Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 04:17 PM GMT on Αύγουστος 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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1714. BrandiQ
Quoting CaneWarning:
After looking at the GFS ensemble models for Bill, I feel much better for the state of Florida. It looks like Bill wants to recurve.


But that's still 8 days from now. The models are bound to change....
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1713. Dakster
Quoting canesrule1:
i understand it too, but some people here aren't so educated, Anyways i'll post the raw from now on.


The other way is "easier", but once you know the format..



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Quoting CaneWarning:
After looking at the GFS ensemble models for Bill, I feel much better for the state of Florida. It looks like Bill wants to recurve.


Remember, they had it in the Caribbean yesterday. To me its to early to talk track, but a lot of the other models still want it to go on the path the NHC is taking.
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1711. hydrus
Quoting Weather456:
Billl is fun to watch now since its harmlessly out there. as they near land, they become a bit more harder to admire.
This is true.I saw one of the models put a storm in the G.O.M. and it grows huge and powerful in a very short amount of time.
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Looks like bill is going south of the next forecast points
NHC Tropical Floater
enable forecast points
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Quoting WeatherStudent:



Ditto, grosero. :)
lol
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1707. Patrap
.."Hebert"..in a Box..

Member Since: Ιούλιος 3, 2005 Posts: 426 Comments: 128875
After looking at the GFS ensemble models for Bill, I feel much better for the state of Florida. It looks like Bill wants to recurve.
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Quoting P451:
GFS 18Z

Drops Ana altogether.
Recurves Bill even more and makes him far more intense than before.
Backs off strength of Claudette (the currently emerging African wave).
Forms a fourth system far east of Caludette - presumably the wave currently over central Africa that looks decent.



Looks like a Hugo event or a Floyd event.
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Quoting KATRINABILOXIGIRL:
yeah I know...we have all decided that we would like to find the guy who originated that phrase and take him out back and beat the $&*! out of him
Are you a Postal worker ? I work for the Cayman Islands Postal Service.
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What happened to the HH plane tracking on Google earth? You used to be able to see where the HH were flying....or was that only for a different recon flight type? I'm getting the data etc...just not the the visual for the plane..
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P451,

you have mail
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Quoting mossyhead:

which hurricanes have you been through?
Don't really remember since it was in my younger years. Been living in Grand Cayman since I was 16 and now 53 so I don't remember names but I do remember events.
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Quoting Tazmanian:
am not going with any mode run in tell the bil gets too 50W


Hey Taz nice to see familiar faces here. You guys helped me get thru Dolly last year when I was in South Padre. I'm in Corpus Christi now and I suspect we are due for a big storm sooner or later.
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Bill looks impressive, organizing fast.
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1698. weld
Hope one of them gets into the gulf. We need rain.
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going out to cut the grass before it all hits the fan with all the rain...might be a while before it dries out enough to cut...be back later
Member Since: Ιούλιος 31, 2009 Posts: 0 Comments: 324
Quoting Dakster:


I understand it perfectly... What is the problem?
i understand it too, but some people here aren't so educated, Anyways i'll post the raw from now on.
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Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 15th day of the month at 22:42Z
Aircraft: Gulfstream IV-SP (G-IV) (Reg. Num. N49RF)
Storm Number: 02
Storm Name: Ana (originating in the North Atlantic basin)
Mission: Non-Tasked Mission
Observation Number: 05


