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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Ok....now a little concerned about a storm impacting my area. Worst for me between Houma, LA and N.O.
Just got word my home elevation approved and can start in a week or two. Murphy's Law may come into play....:p
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Quoting stormchaser19:


The GFS ensemble looks interesting...
Member Since: December 31, 1969 Posts: Comments:
Experimental higher resolution GFS ensemble, 168 hours:






Link
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http://forums.accuweather.com/index.php?showtopic=5 611

Wilma '2' eye
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1722. LargoFl
Quoting Jedkins01:
I've recorded over 2 inches of rain so far and lots of lightning with it, even more about to move in soon, finally the local dry streak ends!
Good morning Jed..yeah finally some great rains
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1721. hydrus
Quoting aislinnpaps:


You're right, Hydrus, I don't like that at all. Thank God it's too far out to worry about.
Another interesting thing I saw was if the tropical wave in the Central Caribbean were to pick up the blob in the extreme S.W.Caribbean, something may develop.
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Quoting LargoFl:
I dunno..looking at 94L in this pic..does not look impressive at all..doesnt even look like its trying to form.....my hope is it stays disorganized..some people might get hurt with this one done the road if it doesnt......................


If these values are true, I don't think you want the storm to stay weak, because then it passes through cat 4 and cat 5 potential zones later on.





If anything, it would be best if it did RI for the next 4 days and hooked hard north before hitting any land.

Staying weak makes it go farther west, where it will then explode over 130kj/cm^2 TCHP...
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1719. LargoFl
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I've recorded over 2 inches of rain so far and lots of lightning with it, even more about to move in soon, finally the local dry streak ends!
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Quoting CarolinaHurricanes87:


Glad you are back from the short vacation WKC. Hope you enjoyed yourself. Do you think 94L will impact the convention (aug 27-30 in Tampa)???


I'm not back yet I'm just checking in seeing whats going on

so far it is good

Hmm I don't know. but my gut is telling me, this will be a Carib/GOM system and the recurves in the GOM into Fl. not sure about the time frame, but thats what me guts telling
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Quoting BahaHurican:
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.



"blow" is the operative word here. Definitely not taking this lightly.

Just noticed I doubled up on the word "are" in my post. Like my mom used to say "Best of men make mistakes". This one was too simple though. Back to weather watching.
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1714. hydrus
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Good Morning, Muggy out West, Heres WHY
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1712. Skyepony (Mod)
Oh yeah~ Wilma.. I was getting ready for it. Can't find pic..
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1711. ncstorm
Quoting redwagon:

Where'd Gro go?

This is still obviously 2 discrete systems, the next ascat/oscat will show that. We still haven't solved the argument of which blob will be absorbed by which..



Yeah..which could make one huge mother..we may see a fujiwhara..its going to be close..
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Quoting hydrus:
The latest Euro is not what a lot of people would want.Link


You're right, Hydrus, I don't like that at all. Thank God it's too far out to worry about.
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1709. LargoFl
I dunno..looking at 94L in this pic..does not look impressive at all..doesnt even look like its trying to form.....my hope is it stays disorganized..some people might get hurt with this one down the road if it doesnt......................
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Quoting Neapolitan:
FWIW, Gordon has moved into second place on the 2012 ACE list. Meanwhile, Helene has a really good chance of staying in last place for the duration:

1: ERNESTO - 7.6625
2: GORDON - 3.1675
3: CHRIS - 2.7675
4: DEBBY - 2.4450
5: BERYL - 2.1600
6: FLORENCE - 1.4375
7: ALBERTO - 1.3750
8: HELENE - 0.4050

ACE

ACE


Issac for sure will go to #1.
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Quoting hydrus:
The latest Euro is not what a lot of people would want.Link


I don't trust the Euro for tropical systems unless they've already been named.

It's notorious for not even initializing something as strong as category 3 anyway, which happened a few times in the past 2 or 3 years...

Plus that screwy map system doesn't even have the pressure values listed for the storms on some of the frames.

Although it's true that scenario would be screwed up, since it would put a developed system going into the Gulf already in tact, and the Antilles and PR would probably get hits or close calls twice within the same week..
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1706. ncstorm
06z GFS Precip map through 6-10 days


11-15 days
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OMG, my heart is pumping


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Quoting wunderkidcayman:
looking at forecast track for the Tropical Depression Helene, depending on if it still has a LLCOC in 4 day. it could redevelop back in the GOM and landfall on Tx. so just keep an eye out for that.

looking at Gordon. he may try to make it to 85-90MPH before hitting that cooler water.

I have a gut feeling that 94L will end up being a Carib/GOM cane, with it recurving in the GOM towards Fl. but for now its too early to be certain. so I shall wait till it reaches 40W.


Glad you are back from the short vacation WKC. Hope you enjoyed yourself. Do you think 94L will impact the convention (aug 27-30 in Tampa)???
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Quoting stormchaser19:


keep on shifting W
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Quoting ncstorm:
94L is greasing up the tracks for the wave train..lots of moisture..


Where'd Gro go?

This is still obviously 2 discrete systems, the next ascat/oscat will show that. We still haven't solved the argument of which blob will be absorbed by which..
Or whether they will go their separate ways, which is looking more likely by the frame.......

