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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While TD3 does have impressive banding features and outflow to the south and west, its eastern side is meak at best almost void of convection, with banding trying to wrap around the eastern side and cut off the dry air.
Member Since: October 21, 2008 Posts: 246 Comments: 3970
Quoting keyzdazeez:
the blob over the keys and to te west is in some really warm water right now . the bouy at vaca cut is showing almost 87 degrees SST and the surrounding waters are at least that warm. alot of energy there and moving very slowly, as well as growing in size. who knows if it moves into that sweet spot to the northwest things could get ugly quick

Rapid intensification?
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Can someone shed some light here cos I am not understanding it..
GFDL has Ana moving more West and evetually taking it into the Gulf while it takes TD3 which is further South (11.5N) well north to become a fish storm!!
How is the weakneed in the ridge affecting less on Ana then on TD3!?
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460. jipmg
Quoting stormwatcherCI:
I truly value your input on this and all jokes aside. How worried do I need to be about both of these systems ?(Grand Cayman in case you didn't know)


eh I dont think you should be worried, they are very far away
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the blob over the keys and to te west is in some really warm water right now . the bouy at vaca cut is showing almost 87 degrees SST and the surrounding waters are at least that warm. alot of energy there and moving very slowly, as well as growing in size. who knows if it moves into that sweet spot to the northwest things could get ugly quick
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Quoting hurricane23:


Great! Hopefully ana's llc continues to race ahead of the convective activity.ECMWF might have been correct all along with a recurve near the islands.


Yep. We definitely don't need a storm in South Florida. I watched Storm Stories on the Weather Channel with Hurricane Andrew and it was incredible the destruction. People were saying their last words to each as they fit their whole family in a single bathroom. Makes you wonder how people can wish for these things to come to their doorstep.
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455. IKE
Quoting Drakoen:
Both systems are very unimpressive. 02L was lucky to get named when it did


It looks terrible. Not sure if a downgrade may be coming.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Anyone on here that is qualified to answer and you know who you are is the little blob off of Florida likely to develop and is this going to be the suprise as others attention is on Ana and #3?
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453. JLPR
now the wave off the coast of Africa isnt looking so bad

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Quoting Drakoen:
Both systems are very unimpressive. 02L was lucky to get named when it did

So you think TD3's beautiful outflow and banding is unimpressive?
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Quoting SELAliveforthetropic:

They are holding hands
brother and sister with mama looking on
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...
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Quoting indianrivguy:
cmon.. someone give me a hand.. please...

354. indianrivguy 1:34 PM EDT on August 15, 2009
I'm confused and need some help understanding something. I just watched the Tropical floater and saw a swirl emerge from the convection center.
http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

I go to the tropical pages here and see TD 3, and 90L just .5 degrees apart. Are they calling these separate systems? I had thought that 90L became TD3.. can someone help me understand this please?


They are the same system. WU just has not updated yet to remove 90L.
Member Since: September 23, 2005 Posts: 14 Comments: 11276
Quoting Drakoen:
NHC will shift the track further south on Ana. HWRF has it into Cuba and GFDL has it going into the Caribbean.
I truly value your input on this and all jokes aside. How worried do I need to be about both of these systems ?(Grand Cayman in case you didn't know)
Member Since: October 9, 2008 Posts: 0 Comments: 8435
Thank you Ike, I appreciate the help.
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NOLA NWS Discussion,Just released

For today...a continuation of the pattern observed the last couple
of days will continue...as a strong upper level trough dominates
the lower Mississippi Valley. A deep layer of dry air aloft will
continue to inhibit convective development...especially over
northern and western zones...with a bit more coverage along the
coast...near a diffuse boundary. With this in mind...have slight
chance probability of precipitation for inland zones...with chance probability of precipitation elsewhere. Heading
into tonight and tomorrow...the tropical wave will begin to pull
closer to the area. Strong moisture advection in advance of the
inverted trough associated with the tropical...along with a broad
area of positive vorticity advection will allow for more
widespread convective activity heading into tomorrow. In fact...it
appears the moisture will be deep enough along the coast and over
the coastal waters to support likely coverage. Farther
inland...the moisture will be a bit slower to return...and have
went with chance probability of precipitation for Sunday. Temperatures will also be a bit
cooler than normal due to the anticipated cloud cover and
rainfall.


