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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Quoting CyberStorm:


the joke is on you.He called it 4 days ago.i saw him when he did it and everyone said HUH?no models showed it and no one took it serious.now look.

Yeah, surrrrre.
I suppose that if we had all listened to Mr Stormtop, all of those lives in danger in Galveston, Houston, Lake Charles, Alexandria, Lafayette, NOLA, Slidell, Jackson, Bay St. Louis, Biloxi, Pascagoula, Montgomery, Mobile, Pensacola, and Destin would be safely evacuated to Minneapolis to be safe from the big bad 91L.
Whatever. Soak it up if you like it.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
3613. Drakoen
Hurricane models take it into the Panhandle region
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Looks to be headed NW in this longer radar loop. The steering currents earlier had 91L moving NW for the next day with a bend to the WNW 12-24 hours before landfall. The further west it goes, the worse it will be. I could honestly see a minimal hurricane coming out of this if it were to manage to go as far west as NOLA. Believe a strong TS with a landfall between MS and Panama City is more likely though.

Link
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Quoting Drakoen:
I have to give props to Patrap who has been tracking the GOM blob all day. Seems we may get Claudette out of this. Hurricane models making this a strong TS.
any idea on direction?i see a more north movement but the models are pointing WNW.It doesn't make sense
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Quoting Stormchaser2007:
With 91L possibly hitting NOLA, is there a possibility of levee breach? I remember hearing something about the city being so vulnerable after Katrina that a TS could flood some of the city. Have the levees been fixed? This was years ago I heard this.
I guess if they survived Gustav....
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3608. KEEPEROFTHEGATE (Mod)
T.C.F.W.
GOM
POSS WITHIN NEXT 12 HRS OR LESS
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting tennisgirl08:
TAZ - where is 91L going??



i think you no where its going



have a good night



looking forword to what AM has


and oh 3 name storms now with olny a few days time???
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3606. Drakoen
I have to give props to Patrap who has been tracking the GOM blob all day. Seems we may get Claudette out of this. Hurricane models making this a strong TS.
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I've always liked Stormtop, it's like adding hot sauce to red beams & rice.
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Anybody got a 'proprietary algorithm' in their back pocket? harrumph!
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3602. KEEPEROFTHEGATE (Mod)
Quoting Patrap:


I think we will see the pinhole eye by dawn on this one Tazaroo..
yeah pat i like to think of it this way

its the tropics ...an its august anything can happen anywhere anyplace anytime
Member Since: July 15, 2006 Posts: 169 Comments: 53296
The NOGAPS, along with the HWRF, has now shifted way south on Bill from it's 18z run.

https://www.fnmoc.navy.mil/wxmap_cgi/dynamic/NGP/2009081600/ngp10.sfc10m.120.atlantic.gif
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i may wake up to a TD or TS in the AM
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TAZ - where is 91L going??
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Quoting caribbeansurvivor1:
Anna's going a little south and will be next to GOM in 72 hrs...


Ana will not survive to make it in the GOM.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
3597. RyanFSU
Hypercane WRF doomcast model has also delivered for 91L to whip up into a 990 mb likely strong tropical storm before landfall late Sunday night.

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Quoting Vortex95:


Hopefully it doesn't hit tally I'm goin up there in a few days.



I'm going back to tally by the 18th.
Member Since: July 27, 2009 Posts: 0 Comments: 96
We will definitely see a TD by 5am. And a TS maybe later sometime on Sunday. So, can anyone speculate as to maybe where this thing is going?
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Quoting Vortex95:


Its not that you don't know anything but you are the biggist doomcaster this blog has had.

And that's why alot of people here have him in our ignore lists
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Anna's going a little south and will be next to GOM in 72 hrs...
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Quoting atmoaggie:

I am laughing at you. And I will be for some time to come. HWRF says 55 mph TS, so it will really be a 40 mph TS. Dangerous? Still not measured to be a closed low.
No, not on board (you just hinted that your office really is that pic I put up a couple of nights ago).


the joke is on you.He called it 4 days ago.i saw him when he did it and everyone said HUH?no models showed it and no one took it serious.now look.
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this is not good


this 91L could TD in the AM and strong TS or cat 1 hurricane by noon
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3590. Patrap
Quoting Tazmanian:



is it me or dos that rader show a eye like thing


I think we will see the pinhole eye by dawn on this one Tazaroo..
Member Since: July 3, 2005 Posts: 420 Comments: 127536
Quoting TexasHurricane:


About when would that be?

