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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I find it interesting that the weather is so bad in miami, naples, brandenton,sarasota, and pretty much everywhere in south florida EXCEPT for fort myers/cape coral. It hasnt rained at all today. overcast and breezy. Strange.
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Member Since: Σεπτέμβριος 7, 2007 Posts: 0 Comments: 1732
Quoting underthunder:
so patrap...what are your thoughts on that blob?


Im just a watching the wheels go round and round..

But in that area,..well..seen screwier things happen.

The Sky here has High curved,banded cirrus,and low scud rolling east to west.

If the engine stars and the flue is open.

Da voodoo man gonna be busy...
Member Since: Ιούλιος 3, 2005 Posts: 424 Comments: 128287
861. whitewabit (Mod)
Ana's mid level coc is uncovered to the west of the convection...
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Still no info on the 18z runs.

Maybe they can't decide what to set for the initial intensities?
Member Since: Αύγουστος 23, 2008 Posts: 7 Comments: 5300
We might see another AOI western gulf. There is some dry air but only a little but we have convection and spin today.
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Quoting WPBHurricane05:


You can educate yourself by reading a NHC TWO. "Surface pressures remain high in the area." Boom...now I know you need low surface pressures for a cyclone to form.


haha hmm, maybe they'll teach me that at Purdue
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I'm not saying Ana doesn't pose a threat by any means, but I really think Bill is going to explode. That'll be the one to watch, especially given Ana's chances at battling the terrain over Hispaniola and Cuba. The Carolinas have been awfully lucky the past several years.
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Quoting serialteg:


totally ignored. lol

well, back to my soup


you weren't ignored. i got a laugh out of it!
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Quoting hunkerdown:
Come on, what does the NHC know, people who are asking here are relying on expert opinions/facts. The NHC is a bunch od amateurs, only concerned about the entertainment....I really don;t know why people don't utilize Wunderground and their links more instead of asking questions that they can see directly for them selves. After all, isn't it easier to go directly to a site and see the image or read the discussion for your self, and maybe even educate yourself ??

Oh crap, sorry guys/gals, its that reality thing agan.


You can educate yourself by reading a NHC TWO. "Surface pressures remain high in the area." Boom...now I know you need low surface pressures for a cyclone to form.
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Quoting truecajun:
ok, that's right. i remember drak saying earlier that there was pressure to keep it from exploding. on that note, i'm off to go shopping.


totally ignored. lol

well, back to my soup
Member Since: Αύγουστος 22, 2006 Posts: 2 Comments: 1983
Quoting JupiterFL:


I highly doubt that its illegal. He's been around since the beginning and it adds a little humor. We all need that when a storm is headed in our general direction. At least he doesn't post non stop crap like some others on this board.
For those of lifers we know who he is, know not to take him too seriously. It's been posted before that it's illegal/immoral to pretend to be an official statement. I'm just looking out for casual readers. I haven't suggested banning or anything, just that he understands that there are people on here that don't know and may rely on his post if it looks official. If I'm wrong, I apologize.
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Quoting WPBHurricane05:
NHC on GOM system:

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SAT AUG 15 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM ANA...LOCATED ABOUT 920 MILES EAST OF THE LEEWARD ISLANDS...
AND ON NEWLY-DEVELOPED TROPICAL DEPRESSION THREE...LOCATED ABOUT
740 MILES WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.

1. THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE HAS BECOME
MORE CONCENTRATED TODAY OVER THE FLORIDA KEYS AND THE ADJACENT
SOUTHEASTERN GULF OF MEXICO. PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.


ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

PUBLIC ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER
WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2. FORECAST/ADVISORIES
ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER WTNT22 KNHC AND
UNDER AWIPS HEADER MIATCMAT2.

PUBLIC ADVISORIES ON TROPICAL DEPRESSION THREE ARE ISSUED UNDER WMO
HEADER WTNT33 KNHC AND UNDER AWIPS HEADER MIATCPAT3.
FORECAST/ADVISORIES ON TROPICAL DEPRESSION THREE ARE ISSUED UNDER
WMO HEADER WTNT23 KNHC AND UNDER AWIPS HEADER MIATCMAT3.

$$
FORECASTER BEVEN
Come on, what does the NHC know, people who are asking here are relying on expert opinions/facts. The NHC is a bunch od amateurs, only concerned about the entertainment....I really don;t know why people don't utilize Wunderground and their links more instead of asking questions that they can see directly for them selves. After all, isn't it easier to go directly to a site and see the image or read the discussion for your self, and maybe even educate yourself ??

Oh crap, sorry guys/gals, its that reality thing agan.
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ok, that's right. i remember drak saying earlier that there was pressure to keep it from exploding. on that note, i'm off to go shopping.
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We'll see how far west these systems shift in the next 60 hours...

