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 stormsurge39:
Its definitely moving more W of N than an hour ago.


You are looking at radar right? because I don't see that at all
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3812. Patrap
Somebody's gonna Have a Close Encounter with a Tight,Cyclone,...Possibly a Hurricane,with a Night Landfall if I did my lil quick Math Right,..

Member Since: July 3, 2005 Posts: 421 Comments: 127559
Wow.....we go from nothing to everything exploding at once. I love August and September! Claudette may very be forming in the Gulf. On radar it already looks to be at least a 40 mph ts!
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I think the bams models were taking it to Louisiana. Don't know if they still are???
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I dont know if we need to go strictly off models right now. Just watching it shows alot.
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Quoting btwntx08:

meant td 4 lol


there ya go, its moving faster than my mind

:)
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:


cant walk before you know how to crawl. It's still an invest


Agreed - just trying to see if my tired eyes are playing tricks on me :) Nice to see folks from last year on. I usually just lurk and try to learn something.
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I dont think anything is close at the surface with 91L yet
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Its definitely moving more W of N than an hour ago.
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Quoting Stormchaser2007:
At this rate Ana will be gone by tomorrow.


Yeah she needs to do something...her fast forward speed is ripping her apart.
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Quoting Giga2001:
Is it my imagination or is 91L trying to close up & form an eye?


cant walk before you know how to crawl. It's still an invest
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Models are very accurate on storms that have formed and where they are going within 1-2 days. 91L is going to the panhandle!
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3799. Patrap
NexSat GOM Day Viz to Current Night IR loop
Member Since: July 3, 2005 Posts: 421 Comments: 127559
3798. drj27
well if it hits pcb then we should be ok in okaloosa county i hope
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Quoting weatherman874:
Patrap, me and you here in New Orleans could be getting it rought Sunday night into monday if it heads NW/ WNW
I bet we get an intermediate advisory at 0200 CST. That's got to me a TD at this point.
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Quoting duprk452:


they must have been updating them b/c they were labeled 2AM but all of them were over LA


they updated! most are going into the FL panhandle
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If TD 3 forms in the GOM, what a weekend this would be
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Is it my imagination or is 91L trying to close up & form an eye?
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3793. jpsb
Quoting tennisgirl08:
I agree with the 2am model consensus. Looks to be a Panama City landfall. That would mean 91L will probably just be a TS. Not too much time left in the gulf.

The models are not showing it even close to going to NOLA.
I would forget about the models and predict landfall based on a N.W. movement. To many things happening to fast for models to keep up.
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Can't believe there are no trolls saying that 91l will "break up" or its a fish, next! lmao
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06Z Bill models ran as:

AL, 03, 2009081606, , BEST, 0, 114N, 374W, 40, 1002, TS
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Quoting tennisgirl08:
I agree with the 2am model consensus. Looks to be a Panama City landfall. That would mean 91L will probably just be a TS. Not too much time left in the gulf.

The models are not showing it even close to going to NOLA.


they must have been updating them b/c they were labeled 2AM but all of them were over LA
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Quoting KerryInNOLA:
Could we be watching the birth of Hurricane Claudette
Undoubtedly. I had a feeling about that wave when it was in Cuba-ish area a day or so, and said it had promise in my eyes. Lucky guess, for my theories don't always come to pass.
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Quoting TexasHurricane:
Nevermind...looks like the model changed for the GOM storm.


Yeah. Just get a little nervous when something hits Louisiana we're always next. Lol. Thanks for the link tho. :)
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3787. Fshhead
Evening Everyone,
WOW!! When that wave came across SE Fla. it was pretty tame. Not too windy, nice breeze actually. Rainfall was rather heavy in spots. As soon as it gets into the Gulf BAM! I sure hope this thing tracks north & the Panhandle takes one for the team cause if it heads across things could get REAL ugly...
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91L up to 35 mph

AL, 91, 2009081606, , BEST, 0, 270N, 835W, 30, 1013, LO, 34, NEQ, 0, 0, 0, 0, 1015, 90, 30, 0, 0, L, 0, , 0, 0, INVEST, M,
Member Since: July 24, 2005 Posts: 407 Comments: 19076
I would say anybody from TX/LA border to the FL. panhandle better watch this one!!!
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You've convinced me to stay awake. I'll have to send out an e-mail alert if watches are issued between Franklin County (Fla.) and Walton County. And I'm thinking watches may be issued at 4 (CDT).

