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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Quoting Patrap:



Well, that's Kinda like rolling the dice here.

: )


yeah... it looks as the storm , if it heads that direction , will start to impact the lesser antillies by Friday and the boat should be on its way home by that time.I'm house and dog sitting for them this week. We all live in Key West.
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1625. LargoFl
gee havent seen mean pouring rain and boomers and tons of lightning like this in a LONG time..and still going..quite a storm coming to you Tampa..long lasting too..stay safe..if your area floods easily..
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Quoting MAweatherboy1:

Actually those intensity models look a good deal lower for intensity than previous cycles, which in the short term I think is more realistic. It's very unlikely 94L will be a Cat 4 in 5 days like some earlier models suggested. Still a good chance it becomes a major eventually, but not within the next few days.

None of them have showed Category 4 intensity yet...the guidance is remaining very straightforward that this will be a major hurricane in a few days.
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1623. Patrap
That feature shows up nicely below Cuba in the WV loop

GOM WV Loop
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Oh My God...

If the GFS is best on timing, and the Ships intensity is within 10kts of the correct value for 120 hours, then it's SW of PR and SE of Dominican republic at 168 hours...

However, the intensity is forecast as 105kts at the 120 hours mark, which the GFS says will still be 12 to 18 hours east of the Lesser Antilles.

If this was to verify, then it would pass the Lesser Antilles as a strong category 3 or weak category 4, and continue intensifying until near landfall (or if it makes the pass anyway).


So these scenarios from the most recent SHIPS and GFS are just terrible compared to earlier runs.
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1621. ackee
I think 94L will track similar to how the GFS is tracking it NE carrb could be hit by a Major I think this year the GFS has been out performing the other models by far. Ecmwf SEEM LIKE it needs a upgrade it has been performing below par this seasons
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1620. Dakster
Quoting washingtonian115:
Around some time late Sunday into Monday.


Thx.

Looking like this could be a long week.
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1619. hydrus
Quoting Patrap:
Tossing Storm Names around TD's that arent a TS yet is awful confusing to Lurkers and others.

Please keep the designation given currently to avoid
Confusion,
Thats why we have names, to keep the Logic flowing.

Thanx
Excellent post Pat, I was thrown off a tad with the misnomers.
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1618. ncstorm
the 00z CMC
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Quoting SLU:
Steady march towards major hurricane status


Actually those intensity models look a good deal lower for intensity than previous cycles, which in the short term I think is more realistic. It's very unlikely 94L will be a Cat 4 in 5 days like some earlier models suggested. Still a good chance it becomes a major eventually, but not within the next few days.
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1616. ncstorm
06z GFS Ensembles Spread







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Quoting TropicalAnalystwx13:
Gordon is pushing Category 2 hurricane intensity according to some satellite-derived intensity estimates.

Eye looks to be clearing out, too.
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Quoting Dakster:
What is the consensus on when 94L will get a name?
Around some time late Sunday into Monday.
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1613. LargoFl
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1612. Patrap
Quoting redwagon:

Pat, I notice you haven't noticed the little spin S of Cuba heading towards the gap. The Wisconsin CIMSS two-day movie shows order out of chaos - ordo ab chao - within the last 48.


Just up from well, one Dog delivered 4 pups here last night but I'll take a gander at it now.

Thanx
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Just a beautiful storm...



(hurricane gordon took today)
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Good morning people,The EURO shows a weaker system,but looks the strong ridge, i´m starting doubting this storm will recurve
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1609. Patrap
Quoting KeyWestwx:
ok- but I wanted the opinions from the experts on this board.



Well, that's Kinda like rolling the dice here.

: )


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1608. Dakster
What is the consensus on when 94L will get a name?
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1607. KEEPEROFTHEGATE (Mod)
Quoting KeyWestwx:
question- it might sound a bit mathmatical.... my friends leave on a cruise from
ft lauderdle on Sunday towards St Thomas/Virgin Islands and they are to return on Saturday AM on the 25th. With the possible progression and intensification of invest 94 and equating in the return time back to FTL from the islands....will this storm pose a possible problem for them and the ship's route. I have my abacus out now! ;)


there will be a storm in the area as per model dipiction 06z saturday the 25th 12 z
keep up to date with cruselines update system and follow NHC/NOAA/local NWS for official updates

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1606. LargoFl
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Yep...NHC seems a bit concerned about it.

