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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Quoting stormsurge39:
Im confused, why is there a yellow circle on the NHC site for 91L?


It's red now. Just a little delay.
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Quoting atmoaggie:
CMC redevelops something and send it to SW LA. And that is NOT 91L, but Ana's remnants...after much travel.



About when would that be?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
You guys are saying there is a surface low after reading that when the NHC said:

"MAY BE DEVELOPING A CLOSED SURFACE CIRCULATION"
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Quoting atmoaggie:
CMC redevelops something and send it to SW LA. And that is NOT 91L, but Ana's remnants...after much travel.



hmmmmm.SW LA - I'm in SE TX about 10-15 min. from LA border.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
3559. Patrap
Hurricane Preparation Entry
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3558. 789
Quoting caribbeansurvivor1:
Good morning everyone, here in Puerto Rico is 1:30 am waiting for any new information about Anna, that look a little disorganized the last hours...and happy 38 to me!
happey b day
Member Since: Posts: Comments:
000
ABNT20 KNHC 160542
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN AUG 16 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 710 MILES EAST-SOUTHEAST OF THE LEEWARD
ISLANDS...AND ON TROPICAL STORM BILL...LOCATED ABOUT 905 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.

SATELLITE AND RADAR DATA INDICATE THAT A SMALL AREA OF LOW PRESSURE
IN THE EASTERN GULF OF MEXICO...CENTERED ABOUT 80 MILES SOUTHWEST
OF TAMPA...IS BECOMING BETTER ORGANIZED AND MAY BE DEVELOPING A
CLOSED SURFACE CIRCULATION. ENVIRONMENTAL CONDITIONS ARE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AND THERE IS A HIGH CHANCE...GREATER
THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
SOMETIME TODAY. THIS SYSTEM IS EXPECTED TO MOVE NORTHWESTWARD OR
NORTH-NORTHWESTWARD AT ABOUT 15 MPH TODAY. INTERESTS ALONG THE GULF
COAST OF FLORIDA SHOULD CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.

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

PUBLIC ADVISORIES ON TROPICAL STORM BILL ARE ISSUED UNDER WMO
HEADER WTNT33 KNHC AND UNDER AWIPS HEADER MIATCPAT3.
FORECAST/ADVISORIES ARE ISSUED UNDER WMO HEADER WTNT23 KNHC AND
UNDER AWIPS HEADER MIATCMAT3.
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Guess its about Claudette time. This would put us about in line with climatology if it does get named.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting atmoaggie:
And HWRF doesn't turn 90L into a cat 5. It showed more restraint than I thought it was capable of.

TS at Pensacola.


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Quoting Twinkster:



i am in contact with jp and he says that it is too early to tell anything about the long range track for bill


dont need to be much of a met to know that by now

wait... its the other way around! I get it!
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Quoting DanielPC:
Many thanks. I'm hoping 90L becomes TD4 before I zonk out for the night. Doubt that will happen.




91L not 90L.
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CMC redevelops something and sends it to SW LA. And that is NOT 91L, but Ana's remnants...after much travel.

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Guess Tampa was right. There is a surface feature.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting atmoaggie:
And HWRF doesn't turn 90L into a cat 5. It showed more restraint than I thought it was capable of.

TS at Pensacola.



91L.
Member Since: Posts: Comments:
WOW

000
ABNT20 KNHC 160542
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN AUG 16 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 710 MILES EAST-SOUTHEAST OF THE LEEWARD
ISLANDS...AND ON TROPICAL STORM BILL...LOCATED ABOUT 905 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.

SATELLITE AND RADAR DATA INDICATE THAT A SMALL AREA OF LOW PRESSURE
IN THE EASTERN GULF OF MEXICO...CENTERED ABOUT 80 MILES SOUTHWEST
OF TAMPA...IS BECOMING BETTER ORGANIZED AND MAY BE DEVELOPING A
CLOSED SURFACE CIRCULATION. ENVIRONMENTAL CONDITIONS ARE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AND THERE IS A HIGH CHANCE...GREATER
THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
SOMETIME TODAY.
THIS SYSTEM IS EXPECTED TO MOVE NORTHWESTWARD OR
NORTH-NORTHWESTWARD AT ABOUT 15 MPH TODAY. INTERESTS ALONG THE GULF
COAST OF FLORIDA SHOULD CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.

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

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

$$
FORECASTER FRANKLIN/BERG
Member Since: Posts: Comments:
May be a Caribbean storm, When Anna was TD2 all models was placing to WNW and look what is going on now. all the models are placing Bill north of the Antilles (thank you Lord!)and aiming more to US east cost...(God have mercy!)
Member Since: Posts: Comments:
Im confused, why is there a yellow circle on the NHC site for 91L?
Member Since: Posts: Comments:
000
ABNT20 KNHC 160542
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN AUG 16 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 710 MILES EAST-SOUTHEAST OF THE LEEWARD
ISLANDS...AND ON TROPICAL STORM BILL...LOCATED ABOUT 905 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.

