Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 04:17 PM GMT on Αύγουστος 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 Stormchaser2007:
Looking much better.



Oh... My... Word...

Bill will be quite a sight to behold at full strength.
Member Since: Σεπτέμβριος 22, 2005 Posts: 18 Comments: 2343
Presslord he does look like he wants to take a walk on the wild side, but funny never the less.
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Quoting atmoaggie:

Yet no convergence? I don't think so.

You are using a dervived product. To me with convection occuring and rotation easily seen on radar, there is some form of convergence at the surface. Doesnt take a rocket scientist to figure that out.
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91L should move in a NW direction

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Quoting flsky:

Go away.
lol
Member Since: Ιούλιος 30, 2007 Posts: 0 Comments: 1474
Quoting iluvjess:
While I don't put to much faith in the insect behaviour theories, marine life does react to tropical weather conditions. The specs shut off today. Been limiting out for two weeks straight. Tonight they disapeared. Got home under a star filled sky and my dog is whining to come inside... Baldwin County, AL.
was siiting outside earlier and noticed all the stars, clear skies and the calm before the storm...
Member Since: Ιούλιος 31, 2009 Posts: 0 Comments: 324
Bouy data from earlier, as 91L passed over the FL Keys, showed a wind shift (with W winds) consistent with a passing low.

Since then the radar, CIMSS vort maps, SSTs, anticyclone forming overhead, all lead me to believe we could see TD04 by 5am.
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Quoting WeatherStudent:


No can do, man. It ain't my bathroom, that's why.

So what are doing having your picture taken in someone's bathroom and you use that as your primary picture on WU?
Wait, don't tell us--You are Al Roker and that picture is a disguise.
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3205. Drakoen
Who takes pictures of themselves in the bathroom...
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3204. Patrap
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Quoting WeatherStudent:


No can do, man. It ain't my bathroom, that's why.

I do not want to know why you are taking a picture of yourself in someone elses bathroom. Is that what you collect? Most people collect shot glasses when they travel but you collect bathroom photos? haha
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Quoting TampaSpin:
There is difintely a surface low already there with 91L

Yet no convergence? I don't think so.
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Quoting FloridaTigers:
91L doesn't even have a surface low.


Yes it does......i just checked surface wind directions at all the local bouys...there is most difinetly a surface low....
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Dean was initially predicted to be a fish storm back when he was a TS in the ECATL.
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Sitting here in Navarre just east of Pensacola, I've been watching 91 all day. I don't think tomorrows pool party is happening;)
Quoting Patrap:


I think its going to be close call on TS strength,but not out the realm of Possibility.

GOM Loop Current and Eddy's 60 Hour Model
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if 91L stalls it could be real trouble,IMO
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WE need to have a bahroom pic contest in the off season lol
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3195. flsky
Quoting KATRINABILOXIGIRL:
are those the only keys that you have your fingers centerd on? that's all you've posted since I've beenon tonight...


All that it's worth....
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3194. IMA
One more thing - sure have missed y'all, even the idiots ('cause they make me feel oh so normal and quite intelligent).

Night-night!
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Quoting Stormchaser2007:
Looking much better.



Bill is bombing out. Cat 5 by noon
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3192. nash28
Well, I think I just reconfirmed why I do not bother to post meteorlogic relevant data in here anymore.

I guess I'll just stick to my blog.
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Quoting FloridaTigers:
91L doesn't even have a surface low.

Stormtop says it does...
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8 MORE HOURS...
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3189. drj27
so hopefully the blob doesnt come to the panhandle
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Quoting WeatherStudent:


No can do, man. It ain't my bathroom, that's why.


Umm your Moms?
Member Since: Οκτώβριος 1, 2007 Posts: 81 Comments: 26511
Quoting DM21Altestic:
WS becoming the primary topic of conversation isn't annoying, it's just LOL funny.

