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:
Satellite blackout sucks... We have the radar though


LOL I agree...I said that on the previous page. It always happens when you need the satellites the most.
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Wait and see now if this thing bombs out or not I guess.
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Quoting Drakoen:
Satellite blackout sucks... We have the radar though


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2 AM TAMPA GRAPICAL MARINE FORCAST

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Quoting tennisgirl08:
I haven't really heard anyone talk about the steering currents for 91L on the blog. Any thoughts? What is pushing it NNW or more west?


The ridge to the North and East of the system should keep it on a NW path until landfall. Believe the Big Bend is a little too far east for landfall. I'd say MS/AL border to PCB is most likely. Just depends on how much of a dent it can manage to put into the ridge.
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3659. stormno
storm they are talking about fla because thats where it is right now ..i really cant say where its going until i look at my latest data...i can tell you it will be big if it takes the nw course over water for at least 36 hours 88-92 degrees will explode this thing...Stormno
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3658. Drakoen
Satellite blackout sucks... We have the radar though
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3657. Patrap
Member Since: July 3, 2005 Posts: 427 Comments: 129411
man alot of blogers are gonna get crazy cause theyre gonna say how did this form so quickly and they are be shocked
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3655. drj27
i sure hope it doesnt come to destin
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I've been watching this all day, although i thought it'd be more west, maybe it will overnight tonight
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Quoting Drakoen:
Seems we have something forming...



It does look really organized for not being anything yet. She might fire up quick tomorrow.
.
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3652. jipmg
any surface observations showing a strong surface circulation on our low off the florida coast?
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I haven't really heard anyone talk about the steering currents for 91L on the blog. Any thoughts? What is pushing it NNW or more west?
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I hate satellite blackout. It seems to always come at the wrong time when things become the most interesting.
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3649. KEEPEROFTHEGATE (Mod)
Quoting TampaSpin:
Guess i got lucky with my magic 8 ball again
TSthere been a few of us watchin it today i myself have been one pat is another and there is yourself
Member Since: July 15, 2006 Posts: 176 Comments: 55517
Quoting TexasHurricane:


What?? I have a hard time reading those maps...

GFDL at 0 UTC has 91L as a 42 knot TS in the panhandle with pressure=1006.9 mb.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Well ladies and gentlemen, have a great morning, and respecfully advice, this is not a place for having competition of who is the better forecaster, this is about to watch to prevent. There's no need of a mayor huricane to have serious damage. Many islands, including, some states can not afford having a tropical system hit. Not for the infrastructure, not for FEMA help, is JUST in people who lost everything that we have to think. Just my opinion. Good day for you all.
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Quoting Drakoen:
I can't imagine how people are gonna be if this becomes a TD at 5am. Waking up to a TD just south of you.


They are going to be extremely nauseated, like I am looking at 91L.

Hey Patrap and others. Long time no see.

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Quoting Drakoen:
I can't imagine how people are gonna be if this becomes a TD at 5am. Waking up to a TD just south of you.


I'm a bit worried not much but a bit. a family friend and I are going up there Tuesday. Me for school @ FSU, and him for his lawfirm. Hopefully we do not have to leave later which is pretty much all i'm worried about.
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Looking very interesting on Radar.

The NHC may release a speacial statement upgrading this if the current trend continues.

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Quoting atmoaggie:
EEEEEEEEEEEKKKKKKK!!!!!



What?? I have a hard time reading those maps...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
I noticed on the last sat loop here, that 91L was starting to jog left.
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Quoting extreme236:
We could have a Humberto like situation...


Lol. Nah. There's too much warning. :)
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Quoting StormThug:
im confused the models have this hitting nola but the nhc is saying florida.what's going on?


Not sure. I'm a little confused there as well. Could be referring to the close proximity to FL at the present time. However, I believe they are thinking a Panhandle hit is more likely at the present time. Who knows though. StormW was thinking a LA/MS landfall around 10pm tonight.
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3639. Patrap


Depending on her Navigating,91L can have a longer time if she Goes over Juicy SST's by WNW,..but if Nnw Holds,Apalachicola,..and over to Ft Walton should be ready to work them Boat Lines and rig for storm Tomorrow ASAP.
Member Since: July 3, 2005 Posts: 427 Comments: 129411
Most non-disappointing invest this year.
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Quoting Drakoen:
Seems we have something forming...



It's really not surprising when you think about the SSTs in the gulf. It won't take any time now for this thing to organize. Good thing land is in its way.
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EEEEEEEEEEEKKKKKKK!!!!!

Member Since: August 16, 2007 Posts: 6 Comments: 12463
3635. KEEPEROFTHEGATE (Mod)


91L/XX/XX
MARK
27.1N83.5W
Member Since: July 15, 2006 Posts: 176 Comments: 55517
Looks like a TD to me... and with it so close to land.. If I were the NHC I would issue some kind of statement about it.
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Hey Stormno werent you the one talking about something developing in the GOM a couple of days ago?
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3632. jpsb
Quoting jpsb:
Yea, that is what I am watching. I've been told not to worry about it since it does not have a surface low, but I am still watching it. lol.
Well as long as ya'll are giving out attacta boys, how bout me? The above was from page 1 or early this AM.
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3631. Drakoen
I can't imagine how people are gonna be if this becomes a TD at 5am. Waking up to a TD just south of you.
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im confused the models have this hitting nola but the nhc is saying florida.what's going on?
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Guess i got lucky with my magic 8 ball again
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Quoting CyberStorm:


click

Yay, enjoy.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
We could have a Humberto like situation...
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Looking at long-range radar loops, 91L seems to be a depression already. Probably doesn't have the winds yet to be a TS.
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3625. Patrap
I just wanna see them Name 91L..."The GOM screamer",as Claudette is so Cajun French,cher..
Member Since: July 3, 2005 Posts: 427 Comments: 129411
Ryan, if you are still about. What is it about HWRF that makes it do that? Convective parameterization too strong? Not many guesses to make, but I am having trouble coming up with more.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Yeah, PAtrap's been watching this for days...I never expected much out of it.
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Quoting MississippiWx:
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.


I thought this too, but was confused by the NHC mention of only FL being affected.
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3621. KEEPEROFTHEGATE (Mod)
Quoting stormno:
weatherman someone is going to get hurricane force winds out of this if it moves more nnw then it will be a minimal hurricane ...if it takes the nw course towards new orleans it could strengthen significantly...we will just have to see...it is a very dangerous situation that is developing though...everyone need to pay close attention to claudette...i will have more after i review the new info at 8am...Stormno
flush real hard

lol

sno your alright just get rid of the caps
Member Since: July 15, 2006 Posts: 176 Comments: 55517
Quoting stormno:
weatherman someone is going to get hurricane force winds out of this if it moves more nnw then it will be a minimal hurricane ...if it takes the nw course towards new orleans it could strengthen significantly...we will just have to see...it is a very dangerous situation that is developing though...everyone need to pay close attention to claudette...i will have more after i review the new info at 8am...Stormno


What not Pass Christian Miss?
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Quoting atmoaggie:

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.


click
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So the more west 91L goes then the more time it has to intensify... this storm could easily rise to a cat 1 if it gets as far west as New Orleans like some models predict. But like many have said in the blog, it has about a day in the gulf of mexico.
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3617. Drakoen
Seems we have something forming...

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3616. Patrap
NEXRAD Radar
Tampa, Velocity Azimuth Display Wind Profile Range 124 NMI


Member Since: July 3, 2005 Posts: 427 Comments: 129411
91L seems to be going through a rapid organization phase.
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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: 12463

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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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