That will be the tell of the tape.

Will one or both track like, say an Ivan?

Soon...we'll know.
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so patrap...what are your thoughts on that blob?
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Quoting centex:
90L outdated

Right. td-3. Talked about 90L so much since the models started sending to us in SE LA, changing the name has been like changing one of kids' names. And RAMMB didn't help by having the same problem I am.
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843. 996tt
Quoting Catfish57:
No offense, but I'd bet you post here a 1000 times a day. Shouldn't a guy your age be more interested in girls or partying , instead of becoming a weather nerd?


Ouch. That is pretty funny. I guess we are all a bunch of nerds.
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842. CJ5
Quoting truecajun:
ok for real......is the "keys wave" something we on the gulf have to worry about or is it just going to be a rain maker?


There is a possibility, but for now there are not any low pressures near it.
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Quoting stormpetrol:

Very often in my years of watching storms, they often don't do what they were suppose to do.


Very well put!
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Ana & Three, spin on the sea
They hope to be a 'cane.
But Ana's breakin' down
And Three's a clown
Yet still they could cause some pain.
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hey everyone, i see the tropics are starting to heat up, well i just moved into my dorm here at Purdue University and i'm majoring in atmospheric science :)
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All I can say living here is SFl is thank God for the Greater Antilles. It SEEMS that the latest model runs are going to destroy the two systems through out the terrain of the GA, so even if they do recurve after, they MAY be greatly diminished...any thoughts
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guys how much longer till the H.H. recon flys
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Quoting stormpetrol:

Very often in my years of watching storms, they often don't do what they were suppose to do.

i keep remembering ivan. it was suppose to north and miss florida, then turn n again to go up over cuba and then the pennisula of florida and did not turn until it was south of the southern tip of cuba.
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Looks like T.D. 3's convection may be trying to fire up a little in the center.
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NEXRAD Radar
Miami, Echo Tops Range 124 NMI



Member Since: Ιούλιος 3, 2005 Posts: 424 Comments: 128287
Quoting hunkerdown:
action in the tropics, hell, theres action on the blog :)


I wish! *dreamy eyes*
Member Since: Αύγουστος 22, 2006 Posts: 2 Comments: 1983
Quoting WPBHurricane05:
Wouldn't be surprised if the NHC keeps Ana at a conservative 35 knots. The intensity forecast is gonna be real tough with wind shear, dry air, and Hispaniola.


LOL...I must have been falling asleep when I wrote that. Lets try it again.

Wouldn't be surprised if the NHC keeps Ana at a generous 35 knots. The intensity forecast is gonna be real tough with wind shear, dry air, and Hispaniola.
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Quoting Catfish57:
No offense, but I'd bet you post here a 1000 times a day. Shouldn't a guy your age be more interested in girls or partying , instead of becoming a weather nerd?


Once your married, you can spend all day on the computer.
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Quoting southfla:
seflagamma, Dr. Master's wording made perfect sense to me :-) I understood exactly what he meant.


Thank you .. I do believe most of us did.

we have so much going on out there to watch for the next few weeks.
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Quoting serialteg:


hi honey, #1 youre gorgeous, #2 i dont know... i sure hope it doesnt amount to much
action in the tropics, hell, theres action on the blog :)
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i have a tendency to believe the ukmet. it seems to be the most realistic GLOBAL model
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826. Skyepony (Mod)
Looks like SWFL is more than 2mb lower than the surounding areas.
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NHC on GOM system:

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SAT AUG 15 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM ANA...LOCATED ABOUT 920 MILES EAST OF THE LEEWARD ISLANDS...
AND ON NEWLY-DEVELOPED TROPICAL DEPRESSION THREE...LOCATED ABOUT
740 MILES WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.

1. THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE HAS BECOME
MORE CONCENTRATED TODAY OVER THE FLORIDA KEYS AND THE ADJACENT
SOUTHEASTERN GULF OF MEXICO. PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.


ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

PUBLIC ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER
WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2. FORECAST/ADVISORIES
ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER WTNT22 KNHC AND
UNDER AWIPS HEADER MIATCMAT2.

