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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3264. sfla82
Quoting reedzone:
Bye bye Bill? You guys are being very premature, you'll see things change with Bill, he's not going anywhere yet.


Ok...LOL
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Just curious - How many on here thinks this "Bill" will not take that north turn and stay on its course to possibly the carribean??
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Amazing the Dam bouys where the surface low is forming is not working......if you look at the wind directions a Low is just above the surface if not there......it may not be completely closed as Stormchaser just showed in his graphic but its coming very quickly.
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3261. flsky
Quoting WeatherStudent:
Sssshhhh, do not reveal does types of secrets about your own self on here that way, Chaser. Frankly, I do not even want to know about them, geeze.


Go away.
Member Since: October 24, 2006 Posts: 0 Comments: 2037
Quoting TampaMishy:
Wow thats alot for my plate!
I miss being in tampa and sarasota. Do you think you will get some rain from 91L?
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Quoting atmoaggie:

No, a met would do, smart a$$.
ULL, and mid-level vort. So what?
Anyone found a buoy with N winds? W winds? They are like fleas on a dog around there and I ain't seeing it.

Whatever dude, I have been a met for a long time. Lets go back to basics shall we? First off to even have a thunderstorm, you must have convergence. That is how you get lift and an updraft. Make sense? Even if it is small scale you still have convergence. Ok if you look at radar you can see cyclonic rotation. i do not need buoy data that is spread out over hundreds of miles when I can see an updated image every 5 minutes and watch it spin.
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Quoting DM21Altestic:
Let's take a vote: Who's been the #1 Successful Troll of the 2009 Hurricane Season on WU?


You are.
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3256. Patrap
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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
.
We are having a bagworm infestation in OKC...last time that happened we were in a recession durring the mid-late 80's around Hurricane Alan time frame...hmmm
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so we have all the bouys showing a pressure drop and winds in 2 directions so far?
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3253. Drakoen
Quoting DM21Altestic:

Stolen from July 2008...



LOL
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Quoting WeatherStudent:
Sssshhhh, do not reveal does types of secrets about your own self on here that way, Chaser. Frankly, I do not even want to know about them, geeze.


LOL

Truth hurts doesnt it bud.
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Quoting CatastrophicDL:
Tampa, the current surface features map shows that 91L is the tail end of two troughs. While the difference isn't significant yet, buoys 42021 and 42003 are showing decreased pressure. Is buoy 42099 off-line?

This time of day, all buoys will show decreasing pressure without a frontal passage.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Poor Anna the vampire storm may have received a stake through the heart. High pushing her to fast to the west while shear is pushing tops to the n.e. Bill going to have to overcome this shear eventually.
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Bye bye Bill? You guys are being very premature, you'll see things change with Bill, he's not going anywhere yet.
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Palmetto bug--large flying roach.
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I think we'll see convergence increase with 91L over the next 3-6 hours to be more inline with the divergence. TD in 6-12 hours.
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Git 'er done!
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3241. flsky
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.


Actually, I got this huge cricket or something that flew in my house when I went outside to see if a weather band was coming my way. Does this count? It's still crawling around on my living room rug!
Member Since: October 24, 2006 Posts: 0 Comments: 2037
Quoting hurricane23:
2 weak systems and a fish :(


Extremely bold prediction, how much you wanna bet?
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Dang!
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TampaSpin, please let us know what buoy has decreasing pressure. I keep on checking all the ones around the disturbance and they are all near normal, although the wind has picked up.
Member Since: August 21, 2007 Posts: 0 Comments: 317
Quoting HaboobsRsweet:

I know right...had a very tropical feel to it outside. If you have ever been through a storm you know what that tropical air feels like outside and it sure felt like that tonight.
yeah was on the phone with my mother in law who lives in Chicago...tried explaining that very thing to her and she just didn't get it...have been experiencing this since Camille..you never lose that sense of feeling for the storms.
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Quoting Drakoen:
Who takes pictures of themselves in the bathroom...


Very lonely people.
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3233. sfla82
Going to bed now!!!! RIP Ana....Bye bye Bill!!! Will check back tomorrow to see if the new wave off Africa is making any noise...
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3232. TXEER
Any of these three coming to Houston?

My natural gas generator won't be installed until the 26th...if I'm going to spend $8,000 on one of those things I want it in before we get hit again!
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Quoting DM21Altestic:
I nominate TampaMishy to be the executive/leader/president/aristocrat of this blog from now on.
Wow thats alot for my plate!
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Quoting TampaSpin:


Yes it does......i just checked surface wind directions at all the local bouys...there is most difinetly a surface low....


As of now...no surface low. Sharp wind shift but nothing yet. This was dead on with 90L in May.

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Tampa, the current surface features map shows that 91L is the tail end of two troughs. While the difference isn't significant yet, buoys 42021 and 42003 are showing decreased pressure. Is buoy 42099 off-line?
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Quoting HaboobsRsweet:

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.

No, a met would do, smart a$$.
ULL, and mid-level vort. So what?
Anyone found a buoy with N winds? W winds? They are like fleas on a dog around there and I ain't seeing it.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
3225. KEEPEROFTHEGATE (Mod)
000
FZNT02 KNHC 160307
HSFAT2

HIGH SEAS FORECAST
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0430 UTC SUN AUG 16 2009

SUPERSEDED BY NEXT ISSUANCE IN 6 HOURS
AMENDED FOR ATLC FORECAST

.WARNINGS.