However...the heaviest and most prolific period of rainfall looks
to be Monday into Tuesday. The tropical wave will begin to pull to
the west of the region...allowing for the strongest lift and deep
moisture to sweep into the area. This moisture will be fed by deep
southerly flow off the Gulf of Mexico. With little convective
inhibition in place...have went with likely probability of precipitation across the
forecast area for Monday. Temperatures will remain below
normal...due to the rainfall and cloud cover expected to be in
place. The heaviest rains look to pull to the west and farther
inland Monday night into Tuesday. However...fairly strong and deep
Omega values on the eastern side of the inverted trough
axis...combined with ample moisture will allow for another round
of likely probability of precipitation for Tuesday afternoon. Given the likelihood of
heavy rainfall...some flooding issues may develop...and will have
to monitor for the need to issue a Flash Flood Watch for Monday.
In addition...some minor coastal flooding may develop due to an
expected higher than average tide and some swells emanating in
from the central Gulf of Mexico.
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445. Skyepony (Mod)
The blob off SWFL~ slumming the buoys looks like pressure may have started to fall a little early for time of day. MSLP has peaked none the less for the day. Have to wait now & see if this thing goes off on that hot bath. It is in an area of higher pressure. Probibly why we see it really spin up on 850 vorticy on several models but not so much drop in sea level pressure. Kinda wonder too if because it is so small & quick the models are missing a potentail drop in pressure due to a lack of resolution.
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Both systems are very unimpressive. 02L was lucky to get named when it did
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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.
Quoting Drakoen:
GFDL 12z looks like it wants Bill to be a fish


Great! Hopefully ana's llc continues to race ahead of the convective activity.ECMWF might have been correct all along with a recurve near the islands.
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12z GFS is the most reasonable track to me (till it truncates at 180).
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will someone please answer me what is up with the trough
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438. IKE
Quoting indianrivguy:
cmon.. someone give me a hand.. please...

354. indianrivguy 1:34 PM EDT on August 15, 2009
I'm confused and need some help understanding something. I just watched the Tropical floater and saw a swirl emerge from the convection center.
http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

I go to the tropical pages here and see TD 3, and 90L just .5 degrees apart. Are they calling these separate systems? I had thought that 90L became TD3.. can someone help me understand this please?


90L is TD3.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
How the HECK the models have TD3 in for rapid Development - currently the whole east side of the LLC has no cenvection to speak of... I have been sayig this all morning that I DO NOT see rapid intensification with TD3...
...on IR it actually look pretty crap and yes I know DMIN is approaching...
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WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0115 PM EDT SAT 15 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 16/1100Z TO 17/1100Z AUGUST 2009
TCPOD NUMBER.....09-079

I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM ANA
FLIGHT ONE -- TEAL 70
A. 16/1800Z,17/0000Z
B. AFXXX 0102A ANA
C. 16/1530Z
D. 15.6N 56.3W
E. 16/1700Z TO 17/0000Z
F. SFC TO 10,000 FT

FLIGHT TWO -- TEAL 71
A. 17/0600Z,17/1200Z
B. AFXXX 0202A ANA
C. 17/0330Z
D. 16.7N 60.0W
E. 17/0500Z TO 17/1200Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES.
A G-IV SURVEILLANCE MISSION IS PLANNED FOR 18/0000Z
WITH TAKEOFF AT 17/1730Z. A FOLLOW-ON G-IV MISSION
IS POSSIBLE FOR 18/1200Z WITH TAKEOFF AT 18/0530Z.

3. REMARK: NOAA43 AND THE G-IV WILL FLY FOUR SUCCESSIVE
RESEARCH MISSIONS INTO AND AROUND ANA DEPARTING FROM
TBPB AT 15/2000Z,
16/0800Z, 16/2000Z, AND 17/0800Z.
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Quoting Bailey1777:
If something is really getting started up off the coast of Florida as sat. seems to be suggesting where would the steering currents take it as things look now?
WNW waters are boiling match hits striker we got fire
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cmon.. someone give me a hand.. please...

