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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Did everybody notice the CMC is predicting something in the GOM in the next couple of weeks...
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1363. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129838
Wow I just got home from work and I'm looking at whats out there and now I see three systems!
Member Since: July 30, 2007 Posts: 0 Comments: 1474
Quoting stormpetrol:

LMAO, BTW stormwatcher I have a bad feeling about these 2 storms , I just don't see them going that far north especially at that forward speed.
I do too. Just a "gut" feeling we are gonna get a 1-2 punch. TKO
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Quoting PensacolaDoug:
Lifted from Joe Bastardi's blog this afternoon. Enjoy!

SATURDAY 5 PM

RAPID FIRE FEEDBACK TRYING TO REV UP HOME BREW IN SOUTHEAST GULF.

I do have Gulf-a noia... the fear of a storm getting into the gulf and going haywire. I have been watching waves this year and noticed that the 2 we can look at have blown up quite a bit on the their way to the coast. A well established storm over the Fla starits could be a real problem this year, even more so than others.

Another example is occuring before our eyes as the tropical wave in the southeast gulf is organizing and quite fast. but above the surface right now. The PSU look pis vivid with the banding features

http://www.meteo.psu.edu/~gadomski/SAT_SE/anim16vis.html

I want to make sure you understand why I am like this. Humberto for instance was a product of one system that split, the eastern side resulted in Gabrielle, the bottom part of the wave got into the area that Erin below up at the last minute. TPC fell asleep, and tried to play it off as rapid development, when in reality the pressure drop was 20 mb in some 20 hours.. respectable but nothing that hasnt happened before. The problem is they wrote the wave off and did not realize that it was approaching storm intensity at 3 am in the morning when we warned our clients. It was described, by one of my friends in the field as an almost mesoscale event. True enough but it came out of a trackable wave that hit its stride. This year is like that in the gulf... fortunately this will be onshore by late tomorrow night.. Unfortunately, if it gets down to the surface and really starts feeding back, it is embedded in high pressure so a 15-20 mb drop would lead to the same kind of excuse. I am on their case about this, because Humberto was predictable if one understood what was going on. I specifically posted that evening as to WHY the convection had fallen apart in the afternoon, a situations that happened in Bob in 1991 as a weak 150mb trough crossed over the storm and capped the upward motion, but once by, off it went.

While a powerful hurricane in this area moving nnw would weaken, a weak system can intensify since its well below the threshold of maximum intensity in the eastern gulf for a storm, which north of Tampa and east of 85 west, may be a cat 2 due to the rapid cooling of water with strong east winds off land, and entrainment of dry air with a strong hurricane paralleling the coast. However a small system can ramp up to a certain level.

The system is suffering now from competition from tstorms over land, but later tonight we may see a big comeback. The Key West radar is very interesting

http://radar.weather.gov/ridge/radar.php?product=N0R&rid=BYX&loop=yes

So folks between the se tip of La and the Fla coast east far east as Cedar Key should watch close here. While one may be going bananas over Ana, and getting a thrill over Bill, there si a chance by tomorrow night we may have to fret, if this feedback and is trying to become Claudette. Given long enough odds, make the bet ( it is a bold idea)..

Lets see if we get the hatched area to go to moderate.

In the end, it may be a tool to use if we get an established system in there.


Very interesting...Thanks!
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Quoting SavannahStorm:


A, B, C, or D?
Ok, if you say so. I guess I'll choose all of the above.
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Quoting stormwatcherCI:
And with him on here they will gather even faster(with his "Avatar")

LMAO, BTW stormwatcher I have a bad feeling about these 2 storms , I just don't see them going that far north especially at that forward speed.
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Quoting stormpetrol:

You know what you are, I'll give you a hint, Its looks just your avatar!!!


Me? I wasn't talking to you.
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1356. jipmg
Quoting weatherblog:


We are definitely not out of the woods.

Anyways, the GOM shouldn't worry about Ana. If it were to head that way, it'll definitely die from passing over Cuba, Haiti, or the DR. The only threat this has it to the islands, the Bahamas, and Florida for now.


I think the models expect ana to be a weaker system not gaining much strength from now until it reaches the islands.. which is why they but it on a West track
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Quoting stormwatcherCI:
What was the question ?


A, B, C, or D?
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Bill is exploding again, likely a moderate TS by morn

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Quoting hurricane23:
If it goes over Cuba/DR its tiny circulation will be done.


Especially if it continues on that WNW track that is forecast. A slight shift south in the track would have it traversing almost the entire length of Hispanola and Cuba. That would certainly mean death for a weak storm with such a small circulation, just as you said. Then again, any small deviation north or south of that would have it over water for the majority of the time. It's something to watch.
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Quoting weatherblog:


We are definitely not out of the woods.

Anyways, the GOM shouldn't worry about Ana. If it were to head that way, it'll definitely die from passing over Cuba, Haiti, or the DR. The only threat this has it to the islands, the Bahamas, and Florida for now.
Do you mean like Ike or Gustav did ? Sorry, I am being sarcastic.
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Bill may take a Gilbert path, and intensity. Jamaica, Yucatan wake up
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Quoting surfsidesindy:

A hard choice, but I'd say definitely A
What was the question ?
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Quoting Patrap:
Not good for me, Stormpetrol,Kman,wunderkid etc if this pans out.
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Has there ever been another instance where two storms received their name on the same day? It's amazing that this has happened with the first two storms of the season!
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Quoting ssmate:
Poll Time:

1) A
2) B
3) C
4) D

I'll tally up all the votes in 20 minutes.