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Quoting Neapolitan:
FWIW, Gordon has moved into second place on the 2012 ACE list. Meanwhile, Helene has a really good chance of staying in last place for the duration:

1: ERNESTO - 7.6625
2: GORDON - 3.1675
3: CHRIS - 2.7675
4: DEBBY - 2.4450
5: BERYL - 2.1600
6: FLORENCE - 1.4375
7: ALBERTO - 1.3750
8: HELENE - 0.4050

ACE

ACE


After Isaac comes through that ACE chart is gonna be filled by him.
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Quoting hydrus:
The latest Euro is not what a lot of people would want.Link
No Gulf storm please.I find it interesting that either way the models send this it ends bad for someone...
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1698. KEEPEROFTHEGATE (Mod)
12z runs will start soon be interesting to see if it keeps the dipiction the same
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1697. Skyepony (Mod)
Recon Plan of the Day was a little later coming out..

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
3. REMARKS: ADDITIONAL DAY OUTLOOK--PSBL LOW LEVEL
INVEST NEAR 14N AND 50W ON 21/1800Z.
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1696. LargoFl
Quoting wunderkidcayman:

I know
maybe by monday we will have a better idea where its going, models are split now, still needs to form then they can get a good handle on it
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Quoting Skyepony:


Odd how storms make 2s.. Wasn't it an I storm that had a very prominent one in it's eye?

Wilma had a '2' in her eye.
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Quoting wunderkidcayman:


As I said gut feeling says Caribbean storm

He was referring to TD Helene.
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1693. Patrap
..."Little by Little, everything change's"..


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Quoting RTSplayer:


GFS is creepy good at 120 hours range, but starts to lose it afterwards.

However, one thing working against the models right now is that the system isn't developed yet, so the initialization could be bad.

If the initialization is good, then the GFS is probably not wrong by more than one degree in any direction at the 120hours mark...

I know
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1691. hydrus
The latest Euro is not what a lot of people would want.Link
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Quoting MAweatherboy1:
Hurricane warning for the Azores. We don't see that much.
Think the last time was for the last Gordon, IIRC...
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Quoting stormchaser19:
Model shifting little by little to the west


As I said gut feeling says Caribbean storm
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Quoting wunderkidcayman:
looking at forecast track for the Tropical Depression Helene, depending on if it still has a LLCOC in 4 day. it could redevelop back in the GOM and landfall on Tx. so just keep an eye out for that.

looking at Gordon. he may try to make it to 85-90MPH before hitting that cooler water.

I have a gut feeling that 94L will end up being a Carib/GOM cane, with it recurving in the GOM towards Fl. but for now its too early to be certain. so I shall wait till it reaches 40W.


GFS is creepy good at 120 hours range, but starts to lose it afterwards.

However, one thing working against the models right now is that the system isn't developed yet, so the initialization could be bad.

If the initialization is good, then the GFS is probably not wrong by more than one degree in any direction at the 120hours mark...
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Quoting Neapolitan:
FWIW, Gordon has moved into second place on the 2012 ACE list. Meanwhile, Helene has a really good chance of staying in last place for the duration:

1: ERNESTO - 7.6625
2: GORDON - 3.1675
3: CHRIS - 2.7675
4: DEBBY - 2.4450
5: BERYL - 2.1600
6: FLORENCE - 1.4375
7: ALBERTO - 1.3750
8: HELENE - 0.4050

ACE

ACE
I love pie charts, good job Neapolitan :)
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1685. ncstorm
94L is greasing up the tracks for the wave train..lots of moisture..

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Quoting 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..

The National Weather Service in Ruskin has issued an

* Urban and Small Stream Flood Advisory for...
northwestern Hillsborough County in Florida.
This includes the cities of... Lutz... Temple Terrace... Tampa
International Airport... Tampa

central Pinellas County in Florida.
This includes the cities of... Clearwater... largo... Pinellas Park...
Seminole


* until 1130 am EDT

* at 1029 am EDT... National Weather Service Doppler radar indicated
rainfall rates of two inches per hour associated with thunderstorms
over the advised area... localized flooding is imminent or occurring.

Precautionary/preparedness actions...

Keep children from being swept away in flooded ditches and drains.
Flood waters are usually deeper than they appear and may stall your
vehicle. Just one foot of flowing water is powerful enough to sweep
vehicles off the Road. Turn around... dont drown.


Lat... Lon 2812 8261 2818 8238 2817 8210 2789 8253
2793 8254 2793 8257 2796 8256 2796 8266
2798 8262 2799 8267 2796 8267 2794 8271
2792 8263 2787 8258 2775 8276 2783 8284
2793 8285
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1683. hydrus
Quoting KEEPEROFTHEGATE:


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

It is entirely to early to make predictions, but I am a bit concerned about Haiti. The CMC has it missing the Caribbean which is good.
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1682. Skyepony (Mod)
Quoting Articuno:

It's actually a 2. :D
I know my ABC's and 123's xD


Odd how storms make 2s.. Wasn't it an I storm that had a very prominent one in it's eye?
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Member Since: December 31, 1969 Posts: Comments:
Quoting stormchaser19:
Model shifting little by little to the west

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Last nights FIM-8 run:

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looking at forecast track for the Tropical Depression Helene, depending on if it still has a LLCOC in 4 day. it could redevelop back in the GOM and landfall on Tx. so just keep an eye out for that.

looking at Gordon. he may try to make it to 85-90MPH before hitting that cooler water.

I have a gut feeling that 94L will end up being a Carib/GOM cane, with it recurving in the GOM towards Fl. but for now its too early to be certain. so I shall wait till it reaches 40W.
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Model shifting little by little to the west
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1676. Skyepony (Mod)
Quoting Tazmanian:



is that a eye in 94L?


No..

ASCAT missed 94L
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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