Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 4:17 PM GMT on August 15, 2009

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Tropical Storm Ana was born this morning, when the remnants of Tropical Depression Two made a comeback and organized into the first tropical storm of the 2009 Atlantic hurricane season. Ana is the latest first named storm of the season since Hurricane Andrew got its name on August 17, 1992. The two storms have some similarities, as Andrew formed in the same part of the ocean, and also struggled in its early days with high wind shear and dry air. Let's hope the similarities end there.

Ana is struggling this afternoon. After an modest burst of heavy thunderstorm activity prompted NHC to upgrade Ana to a tropical storm early this morning, Ana has run into strong upper-level winds from the west that are creating high wind shear. This shear was not forecast, and it is not clear how long it will last. The shear has acted to drive dry air into the core of Ana, destroying almost all of Ana's heavy thunderstorms. The low-level center of the storm is now exposed to view, something that often foreshadows the death of a storm. It is possible the shear will destroy Ana, and several models (the GFS and ECMWF) forecast this may be the case. However, the shear forecast calls for shear to drop into the low range, 5 - 10 knots, tonight through Tuesday. If the shear does drop as forecast, Ana should be able to moisten the atmosphere around it sufficiently to protest itself from the dry Saharan air that surrounds it (Figure 1). SSTs are 27°C today, and will increase to 28°C by Sunday. By the time Ana moves into the Bahamas, total ocean heat content rises steeply (Figure 2), and rapid intensification of Ana is possible, if the shear and dry air haven't disrupted the storm. The intensity forecast models, for the most part, predict a steady intensification of Ana to the threshold of hurricane strength five days from now. The HWRF model is on the strong side, predicting a Category 2 hurricane. The GFDL predicts a weak tropical storm five days from now, but that is because the model has Ana passing over the rugged terrain of Hispaniola, something the other models do not predict. In summary, the intensity forecast for Ana has higher than usual uncertainty, and I give equal chances that the storm will be a hurricane--or non-existent--four days from now.


Figure 1. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the north of Tropical Depression Three. Image credit: NOAA/SSD

Tropical Depression Three forms, could be Bill later today
QuikSCAT data from this morning and satellite loops revealed that the tropical wave (90L) in the middle Atlantic has finally developed a well developed surface circulation and can be classified as Tropical Depression Three. Recent satellite imagery suggests that TD 3 may already be Tropical Storm Bill. Water vapor imagery (Figure 1) shows that TD 3's center consolidated a few hundred miles south of the dry air of the Saharan Air Layer (SAL). Thus, the storm should not be affected by dry air and dust as much as Ana has been. Ana may also act to moisten the atmosphere in front of TD 3, helping protect the storm from the SAL as it edges farther north over the the three days.



Figure 2. Heat content of the ocean, in kJ per square cm. Oceanic heat content steadily increases for Ana and TD 3 as they approach the Lesser Antilles Islands. Oceanic heat content levels of 90 kJ per square cm are frequently associated with rapid intensification of hurricanes. Image credit: University of Miami.

Wind shear is moderate, 15 knots, but is forecast to fall to 10 - 15 knots on days 2 - 5. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow TD 3 to intensify steadily, and I expect the storm will be at hurricane strength by Wednesday, when it will be near the northern Lesser Antilles Islands. Most of our reliable intensity models strengthen TD 3 into a hurricane by Wednesday. Oceanic heat content (Figure 2) increases sharply just before the islands, so TD 3 could be intensifying rapidly as it moves through or just north of the Lesser Antilles on Thursday. TD 3 consolidated farther south than expected, so the track models calling for a more northerly path were probably incorrect. In particular, the ECMWF model, which had TD 3 turning sharply northwestward and missing the Lesser Antilles Islands, was probably much too far to the north in this morning's 00Z run. TD 3 will probably pass very close to the northern Lesser Antilles islands on Wednesday and Thursday.

I'll have an update Sunday.

Jeff Masters

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2864. Skyepony (Mod)
Keith's note: Sources report that the LRO team has assembled a series of polar images into a mosaic but they are refusing to release these mosaics - or the images - to interested parties - or to the public.
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im not buying the forecast for the storms right now, especially bill. I cant see a storm making such a hard turn! When is the recon flying into bill?
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I know this may be going out too far in the forecast period, but do you think that Bill could pose a threat to the Northeast, specifically the NYC area? The models are indicating that this may occur about a week and a half out.
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I think I'm gonna turn in for tonight.

Maybe we might see Bill strengthen by 5am, and who knows what Ana might do by that time.
Member Since: August 9, 2009 Posts: 10 Comments: 4898
2860. srada
Quoting Weather456:





Thats the problem, becuz its 5 days away, how much will that track will shift? More than often, the storm never ends up at the 5 day point.


