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:
Quoting stormchaser19:
174 hours and PR in the radar :(
I see Kirk that is September or is still August will be amazing to have 7 name storm for August.
Member Since: December 31, 1969 Posts: Comments:
A lot of freaking out for a storm that has yet to develop...
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873. JLPR2
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.... This is serious and looks like we talking about much destruction and posible loss of life....


Depending on what I see tomorrow on the models I'll inform my family and take action.
Member Since: December 31, 1969 Posts: Comments:
Quoting CaribBoy:
WORST CASE SCENARIO FOR THE WINDWARDS/LEEWARDS


Posible Double hit....

Member Since: December 31, 1969 Posts: Comments:
Just north of PR by 204
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Boy the Caribbean needs to watch what looks to become Issac. That looks no bueno.
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Quoting Stormchaser2007:
Slows significantly then moves WNW at PR by 186 hours.

Hurricane for winds for the island.


I dont like a bit that slow word,oh boy!
Member Since: December 31, 1969 Posts: Comments:
Yes Finally starting to pop convection
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Quoting washingtonian115:
Yeah.Might be just far enough away to avoid it.Or else this is going to be another Earl/Fiona situation.
Was thinking that with the earlier run.
Quoting CaribBoy:
00Z GFS SHOWS A DIRECT HIT TO MOST ISLANDS OF THE LESSER ANTILLES. OMFG THATS CRAZY!!!!!!!!!!!!!!!
You may be the next on his way.
Member Since: December 31, 1969 Posts: Comments:
174 hours and PR in the radar ¨:(
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Member Since: December 31, 1969 Posts: Comments:
Quoting fmhurricane2009:

As low as 1 knot of Shear, under 8 knots past 3 days. rising SST's and TCHP over predicted track
Gulp


RI FLAG ON!!!!!!!!!!!
Member Since: December 31, 1969 Posts: Comments:
863. Relix
Well Isaac... let's do this. *cracks knuckles*
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862. wxmod
Greenland ice. MODIS

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Quoting tropicfreak:


Or Igor/Julia.


?? Julia became a major hurricane
Member Since: December 31, 1969 Posts: Comments:
Another look at Isaac in retrospect to the Pattern across the CONUS.

Member Since: December 31, 1969 Posts: Comments:
Slows significantly then moves WNW at PR by 186 hours.

Hurricane for winds for the island.
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PR looks like it's going to be hit hard.
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Quoting JLPR2:


By 114hrs still a mirror. :\ I'm thinking buying supplies after a second identical run might not be a bad idea. XD


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....
Member Since: December 31, 1969 Posts: Comments:


174 @ 984
Member Since: December 31, 1969 Posts: Comments:
WORST CASE SCENARIO FOR THE WINDWARDS/LEEWARDS
Member Since: December 31, 1969 Posts: Comments:
Quoting washingtonian115:
Yeah.Might be just far enough away to avoid it.Or else this is going to be another Earl/Fiona situation.


Or Igor/Julia.
Member Since: December 31, 1969 Posts: Comments:
Member Since: December 31, 1969 Posts: Comments:
Evening bloggers! So, Isaac it is, huh?

Everyone has been saying that would be the storm to watch this year. Those model runs are scary. Not showing early recurvature.....and a much larger system.


Not sure what the deal is with Helene...haha.
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851. JLPR2
Quoting Tropicsweatherpr:


Or a Hugo track.


Nah, Hugo entered the Caribbean farther to the north.
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Quoting 954FtLCane:

guessing wnw


Looks like in the latest frames it has taken a jog to the N... maybe a slight westward component.
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162, @985.. def looks like a wnw to nw move and a week from today PR is in trouble
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162 hours and the recurve start
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Quoting JLPR2:


Oh snap! I was afraid of this, the 18z was too to the west.



Looking like a Marilyn now. :\


Or a Hugo track.
Member Since: December 31, 1969 Posts: Comments:
Quoting tropicfreak:


Considering the outflow shear that Isaac would be generating pretty impressive.
Yeah.Might be just far enough away to avoid it.Or else this is going to be another Earl/Fiona situation.
Member Since: December 31, 1969 Posts: Comments:
Moving NW through all of the Islands.

St. Kitts looks like its getting hard. Seeing 90+ knot winds right over them.
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844. JLPR2
Quoting washingtonian115:
Joyce seems to be holding up good as well.Isaac is coming for PR next.


Oh snap! I was afraid of this, the 18z was too to the west.



Looking like a Marilyn now. :\
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162, @ 986 again. seems to be pointing at the PR. we will see.
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Quoting washingtonian115:
Joyce seems to be holding up good as well.Isaac is coming for PR next.


Considering the outflow shear that Isaac would be generating pretty impressive.
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Quoting Gearsts:
Moving NW?

guessing wnw
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Member Since: December 31, 1969 Posts: Comments:
Quoting ncstorm:
back to back hits for the islands..


Going to be an active season for the Antillies. They put up with Ernesto, TD 7, and now potentially Isaac, and maybe Joyce.
Member Since: December 31, 1969 Posts: Comments:
00Z GFS SHOWS A DIRECT HIT TO MOST ISLANDS OF THE LESSER ANTILLES. OMFG THATS CRAZY!!!!!!!!!!!!!!!
Member Since: December 31, 1969 Posts: Comments:
Joyce seems to be holding up good as well.Isaac is coming for PR next.
Member Since: December 31, 1969 Posts: Comments:


156, @988
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150 hours, yes IS MOVING WNW
Member Since: December 31, 1969 Posts: Comments:
back to back hits for the islands..
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Member Since: December 31, 1969 Posts: Comments:
Quoting floridaT:
is there any history of a storm forming there then going north or north east?


I don't believe anyone has mentioned Hurricane Audrey yet. It began life as a remnant low in the Bay of Campeche and headed straight to Cameron Parish. Track appears to take it almost due north.
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Quoting 954FtLCane:


150, @986
Moving NW?
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150, @986
Member Since: December 31, 1969 Posts: Comments:
Man the islands really need to look out for this one.Ernesto and T.D 7(now Helene) were just the appetizers..
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828. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #2
TROPICAL DEPRESSION 16
12:00 PM JST August 18 2012
====================================

SUBJECT: Tropical Depression In Sea East Of The Philippines

At 3:00 AM UTC, Tropical Depression (1008 hPa) located at 18.7N 126.1E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as moving south slowly.

Dvorak Intensity: T2.0

Forecast and Intensity
========================

24 HRS: 18.5N 124.6E - 35 knots (CAT 1/Tropical Storm)

Japan Meteorological Agency
Tropical Cyclone Advisory #46
TROPICAL STORM KAI-TAK (T1213)
12:00 PM JST August 18 2012
====================================

SUBJECT: Category One Typhoon Overland Vietnam

At 3:00 AM UTC, Tropical Storm Kai-Tak (992 hPa) located at 22.0N 104.6E has 10 minute sustained winds of 40 knots with gusts of 60 knots. The cyclone is reported as moving west northwest at 10 knots.

Dvorak Intensity: OVERLAND

Gale Force Winds
================
150 NM from the center

Forecast and Intensity
========================

24 HRS: 22.9N 100.6E - Tropical Depression Overland Southern China
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138 hours, recurve?
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988 mb hitting the lesser antilles..
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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