SATELLITE AND RADAR DATA INDICATE THAT A SMALL AREA OF LOW PRESSURE
IN THE EASTERN GULF OF MEXICO...CENTERED ABOUT 80 MILES SOUTHWEST
OF TAMPA...IS BECOMING BETTER ORGANIZED AND MAY BE DEVELOPING A
CLOSED SURFACE CIRCULATION. ENVIRONMENTAL CONDITIONS ARE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AND THERE IS A HIGH CHANCE...GREATER
THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
SOMETIME TODAY. THIS SYSTEM IS EXPECTED TO MOVE NORTHWESTWARD OR
NORTH-NORTHWESTWARD AT ABOUT 15 MPH TODAY. INTERESTS ALONG THE GULF
COAST OF FLORIDA SHOULD CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.


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

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

$$
FORECASTER FRANKLIN/BERG
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Many thanks. I'm hoping 90L becomes TD4 before I zonk out for the night. Doubt that will happen.

Quoting atmoaggie:

The Recon plans always here: http://www.nhc.noaa.gov/reconlist.shtml
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3542. Patrap
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And HWRF doesn't turn 90L into a cat 5. It showed more restraint than I thought it was capable of.

TS at Pensacola.

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Quoting Skyepony:


Tonight the fastest they were flying out of Gonzo was 1 every 2 minutes.

Wonder if that was on purpose or the limit?
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Goodnite everyone!
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Quoting hurricane23:


Actually my thinking is the threat to the U.S. has decreased based on the present model consensus.GFS/ECMWF have abig trough along the eastern conus which should induce recurvature out to sea which usually happens with approaching tc's from the east.Here's a glance at the 00z guidance hinting at a northwesterly motion at the end of the forcast period.

Adrian

And the 00 Z GFDL has Bill again further north of the lesser islands (I know, I know, they are called Antillies)

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http://moe.met.fsu.edu/cgi-bin/hwrftc2.cgi?time=2009081600-bill03l&field=Sea+Level+Pressure&hour=Anim ation

Alright...HWRF has definitely made a slight southern shift at 00z...from 22N 63W on 18z 126h to 21.6N 64.5W on the 00z 126h.
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Hey Ponce!! what my post let you thinking?
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Quoting WeatherStudent:


Is it the initiation of a potential trend? Let's hope so, :)


Well, is not good to the Antilles after the possibility of getting Anna, that Bill turn a little south, it will put Bill more to pass over the islands.
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Quoting caribbeansurvivor1:
Good morning everyone, here in Puerto Rico is 1:30 am waiting for any new information about Anna, that look a little disorganized the last hours...and happy 38 to me!


felicidades, ponce representando

im on the verge of 27... wow

your post made me think.
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3530. Skyepony (Mod)
Quoting atmoaggie:

I think they were adding the capability to launch GPS sondes to one of the fleet last year...or, I know, the Air Force HH launch method only allowed them to launch a sonde about once per couple of minutes, whereas to NOAA planes could do more than one a minute. Maybe that got changed?


Tonight the fastest they were flying out of Gonzo was 1 every 2 minutes.
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Thanks Atmo! Good night all! It will be interesting to see what happens tomorrow!
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Quoting DanielPC:
Forgive me if someone has answered this already, but does anyone know if there are plans for a HH/AF plane to investigate 90L in the next 12 hours?

The Recon plans always here: http://www.nhc.noaa.gov/reconlist.shtml
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Quoting HurricaneKyle:


I think Adrian was making fun of the posters on here.. he knows well that this is well out and the models almost always change.


Actually my thinking is the threat to the U.S.with bill has decreased based on thepresent model consensus.GFS/ECMWF have abig trough along the eastern conus which should induce recurvature out to sea which usually happens with approaching tc's from the east.Here's a glance at the 00z guidance hinting at a northwesterly motion at the end of the forcast period.

Adrian
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hadn't been on all day... but what's going on with 91L? are the model runs trustworthy yet? and how strong can it get in this short amount of time? Just wondering because a few of the model runs have it in my back yard...
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91L is move more NNW - don't see getting to LA
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Quoting CatastrophicDL:

Wasn't NOAA or the military dropping new specialized dropsondes last year for data collection? Doesn't the info from them get fed into the GFDL and HWRF models?

I think they were adding the capability to launch GPS sondes to one of the fleet last year...or, I know, the Air Force HH launch method only allowed them to launch a sonde about once per couple of minutes, whereas to NOAA planes could do more than one a minute. Maybe that got changed?

Yes about the assimilation of the obs into the models. In certain circumstances some of the NCEP model runs will be held up if they can wait a few minutes for those obs. (Very infrequently, but has happened.)
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Forgive me if someone has answered this already, but does anyone know if there are plans for a HH/AF plane to investigate 90L in the next 12 hours?
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How many hours does 91L have over water before land?
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3517. code1
MLC thinks he knows more of the "real" workings than the rest of us for the most part of late. I miss the old one as well. hmmm, you sound familiar. Not gonna speculate though. I suppose you have your reasons. I follow the good Doc Master's posts for the most part myself, and bypasss this fluff. Was an interesting read tonight though, and one I won't repeat very often until after school starts for all again though.
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Good morning everyone, here in Puerto Rico is 1:30 am waiting for any new information about Anna, that look a little disorganized the last hours...and happy 38 to me!
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Quoting presslord:


Stormjunkie is outta town this weekend...he'll be around again Tuesday...


Presslord i hope he didn't go to CANADA.....LMAO
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Well if nothing else, maybe 91 will stir up and cool off the hot tub before anybody else gets in.
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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.