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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Quoting ryang:
Steering for 94L


It gets pulled around in circles and lives forever.
Member Since: December 31, 1969 Posts: Comments:
1425. Walshy
Hopefully 94L can bust the drought in Georgia. Anything productive.

North Carolina does not need it. Economy here is bad enough.
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1424. WxLogic
Quoting Grothar:


I don't think so. Mrs. Grothar is away for the week.


LOL!!!
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1423. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #5
TROPICAL DEPRESSION 16
21:00 PM JST August 18 2012
====================================

SUBJECT: Tropical Depression In Sea East Of The Philippines

At 12:00 PM UTC, Tropical Depression (1006 hPa) located at 18.5N 125.8E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as almost stationary.

Dvorak Intensity: T2.0

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

24 HRS: 18.1N 125.6E - 35 knots (CAT 1/Tropical Storm)
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Quoting trHUrrIXC5MMX:



THIS COULD BE WORSE THAN IRENE!
GFS could be wrong too. Let's see consensus on not going out to sea, like some models are saying.
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Folks the long range run of the GFS should not be trusted just yet. the short term is scary for 3 straight runs into the carribean. lots of factors in 10 days. for now lets focus on the short term track
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1420. Grothar
Quoting WxLogic:
Good Morning... Things could be heating up even further soon.


I don't think so. Mrs. Grothar is away for the week.
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1419. ryang
Steering for 94L

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Quoting trHUrrIXC5MMX:



THIS COULD BE WORSE THAN IRENE!



Oh yes.

If that Massachusetts scenario shown earlier were to verify, I figure at least $10 to 20 billion just to start. It had 967mb north of the Cape, so it would have had to hit land at like 955mb or 960mb to maintain that intensity (which probably happens between frames on the model).


Yes, I could agree, verification would be worse than the actual events of Irene, but then again, Irene was forecast to be much stronger on landfall, and look what happened...it hit a couple categories weaker than the GFDL or HWRF predicted.
Member Since: December 31, 1969 Posts: Comments:
The "I" storm.
Dun dun dun
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Quoting SLU:


Goes to show you how anomalously strong the ridge is expected to be.
I've been watching this ridge all season... it's been worrisome...

I need to find the link to the MSLP means that I have in my favorites somewhere...
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1415. WxLogic
Quoting SLU:


Goes to show you how anomalously strong the ridge is expected to be.


I agree... so far ridging has been quite strong so far this year and if it keeps up then there could be a chance of another Carib. system instead of a recurve out to the open sea.
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1414. Grothar
Quoting trHUrrIXC5MMX:



THIS COULD BE WORSE THAN IRENE!


It could, if the models were to be accurate. Irene was weakened from a Cat 3 when it struck North Carolina and hugged the Coast. The waters are extremely warm in the NE, even for this time of year.

There are very warm temperature for the NE.

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1413. ryang
Quoting SLU:


Goes to show you how anomalously strong the ridge is expected to be.


Indeed!
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A Category 3, heck even a Category 2 to the New York City would be an unmitigated disaster. Automatic retirement if that happens.
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Quoting RTSplayer:



There's a meso-cyclone in there, and possible weak disturbance.
because it appears to be dying quickly.

Thanks, RIPcaster! :) I'll stick around to watch it 'die'
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"Caribbean Cruiser" is still on the table.
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1408. SLU
Quoting SLU:
Very rare for a storm at 13n 30w to reach the islands


Goes to show you how anomalously strong the ridge is expected to be.
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1407. SLU
Very rare for a storm at 13n 30w to reach the islands
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1406. Grothar
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Quoting TampaBayStormChaser:
Torrential Rain and DAMAGING winds of 40-50 mph here near Tampa Bay on the north side of St. Pete with a strong storm over the bay. Trees are swaying hard with branches flying off trees. Wind damage is likely with this storm. Small trees have been partially uprooted in the area.


The NWS hasn't noticed yet.

There isn't even a watch box up, never mind a warning box...
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Quoting Grothar:
I don't like working the morning shift on here. We post all the models, post all the images, see all the trends. Then everyone comes on later and starts writing, "Hey look what I found" LOL


I know lol.
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Quoting Grothar:
That's not good. It appears we could be looking at a Cat 3 or 4 very soon.