PUBLIC ADVISORIES ON TROPICAL DEPRESSION THREE ARE ISSUED UNDER WMO
HEADER WTNT33 KNHC AND UNDER AWIPS HEADER MIATCPAT3.
FORECAST/ADVISORIES ON TROPICAL DEPRESSION THREE ARE ISSUED UNDER
WMO HEADER WTNT23 KNHC AND UNDER AWIPS HEADER MIATCMAT3.

$$
FORECASTER BEVEN
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Quoting Drakoen:
Did anybody's roof come off yet that lives in the Keys?
my trashcan blew over earlier, but then again I don't live in the keys.
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NEXRAD Radar
Miami, Base Reflectivity 0.50 Degree Elevation Range 248 NMI


Member Since: Ιούλιος 3, 2005 Posts: 424 Comments: 128287
Finally action in the tropics! Looks like Florida could be in big trouble according to the projected path. Will have to wait and see!
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Quoting truecajun:
ok for real......is the "keys wave" something we on the gulf have to worry about or is it just going to be a rain maker?


hi honey, #1 youre gorgeous, #2 i dont know... i sure hope it doesnt amount to much

after watching patrap's radar image, it does look kinda worth watchin. keep those met eyes peeled

there was a nhc discussion i believe posted in latter pages about it. called for attention but low chance of it developing.
Member Since: Αύγουστος 22, 2006 Posts: 2 Comments: 1983
..
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Quoting Skylink:
Humm seems to be quite a bit of convection in the western central gulf.
and spin
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12Z UKMET takes TD3 right through the central Lesser Antilles... this is the most southern outlier but it's one of the major models not be ignored!!!
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here is the latest from NWS Key West concerning the tropical "WAVE" currently moving through the Keys.............DISCUSSION...
.CURRENTLY...
THE NORTHERN EXTENT OF A WESTWARD MOVING TROPICAL WAVE IS TRAVERSING
THE KEYS AND COASTAL WATERS. THE AXIS OF THE WAVE APPEARS TO BE
MOVING THROUGH THE LOWER KEYS AND THE FLORIDA STRAITS SOUTH OF THE
LOWER KEYS...WITH A BROAD CIRCULATION FROM AROUND 850 TO 700MB STILL
NOTICEABLE ON KEY WEST RADAR IN THE GENERAL VICINITY OF THE LOWER
KEYS. A SHEAR ZONE ALONG THE AXIS HAS BEEN EVIDENT ON KBYX RADAR
THROUGH THE MORNING...WITH NEAR SURFACE SOUTHWESTERLY WINDS OPPOSING
SOUTHEASTERLY WINDS. LOOKING AT BOTH THE KBYX AND KAMX RADARS...A
NORTHEASTWARD PROPAGATING WIND MAXIMUM FROM AROUND 2KFT TO 5KFT
SEEMS TO BE MOVING ALONG THE SHEAR LINE...WHICH MAY HAVE HELPED
INITIATE SOME OF THE STRONGER CELLS. THIS SHEAR ZONE HAS FORCED
SEVERAL VERY STRONG CELLS FROM 15 TO 40 MILES SOUTH OF THE LOWER
KEYS...INCLUDING AT LEAST THREE RELATIVELY DEEP MESOCYCLONES...
BASICALLY IN THE SAME GENERAL AREA...ONE OF WHICH TRIGGERED A MESO
ALERT. THE MESOS WERE FAIRLY SHORT LIVED...LASTING LESS THAT ONE HALF
HOUR. ALL OF THESE MESOCYCLONES WERE PRODUCING IMPRESSIVE
UPDRAFTS...WITH TOPS EXCEEDING 55KFT ABOVE THEM. THE SHEAR ZONE HAS
BEEN ALMOST STATIONARY FOR THE PAST SEVERAL HOURS...THUS THE
STRONGEST CELLS HAVE THANKFULLY REMAINED SOUTH OF THE LOWER KEYS.
EVEN WITH THE WORST SOUTH OF THE KEYS...AREAS ALONG THE LOWER KEYS
HAVE EXPERIENCED HEAVY RAIN WITHIN A RELATIVELY SHORT PERIOD OF TIME.
A SPOTTER ON CUDJOE KEY CALLED IN WITH 2 INCHES OF RAIN SINCE THE
BEGINNING OF THE EVENT EARLIER THIS MORNING. AN OFF DUTY NWS EMPLOYEE
ON BIG COPPITT KEY REPORTED ABOUT AN INCH OF STANDING WATER ON THE
LOWEST FLOOR OF HIS HOUSE...THE ACCUMULATION OF WATER POSSIBLY AIDED
BY 30MPH WINDS WHICH ACCOMPANIED THE HEAVER STORMS THAT TRAVERSED THE
LOWER KEYS.Link
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No offense, but I'd bet you post here a 1000 times a day. Shouldn't a guy your age be more interested in girls or partying , instead of becoming a weather nerd?
Member Since: Ιούλιος 29, 2009 Posts: 0 Comments: 72
Humm seems to be quite a bit of convection in the western central gulf.
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Quoting JupiterFL:


If you stopped posting and looked around the site you could find it.


Been here for so long and still doesn't know how to get to the ECWMF
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30491

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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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