Like it says, 144 hours after 00 UTC today (Sunday)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Congrats to StormTop for getting this right. He was predicting this from the start.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
Quoting RyanFSU:
00Z Hypercane WRF forecast doesn't disappoint with a full-fledged Category 5 or 6 hurricane (fish storm). Still North of Puerto Rico.






when did they decide to make a Cat 6???? Isn't Cat 5 open ended??
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3585. Patrap

NEXRAD Radar
Tampa, Storm Relative Mean Radial Velocity 0.50 Degree Elevation Range 124 NMI


Member Since: July 3, 2005 Posts: 420 Comments: 127536
Quoting stormno:
NOW PEOPLE WHOS LAUGHING AT ME NOW I GUESS ALL OF YOU ON BOARD NOW...I SAID IT WAS A CLOSED LOW AT MY 930PM ADVISORY...IM TELLING YOU FOLKS THIS IS A DANGEROUS SITUATION DEVELOPING AND YOU BETTER TAKE IT SERIOUSLY...Stormno

I am laughing at you. And I will be for some time to come. HWRF says 55 mph TS, so it will really be a 40 mph TS. Dangerous? Still not measured to be a closed low.
No, not on board (you just hinted that your office really is that pic I put up a couple of nights ago).
Member Since: August 16, 2007 Posts: 6 Comments: 12461
I think the NHC has been to acting to slow with 91L. Some people may be waking up to a TS in the morning. A lot of people sleep late on Sunday.
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Hmmm, the NHC is saying the Florida gulf coast should monitor this. Kind of weird they didn't mention Alabama, Mississippi, or Lousiana.

SATELLITE AND RADAR DATA INDICATE THAT A SMALL AREA OF LOW PRESSURE
IN THE EASTERN GULF OF MEXICO...CENTERED ABOUT 80 MILES SOUTHWEST
OF TAMPA...IS BECOMING BETTER ORGANIZED AND MAY BE DEVELOPING A
CLOSED SURFACE CIRCULATION. ENVIRONMENTAL CONDITIONS ARE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AND THERE IS A HIGH CHANCE...GREATER
THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
SOMETIME TODAY. THIS SYSTEM IS EXPECTED TO MOVE NORTHWESTWARD OR
NORTH-NORTHWESTWARD AT ABOUT 15 MPH TODAY. INTERESTS ALONG THE GULF
COAST OF FLORIDA SHOULD CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
Quoting stormno:
NOW PEOPLE WHOS LAUGHING AT ME NOW I GUESS ALL OF YOU ON BOARD NOW...I SAID IT WAS A CLOSED LOW AT MY 930PM ADVISORY...IM TELLING YOU FOLKS THIS IS A DANGEROUS SITUATION DEVELOPING AND YOU BETTER TAKE IT SERIOUSLY...Stormno


Im in New Orleans, what to expect?
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Quoting superweatherman:
dam I good... i told weather456 and everyone that 91L will be at red tonight and at 8am it will be a TD and a TS by 8pm sunday
It looks like 91L is heading more NNW than N.W. thoughts???? Whatever it ends up being this looks like a soaker for The Big Bend Of Fla.
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Link
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3578. KEEPEROFTHEGATE (Mod)
T.C.F.W.
GOM
POSS WITHIN NEXT 12 HRS OR LESS
Member Since: July 15, 2006 Posts: 169 Comments: 53296
3575. RyanFSU
00Z Hypercane WRF forecast doesn't disappoint with a full-fledged Category 5 or 6 hurricane (fish storm). Still North of Puerto Rico.




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Quoting Patrap:



is it me or dos that rader show a eye like thing
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Quoting Elena85Vet:


It's red now. Just a little delay.
Quoting stormsurge39:
Im confused, why is there a yellow circle on the NHC site for 91L?

It's all red now.
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I see RED
Member Since: July 18, 2009 Posts: 0 Comments: 306
3568. Patrap
Member Since: July 3, 2005 Posts: 420 Comments: 127536
Quoting TexasHurricane:


hmmmmm.SW LA - I'm in SE TX about 10-15 min. from LA border.


Don't worry the CMC is not a very good model.
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Member Since: July 18, 2009 Posts: 0 Comments: 306
dam I good... i told weather456 and everyone that 91L will be at red tonight and at 8am it will be a TD and a TS by 8pm sunday
Member Since: July 18, 2009 Posts: 0 Comments: 306
Quoting stormsurge39:
Im confused, why is there a yellow circle on the NHC site for 91L?


It's red now. Just a little delay.
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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.