938mb 80° (from the E) 35 knots (40 mph)
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winds at 41041 holding at 11.7kts....
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1692. Dakster
Quoting canesrule1:
Yeah if u understand this:
UZNT13 KWBC 152242
XXAA 65222 99174 70521 04272 99012 27631 08528 00106 26625 08026
92791 21613 08534 85522 18013 09532 70166 09857 11030 50589 05359
07512 40760 16560 07510 30970 31748 28004 25097 41563 21011 20244
537// 17020 88999 77162 28598 499//
31313 09608 82205
51515 10190 15424
61616 NOAA9 WX02A ANA OB 05
62626 SPL 1737N05220W 2219 MBL WND 08029 AEV 20801 DLM WND 11011
011152 WL150 08026 084 REL 1735N05213W 220459 SPG 1737N05220W 221
935 =
XXBB 65228 99174 70521 04272 00012 27631 11939 22008 22850 18013
33762 13623 44730 12056 55673 07850 66661 07662 77648 06456 88620
04257 99592 01835 11581 01257 22561 00537 33527 02546 44507 04938
55497 05761 66482 07161 77475 07776 88456 10157 99437 11778 11407
15577 22399 16560 33393 16975 44388 17573 55371 19968 66364 20978
77356 21960 88347 23177 99337 24566 11331 25571 22325 26571 33291
33524 44269 37356 55246 42364 66222 48760 77203 52966 88179 597//
99152 63944
21212 00012 08528 11002 08026 22990 08531 33938 08035 44899 09532
55880 09535 66850 09532 77706 11031 88601 10032 99546 11520 11487
07009 22471 05511 33456 07011 44418 06011 55401 07510 66385 06510
77280 19003 88251 21010 99238 19016 11224 19015 22211 15515 33190
18023 44174 17031 55170 20022 66167 25539 77162 28598
31313 09608 82205
51515 10190 15424
61616 NOAA9 WX02A ANA OB 05
62626 SPL 1737N05220W 2219 MBL WND 08029 AEV 20801 DLM WND 11011
011152 WL150 08026 084 REL 1735N05213W 220459 SPG 1737N05220W 221
935 =


I understand it perfectly... What is the problem?
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1691. jdjnola
Xmas, I mean Dmax came early this year, I mean today. Ana and Bill are putting on a bout of convection, the both of them.
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Yeah,, and the last few frames of the loop looked like she was getting squeezed like a grape.
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Quoting mobilegirl81:

???????
Do you have any messengers
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quicker ana strengthens, more North she goes?
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Quoting weathersp:


If you manually decode it on the Tropical ATL site you can select plain text format.. that might help.
YEAH IF U UNDERSTAND THIS:

UZNT13 KWBC 152242
XXAA 65222 99174 70521 04272 99012 27631 08528 00106 26625 08026
92791 21613 08534 85522 18013 09532 70166 09857 11030 50589 05359
07512 40760 16560 07510 30970 31748 28004 25097 41563 21011 20244
537// 17020 88999 77162 28598 499//
31313 09608 82205
51515 10190 15424
61616 NOAA9 WX02A ANA OB 05
62626 SPL 1737N05220W 2219 MBL WND 08029 AEV 20801 DLM WND 11011
011152 WL150 08026 084 REL 1735N05213W 220459 SPG 1737N05220W 221
935 =
XXBB 65228 99174 70521 04272 00012 27631 11939 22008 22850 18013
33762 13623 44730 12056 55673 07850 66661 07662 77648 06456 88620
04257 99592 01835 11581 01257 22561 00537 33527 02546 44507 04938
55497 05761 66482 07161 77475 07776 88456 10157 99437 11778 11407
15577 22399 16560 33393 16975 44388 17573 55371 19968 66364 20978
77356 21960 88347 23177 99337 24566 11331 25571 22325 26571 33291
33524 44269 37356 55246 42364 66222 48760 77203 52966 88179 597//
99152 63944
21212 00012 08528 11002 08026 22990 08531 33938 08035 44899 09532
55880 09535 66850 09532 77706 11031 88601 10032 99546 11520 11487
07009 22471 05511 33456 07011 44418 06011 55401 07510 66385 06510
77280 19003 88251 21010 99238 19016 11224 19015 22211 15515 33190
18023 44174 17031 55170 20022 66167 25539 77162 28598
31313 09608 82205
51515 10190 15424
61616 NOAA9 WX02A ANA OB 05
62626 SPL 1737N05220W 2219 MBL WND 08029 AEV 20801 DLM WND 11011
011152 WL150 08026 084 REL 1735N05213W 220459 SPG 1737N05220W 221
935 =
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Quoting ALCoastGambler:
Mobilegirl, Are you on msn mess?