No, you aren't.
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Quoting TampaSpin:
There is difintely a surface low already there with 91L


link?
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3185. Drakoen
Looks like a fish on the GFS 00z
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While I don't put to much faith in the insect behaviour theories, marine life does react to tropical weather conditions. The specs shut off today. Been limiting out for two weeks straight. Tonight they disapeared. Got home under a star filled sky and my dog is whining to come inside... Baldwin County, AL.
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Quoting Category5hitsNewYork:
Will Bill be a fish storm? Will Ana kill herself over the mountains of the Domincan Republic, and how strong will 91L get? I guess only time can tell. Anyone have any reasonable assumptions?


Bill will be a category5hitsNewYork... *eyeroll* what a dumb username. 91L will rapidly intensify to a 40mph TS overnight then make landfall, Ana will remain weak through the Carrib. then somehow survive to the gulf and explode, Bill will scare the coast but ultimately go out to sea.

NEXT. jk
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Quoting flsky:

Go away.
are those the only keys that you have your fingers centerd on? that's all you've posted since I've beenon tonight...
Member Since: Ιούλιος 31, 2009 Posts: 0 Comments: 324
Looking much better.

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3180. flsky
Quoting WeatherStudent:


No can do, man. It ain't my bathroom, that's why.

Go away.
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The Title of that pic, the one taken in the bathroom is "Self Contemplation"...

wow man...
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3177. jipmg
any links to the latest model runs
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91L doesn't even have a surface low.
Member Since: Μάιος 17, 2009 Posts: 0 Comments: 559
Quoting Chucktown:
What up Press? Little sigh of relief with the current thinking on Bill. Not set in stone, but nice to see 95% of the models keep Bill well offshore and out to sea. Still not out of the woods with all the other waves exiting Africa so we'll have to sea (get the pun?)
Quoting Patrap:
Central Atlantic WV Loop

this satelite view says more then a thousand words
Member Since: Ιούλιος 7, 2008 Posts: 0 Comments: 473
Quoting superweatherman:
I am given 91L TD by 8am and TS by 2pm Sunday

i think u got them mixed up....at 2am 8 am and 2 pm 8 pm are TWO'S like ex yello,orange,red chances on developments and 5am 11am also pm is when they issued advisories to td's and ts's so if they were upgrade this it would be 5am 11am than same in the pm
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3173. sfla82
My wife and I where about to cancel our little get away to the Keys at the end of next week because of the 2 storms but Ana is fading fast and is going way south now and Bill is headed out to sea!!!! The trip is still on! I can put away the hurricane kit until Sept or most likely not until next year...
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Quoting HaboobsRsweet:
WS...you def need an upgrade to your shower curtain haha. Might want to get something with just stripes or one solid color haha.


No can do, man. It ain't my bathroom, that's why.
WS becoming the primary topic of conversation isn't annoying, it's just LOL funny.
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Quoting TampaSpin:


No i believe there is a surface low.....just checked bouy data

It does look like pressures are dropping. Isn't 91L the tail end of a trough?
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3169. IMA
Quoting Elena85Vet:
Oh Oh Oh. What are the chances the wave 3000 miles away hits S. Fla?



ROFLMAO - that's my favorite today :) Have a great night, y'all. Roommate already gave up on me providing any conversation that isn't weather-related & went to bed. I think I'll do the same. Plenty of late nights to come, me thinks!
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3168. flsky
Quoting WeatherStudent:


She's right, PressLord. You do not behave your age AT ALL, bud.

Go away.
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Models change people! Don't be so quick to call it a fish, it still has a decent chance on going up the East Coast.
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3166. Mclem1
Quoting iluvjess:
SHIPS has 91L at 40 knots at lanfall. Seems fairly conservitave to me. Any flights scheduled out there in the AM?


I've never trusted SHIPS. I dont think 91L will even strengthen to TS let alone TD unless it lowers. And I'm not seeing a whole lot of evidence of that.
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There is difintely a surface low already there with 91L
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Quoting WeatherStudent:


She's right, PressLord. You do not behave your age AT ALL, bud.
O man I might die form Laughter, I cant even push 911!!!1
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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.

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