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 Drakoen:


MY Melodramatics? Please. Don't flatter yourself.
Though a 6 year lurker, I am new to posting. I noticed that Weather Student's posts have been shaded out. has he been banned?
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Quoting jipmg:


eh I dont think you should be worried, they are very far away
For now.
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485. sammywammybamy 6:04 PM GMT on August 15, 2009
Quoting tropicaltank:
Get ready for explosive development in the gulf.



WISHCASTER LISTEN TO THE NHC

PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.



um no wishcaster here..look for yourself is all i can say...the NHC isn't always perfect...
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510. IKE
Quoting Bailey1777:
Any chance the blob in the GOM gets far enough West to give us some precip in Houston?


NHC says it's moving NW. That would put it coming in around Mobile/Pensacola.

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting philliesrock:
Key West blob is growing fast...TD by tomorrow afternoon?

I don't know about tomorrow, but there is a possibility during the next 48 hours or so.
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No better SSt area in the Basin that what the GOM AOI is Heading for,,juicy,Hot and Moist
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Quoting presslord:


most sensible post of the day...


I agree - I was right in the Lion's mouth so to speak (the north eye wall of Andrew) huddled in the bathroom with my husband - it was terrifying!! Needless to say the only thing I had left after the storm were the clothes on my back.
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Lower pressures should be found in the next 6-12 hours as the low pressure begins to deepen west of the Everglades of Southern FL. As it heads further into the Gulf of Mexico formation into a tropical cyclone is possible. Wind shear is a low 5-10 knots, SSTs are roughly higher than 85F in most of the Gulf and a surface low is in the vicinity. Convection is expanding, but currently could be weakening in a cycle. The next 6-12 hours will be interesting to see if this is just a cycle or a trend towards a developing tropical system. These water temps are very high and dangerous.
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Quoting TheDawnAwakening:
GOM wave is looking very interesting and its clear that there is an area of low pressure south of Naples, FL.


Seem's to def be a surface reflection Forming there,Sliding WNW

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Quoting sammywammybamy:


I agree.. Jfv... I mean WS.. Is going Overboard..


Don't forget PE
Member Since: June 12, 2005 Posts: 6 Comments: 8186
I know that this started out as a little cloud cover yesterday and look what it has become in a very short time. We'll have to wait and see what happens. But there isn't any dry air or shear to really slow it down and it is growing up quick. maybe warrants a closer look by someone alot smarter than me. I've just began my reeducation after being on the site for a while and lurking instead of babbleing about things that I'm not sure of like other people
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Quoting presslord:


most sensible post of the day...


I went down to help clean up after Andrew. It looked like someone dropped an atomic bomb on Naranja, Cutler Bay and Homestead. I told myself then that I would never see anything like that again in my life.
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yea IKE...and I couldn't hold back any longer either...time to let the Admins handle this nutbag...
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Any chance the blob in the GOM gets far enough West to give us some precip in Houston?
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498. JLPR
Quoting Drakoen:


Large ugly banding. I can see it's low level circulation through the thin high clouds.


That is what I was thinking convection is decreasing and it doesn't look so good but I guess its circulation was enough to get the classification

as for Ana I think it could end up downgraded to a TD soon xD
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Quoting WeatherStudent:
Oh plz, Drak. As you would say, drama, drama, drama. Spare me your mellow dramatics. Go write a soap why don't you? LOL


Drak has mentioned nothing but actual facts,both systems are having issues with the dry air pockets in the tropical atlantic.Maybe this new 12z GFDL run is a sign of things to come with TD3 and like i previously said the ECMWF might not be wrong with a recurve of this system out to sea.
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Y'all need to chill on this key west blob, it's just a blob or blowup that is commom to the genesis of a tropical wave, as mentioned by the NHC the pressures remain high and strengthening if any will be SLOW to occur.....
OMG go watch Tiger play already
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Link EYW radar loop
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Actually, this area looks much more impressive than TS ana.
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Quoting indianrivguy:
cmon.. someone give me a hand.. please...

354. indianrivguy 1:34 PM EDT on August 15, 2009
I'm confused and need some help understanding something. I just watched the Tropical floater and saw a swirl emerge from the convection center.
http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

I go to the tropical pages here and see TD 3, and 90L just .5 degrees apart. Are they calling these separate systems? I had thought that 90L became TD3.. can someone help me understand this please?