...TROPICAL STORM WARNING...
.TROPICAL STORM ANA NEAR 14.4N 51.5W 1004 MB AT 0300 UTC AUG 16
MOVING W OR 270 DEG AT 15 KT. MAXIMUM SUSTAINED WINDS 35 KT
GUSTS 45 KT. TROPICAL STORM FORCE WINDS WITHIN 60 NM N
SEMICIRCLE AND 0 NM S SEMICIRCLE. SEAS 12 FT OR GREATER WITHIN
90 NM N SEMICIRCLE AND 0 NM S SEMICIRCLE WITH SEAS TO 15 FT.
.24 HOUR FORECAST TROPICAL STORM ANA NEAR 15.4N 57.5W. MAXIMUM
SUSTAINED WINDS 40 KT GUSTS 50 KT. TROPICAL STORM FORCE WINDS
WITHIN 60 NM N SEMICIRCLE AND 0 NM S SEMICIRCLE. SEAS 12 FT OR
GREATER WITHIN 120 NM N AND 30 NM S SEMICIRCLES WITH SEAS TO 18
FT.
.48 HOUR FORECAST TROPICAL STORM ANA NEAR 17.5N 65.0W. MAXIMUM
SUSTAINED WINDS 50 KT GUSTS 60 KT. TROPICAL STORM FORCE WINDS
WITHIN 90 NM NE AND 75 NM QUADRANTS...AND 40 NM SEMICIRCLE. SEAS
12 FT OR GREATER WITHIN 150 NM N AND 60 NM S SEMICIRCLES WITH
SEAS TO 20 FT.
.72 HOUR FORECAST TROPICAL DEPRESSION ANA JUST INLAND COAST
OF HAITI NEAR 19.5N 73.0W. MAXIMUM SUSTAINED WINDS 30 KT GUSTS
40 KT.
EXTENDED OUTLOOK...USE FOR GUIDANCE ONLY...ERRORS MAY BE LARGE.
.96 HOUR FORECAST TROPICAL STORM ANA OVER WATER NEAR 22.5N
78.9W. MAXIMUM SUSTAINED WINDS 35 KT GUSTS 45 KT.
.120 HOUR FORECAST TROPICAL STORM ANA NEAR 25.0N 83.6W. MAXIMUM
SUSTAINED WINDS 40 KT GUSTS 50 KT.

...HURRICANE WARNING...
.TROPICAL STORM BILL NEAR 11.3N 36.6W 1004 MB AT 0300 UTC AUG 16
MOVING W OR 265 DEG AT 14 KT. MAXIMUM SUSTAINED WINDS 35 KT
GUSTS 45 KT. TROPICAL STORM FORCE WINDS WITHIN 25 NM OF CENTER
EXCEPT 0 NM SW QUADRANT. SEAS 12 FT OR GREATER WITHIN 25 NM NW
AND SE QUADRANTS...60 NM NE QUADRANT AND 0 NM SW QUADRANT WITH
SEAS TO 15 FT.
.24 HOUR FORECAST TROPICAL STORM BILL NEAR 12.0N 41.5W. MAXIMUM
SUSTAINED WINDS 50 KT GUSTS 60 KT. TROPICAL STORM FORCE WINDS
WITHIN 60 NM NE QUADRANT...25 NM SE AND NW QUADRANTS AND 0 NM SW
QUADRANT. SEAS 12 FT OR GREATER WITHIN 60 NM N SEMICIRCLE AND 30
NM SE QUADRANT WITH SEAS TO 20 FT.
.48 HOUR FORECAST HURRICANE BILL NEAR 14.0N 46.9W. MAXIMUM
SUSTAINED WINDS 65 KT GUSTS 80 KT. TROPICAL STORM FORCE WINDS
WITHIN 75 NM NE QUADRANT...60 NM SE AND NW QUADRANTS...AND 30 NM
SW QUADRANT. SEAS 12 FT OR GREATER WITHIN 120 NM N SEMICIRCLE
...90 NM SE QUADRANT AND 45 NM SW QUADRANT WITH SEAS TO 24 FT.
.72 HOUR FORECAST HURRICANE BILL NEAR 15.5N 52.5W. MAXIMUM
SUSTAINED WINDS 75 KT GUSTS 90 KT.
EXTENDED OUTLOOK...USE FOR GUIDANCE ONLY...ERRORS MAY BE LARGE.
.96 HOUR FORECAST HURRICANE BILL NEAR 17.9N 58.5W. MAXIMUM
SUSTAINED WINDS 85 KT GUSTS 105 KT.
.120 HOUR FORECAST HURRICANE BILL NEAR 21.0N 64.0W. MAXIMUM
SUSTAINED WINDS 95 KT GUSTS 115 KT.

$$
.FORECASTER AGUIRRE. TROPICAL PREDICTION CENTER.

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the surface low appears to be about 80 miles due west of ft myers...
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3223. Patrap
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91L looks ragged, nowheres near TD status lol. Bill looks like a strong TS already, and Ana.. no comment.

Bill is not officially a fish yet, models will go back and forth, today models went fish, maybe another shift up the east coast tomorrow or Monday? We'll see. VERY premature to say Bill will go out to sea.
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Quoting btwntx08:

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



"This product is updated at approximately 2 AM, 8 AM, 2 PM, and 8 PM EDT from June 1 to November 30. Special outlooks may be issued as conditions warrant."
look at the last sentence....
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Looks like 91L may never make it off the shelf. I may just fall off the nipple if it heads to NOLA.
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Quoting HaboobsRsweet:

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
I have fallen and I Can't get up
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Quoting KATRINABILOXIGIRL:
was siiting outside earlier and noticed all the stars, clear skies and the calm before the storm...

I know right...had a very tropical feel to it outside. If you have ever been through a storm you know what that tropical air feels like outside and it sure felt like that tonight.
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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: September 22, 2005 Posts: 18 Comments: 2343

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.