"Lastly, a westward-moving tropical wave is located a couple of hundred miles southwest of the Cape Verde Islands in the eastern tropical Atlantic. This system now has about a 40% chance of becoming a tropical cyclone during the next 48 hours. This is the time of year for those long-track Cape Verde cyclones, and it seems likely we'll be talking about this system for a week or longer. Stay tuned."
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Quoting Patrap:


Best to contact your Travel Agent or check directly with the Cruise Line for their updates, they do them every 6 Hrs.


ok- but I wanted the opinions from the experts on this board.
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Quoting Patrap:



Pat, I notice you haven't noticed the little spin S of Cuba heading towards the gap. The Wisconsin CIMSS two-day movie shows order out of chaos - ordo ab chao - within the last 48.
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1602. SLU
Steady march towards major hurricane status

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1601. Gorty
Quoting Gorty:


And this year it could be the "I" storm.


Actually let's put this in retrospective (not sure if I used that word right :p) 2012 has been so active that when Issac forms we will only be two storms away from where 2005 was around the time when Issac forms.
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1600. LargoFl
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Quoting islandgirls:


Yes. Just wanted to know what I am (we are) are up against
Cool... I remembered [a great accomplishment for me lol] ...

Yeah, Antigua definitely needs to keep an eye on this one... even if it misses most of the rest of the Antilles, u guys still might get a bit of a blow.

Member Since: December 31, 1969 Posts: Comments:
Well, the Ships isn't playing games at all with 94L. It says 105kts, land or no land, at 120 hours.

Somebody in the Lesser Antilles and PR area is going to get it right on the chin.

May as well start getting ready now.


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1597. LargoFl
Quoting KeyWestwx:
oh yes..great rains here..and still pouring down
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1596. Gorty
Quoting washingtonian115:
But you see in August the "K" storm had formed and made the month and year very memorable..


And this year it could be the "I" storm.
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1595. mati
Quoting sar2401:


Gordon 2006. Caused damage in Portugal and Spain.


OHO, the return of Gordon, Gordon Gordonson?
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1594. LargoFl
Quoting dearmas:


Guess what will be here in Tampa about that time frame....RNC. Guess we will seeif all the drills//training that has been going on for months will be needed
..well so far so good for the Tampa area..but things can and do often change with time..this storm may well go up the east coast, in which case we may get some rains etc..this front coming down to us may well be our savior..pushing it east of us..hopefully
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06z GFS animation:

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Quoting Gorty:
With Issac, 2012 will be more active then 2005 in August!
But you see in August the "K" storm had formed and made the month and year very memorable..
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Heavy rain just started here too. We already got a fair amount of rain overnight.



Doesn't look like it'll last too long... and not at all windy.
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Quoting LargoFl:
<
Quoting LargoFl:
good soaking rain there! my lawn service has to come twice a month now with all the rain. I have a house in venice, south of Sarasota
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Ok i will:)
Quoting sar2401:


From you...for a week out...but still has the Accu Weather name on it. Since you're doing this in Paintshop, maybe you can clean that up some.
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1588. ncstorm


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Should see a Code Red later.

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Q. What will 94L be at 2PM
A. 40%
B. 50%
C. 60%
D. 70%
I will say 50 to 60% at 2PM
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1585. sar2401
Quoting SFLWeatherman:
From me


From you...for a week out...but still has the Accu Weather name on it. Since you're doing this in Paintshop, maybe you can clean that up some.
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1584. Patrap
Quoting KeyWestwx:
question- it might sound a bit mathmatical.... my friends leave on a cruise from
ft lauderdle on Sunday towards St Thomas/Virgin Islands and they are to return on Saturday AM on the 25th. With the possible progression and intensification of invest 94 and equating in the return time back to FTL from the islands....will this storm pose a possible problem for them and the ship's route. I have my abacus out now! ;)


Best to contact your Travel Agent or check directly with the Cruise Line for their updates, they do them every 6 Hrs.


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1583. Gorty
With Issac, 2012 will be more active then 2005 in August!
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1582. LargoFl
Quoting wxmobilejim:
This shows wave heights are forecast to be 35-40 ft. when 94L gets to the islands.
my god..we sure hope this turns
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1581. KEEPEROFTHEGATE (Mod)
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1580. Patrap


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question- it might sound a bit mathmatical.... my friends leave on a cruise from
ft lauderdle on Sunday towards St Thomas/Virgin Islands and they are to return on Saturday AM on the 25th. With the possible progression and intensification of invest 94 and equating in the return time back to FTL from the islands....will this storm pose a possible problem for them and the ship's route. I have my abacus out now! ;)
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This shows wave heights are forecast to be 35-40 ft. when 94L gets to the islands.
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1577. sar2401
Quoting Patrap:
Tossing Storm Names around TD's that arent a TS yet is awful confusing to Lurkers and others.

Please keep the designation given currently to avoid
Confusion,
Thats why we have names, to keep the Logic flowing.

Thanx


Excellent point, Pat. 94L is still 94L until the NHC changes things. Issac is still in the future, along with Joyce and all the rest of the alphabet. :)
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From me
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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