Your right 90L is now TD#3 WU has not removed it from the page sorry your post was lost :)
Member Since: July 7, 2005 Posts: 0 Comments: 5306
Quoting WeatherStudent:
Given the storm's current extraordinarily low long. and lat., I very mcuh doubt that it'll be recurving on out to sea anytime soon, if at all. With no throughs in sight. As we Cubans would say ''sientate para que no te cances''. :)

how does a storm have low longitude? lol.

how can you say no troughs in site? the models are coming into agreement on there being a trough coming down to sweep TD3/Bill out to sea.
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490. jpsb
Quoting mobilegirl81:

Rapid intensification?
The ULL in the central gulf is suppost to prevent that. We shall see, but at last our little blob is getting a little (well deserved) attention. Here in Texas we need rain badly, even the grass is dying, I have my fingers crossed that we get some rain out of this.
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489. IKE
Quoting presslord:


OK...that's it...I have thus far been able to resist the urge to report this clown...no longer...


WS couldn't hold back anymore. Talk about going off the deep end.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
NexSat Africa Viz loop,next Wave Exiting
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Drak, what do you think the GOM low pressure area will do? I think it will intensify into a storm.
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12Z HWRF takes Ana right through the lenght of Cuba and in to GOM! 12Z GFDL a little south of HWRF...
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Quoting sammywammybamy:


THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE HAS BECOME
MORE CONCENTRATED TODAY OVER THE FLORIDA KEYS AND THE ADJACENT
SOUTHEASTERN GULF OF MEXICO. PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.




How fast?
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Quoting WeatherStudent:
Oh plz, Drak. As you would say, drama, drama, drama. Spare me your mellow dramatics. Go write a soap why don't you? LOL


MY Melodramatics? Please. Don't flatter yourself.
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Quoting Drakoen:


Yep. We definitely don't need a storm in South Florida. I watched Storm Stories on the Weather Channel with Hurricane Andrew and it was incredible the destruction. People were saying their last words to each as they fit their whole family in a single bathroom. Makes you wonder how people can wish for these things to come to their doorstep.


I completely agree. Been through a couple of Hurricanes now and don't want to see another. I was north of Fort Lauderdale when Andrew hit; but got to see the damage upfront and personal the day after. One storm knocked out power for 15 days. Nope, don't want anything coming in this direction. And don't wish this on anyone.
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Quoting WeatherStudent:
Oh plz, Drak. As you would say, drama, drama, drama. Spare me your mellow dramatics. Go write a soap why don't you? LOL


OK...that's it...I have thus far been able to resist the urge to report this clown...no longer...
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Key West blob is growing fast...TD by tomorrow afternoon?
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Quoting KEEPEROFTHEGATE:
WNW waters are boiling match hits striker we got fire
Get ready for explosive development in the gulf.
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Most of what I am reading says the keys area is really nothing to worry about due to high pressure etc. Right??
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GOM wave is looking very interesting and its clear that there is an area of low pressure south of Naples, FL.
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Area on the Africa coast looks very nice being supported by the upper level diffluence
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Quoting Drakoen:


Yep. We definitely don't need a storm in South Florida. I watched Storm Stories on the Weather Channel with Hurricane Andrew and it was incredible the destruction. People were saying their last words to each as they fit their whole family in a single bathroom. Makes you wonder how people can wish for these things to come to their doorstep.


most sensible post of the day...
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471. IKE
Looks like the GOM blob should head to between NO,LA to the western Florida panhandle.

Maybe stormno was right about it developing. He was wrong on it being Ana, although it looks better then Ana.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
DRAK:

I agree, both systems looks crap in IR - Bill looks okay in visible though...both lacking any convection to speak of..
Really not believing the rapid intensification on nay of these two systems.. NO way!
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my point exactly
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Quoting philliesrock:

So you think TD3's beautiful outflow and banding is unimpressive?


Large ugly banding. I can see it's low level circulation through the thin high clouds.
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While TD3 does have impressive banding features and outflow to the south and west, its eastern side is meak at best almost void of convection, with banding trying to wrap around the eastern side and cut off the dry air.
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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.