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 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


Yes, but it also tends to be more troll free.
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1475. LargoFl
Quoting SFLWeatherman:
8Am not good for S FL!!
..whew we must watch THIS one closely, wow
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Not to bad!
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Could Gordon be turning annular?
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Quoting LargoFl:
yes even over here to florida..got some storms about to move in as i write this..hope no water spouts etc...winds picking up now



Already storms everywhere
Quoting bayoubug:
Yea we had 2.45 in about 30 mins here in st.charles parish..Going to cut wet grass now.


We didn't get a lot the outflow kinda missed us
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8Am not good for S FL!!
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Quoting weatherh98:


South of Hammond lousiana so directly west of me abOut 30 miles


Yeah.


I gave it some thought, and it's possible the storm was weak enough to be under the radars from Baton Rouge and Nola, if the circulation wasn't especially deep, because that was Spring in 2003, but how would I know, since I was inside the house.

We opened the door to look at it since it was obviously not strong enough to tear down the house, but it was so strong it would yank the door back out of your hand.

We had floodlights and flashlights, so we could see the rain.

Obviously they didn't have Dual-Pol radars then, and the updates online were nowhere near as fast or accurate. A lot of improvements have been made since the 2005 hurricane season.

But I can still go back to the forest behind the house and point to some of the trees and tops that were blown down by that storm, 2 years before Katrina even happened. It actually destroyed more trees in the immediate area than the hurricane.

However, Katrina defoliated more stuff near the roads where there is open air for the wind speeds to pick up...

But between our property, the guy behind us, and my brother, the "thing" did more tree damage than Katrina.

My brother's house got hit by a tree fall from Katrina, but it only barely punctured the wall, nothing too major. Plus that was probably a water-assisted tree-fall, as the creek came up so high that the water may have undermined the roots...

Anyway, I'm getting on another subject entirely.


The tornado thingy was pretty bad to have gone un-detected by NWS.

If it had passed directly over a house trailer, somebody might have been killed or injured.

We live in a foam paneled, brick house, so it takes about 150mph sustained to damage this thing significantly. The roof could peel and it probably wouldn't even matter inside the house...though I wouldn't want to test it.
Member Since: December 31, 1969 Posts: Comments:
1469. SLU
684

WHXX01 KWBC 181319

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1319 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



DISTURBANCE INVEST (AL942012) 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 12.3N 27.7W 13.3N 29.8W 14.0N 32.7W 14.9N 36.3W

BAMD 12.3N 27.7W 12.8N 30.4W 13.4N 32.9W 14.0N 35.2W

BAMM 12.3N 27.7W 13.4N 30.3W 14.3N 33.2W 15.1N 36.4W

LBAR 12.3N 27.7W 12.9N 30.6W 13.3N 33.7W 13.8N 36.9W

SHIP 25KTS 33KTS 41KTS 50KTS

DSHP 25KTS 33KTS 41KTS 50KTS



...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 15.4N 40.7W 15.5N 50.8W 13.4N 58.8W 10.6N 61.8W

BAMD 14.6N 37.7W 15.7N 43.0W 16.9N 47.2W 18.8N 48.9W

BAMM 15.7N 40.0W 16.3N 48.5W 15.4N 56.6W 13.3N 62.1W

LBAR 14.3N 40.4W 14.5N 48.3W .0N .0W .0N .0W

SHIP 58KTS 75KTS 90KTS 105KTS

DSHP 58KTS 75KTS 90KTS 105KTS



...INITIAL CONDITIONS...

LATCUR = 12.3N LONCUR = 27.7W DIRCUR = 280DEG SPDCUR = 14KT

LATM12 = 11.9N LONM12 = 25.1W DIRM12 = 278DEG SPDM12 = 16KT

LATM24 = 11.5N LONM24 = 21.9W

WNDCUR = 25KT RMAXWD = 50NM WNDM12 = 20KT

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

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



$$

NNNN

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Quoting floridaboy14:
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
Thing is, I - and others - have been noting that GFS has been getting better at the long range IF consistency is displayed... not saying the 10-day outlook = DOOM for any unfortunate parties under the gun, but repeated forecasts suggesting such an outcome do imply that at least a heightened awareness of the possibilities is advisable...
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1467. Grothar
Quoting NEFLWATCHING:

just kidding! I am almost as old as you. In other words, i was around when they invented dirt...


