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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The only proof you need is the satellite. The enviornment is extremely hostile with the dry air and shear. ana is a small circulation and will get torn up. I have been saying from the beginning nothing will amount too much so in the end we shall see who is right.
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Quoting GetReal:
I was just going to mention that radar loop Auburn... There is definately a cyclonic circulation centered just north of a Key West... The convection is also increasing and getting better organized... IMO


Been mentioned and talked about all morning.

No convergence is the biggie. Other things too, but until it gets that, no point, imo, with the other stuff going on.

Not saying it's not worth watching, though. Have it up. ;)
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62. P451
Quoting auburn:
whats this...someone posted this on another blog...looks odd to me ...but what do I know



It's a wave that has been tracked over the days since it was around 55W.

Seems to be getting some rotation on radar.





Member Since: December 16, 2007 Posts: 7 Comments: 10202
FLHurricanechaser..in what part of florida do you live?
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Quoting CaneLover:


pardpn my ignorance Drak, but what is a "trough scenario"?


A strong trough grabs this thing and takes it out to sea or it parallels the eastern seaboard
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All of a sudden, within a few days, there is yet another August Atlantic shooting gallery taking form.

And what is the deal with that activity around Key West? Wow.
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Quoting Drakoen:
The models may be leaning to a trough scenario for Bill.


From what I read that Dr. Masters posted, the models calling for a more northerly path were probably incorrect because TD3's convection came together more south than expected. So we'll have to watch it right now, but it's going to be hard for it to curve out to see IMO.
Member Since: August 10, 2009 Posts: 3 Comments: 672
Blog Update
Reflector site for those at work, which includes Weather456, daily update.


ANA

TD3

Quote of the Day, and shows how the day is going to unfold.

" 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"
Dr Jeff Masters
Member Since: October 1, 2007 Posts: 81 Comments: 26511
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

Hmmmmmmm, could definitely get interesting. I say those in the GOM need to pay attention to this one for sure.
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The train is definitely moving now. Lots to watch!
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Quoting Vortex95:
thanks Dr. Masters that is a very uncertain forcast. That shear forcast drop tonight is crucial to the survival of Ana.

As "you know who will say"

THE PLOT THICKENS!!!!!!!!!!!!!


lmao
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Ana and Bill are far away...what about the area in the central Gulf and now the blowup from the wave over the Keys? Wow...the switch has been flipped! Hey StormW. Hard keeping up at this point, huh? Things are popping up right and left!
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Quoting hurricanelover236:
Mark my words. Anna wont survive and wont cause florida or the islands any problems. Td 3 may become stronger but i dont c that hitting the us either. We are in the clear. Time to celebrate.

Proof plz
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In all seriousness, First off I would like to see if Ana is coming to the bahamas at all. Then if so I am slightly concerned for I am going up to FSU this week on Tuesday. By monday do you think it is possible for me to know wheater to shutter up (have accoridan shutters so its easy).
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Quoting Drakoen:
The models may be leaning to a trough scenario for Bill.


pardpn my ignorance Drak, but what is a "trough scenario"?
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Quoting mikatnight:


Good idea! Thanks Aussie!

Pity you said it 1st
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47. jpsb
Quoting auburn:
whats this...someone posted this on another blog...looks odd to me ...but what do I know
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.
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46. P451
MODIS captures the newest African Wave that the GFS develops on the heels of TD3.

Member Since: December 16, 2007 Posts: 7 Comments: 10202
I was just going to mention that radar loop Auburn... There is definately a cyclonic circulation centered just north of a Key West... The convection is also increasing and getting better organized... IMO
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The models may be leaning to a trough scenario for Bill.
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Quoting pottery:
Very interesting.
SAL rules? Or will these systems be able to make the forecasts come true.
Stay tuned, and dont blink!
well well well look what he cat dragged in

afternoon pottery good to see ya doing good i hope
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I think next week its time for Floridians to get prepared for the season pronto.
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Mark my words. Anna wont survive and wont cause florida or the islands any problems. Td 3 may become stronger but i dont c that hitting the us either. We are in the clear. Time to celebrate.
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Link

looks impressive
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I think ana will survive IF
the shear stops tonight. She has been rather persistant.
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not to say anything bad about the docs posts,but he has the date of andrews formation incorrect. he has it listed as aug 17th, 2009; which is impossible seeing how that date has yet to arrive. i think he meant to say andrew formed on aug 17th 1992.

im also surprised he did not mention the wave thats currently effecting the keys, as even the NHC gives it a slight chance for formation.
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Great Blog! I'm going to enjoy tracking this one
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Quoting JeffMasters: 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.
Talk about a bet each way.
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Quoting RadarNerd:
Aside from everything else going on..

Can someone with a better eye than mine comment on what looks like rotation at roughly 67W 25N? Seems to be an accumulation of vapor there under the Bermuda high and vorticity maps are starting to pick up on it as well.


Nevermind.. I see it Dr. Master's entry as the ULL.

Thx Doc!
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If Ana don't get us.. Bill and Claudette will

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Quoting auburn:
whats this...someone posted this on another blog...looks odd to me ...but what do I know



Its been real rainy and windy in South Florida. Wonder if it will become something in the GOM.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
I was going to mention that too Auburn...not a good fishing day in the lowers.
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31. auburn (Mod)
whats this...someone posted this on another blog...looks odd to me ...but what do I know

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Very interesting.
SAL rules? Or will these systems be able to make the forecasts come true.
Stay tuned, and dont blink!
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nice update doc as always good info hopefully dry air shear keeps them in check but like i always say "this is the tropics...and its august anything can happen".
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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
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Thanks for the update Dr. Masters.
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thanks Dr. Masters that is a very uncertain forcast. That shear forcast drop tonight is crucial to the survival of Ana.

As "you know who will say"

THE PLOT THICKENS!!!!!!!!!!!!!
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Quoting AussieStorm:
Can we please have no "thanks Doc" posts


Good idea! Thanks Aussie!
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Dr.Masters thank you I hope you have a wonderful weekend and I hope those in the Leeward Islands are ready.
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Ana is the latest first named storm of the season since Hurricane Andrew got its name on August 17, 2009. 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.

I think anyone in Miami reading that just got goosebumps...Let's hope indeed.

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Thank you for your intelligent, informative blog entry this morning. It is the one place beside the NHC I can find calm and cool information, rather than wishcasting.
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thanks doc
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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

Interesting.
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NOGAPS is overdoing Ana
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Thanks Doc! Also looks like it's shaping up to be a busy upcoming few weeks with strong waves emerging off the coast that do have some model support. Tis' the season!
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Thanks for the fresh blog and update Dr. Masters!
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I give equal chances that the storm (Ana)will be a hurricane--or non-existent--four days from now.


Interesting..
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14. P451
TD3 - On towards DMIN we go....




And MODIS image of TD3 a couple of hours ago.

Member Since: December 16, 2007 Posts: 7 Comments: 10202

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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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