BIGGEST
CHALLENGE WILL CONCERN TIMING THE ARRIVAL OF THIS FEATURE. GFS HAS
BEEN SHOWING SOME CONSISTENCY WHILE THE ECMWF HAS BEEN VERY
INCONSISTENT


Im quite confused because our local NWS is saying its the other way around with the ECmWF? Am I reading that wrong?
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2859. sfla82
Quoting 100l:
anyone thinking bill could be a fish storm?


Oh, Bill is definetly a fish storm, unless it hits Bermuda....
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If Bill does not curve SFLA is in danger:

ANA

TD3

91L

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Quoting flsky:


I can see the flashes of lightning now from DB Shores. Guess it's coming my way.

Port Orange here
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2854. Drakoen
At the present time, according to the quickscat, 91L only has an 850mb vort maximum.
Member Since: October 28, 2006 Posts: 57 Comments: 29887
Quoting HurricaneKyle:


Ike at 5 days was going forcasted to hit Florida. Bill though is very far south, It will have start moving NW by 5 AM for it to be a fish storm. Its still moving W-WSW at 260 degrees.


Yeah, I think its hilarious people are calling it a fish storm already. Leave it up to this blog. It might turn, but its way too far away to know when, where, and if.
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2852. jipmg
Quoting CosmicEvents:
I think by now it's pretty well obvious to all of us what's going to happen here. There are those that can accept and deal with it....and those of us who can not.


I dont think its obvious.. whats going to happen ?
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2851. Skyepony (Mod)
Keith's note: Sources report that the LRO team has assembled a series of polar images into a mosaic but they are refusing to release these mosaics - or the images - to interested parties - or to the public.
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...waves at patrap!

Thanks for the radar I was just looking for that..
;=)
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Quoting 100l:
anyone thinking bill could be a fish storm?




read a few commets back and you find out
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No Max Mayfield on ABC MIAMI at 11pm. must be getting some rest
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I think by now it's pretty well obvious to all of us what's going to happen here. There are those that can accept and deal with it....and those of us who can not.
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2846. sfla82
Quoting FloridaTigers:
Ana's track didn't trend further south at all. Its exactly the same almost.


You must have a diffrent track for Ana then the rest of us....LOL!
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Looks like a weak TS by the time it passes SFLA:
2843. Grothar
TO: 456
I do not enough about the dynamics. But I do not see it either. What could the models be looking at to arrive at that assumption? I look at the water vapor images and do not see anything forthcoming to justify such a quick turn. I know it has happened.
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2842. 100l
anyone thinking bill could be a fish storm?
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Quoting btwntx08:

told u what u didn't say anything


You have to see my posts earlier!
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2840. Patrap
91L


Member Since: July 3, 2005 Posts: 421 Comments: 127550
2839. Skyepony (Mod)
Keith's note: Sources report that the LRO team has assembled a series of polar images into a mosaic but they are refusing to release these mosaics - or the images - to interested parties - or to the public.
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Quoting Weather456:





Thats the problem, becuz its 5 days away, how much will that track will shift? More than often, the storm never ends up at the 5 day point.


Ike at 5 days was going forcasted to hit Florida. Bill though is very far south, It will have start moving NW by 5 AM for it to be a fish storm. Its still moving W-WSW at 260 degrees.
Member Since: August 10, 2009 Posts: 3 Comments: 672
The ECMWF had Ana hitting S. Florida for a few runs a couple of days ago. Now it takes it through "Death Valley" (Hispaniola/Cuba).
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AT 11 PM AST...0300 UTC...THE GOVERNMENT OF THE BRITISH VIRGIN
ISLANDS HAS ISSUED A TROPICAL STORM WATCH FOR THE BRITISH VIRGIN
ISLANDS WHICH INCLUDES MONTSERRAT... ANTIGUA...BARBUDA...
ST.KITTS...NEVIS AND ANGUILLA. AT 11 PM AST...0300 UTC...A
TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE U.S. VIRGIN ISLANDS. A
TROPICAL STORM WATCH REMAINS IN EFFECT FOR ST. MAARTEN...SABA...AND
ST. EUSTATIUS. A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM
CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36
HOURS.

hope for the welcomed rain and nothing more.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
i have some nic crow for the nhc
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Quoting TayTay:
Bill is large storm and it is a lot harder to predict its path and intensity. Right now it's almost impossible to forecast.
I am reminded of something I heard many years ago when hugo was approaching the south east. A met said hugo is so strong it is now making its own weather. The implication was that the strength of the storm itself was affecting its environment and that conventional factors that would normally affect its direction ceased to be as significant. Are there any mets on the blog that may assist with this concept?
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2832. Grothar
Hey AllStar, I agree!! Being a dark-haired Norwegian I wanted to marry a blond. Fell in love with a brunette. Nothing is ever written in stone. (is that a correct phrase?)
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IKE is that Jimmy and Robert in your avatar?
My LCD screen is huge it is so hard to tell for me with these high rez settings..