I know you were. Just joshing back.
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1466. LargoFl
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1465. SLU
Quoting islandgirls:
Good morning all. I see there's much excitement re: 94L
where the Lesser Antilles comes into focus. What are the chances of it affecting the Northern Antilles, more particularly Guadeloupe to Anguilla?

Anticipating a response

Thanks


Very high.
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Quoting weatherh98:


Whole northern gulf to Florida looks like it will light up
Yea we had 2.45 in about 30 mins here in st.charles parish..Going to cut wet grass now.
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1463. LargoFl
Quoting weatherh98:


Whole northern gulf to Florida looks like it will light up
yes even over here to florida..got some storms about to move in as i write this..hope no water spouts etc...winds picking up now
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But, I do agree with Levi's prior assessment on a re-curve between 65-80. Personally think it will be closer to the 75-80 mark.
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1461. LargoFl
THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
AND SOUTHWEST ARKANSAS...NORTH CENTRAL AND NORTHWEST
LOUISIANA...SOUTHEAST OKLAHOMA...AND EAST AND NORTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT...

UPPER LEVEL DISTURBANCES MOVING SOUTHEAST INTO THE AREA OVER A
NEARLY STATIONARY FRONTAL BOUNDARY WILL PRODUCE SHOWERS AND
THUNDERSTORMS. A FEW OF THESE STORMS WILL BE STRONG TO SEVERE
PRODUCING DAMAGING WINDS...LOCALLY HEAVY DOWNPOURS...AND ISOLATED
LARGE HAIL. THERE WILL BE SEVERAL OF THE UPPER DISTURBANCES AND
NOT JUST ONE ROUND OF POSSIBLE CONVECTION PERIODS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY...

STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS THE REGION
SUNDAY AS THE FRONTAL BOUNDARY STARTS TO MOVE SOUTH IN RESPONSE TO
UPPER DISTURBANCES MOVING INTO THE BASE OF AN UPPER TROUGH. BY
LATE SUNDAY NIGHT INTO EARLY MONDAY...RAIN AND THUNDERSTORMS WILL
END FROM WEST TO EAST AS THE FRONT MOVES TOWARD THE GULF COAST.
DAMAGING WINDS...ISOLATED LARGE HAIL EVENTS...AND HEAVY DOWNPOURS
WILL BE POSSIBLE UNTIL THE STORMS MOVE OUT OF THE AREA. WITH HIGH
PRESSURE AND DRIER AIR MOVING INTO THE FOUR STATE REGION...THERE
WILL BE A BREAK IN THE RAINFALL UNTIL RAIN RETURN TOWARD NEXT WEEKEND.

.SPOTTER INFORMATION STATEMENT...

THE ACTIVATION OF HAM RADIO OPERATORS,,,SPOTTER NETWORKS...AND
EMERGENCY MANAGEMENT MAY BE NECESSARY TODAY AND TONIGHT.

$$
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Quoting LargoFl:
ok ty..be careful over there ok..going to be a bad day for all of us i think


Whole northern gulf to Florida looks like it will light up
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Quoting RTSplayer:


"Florida Parishes" region in Louisiana.



Yeaa buddy
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1458. LargoFl
Quoting RTSplayer:


"Florida Parishes" region in Louisiana.
ok ty..be careful over there ok..going to be a bad day for all of us i think
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Quoting Grothar:


It's not good to make too much sense this early in the morning.

The academic types roll in around 11a and work until 8p or so. The early morning and late night crew can get a word in edgewise :)
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Quoting LargoFl:
..RTS where are you located?


South of Hammond lousiana so directly west of me abOut 30 miles
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Quoting RTSplayer:



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.
It's really pretty difficult to get a cat 3 storm into the NY area. Keep in mind the storms approaching the NC coast have had at least some support from Gulf Stream warmth. Nevertheless, there have been some consistently warmer than average water in that area between NY and NS... so a New England hurricane redux might be possible.

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Quoting Grothar:


It's not good to make too much sense this early in the morning.



Yeah, your right. I have too much blood in my coffee stream this morning ;b
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Quoting LargoFl:
..RTS where are you located?