Quoting homelesswanderer:


Y'all when we went to bed after the 10 oclock news on september 12,2007 there was no hint that we would wake up to a 90mph hurricane at 2a.m. on September 13. These can bottom out fast. I'm glad Humberto didn't have more time it wouldve been even worse. So this has the potential to get dangerous. Hope not but it can.
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Morning

Bill will be 45 mph at 5am

AL, 03, 2009081606, , BEST, 0, 114N, 374W, 40, 1002, TS, 34, NEQ, 60, 25, 0, 25, 1011, 200, 25, 0, 0, L, 0, , 0, 0, BILL, M,
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3782. Drakoen
I hope the NHC sent Jim the text to set up in Fort Walton Beach lol
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I agree with the 2am model consensus. Looks to be a Panama City landfall. That would mean 91L will probably just be a TS. Not too much time left in the gulf.

The models are not showing it even close to going to NOLA.
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Quoting Drakoen:
good consensus taking into the western panhandle region

You're going to have to come up with a better plan.
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At this rate Ana will be gone by tomorrow.
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Bill is now initialised at 40kts, or 45mph. So a slight increase.

Pressure of 1002mb.

Member Since: August 23, 2008 Posts: 7 Comments: 5300
91L looks like elena...Bill looks like Gloria...maybe Bastardi's right, and the pattern is like 1985...
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I got Great News...

The Good News is that TRMM is going to pass over at 7:24 followed by AQUA at 7:34 and CloudSAT at 7:36 with (get this... a 0 NM deviation from 91L's current position)

Future POES passes can be found
http://www.nrlmry.navy.mil/tc-bin/display_passes.cgi?SIZE=thumb&FILE=/SATPRODUCTS/TC/tc09/ATL/91L.I NVEST/ssmi/passtimes/passtimes.txt&STORM_NAME=91L.INVEST

The bad news is.. the data's process time is about an hour.
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Nevermind...looks like the model changed for the GOM storm.
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http://www.goes.noaa.gov/HURRLOOPS/gulfir.html

This shows the rapid explosion of convection rather well around 91 L center
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Looks more NW to me.
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3772. drj27
so everyone thinking nola now are from the panhandle to nola
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Quoting Stormchaser2007:

Wow, Bill is really growing huge! I would start praying it doesn't hit land. That looks more than a tropical storm...
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Does anybody know how many miles it is from the N Gulf Coast?
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3769. Drakoen
good consensus taking into the western panhandle region
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3768. Michfan
At its current motion im betting Panama City area for a landfall. Looks to be heading a bit N of NW on radar. I think at 5am we will have Claudette.
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Quoting jojofsu75:


I'm in Tallahassee also and just checked the local tv stations weather and they have us at 60% also. I haven't seen the 90% reported earlier (I'm not saying the other person was lying, I just can't find it).



I heard it on the evening news at 11pm but just checked the graphics on WCTV6 and they have our rain chance at 70% still. Maybe they will update it in the morning but this has seemed to catch everyone off guard.

I still don't think it has much time to strengthen. Would expect landfall, if you track the movement from Key West to west of Tampa today, to be around 4pm to 6pm tomorrow (of course, any slowing down or change of direction would change this).
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3766. Drakoen
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Quoting homelesswanderer:


Huh?? What update?


2AM model photo.

Try this link..
http://www.wunderground.com/tropical/tracking/at200991_model.html#a_topad

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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.