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 jipmg:
if there are any recent quick skats on BILL it would be aprreciated if someone could post them

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4113. IKE
Buoy at 28.5N and 84.5W....

Wind Direction (WDIR): ESE ( 110 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 17.5 kts
5-day plot - Wind Gust Wind Gust (GST): 21.4 kts
5-day plot - Wave Height Wave Height (WVHT): 5.2 ft
5-day plot - Dominant Wave Period Dominant Wave Period (DPD): 5 sec
5-day plot - Average Period Average Period (APD): 4.5 sec
5-day plot - Mean Wave Direction Mean Wave Direction (MWD): ESE ( 108 deg true )
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES): 29.94 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY): -0.06 in ( Falling )
5-day plot - Air Temperature Air Temperature (ATMP): 82.9 °F
5-day plot - Water Temperature Water Temperature (WTMP): 86.2 °F
5-day plot - Dew Point Dew Point (DEWP): 74.1 °F
5-day plot - Heat Index Heat Index (HEAT): 89.6 °F
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting Weather456:


where?



This is the one hes talking about.

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4111. jipmg
Quoting Weather456:


where?



its clearer here:

http://www.ssd.noaa.gov/goes/east/catl/loop-wv.html
Quoting DanielPC:
WJHG meteorologist here in P.C. saying warnings could be posted for the Panhandle within the hour.


likely since the advsiory comes out at 5am
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Quoting jipmg:


look at the water vapor you can see some dry air being embedded in the circulation


where?

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Quoting Weather456:


cha-zig! lol

It's 3am at my house, I've got a gallon of fresh sweet tea, a pan of homemade rice krispy treats, a fascinating storm to watch and a chance to tell someone I told you so in a few hours. I might occasionally post something amusing.
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4107. jipmg
if there are any recent quick skats on BILL it would be aprreciated if someone could post them
WJHG meteorologist here in P.C. saying warnings could be posted for the Panhandle within the hour.
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Quoting Catfish57:
No I was talking about TD4. Guess I was wrong to assume that LLC was around that pseudo eye looking stucture in the radar


I was talking about Ana. My fault.
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Good evening to all from Pensacola. I've been a lurker and student of this blog since Ivan. First I'd like to say thanks to all of you that keep us informed and take the time to explain the complex tropics.

I still have a hard time picking out the center of a developing storm. Could someone please give there take on where the center is currently located. TIA :)
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I would like to see the NHC reasoning and forecast behind TD 4
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4102. jipmg
Quoting Weather456:


i dont see any dry air but a strengthening tropical storm.


look at the water vapor you can see some dry air being embedded in the circulation
Quoting Giga2001:

Perhaps she should've been named Monica?


cha-zig! lol
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Quoting Weather456:
Ana is exposing herself for Bill, and that's got him all fired up. Now that jus aint right.


Zing!
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Quoting FLHurricaneChaser:
Weatherstudent I know how you feel. I always wanted storms as a kid and still do. Don't worry we'll get one soon.

You could be a stormchaser like Mike Theiss and go after them yourself :)
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Quoting jipmg:


Bill has some dry air spinning on its NW side, so I dont see a hurricane until that dry air is moistened up


i dont see any dry air but a strengthening tropical storm.
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4097. TX2FL
Quoting Giga2001:
There's only one thing I can think of to say to WS's comments - Delta is ready when you are, and they'll take you to anywhere you think "the big one" is going to be.


LOL..I think WS lives in South Florida so he'll probably need to take American...
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lol...
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Quoting IKE:
It's not showing up yet on the 240NM radar out of Red Bay,FL.(near Ponce DeLeon).

This may have a good 24 hours over water unless it turns NNE to NE, which seems unlikely.


agreed
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No I was talking about TD4. Guess I was wrong to assume that LLC was around that pseudo eye looking stucture in the radar
Member Since: July 29, 2009 Posts: 0 Comments: 72
Quoting jipmg:


he is talking about Bill I think


Oh okay.
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Quoting Weather456:
Ana is exposing herself for Bill, and that's got him all fired up. Now that jus aint right.

Perhaps she should've been named Monica?
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4091. drj27
yea looks like it will hit panama city to tallahassee
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4090. jipmg
Quoting Weather456:
Ana is exposing herself for Bill, and that's got him all fired up. Now that jus aint right.