"Florida Parishes" region in Louisiana.
Member Since: December 31, 1969 Posts: Comments:
Quick question for you guys… I have just recently moved to Charleston S.C. and I was wondering if I should be worried about 94L??? I have never lived by the ocean before and I obviously have never experienced a tropical storm or hurricane before. The funny thing is I always wanted to experience what one would be like but I don’t want to be blown away by a Cat. 3 or higher. I guess I have mixed feelings about it.
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1451. LargoFl
...............Jedkins..you online yet?
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1450. LargoFl
Quoting RTSplayer:



Don't take it personally, it happened to me once.

"Something" tornadic passed right over our house, up-rooted the okra in the garden, beat all the plants down worse than Katrina, and uprooted or topped several trees in the forest behind our house.

I'm serious, the grass and flowers around the house were beat down in a spiral even the next morning.

It was black as night in the mid-afternoon, and raining about as hard as I've ever seen.

The Weather Channel said "Fair Skies" for the current conditions.


Ironically, we did not lose power, though the lights flashed off several times.
..RTS where are you located?
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Good morning all. I see there's much excitement re: 94L
where the Lesser Antilles comes into focus. What are the chances of it affecting the Northern Antilles, more particularly Guadeloupe to Anguilla?

Anticipating a response

Thanks
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1448. Grothar
Quoting ProgressivePulse:


On the flip side of the mornings conversation and looking at the current facts, I agree. For one, there is no storm yet and only a 40% of one developing. For two, there is still a great possibility that it re-curves well east of the islands. If it we me, I'd wait till the NHC at least gives it a High Chance. I'd imagine you'll start to hear more chatter at the start of the work week.


It's not good to make too much sense this early in the morning.
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Quoting Grothar:
Another one ready to go for a swim. Hey, who was the guy who wrote that there wouldn't be much of a Cape Verde season this year. That the Atlantic would shut down?



Well Gro two, Klotzbach/Gray.
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Quoting Grothar:


That hurt!

just kidding! I am almost as old as you. In other words, i was around when they invented dirt...
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Quoting TampaBayStormChaser:

yes it did weaken quickly but I did see a low hanging cloud with the cell...I can't say if it became tornadic but it was there.



Don't take it personally, it happened to me once.

"Something" tornadic passed right over our house, up-rooted the okra in the garden, beat all the plants down worse than Katrina, and uprooted or topped several trees in the forest behind our house.

I'm serious, the grass and flowers around the house were beat down in a spiral even the next morning.

It was black as night in the mid-afternoon, and raining about as hard as I've ever seen.

The Weather Channel said "Fair Skies" for the current conditions.


Ironically, we did not lose power, though the lights flashed off several times.
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Quoting Grothar:
Another one ready to go for a swim. Hey, who was the guy who wrote that there wouldn't be much of a Cape Verde season this year. That the Atlantic would shut down?



Jeff masters the NHC and yes Cody Fields
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Quoting Grothar:
I just happened to have this lying around.



You act like you know what your talking about Gro? Posting all these interesting maps and such.
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1442. LargoFl
Hmmmm the weather here by me is getting very interesting, dark clouds all around, but not a drop of rain yet by my house..i see a good one gearing up to come onshore shortly..might get some bad weather here in pinellas..............
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ISLANDERS 6 DAYS TO ISAAC ARRIVAL. BARRING A MIRACULOUS RECURVE.
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Quoting Tropicsweatherpr:
Good morning. Here is the San Juan NWS take on this.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
506 AM AST SAT AUG 18 2012