A hard choice, but I'd say definitely A
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Quoting RescueAFR:
Good evening...From South Fla..
Do I read the GFS and GDL correct, South Fla appears out of the woods?....at the moment for both of these storms?


We are definitely not out of the woods.

Anyways, the GOM shouldn't worry about Ana. If it were to head that way, it'll definitely die from passing over Cuba, Haiti, or the DR. The only threat this has it to the islands, the Bahamas, and Florida for now.
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Quoting jipmg:
alright so can I have a link to the forecast models


At the top of this page click on the link:
Tropical / Hurricane

http://www.wunderground.com/tropical/

Under:
Helpful Online Resources

See:
Computer model forecasts

for a list of Model sites.
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1343. BrandiQ
Quoting JupiterFL:


http://moe.met.fsu.edu/cgi-bin/gfstc2.cgi?time=2009081512&field=850mb+Vorticity&hour=Animat ion


thanks!
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1342. KEEPEROFTHEGATE (Mod)
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1341. JLPR
Quoting jurakantaino:
Bad News for us in Puerto Rico and V.I.


yep those look bad =\
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Quoting aspectre:
1152 wunderkidcayman "did anyone found out that now TS ANA is moving faster than TS BILL"

Yep, been tracking their positions to see if the two would get close enough to begin watching for the mutual interaction which would pull TSAna south and TSBill north.
Instead they've gotten 0.37degrees farther apart to nearly 15degrees of separation.
And to cap it off, TSAna has a northerward component in its mostly westward movement, while TSBill has a southward component to its mostly westward movement.

* Less than 13degrees separation


ana doesnt have that much mass to begin with
Member Since: August 22, 2006 Posts: 2 Comments: 1988
1339. Patrap
T S Bill Enhanced Infrared (IR) Imagery (4 km Mercator)

Time of Latest Image: 20090815 2045 UTC




4km Remapped Color Enhanced Infrared Imagery

Current imagery and loops of 4km remapped and color enhanced infrared (IR) imagery is displayed in an earth fixed coordinate system. IR imagery (~11 um) from five geostationary satellites are remapped to a common 4km resolution Mercator projection in an identical manner as the CIRA Tropical Cyclone Image Archive described in (Mueller et al. (2006) . These images are then centered and displayed using the nearest 5 degree latitude/longitude earth coordinate based on the most recent location and past 12-h movement. The images are also color enhanced with the coldest temperatures/highest clouds displayed as colored shades as shown in this color bar.
Member Since: July 3, 2005 Posts: 428 Comments: 129838
It's way too early to put much stock in any long range track or intensity forecast for either Ana or Bill. Let the speculation and games begin!! Gas prices are surely gonna geaux up in the next week*** "Greed is good." Gordon Gecko..........not!!
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Quoting RescueAFR:

Excellent...it would be sweet if those moments turn to hours then to days....Gotta love living in the tropics...


WORD
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting stormpetrol:

Sorry I just couldn't help it, I see so much bull here this evening the flies are starting to gather on my monitor again.
And with him on here they will gather even faster(with his "Avatar")
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1152 wunderkidcayman "did anyone found out that now TS ANA is moving faster than TS BILL"

Yep, been tracking their positions to see if the two would get close*enough to begin watching for the mutual interaction which would pull TSAna south and TSBill north.
Instead they've gotten 0.37degrees farther apart to nearly 15degrees of separation.
And to cap it off, TSAna has a northerward component in its mostly westward movement, while TSBill has a southward component to its mostly westward movement.

* Less than 13degrees separation
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Quoting BrandiQ:
Can some please post the link to the GFS model.


http://moe.met.fsu.edu/cgi-bin/gfstc2.cgi?time=2009081512&field=850mb+Vorticity&hour=Animation
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1333. BrandiQ
Quoting jurakantaino:
Bad News for us in Puerto Rico and V.I.


The link doesn't work.
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Quoting jurakantaino:
Bad News for us in Puerto Rico and V.I.


then again...



which is why...
Member Since: August 22, 2006 Posts: 2 Comments: 1988
NHC putting track now West of Florida Keys...too far out folks, but you get the drift, more and more west means one thing, GULF storm
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1329. gtownTX
Just one of the millions of earthlings who pay attention to weather and learning what I can. Storm tracking seems a lot like trying to nail Jello to the wall.....

Anyway I was wondering...why so many different models with different conclusions? Is one more reliable than another?
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Quoting P451:


Surface Wind Streamlines 21Z



that "blob" sure looks uglier by the minute.
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting Funkadelic:
Newer models have shifted a tad west for Bill.. Here take a look:


Link
Bad News for us in Puerto Rico and V.I.
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1325. jipmg
Im starting to disagree with the models.. some of them have ana moving West or WSW in the short term when the thing is currently moving north of due west..
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Quoting stormwatcherCI:
You said it. At the moment. Time will tell.

Excellent...it would be sweet if those moments turn to hours then to days....Gotta love living in the tropics...
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does anyone have a link to the models that go out 200+ hrs?
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By Kingfan104. Have a nice life.Admin???
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Quoting stormwatcherCI:
ROFLMAO

Sorry I just couldn't help it, I see so much bull here this evening the flies are starting to gather on my monitor again.
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Quoting java162:


i think bill is way too south for it to go all the way to the north( ignoring steering paterns)


Definetly with you on that.
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Quoting stormpetrol:

You know what you are, I'll give you a hint, Its looks just your avatar!!!


Perfect...
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Quoting weathersp:
NOAA 49 has sent its first sonde back..

please help me with that I am on the tropical atlantic recon site
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Nat' weather service for Miami area states tropical storm conditions for wednesday night..
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1315. jipmg
alright so can I have a link to the forecast models
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1314. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129838

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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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