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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LOL.

The GFS has a third system classified as a full Tropical Storm before it even exits the African coast.

There's also a FOURTH system which forms SW of Haiti on the 25th and moves NE...

Member Since: December 31, 1969 Posts: Comments:
1375. pottery
Quoting SLU:


It reminds me a lot of those killer hurricanes of the 90's in the NE Caribbean.

Lets not go there !

But yeah, this one looks Ominising....
Member Since: December 31, 1969 Posts: Comments:
Quoting clwstmchasr:
Some early morning rain for Central Florida.

It's been mostly cloudy here this morning, too... though sat pics don't show much...
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Quoting Grothar:


I'm with you Wash, I never like the "I" storms. Nothing but trouble. The thing is no matter what they are, you can always see the "I". :)
Booo.Lol.
Quoting Grothar:


When you see 4 models all indicating it, it is a pretty good indication.
Shhhh don't say that Gro.Your gonna freak some people out.Especially people that think we're hyping.
Member Since: December 31, 1969 Posts: Comments:
That is one big Hurricane
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1371. pottery
Quoting Grothar:


You mean Easter.

Of course !
Member Since: December 31, 1969 Posts: Comments:
I think 94L will strengthen gradually - as opposed to rapidly - because it is so large. The scary thing about this is that it's in the open Atlantic with plenty of time to strengthen. I also don't thing it will be affected by the enviromental conditons as much as a smaller storm would be.
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1369. Grothar
Quoting pottery:

Well, there's always East.......


You mean Easter.
Member Since: December 31, 1969 Posts: Comments:
1368. SLU
Quoting pottery:

That's what concerns me the most.
84 degrees SST there is quite enough for Bad News.


It reminds me a lot of those killer hurricanes of the 90's in the NE Caribbean.
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1367. Grothar
Quoting Abacosurf:
That's the onliest way....


Yeah, it could go even westerer than it's showing. :)
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1366. pottery
Quoting Abacosurf:
That's the onliest way....

Well, there's always East.......
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1365. SLU
432

WHXX01 KWBC 181236

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1236 UTC SAT AUG 18 2012



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



TROPICAL CYCLONE HELENE (AL072012) 20120818 1200 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

120818 1200 120819 0000 120819 1200 120820 0000



LAT LON LAT LON LAT LON LAT LON

BAMS 22.2N 97.8W 23.2N 98.9W 24.0N 99.8W 24.5N 100.6W

BAMD 22.2N 97.8W 22.6N 98.9W 22.9N 99.8W 23.0N 100.6W

BAMM 22.2N 97.8W 22.9N 99.0W 23.4N 99.9W 23.8N 100.7W

LBAR 22.2N 97.8W 23.0N 99.0W 24.1N 99.7W 25.4N 99.8W

SHIP 30KTS 31KTS 35KTS 41KTS

DSHP 30KTS 27KTS 27KTS 27KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

120820 1200 120821 1200 120822 1200 120823 1200



LAT LON LAT LON LAT LON LAT LON

BAMS 24.6N 101.6W 24.7N 104.0W 25.4N 106.3W 26.8N 108.1W

BAMD 23.0N 101.5W 22.6N 104.1W 22.9N 107.3W 23.7N 110.2W

BAMM 23.8N 101.6W 23.6N 104.1W 24.2N 106.8W 25.3N 109.2W

LBAR 26.6N 99.2W 29.1N 95.2W 32.8N 88.0W 37.1N 77.5W

SHIP 46KTS 53KTS 49KTS 46KTS

DSHP 27KTS 27KTS 27KTS 27KTS



...INITIAL CONDITIONS...

LATCUR = 22.2N LONCUR = 97.8W DIRCUR = 310DEG SPDCUR = 10KT

LATM12 = 20.8N LONM12 = 96.1W DIRM12 = 325DEG SPDM12 = 7KT

LATM24 = 19.9N LONM24 = 95.7W

WNDCUR = 30KT RMAXWD = 20NM WNDM12 = 35KT

CENPRS = 1008MB OUTPRS = 1012MB OUTRAD = 100NM SDEPTH = M

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



$$

NNNN
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1364. Grothar
Quoting washingtonian115:
No Irene/Isabel part two.And it doesn't help that this storm will start with a "I" to.


I'm with you Wash, I never like the "I" storms. Nothing but trouble. The thing is no matter what they are, you can always see the "I". :)
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Quoting Grothar:
Looks like it is going wester and wester.



GFS Ensemble


That's the onliest way....
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1362. pottery
Quoting SLU:


The strong ridge could take it to the Islands before a breaking down of the ridge allows for it to slow down near the Islands and then turn NW towards PR.

That's what concerns me the most.
84 degrees SST there is quite enough for Bad News.
Member Since: December 31, 1969 Posts: Comments:
I wouldn't be surprised to see future 94L go through the southern/central Antilies as that have been one of the favored tracks by storms this year..(T.D 7,Ernesto...)
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1360. Grothar
Quoting washingtonian115:
Some of the intensity models bring this monster up to a cat 4 almost.That is yet to be seen though.94L could become our fist major though without a doubt.


When you see 4 models all indicating it, it is a pretty good indication.
Member Since: December 31, 1969 Posts: Comments:
1359. SLU
Quoting stoormfury:
SLU it looks like 13n 30w moving north of west.it will continue on this track for a few hrs ,then resume a west track and then a wsw movement before coming back west again.This what the 750-659 mb steering is showing at the moment.


The strong ridge could take it to the Islands before a breaking down of the ridge allows for it to slow down near the Islands and then turn NW towards PR.
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1358. Grothar
Looks like it is going wester and wester.



GFS Ensemble


Member Since: December 31, 1969 Posts: Comments:
They go up to Cat 4 but TS and 12 to 24HR
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Quoting Grothar:
That's not good. It appears we could be looking at a Cat 3 or 4 very soon.