THE ELEPHANT IN THE KITCHEN...SO TO SPEAK...IS THE GFS FORECAST OF A
HURRICANE PASSING BETWEEN CULEBRA AND SAINT THOMAS LATE SATURDAY.
THIS CAUSES NORTHEAST FLOW AT THE SURFACE TO BEGIN THURSDAY AND
STRENGTHEN FRIDAY AND SATURDAY. ENSEMBLE SOLUTIONS SHOW A WIDE
RANGE OF TRACKS AND THE GFS LIKELY HAS NOT STABILIZED SUFFICIENTLY.
THE GFS TRACK SOLUTION WAS WELL TO THE NORTHEAST OF THE ISLANDS 24
HOURS AGO AND THE 18Z RUN SHOWED THE STORM PASSING TO THE SOUTH A
LITTLE EARLIER...BUT AM UNABLE TO LOAD MOST OF THE PARAMETERS FROM
THIS...18/00Z...MODEL FORECAST PACKAGE DUE TO THE UNCERTAINTY YET IN THE
FORECAST AND THE SEVERITY OF THE CONDITIONS FORECAST...EVEN FOR A
SYNOPTIC SCALE MODEL. SOME CHANGE TO THE TRACK IS LIKELY AND IT IS
IMPOSSIBLE TO TELL IF THIS WOULD TAKE THE CYCLONE NORTH OR SOUTH
OF THE AREA...ALTHOUGH FORMATION IN THE NEXT 72 HOURS SEEMS MORE
LIKELY THAN IT WAS YESTERDAY. THEREFORE WILL SIMPLY SAY THAT THIS
SOLUTION IS PLAUSIBLE AND PRELIMINARY SEASONAL PREPARATIONS SHOULD
BE COMPLETED AND DOUBLE CHECKED...BUT NO CONFIDENCE CAN BE GIVEN
TO THE CLOSE-PASSAGE SCENARIO YET.


Ahhhhh....nothing like sitting down for my morning coffee and reading THIS! *cleans up the keyboard*
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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


HEY LOOK WHAT I FOUND
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1438. Grothar
Another one ready to go for a swim. Hey, who was the guy who wrote that there wouldn't be much of a Cape Verde season this year. That the Atlantic would shut down?

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Quoting gugi182:
There still not talking in the local newspapers here in Puerto Rico about 94L must be waiting until a couple of days now to alarm the citizens of PR or other Caribbean islands. This looks like our first MAJOR HURRICANE. Crossing my fingers for it to go out to sea. But that scenario looks to be fading away as every advisory comes up.


On the flip side of the mornings conversation and looking at the current facts, I agree. For one, there is no storm yet and only a 40% of one developing. For two, there is still a great possibility that it re-curves well east of the islands. If it we me, I'd wait till the NHC at least gives it a High Chance. I'd imagine you'll start to hear more chatter at the start of the work week.
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1436. Grothar
Quoting NEFLWATCHING:
Tceps, Gro? In your case would thaat be triceps, or triceratops?


That hurt!
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1435. Grothar
I just happened to have this lying around.

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1433. gugi182
There still not talking in the local newspapers here in Puerto Rico about 94L must be waiting until a couple of days now to alarm the citizens of PR or other Caribbean islands. This looks like our first MAJOR HURRICANE. Crossing my fingers for it to go out to sea. But that scenario looks to be fading away as every advisory comes up.
Member Since: December 31, 1969 Posts: Comments:
Tceps, Gro? In your case would thaat be triceps, or triceratops?
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If that were to happen we'll be hearing Isaac's name in the history books for years to come and it'll be the new benchmark for hurricanes.I'm not buying it for now as the models have shown storms plow into the coast only to go harmlessly out to sea.I remember that the models showed Fiona as a cat 5 cane slamming into Charleston S.C only to be a sheared weak system.Goood times..good times...
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Assuming it develops as modeled, 94L will be a major threat to the Antilles as outlined in Dr. Masters blog writing, maybe both the Lesser and the Greater.
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Quoting TampaBayStormChaser:

If you play the velocity radar for tampa...you will see the storm pulse up and create an area of light green that is consistent of 60 mph aloft which would be 40-55 mph surface wind gusts with the cell over the bay that just moved into hillsborough
Link
You can see the pulse of light green = 55 kt aloft so 40-50 kt surface right over the bay which then propagated northwards into NE st.pete




I know, I saw it.

I suspect you may have an EF0 tornado in the area, because the green is embedded in reds...

Possible water spout that hit land?

It seems to have come down in wind speed about 10 to 20mph from it's max though...
Member Since: December 31, 1969 Posts: Comments:
Quoting BahaHurican:
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...
Ridge does not look as strong as earlier in the season, unless it get a big reinforcement.
Member Since: December 31, 1969 Posts: Comments:
1427. Grothar
I hope you all have one of these.

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Quoting ryang:
Steering for 94L


It gets pulled around in circles and lives forever.
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Category 6™

About

Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather