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 Chucktown:
What up Press? Little sigh of relief with the current thinking on Bill. Not set in stone, but nice to see 95% of the models keep Bill well offshore and out to sea. Still not out of the woods with all the other waves exiting Africa so we'll have to sea (get the pun?)



yea...I feel better...
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Quoting Weather456:


the models have Bill moving NW from the intial point.

The argument is, Bill is slightly south of due west, then will move west and turn west northwest. Surely then track cannot be in line with the models which have Bill moving directly NW.


Some of the models in the first 6-12 hours show a WSW movement, then turning WNW. You just can't see that initial motion on the plots that show 120 hrs.
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2662. Drakoen
Quoting weatherboykris:


drak is a freshman? Wow, I'm a senior and thought I was young...


Do you really believe that? LOL!
Member Since: October 28, 2006 Posts: 57 Comments: 29888
It is amazing the damage that hurricanes can well inland. I am a catastrophe adjuster and deployed at ground zero for Hurriane Ike just 2 days after landfall. I was shocked to get a call a day or so later that my roof with 40 year dimensional shingles was a total loss. I was suprised because I live in the heartland of america in Western Ky. Apparently Ike had met up withanother system and strengthened and the damage in Arkansas,Ky,Ohio, and Indiana was widespread and heavy...go figure!
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as of now...does it seem the east coast will be spared any affects from bill?? I noticed models r trending to curve it north around 70-75W longitude??
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Hello to all the WU blog. (good work)
As I have previously stated, immensly enjoy lurking & learning in here whenever I can. Long day at the office today, had to play some golf late in the day with some students, and was constantly watching the skies overhead in South Palm beach county, Boca Raton. the weather conditions were very squally due to the wave, (now 91L) moving through the keys into the GOM. Its amazing how systems produce these quick windy condition, along with the quick/short lasting rain squalls. Hence, tropical in nature rather than an ordinary rain event.
Just catching up on all the new information from today and see we are in for some interesting days ahead, if not weeks.
Just MY Opinion for our systems coming at us after sifting through many comments posted here and all models looked at, and other variables, etc..

Anna: Will hang tough and remain a tropical storm in the upcoming week as it passes through the Northern Antilles, potential a hit on PR, and continuing west just south of Florida as a TS and then entering the GOM with many scenarios involved there as we all are well aware.

Bill: Will also survive any shear and dry air at this time and will follow a very similar path of Anna, but, maybe a curve more to the North since this system will be strongr in the days ahead and have a more poleward bias, unless a stronger ridge inhibits this movement.

New Low just off Africa: similar tracks of Anna & Bill initially in the sequence since it will be embedded in the ITZ easterly flow set in place, way too early for an designated landfalls, if any.

91L: North west slow movement with potential for a surface low in the next day or so, and then a slight turn to the NNE, panhandle area as a minimal TS. Rapid intensification possible as always but unlikely, I believe, since it has not shown any indications of dropping down to the surface quick enough to warrent that intensification.

All that being said, Pardon the Interruption and carry on Folks, Rich

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hi all....anyone care to update me on the chances and info of what's going on with 91???
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Gulf disturbance has potential, but limited time. 2 days may be enough for a minimal TS to form under the favorable conditions it has, but that should be it. Let's not forget about storms like Humberto and Lorenzo from 2007 that ramped up extraordinarily fast under similar circumstances, that is a small possibility, though unlikely.
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When did NHC do away with the line in the cone? I remember Max Mayfield for years wanted to get rid of it.
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Quoting Weather456:


the models have Bill moving NW from the intial point.

The argument is, Bill is slightly south of due west, then will move west and turn west northwest. Surely then track cannot be in line with the models which have Bill moving directly NW.

Yeah, I don't see Bill making that sharp a turn. Very rare.
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2654. Skylink
Quoting AllStar17:


No....no.....no.....no....no

El Nino will certainly not last a couple of years, and some signs show it has already peaked, and is weakening.



Please see the following link, http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf
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Quoting StormW:
Thanks KOG!
Storm, You are the most acurrate I have ever seen. Thanks a bunch
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2652. Patrap


91L Short Floater - JSL Color Infrared Loop
Member Since: July 3, 2005 Posts: 421 Comments: 127559
What up Press? Little sigh of relief with the current thinking on Bill. Not set in stone, but nice to see 95% of the models keep Bill well offshore and out to sea. Still not out of the woods with all the other waves exiting Africa so we'll have to sea (get the pun?)
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Quoting wunderkidcayman:

yes sorry
I told you before. Don't get so excited. Calm down.
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Quoting zoomiami:
We have a dog that goes crazy following the light - from a flashlight, from the reflection off your watch, from the glass on the door when it opens. That's what us watching all these storms reminds me of. lol

Before the last sentence, I really thought you were going to compare your dog to one of our posters, here. I really did.
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Quoting viman:


Het, good evening W456. How are things?


everything is aight. you?

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting stormwatcherCI:
Do you read ? October 6, 2008.

yes sorry
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2645. DDR
Quoting Weather456:


Dean,



Thanks alot 456,respect...
off to bed now,i'm going to the beach tomorrow,hope it doesnt rain lol
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Quoting Stoopid1:


That's where the models shift in direction comes. People are already discounting them, but I think they have the right idea.


the models have Bill moving NW from the intial point.

The argument is, Bill is slightly south of due west, then will move west and turn west northwest. Surely this track cannot be in line with the models which have Bill moving directly NW.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2643. jpsb
Quoting StormW:
Regarding 91L:

Just to show you how fast things change
Thanks! Anyway to tell if the surface low forms?
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91L radar.
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Quoting flsky:

Go away.


Can you go away?
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2639. Patrap
T S ANA Archive,with current track
Member Since: July 3, 2005 Posts: 421 Comments: 127559
2638. viman
Quoting Weather456:



thank you


Het, good evening W456. How are things?
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Quoting eye:
Alot of yall do not realize that Drak is only a freshman in high school, when he started in this blog he was in 6th grade.


drak is a freshman? Wow, I'm a senior and thought I was young...
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Quoting Barbados:


Stormdude, Bill is looking a little ominous. We may yet have a touch.


We'll see. Let's see what the NHC says at 11:00pm...
Should residents of the southeast coast be worried about bill or is the consensus that the storm will continue westward?
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I have a bad feeling about Bill, if indeed he turns out to sea, a lot of people should feel lucky!
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91L sure looks to be trying to close off a low level circulation. I agree this is likely to blow up tonight.
Link
Tampa radar
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South of Tampa is interesting.....

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Quoting Stoopid1:


That's where the models shift in direction comes. People are already discounting them, but I think they have the right idea.


Wow! 2 minutes without a post
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Quoting DDR:

Thanks,my memory is bad,but wasn't there one though in recent years?


Dean,


Member Since: July 24, 2005 Posts: 407 Comments: 19076
2614. midgulfmom 2:18 AM GMT on August 16, 2009
Quoting stormbottom:

great...just what i needed..a big HIT HERE sign on my roof !

LMAO, We're all just sittin ducks....


yep the local weather people are going to freak out...
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2627. KEEPEROFTHEGATE (Mod)
Quoting StormW:
Regarding 91L:

Just to show you how fast things change.

A well established upper level anticyclone is over 91L...this is now forecast by the GFS wind shear to move in tandem. Doesn't look like it's at the surface quite yet. However, if it works down before getting to the coast...the possibility MAY exist for this to begin to spin up quicker. This could, if it works to the surface, become a depression. Based on current flow and forecast steering, right now it looks as if it could come ashore bewteen MS/LA. I may no be able to be on in the morning, so I recommend staying tuned to local wx. Fortunately, it mst likely will run out of time forany significant development.

i am watchin all night long stormw if i see any sign at all those on here will know
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Quoting Drakoen:
If Bill is intensifying now as the quickscat and objective guidance suggests, it will start moving to the WNW.


That's where the models shift in direction comes. People are already discounting them, but I think the models have the right idea, though a slight shift south may be in order.
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Quoting stormwatcherCI:
Do you read ? October 6, 2008.


LOL
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Quoting StormW:
Regarding 91L:

Just to show you how fast things change.

A well established upper level anticyclone is over 91L...this is now forecast by the GFS wind shear to move in tandem. Doesn't look like it's at the surface quite yet. However, if it works down before getting to the coast...the possibility MAY exist for this to begin to spin up quicker. This could, if it works to the surface, become a depression. Based on current flow and forecast steering, right now it looks as if it could come ashore bewteen MS/LA. I may no be able to be on in the morning, so I recommend staying tuned to local wx. Fortunately, it mst likely will run out of time forany significant development.


Thanks Storm - nice to know you are always on the lookout for us! {{hug}}
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Quoting stormdude77:
Can anyone give me an updated satellite image (link) of the African coast?

TIA


Stormdude, Bill is looking a little ominous. We may yet have a touch.
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2621. Patrap
GOM INVEST Rainbow Image

01:15 UTC


Member Since: July 3, 2005 Posts: 421 Comments: 127559
Analysis on Ana, Bill, and Invest 91L

Ok, instead of putting 3 separate bulletins together, I found a way to do the map with all 3 storms. Soo.. Lets get going

Starting with...

Tropical Storm Bill
Heavy thunderstorms are beginning to reform with the storm, it was named Bill at 5 p.m. The track is beginning to become a bit clear. I doubt and have always doubted that it would reach the Gulf of Mexico. My "gut feeling" is still possible where it heads up the East Coast and strikes Long Island, not that I wish it on them, but this is the way the pattern is set up. Bill has winds of 40 mph., though it seems to be organizing quite well tonight. Might be 50-55 mph. by 5 a.m. tomorrow. The track of Bill is all about timing. If Bill is fast, it will head more west. though if Bill is slow, out to sea he goes. It will become a Hurricane in about 2-3 days, maybe even making major Hurricane status when it gets to the Bahamas. 2 weeks away, we have plenty of time to watch Bill, but please make Hurricane prep plans just in case. I'm checking my generator out next week.

Tropical Storm Ana
Ana formed 5 a.m. this morning from what was a pesky Tropical Depression that was classified earlier a few days ago, then downgraded to a wave, then re-classified 24 hours ago. Tropical Storm watches are up for the northern Leeward Islands. Ana might impact South Florida in 5 days, but also has a good chance of weakening back to a wave due to some dry air entraining into it. This is clearing all the dry air for Bill to strengthen.. It's like Ana is a shield for Bill. I'm not as concerned about TS Ana as I am with TS Bill but I would not be surprised if Ana were to strengthen in a few days due to very warm water temperatures.

Invest 91L
Warm temperatures is what might cause 91L to repeat a similar storm that happened to strengthen to a Hurricane in 24 hours. I am not saying 91L is going to become a Hurricane, but possibly a Tropical Storm before making landfall on the northern Gulf Coast, most likely Louisiana. I don't like the looks of this.. This is really cranking up and I find no reason why it shouldn't. these conditions are more ripe then what Wilma (2005) formed in. Folks on the northern Gulf Coast may be waking up to Tropical Storm Claudette with warnings. I hope that people are cautious on what might just occur tonight..


After those 3 analysis, I made a map concerning possible tracks of those 3 systems. Ana is yellow, Bill is red, and 91L is blue

Photobucket
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Quoting Funkadelic:
Lets say Bill stops the WSW motion right now as of 10:16pmEST...

It would have to move almost NW to match the models.



thank you
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting flsky:


Go away.



...ditto...
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Quoting wunderkidcayman:
where are these guys going
ANA?
Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KBIX)
Disseminated Through: Keesler AFB, backup for KNHC (TPC/NHC)
Transmitted: 7th day of the month at 02:35Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Mission: Non-Tasked Mission, possibly not tropical (originating in the North Atlantic basin)
Mission Identifier: 08100622302 (2 digit year/2 digit month/2 digit day/2 digit hour of mission start/Last 3 digits of aircraft tail number)
Date Mission Started: October 6th in '08
Hour Mission Started: 22Z
Observation Number: 03

Part A...

Date: Near the closest hour of 0Z on the 7th day of the month
Highest Mandatory Level For Which Wind Was Reported: 400mb
Coordinates: 28.4N 88.1W (View map)
Location: 150 miles (242 km) to the SSE (157) from Gulfport, MS, USA.
Marsden Square: 081 (About)
Do you read ? October 6, 2008.
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IMHO 91L is ready to take off...it has extremely rich PW environment, optimal STT's, anticyclone aloft..good structure and windfield as derived from radar. Its proximity to land is both a short and longer term inhibitor, but I would not be surprised at all to see a strong TD this time tomorrow.
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2615. ssmate
Quoting szqrn1:


I think thatwas his prom pic from last year!..seriously!

Nah, back in the day in my prom picture a girl was included.

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Quoting stormbottom:

great...just what i needed..a big HIT HERE sign on my roof !

LMAO, We're all just sittin ducks....
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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.