Bill has some dry air spinning on its NW side, so I dont see a hurricane until that dry air is moistened up
4089. IKE
It's not showing up yet on the 240NM radar out of Red Bay,FL.(near Ponce DeLeon).

This may have a good 24 hours over water unless it turns NNE to NE, which seems unlikely.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Ana is exposing herself for Bill, and that's got him all fired up. Now that jus aint right.
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Quoting Drakoen:


The bottom purple is the time of the pass. That was from 8hrs+ ago

I gotcha, okay, I apologize! Well that sure as hell makes more sense now with the radar showing a much more organized system than the QuikSCAT showed. I'm guessing then that it's in the process of dropping that mid-level circulation to the surface, but the data from the buoys, (Which stopped reporting at 1:48 am) indicates that it hadn't yet reached the surface as of then.. However, it looks like the radar presentation has improved over the last few hours (Even some banding features initiating to the East and NE?!), so I wouldn't be surprised to see at 5am, or the next QuikSCAT, that the circulation has finally dropped to the surface in the past 6 hours or so.

What is interesting is that the OHC increases as it moves NW, which gives even more credence to the likely prediction that this could strengthen rather quickly in the next day or so.
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I think we may just have Claudette when we wake up, or after lunch. Is it moving more NNW than NW? Is that movement forecast 2 change any? Sorry 4 the questions, but we tend 2 panic a little in SLA after the big K in '05 and then Gustav '08.
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4084. jipmg
Quoting Stormchaser2007:


The center is a good 50 miles from the convection. Its pretty pitiful right now.


he is talking about Bill I think
If the seasonal predictions of 4 named storm are true then the Atlantic hurricane season should be over with soon.
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There's only one thing I can think of to say to WS's comments - Delta is ready when you are, and they'll take you to anywhere you think "the big one" is going to be.
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My my, Bill's looking massive this morning. But TD4's impressing, too, especially since I live a block from the bay in Panama City.
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i dont see it coming further west than Apalachicola.it looks to be moving way more north than west.i see ;landfall a little east of Tallahassee as a medium tropical storm
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Quoting TampaSpin:


200 miles off shores its crazy......LOL...i put that update together as fast as i could i was watching football and baseball and after they was over logged on and wammy......i haven't been on since 8am yesterday morning...when i did a quick update on this system telling all it was developing....if you read my blog!...LOL

Well since you mentioned baseball, I can't help but brag that a little league team from my hometown is headed to the LLWS for the 2nd time in 3 years! Perhaps y'all should start recruiting future baseball players in GA?
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Quoting Catfish57:
I don't know..... Look at that significant convection winding around the center. You might be right, but I am thinking otherwise


The center is a good 50 miles from the convection. Its pretty pitiful right now.
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Quoting Weather456:
Nice



Classic clip. Better save that.
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Weatherstudent I know how you feel. I always wanted storms as a kid and still do. Don't worry we'll get one soon.
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I don't know..... Look at that significant convection winding around the center. You might be right, but I am thinking otherwise
Member Since: July 29, 2009 Posts: 0 Comments: 72
NWS Wx radio in NO broadcasting alot more trop wx info/ now..bet the boys in Miami are busy.
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Quoting Weather456:


WTH?

his meds must have worn off
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Ana convection? Where?

lol

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4069. jipmg
Bill still moving due west, and is getting organized slowly, dry air harming its Northwestern side keeping it from ramping up fast
Quoting WeatherStudent:
Ike, you lucky dawg, your about to get hit by a storm. While I on the other hand, who actually wants one, it doesn't look like that wish will become a reality anytime soon, :(


WTH?
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Quoting Giga2001:

I'm good, tomorrow will be fun when my friend in TX wakes up to TD4 in the gulf after 3 days or so of "no storms in the gulf" from him, while I said, "it's coming." I love this blog a little more every time. How's things in your corner of the world?


200 miles off shores its crazy......LOL...i put that update together as fast as i could i was watching football and baseball and after they was over logged on and wammy......i haven't been on since 8am yesterday morning...when i did a quick update on this system telling all it was developing....if you read my blog!...LOL
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he needs to watch the swirlies in his bathroom and chill
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It was like around 6 hours ago weather567.... what you think about ANA... you think it will make it by the end of the day Sunday?...The last frame in the Floater is attempting to pop some convention around it center....
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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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