???????
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Quoting Orcasystems:


remember that rain snow sleet thingie you guys like to say...
yeah I know...we have all decided that we would like to find the guy who originated that phrase and take him out back and beat the $&*! out of him
Member Since: Ιούλιος 31, 2009 Posts: 0 Comments: 324
Quoting nrtiwlnvragn:
I haven't seen any data from the NOAA P-3 plane, considering the current state of Ana they may have cancelled the mission. (P-3 is a low level, not the G-IV)

that is what I was saying but I think they will do later tonight
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Quoting WeatherStudent:


None, but I've still got hope for Ana to potentially impact us, fingers and toes tightly crossed.
I think as you get older you will find that you never say none, or never when it comes to forecasting storms. Some behave, and some have minds of their own.
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Quoting WeatherMSK:
Well it appears to be shaping up that way, especially with that upper level lower up front.


agree
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Quoting KATRINABILOXIGIRL:
thanks will do..bad thing is I will be out delivering the mail in all that mess on Monday..yuck!!!!


remember that rain snow sleet thingie you guys like to say...
Member Since: Οκτώβριος 1, 2007 Posts: 81 Comments: 26511
1679. Dakster
Quoting popartpete:
While not worthless, computer models are notoriously incorrect, and all disagree with each other. Some I hear are more reliable than others, although I do not specifically know the best. It seems that GFS is quoted a lot, but there are probably others mets who think another is far better. They are tools but not crystal balls. The computers take in information, and try to make sense out of it by way of an educated guess. There are other factors the NHC takes into consideration when predicting projected path. It's an evolving science, better all the time, but not flawless, thus the huge disclaimers on them stating to heed official warnings in your area, and not to use the model as gospel. That's my best understanding and theory of how they work: a complete layman's perspective


AS a fellow layman with enough knowledge to be dangeorus that is how I understand it.

My .02's is that the reason there are so many models is that each year one seems to be better than the other and some seem to track different storms better than the other, but yes it takes a met to look at ALL of the data and interpet the results. Also, some of the models go by different steering layers in the atmosphere, like the BAM suite for a shallow system, medium, and deep system. (TS, Hurricane, and Major Hurricane)

So some computer help, knowledge, and expereince go into the forecasting...
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I haven't seen any data from the NOAA P-3 plane, considering the current state of Ana they may have cancelled the mission. (P-3 is a low level, not the G-IV)
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Well it appears to be shaping up that way, especially with that upper level low up front.
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am not going with any mode run in tell the bil gets too 50W
Member Since: Μάιος 21, 2006 Posts: 5091 Comments: 115255
Now that we know Bill WILL become a hurricane, what is it with the forecast track? The projected path again seems to northern and, considering the track record of this year's models, i wonder if they are correct. Bill is quite south. Can anyone explain how the steering currents are gonna change to explain what the models are saying?
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Quoting mobilegirl81:

Ya'll do the same.
Mobilegirl, Are you on msn mess?
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Quoting mobilegirl81:

Ya'll do the same.
thanks will do..bad thing is I will be out delivering the mail in all that mess on Monday..yuck!!!!
Member Since: Ιούλιος 31, 2009 Posts: 0 Comments: 324
Quoting Kmanwoodie:
Thanks for your take,Kman. It is a bit chancy going over with all the activity in the ATL. May organize everything here just in case with our house, office, boats etc... before we go. Miss Universe is there this week, so you know things will be crazy over there. I wonder what their back-up plan would be in the case of a storm during the pageant's week of activities? Anyway, I'll leave you to the discussion of the weather. Keep your points/observations coming.


You're welcome. The beauties would probably get the red carpet treatment flying out by private charter loaded up with shrimp and champagne while everyone else waved them good bye from the terminal.

I'm out for now. Back for a bit later.
Member Since: Αύγουστος 19, 2006 Posts: 0 Comments: 15842
1671. Guiness
Hi from the British Virgin Islands. Looks like we are in for a rough week here..
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Quoting canesrule1:
ok no prob


If you manually decode it on the Tropical ATL site you can select plain text format.. that might help.
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Billl is fun to watch now since its harmlessly out there. as they near land, they become a bit more harder to admire.
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Quoting KATRINABILOXIGIRL:
from the looks of post 1626 taking us through Tuesday, looks like it's gonna be really wet here for the next three days or so...stay safe..

Ya'll do the same.
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Quoting flsky:
canesrule1 please post a link for the dropsonde info instead of the entire listing. Thank you.
ok no prob
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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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