LOL got a question for everyone and no this is not a joke!
I have a wedding to attend in the Caicos Island on Tuesday
and it is on the beach something tells me it is going to be interesting should I cancel my trip??
Anyone care to take a stab at this hehe..
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2828. dearmas
Quoting Patrap:


What is this, I'm in Tampa FL
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Quoting IKE:
I'll never doubt you again ECMWF....on William,...er...Bill...

"THE ECMWF
WAS THE LEADER SHOWING A GRADUAL NORTHWARD TREND AHEAD OF A TROUGH
OVER THE EASTERN UNITED STATES A FEW RUNS AGO. NOW...THE REST OF
THE MODELS...WITH THE EXCEPTION OF THE UK MODEL...ARE FOLLOWING THE
ECMWF TUNE...AND ALL TURN BILL MORE THE WEST-NORTHWEST AND NORTHWEST
BY THE END OF THE FORECAST PERIOD."......


There is a chance Bill never crosses any land, except a threat for Bermuda.





Thats the problem, becuz its 5 days away, how much will that track will shift? More than often, the storm never ends up at the 5 day point.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2825. TayTay
Larger systems like Bill seem to be a lot more sensitive to steering patterns compared to smaller more compact storms.
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bill is way too far S too be a fis storm sorry i this dont see it being a fish storm
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Remember, it could shift right back. They had the ridge building in yesterday, today they have the trough sending it out to sea. Tomorrow they could have it in the Caribbean you never know.
I'm off to bed, even if its a fish it still will be impressive to watch from sea.
Member Since: August 10, 2009 Posts: 3 Comments: 672



latest quikscat no surface rotation under 91L
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Looks like Ana's gonna weaken to a depression over Haiti.
Member Since: August 9, 2009 Posts: 10 Comments: 4898
Quoting nash28:
As for Bill, we still need to wait until he deepens enough and then look at the mid to upper level steering flow in accordance to the strength. Currently, Bill is being directed in the low level flow which will drive him on a 270-275 degree heading for the next few days. As he strengthens, he will begin to feel the mid to upper level influences and that is a few days away. There is a trough expected near the Great Lakes region in a few days. The stregth, position and orientation of that front will determine the ultimate fate of Bill and a U.S. landfall.


very good point. no one has mentioned fronts until you
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Ana's track didn't trend further south at all. Its exactly the same almost.
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2817. srada
from the NWS in Wilm

LONG TERM /TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --AS OF 9 PM SATURDAY...UPPER RIDGE OVER THE SOUTHERN US WILL BEGIN
BREAKING DOWN ON FRI. SHORTWAVE TROF ROTATING AROUND UPPER LOW NORTH
OF THE GREAT LAKES WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
AND INTO THE OH VALLEY FRI NIGHT. HEIGHTS WILL START TO FALL ON FRI
BUT THE LARGEST HEIGHT FALLS OCCUR FRI NIGHT AND SAT. SUBSIDENCE
FROM UPPER RIDGE WILL LIMIT DIURNAL CONVECTION...BEST CHANCES WILL
BE ALONG THE DAILY SEA BREEZE AND PIEDMONT TROF. PRECIP CHANCES
INCREASE SAT WITH UPPER TROF AXIS OVER WESTERN NC. LOCATION OF TROF
AXIS PLACES FORECAST AREA IN AREA FAVORABLE FOR CONVECTION. BIGGEST
CHALLENGE WILL CONCERN TIMING THE ARRIVAL OF THIS FEATURE. GFS HAS
BEEN SHOWING SOME CONSISTENCY WHILE THE ECMWF HAS BEEN VERY
INCONSISTENT. HIGHEST POPS WILL BE SAT...BUT ONLY GOING 30S WHICH IS
BASICALLY CLIMO. HIGHS NEAR TO SLIGHTLY ABOVE CLIMO...WARMEST WED
AND THU...WITH LOWS RUNNING 3 TO 5 DEGREES ABOVE CLIMO.

OF MINIMAL CONCERN RIGHT NOW...BUT STILL POTENTIALLY IMPORTANT...IS
TS ANA AND BILL. NHC FORECAST...AS WELL AS MOST GUIDANCE...KEEPS ANA
SOUTH OF THE AREA THROUGH THE PERIOD. OF THE 2...BILL SEEMS TO HAVE
A BETTER CHANCE OF HAVING SOME IMPACT ON THE AREA.
GIVEN THE LARGE
AMOUNT OF UNCERTAINTY AND THE FACT THAT ANY LOCAL IMPACT WILL OCCUR
BEYOND THE END OF THE FORECAST PERIOD THERE IS NO USE CONTEMPLATING
WHERE IT MAY OR MAY NOT GO...IF IT DOES DEVELOP.
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Quoting washingaway:
I think Bill Gates is conducting experiments on Ana.


Ana is just hyperventilating because such a big and hunky guy is chasing her.
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Bill and the US Uncertain


while the NHC continues to forecast a very close area of approach to the islands.
Member Since: July 24, 2005 Posts: 407 Comments: 19076

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.