No Irene/Isabel part two.And it doesn't help that this storm will start with a "I" to.
Member Since: December 31, 1969 Posts: Comments:
ATCF has Gordon up to 70 knots. The little engine that could...

AL, 08, 2012081812, , BEST, 0, 340N, 396W, 70, 983, HU, 64, NEQ, 0, 30, 30, 0, 1013, 175, 25, 0, 0, L, 0, , 0, 0, GORDON, D,
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1354. pottery
Quoting Grothar:
That's not good. It appears we could be looking at a Cat 3 or 4 very soon.


Indeed!
Member Since: December 31, 1969 Posts: Comments:
This...



with this






vs this

Member Since: December 31, 1969 Posts: Comments:


Member Since: December 31, 1969 Posts: Comments:
1351. Grothar
That's not good. It appears we could be looking at a Cat 3 or 4 very soon.

Member Since: December 31, 1969 Posts: Comments:
Quoting RTSplayer:
I think Helene's mid-level circulation has been totally ejected to the west.

It may actually back-build over the BoC again...

Look on RGB how pathetic the circulation is, and all the convection is back several degrees to the east again...
there is still SE wind on the 055 buoy 25knts. I agree...give this about 4 hours and the satelite presentation should look much better. Reformation to the east very possible.
Member Since: Posts: Comments:
SLU it looks like 13n 30w moving north of west.it will continue on this track for a few hrs ,then resume a west track and then a wsw movement before coming back west again.This what the 750-659 mb steering is showing at the moment.
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Q.What day will we get TD 9
A.Sunday
B.Monday
C.tuesday
D.wednesday
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1347. SLU
18/1145 UTC 21.9N 97.6W T1.0/1.0 HELENE -- Atlantic
18/1145 UTC 33.8N 39.4W T4.0/4.0 GORDON -- Atlantic
Member Since: Posts: Comments:
I think Helene's mid-level circulation has been totally ejected to the west.

It may actually back-build over the BoC again...

Look on RGB how pathetic the circulation is, and all the convection is back several degrees to the east again...
Member Since: December 31, 1969 Posts: Comments:
Quoting RTSplayer:
Gordon tapping the trough for assisted outflow.

There's no real anti-cyclone at all. The southern side is actually blowing in the wrong direction in the upper levels, so it's actually being sheared on the south side, but still intensifying.

GFDL from 0600z wants to take it to 90mph...


I figure the water temps can maintain hurricane status for another 24 to 30 hours...

With the forward speed so high, it may even be able to coast into the 25C or 24C zones as a minimal hurricane...


Well that was my mistake...I thought he was going to hook up to that trough and get whisked away and not be able to strengthen any further...
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Big rain for the GOM
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1343. SLU
Looks like 13n 30w to me ...
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Quoting CybrTeddy:

Almost a cat4 in 5 days... would have to suck up ALL the EATL moisture to pull that off, leaving everything else black and dry!
Member Since: December 31, 1969 Posts: Comments:
Some of the intensity models bring this monster up to a cat 4 almost.That is yet to be seen though.94L could become our fist major though without a doubt.
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1340. pottery
Good Morning.
The models are being pretty consistent regarding 94L and the Caribbean.

Kind of worrying, that.
Member Since: December 31, 1969 Posts: Comments:
Looks like a little mesoscale low popped off Cuba approaching the Caymans from the east.
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Member Since: December 31, 1969 Posts: Comments:
Gordon's peak:
A: 80mph
B: 85mph
C: Strongest storm of the season
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At this point, I think Gordon will hold better then the current NHC speeds.
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Quoting JrWeathermanFL:

So we need 2 tropical storms in 4 days?
That aint happenin.
very possible within 5-7 days.
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Quoting WeatherNerdPR:

The GFS forecasts a storm to develop behind Isaac in 4-5 days.




It actually forecasts the "K" storm at the end of the model run, but that's too far out to be reliable.
Member Since: December 31, 1969 Posts: Comments:
Quoting JrWeathermanFL:

So we need 2 tropical storms in 4 days?
That aint happenin.
OTOH, it's entirely possible... happened last year, IIRC.

Edit: I checked, and we had Jerry form on the 19th, Irene on the 20th... and it happens all the time. Clusters of storm formation are very likely.
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F5
*no new comments
F5
*no new comments
F5F5F5!!!
*no new comments

-________-
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Quoting JrWeathermanFL:

So we need 2 tropical storms in 4 days?
That aint happenin.

The GFS forecasts a storm to develop behind Isaac in 4-5 days.

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Quoting SLU:
OF NOTE:

The formation of TS Helene yesterday marks the 3rd earliest date for the formation of the 8th named storm after only 2005 and 1936.

If Joyce forms before the 22nd of August, it will break the record set by TS Jerry in 1995 for the earliest formation of the 10th named storm in recorded history.

WHAT A BUST OF A SEASON!

So we need 2 tropical storms in 4 days?
That aint happenin.
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I hope this next one off Africa splits us in NC and Bermuda. Irene made a mess here and I don't want to mess with another storm. After Isabel and Irene I am starting to worry about those "I" storms....
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Quoting MAweatherboy1:

If this were to verify you wouldn't see me for awhile!



um...

967mb...after crossing the cape...

That would be so bad...so, so bad...
Member Since: December 31, 1969 Posts: Comments:
1326. SLU
OF NOTE:

The formation of TS Helene yesterday marks the 3rd earliest date for the formation of the 8th named storm after only 2005 and 1936.

If Joyce forms before the 22nd of August, it will break the record set by TS Jerry in 1995 for the earliest formation of the 10th named storm in recorded history.

WHAT A BUST OF A SEASON!
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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