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Quoting floridaT:
is there any history of a storm forming there then going north or north east?


I think one of the F storms did it one year, developed in that area and went all the way across the gulf and hit the panhandle
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Quoting floridaT:
good evening Helene has got to be the weakest ts ive ever seen. and not long lasting either.


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I have a link from a very interesting article about SAL. Here is an excerpt.


Ever since Charles Darwin noted "the falling of impalpably fine dust" while crossing the Atlantic during his famous scientific voyage aboard the Beagle, seafarers and researchers have observed African particulates far out to sea. But most studies of atmospheric dust have focused on its potential impacts on the global climate. Only recently have researchers begun exploring the possibility that the hundreds of millions of tons of African topsoil blown by prevailing winds to the Caribbean each year might be having direct, harmful effects on ecosystems and people there.

Dust reaching the opposite shore of the Atlantic is nothing new. Haze from the Sahel occasionally reduces visibility and reddens sunsets from Miami to Caracas, and is the source of up to half the particulates in Miami's summertime air. Pre-Columbian pottery in the Bahamas is made of windborne deposits of African clay; orchids and other epiphytes growing in the rainforest canopy of the Amazon depend on African dust for a large share of their nutrients.

Joseph Prospero of the University of Miami has tracked dust falling on Barbados, at the far eastern edge of the Caribbean, since 1965. He discovered a sharp increase in dustfall around 1970, coinciding with the onset of prolonged drought in North Africa. The changed African climate, combined with widespread overgrazing of livestock and the spread of destructive, often export-oriented farming practices in the Sahel, were sending vastly greater quantities of exposed soil into the sky. In peak years, winds now drop four times more dust on Barbados than they did before 1970. Satellite photos of the largest dust event ever recorded, in February 2000, show a continuous dust bridge connecting Africa and the Americas.


Link
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Quoting kmanislander:


I posted about the topographic effects even before the first discussion came out. If it had not been that far South and close to the coast it may never have developed a closed low.
is there any history of a storm forming there then going north or north east?
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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