THIS COULD BE WORSE THAN IRENE!
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1402. ryang
Quoting Tropicsweatherpr:
A good jump of reforming center more north.


18/1200 UTC 13.2N 30.0W T1.0/1.0 94L -- Atlantic


The GFS actually shows that northward jump, then it takes a dive to the WSW (around 40W) under the strengthening subtropical ridge.
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1401. WxLogic
Good Morning... Things could be heating up even further soon.
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Quoting TampaBayStormChaser:
Torrential Rain and DAMAGING winds of 40-50 mph here near Tampa Bay on the north side of St. Pete with a strong storm over the bay. Trees are swaying hard with branches flying off trees. Wind damage is likely with this storm. Small trees have been partially uprooted in the area.


Stay safe!
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1399. Grothar
I don't like working the morning shift on here. We post all the models, post all the images, see all the trends. Then everyone comes on later and starts writing, "Hey look what I found" LOL
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Quoting redwagon:

Hey, what's that round thing at N19 W79?



There's a meso-cyclone in there, and possible weak disturbance.

Yesterday, some of the models had a weak low moving NW out of that area, and crossing W. Cuba into the Gulf.

I'm talking like "invest" strength or TD at most, and it was only one or two models.

The newer model runs either killed it right away, or never initialized it, which is good, because it appears to be dying quickly.
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One of the 18Z
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Quoting redwagon:

I mean that small round thing under Cuba that's about to shoot the gap.



That round thing.
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When will 94L be an actual trackable real eye present system?
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1393. Grothar
Quoting ProgressivePulse:


Morning Gro. 94L swinging around to the left today. I think this may end up being a threat to landmasses down the line.


It sure looks that way. The newer models keep in much further South than earlier runs and much longer to the West. By 8 days it does look like it could take a swing more to WNW or even NW. He looks like he could be a big one, too.
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Quoting redwagon:

Hey, what's that round thing at N19 W79?

I mean that small round thing under Cuba that's about to shoot the gap.
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Quoting ryang:
94L certainly has my attention. Tomas caused a lot of damage here in 2010, so if this system strengthens as much as the models show, well we'll have a VERY BIG problem.
Very good point.It wasn't a strong cat 2 but caused big problems for the islanders in terms of flooding and moderate wind damage.Looks like the GFS sends you all a Major.Don't take it into account as this is still a ways out.
Member Since: December 31, 1969 Posts: Comments:
Look at these "weird" typhoon tracks:

Note: Yes, this is one storm...



and



and




cyclone



Talk about a headache.

I think one of them was tracked for 22 days. Sickening...
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1389. Grothar
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1388. pottery
Quoting ryang:
94L certainly has my attention. Tomas caused a lot of damage here in 2010, so if this system strengthens as much as the models show, well we'll have a VERY BIG problem.

I'm not surprised!
By this evening everyone in the Islands will have heard of this.....
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Quoting Grothar:
Would anyone like to see my Tceps?





Morning Gro. 94L swinging around to the left today. I think this may end up being a threat to landmasses down the line.
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94L is doing good
Link
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A good jump of reforming center more north.


18/1200 UTC 13.2N 30.0W T1.0/1.0 94L -- Atlantic
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1383. sar2401
Quoting SFLWeatherman:
Q. If 94L to the U.S as a Hurricane
A. FL
B. GA
C. SC
D. NC
E. NY


B through E would be my guess, although I'm not convinced 94L will ever be a CONUS hurricane.
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1382. ryang
94L certainly has my attention. Tomas caused a lot of damage here in 2010, so if this system strengthens as much as the models show, well we'll have a VERY BIG problem.
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1381. Grothar
Quoting pottery:

Lets not go there !

But yeah, this one looks Ominising....


LOL.
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Quoting pottery:

Well, there's always East.......
Maybe in the southern hemisphere.... :)
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Q. If 94L to the U.S as a Hurricane
A. FL
B. GA
C. SC
D. NC
E. NY
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1378. Grothar
Would anyone like to see my Tceps?



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Quoting RTSplayer:
This...



with this






vs this


Hey, what's that round thing at N19 W79?
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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...

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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