354. indianrivguy 1:34 PM EDT on August 15, 2009
I'm confused and need some help understanding something. I just watched the Tropical floater and saw a swirl emerge from the convection center.
http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

I go to the tropical pages here and see TD 3, and 90L just .5 degrees apart. Are they calling these separate systems? I had thought that 90L became TD3.. can someone help me understand this please?
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Quoting IKE:


Looks like that's becoming the trend...NOGAPS does too.


Not a trend, just the latest.
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428. 7544
its only one run see if it continues for now
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Quoting WeatherStudent:
The latest runs of the HWRL and GFDL models clearly continue to indicate South Florida threaters in the long halt. No surprise there, I'd say.


Negative there...Track will likely shift south towards 12z models for ana or what ever is left of it.
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426. IKE
Quoting Drakoen:
GFDL 12z looks like it wants Bill to be a fish


Looks like that's becoming the trend...NOGAPS does too.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting chevycanes:
Bill going out to sea on GFDL it looks like.
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The dry area over Southern Louisiana is giving way to the moist air preceeding that low rather quickly, its easy to see in the cloud formations in the sky this afternoon.....flood watch is already in effect for Monday, but Slidell Met office indicates chance for heavy rain from Sunday to Tuesday as the low moves W and N.
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Bill going out so sea on GFDL it looks like.
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1100 AM AST SABADO 15 DE AGOSTO DE 2009

LA TORMENTA TROPICAL ANA ESTABA LOCALIZADA A 14.3 NORTE...48.3 OESTE O CERCA DE 920 MILLAS AL ESTE DE LAS ISLAS DE SOTAVENTO A LAS 1100 AM AST ESTA MANANA. EL PRONOSTICO ES QUE ANA PASE BIEN CERCA DE O PASANDO POR PUERTO RICO PARA EL LUNES. TAMBIEN A LAS 1100 AMAST...LA DEPRESION TROPICAL TRES SE HA FORMADO...Y TAMBIEN ESTA PRONOSTICADA QUE PASE CERCA DEL AREA LOCAL PARA EL FINAL DE LA SEMANA. ESTE SISTEMA ESTA LO LEJOS SUFICIENTE Y TIENE MUCHA INCERTIDUMBRE EN LA TRAYECTORIA Y EN LA INTENSIDAD... PERO EL PUBLICO DEBE MANTENERSE ALERTA. EL SERVICIO NACIONAL DE METEOROLOGIA EN SAN JUAN EMITIRA MAS BOLETINES DE ESTOS SISTEMAS A MEDIDA QUE SE SEPA MAS INFORMACION DE LA LLUVIA...INTENSIDAD...Y TRAYECTORIA QUE ESPERADA PARA ESTOS SISTEMAS. UNA VIGILANCIA DE TORMENTA TROPICALPUEDE SER EMITIDA MAS TARDE EN EL DIA DE HOY PARA LAS ISLAS VIRGENES Y PUERTO RICO. MIENTRAS TANTO...SE LES PIDE A LOS RESIDENTES Y VISITANTES QUE HAGAN PREPARATIVOS PRELIMINARES POR EL MAL TIEMPO.

EL OLEAJE PERMANECERA BAJO EL CRITERIO DE ADVERTENCIA PARA EMBARCACIONES PEQUENAS HASTA EL LUNES...CUANDO EL OLEAJE Y EL VIENTO AUMENTARA DEBIDO A LA TORMENTE TROPICAL ANA.
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Convection still holding on with Ana despite the exposed center.
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GFDL 12z looks like it wants Bill to be a fish
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Quoting P451:
MODIS catches TD3 at 1605Z



Starting to look like its developing an eye lol.
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416. IKE
Not sure if this was posted...12Z NOGAPS..
Member Since: June 9, 2005 Posts: 23 Comments: 37860

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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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