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 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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Quoting stormwatcherCI:
He still seems to know what he is talking about.


Dont bother with eye, again, he is a troll
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2612. DDR
Quoting Weather456:


nah, I was forecast to remain south


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

I believe you are right. The radar makes it look like your town is up in the next 30 minutes to an hour. Since it will be raining cats and dogs for you soon, if you see my dog will you tell it to go back home? :)
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Quoting weatherfan92:
Does anyone else think Bill will be a hurricane tomorrow?
I do.
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Quoting Skylink:


The EL NINO will not take effect on the Atlantic until late fall and through the next couple of years.


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.
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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.
He still seems to know what he is talking about.
Member Since: October 9, 2008 Posts: 0 Comments: 8322
2606. snotly
Bill's CDO has a slightly warmer area near the center. Eye? ... guess not I suppose.
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Ike, seems like it would be piling up where its at
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Just tuned in. Any discussion on invest 91?
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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)
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Quoting DDR:

456
I Don't recall but Wasn't ivan forcasted to take a path out to sea.Do you remember?


nah, Ivan was forecast to remain south

Member Since: July 24, 2005 Posts: 407 Comments: 19076
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.


and what dos that have to do with hurricanes???
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2599. flsky
Quoting WeatherStudent:
LOL, guys.


Go away.
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2598. Skylink
Quoting Weather456:



I posted a comment earlier today indicating El Nino may have peaked in late July. Waters have not warmed during the first half of August.


The EL NINO will not take effect on the Atlantic until late fall and through the next couple of years.
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Quoting Weather456:
Bill continues on its organization spree tonight



If this trend continues, hurricane tomorrow is not out of the question
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Quoting DDR:

456
I Don't recall but Wasn't ivan forcasted to take a path out to sea.Do you remember?

yes, and then over cuba and through the penisula of florida until it finally turned north south of cuba's west end.
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2595. 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.
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Quoting Ameister12:
An F5 spree is going to start in the next 30 to 40 minutes.


The F5 spree will probably begin around 10:35, I would not imagine people refreshing now, as advisories never come out this early.
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Bill continues on its organization spree tonight

Member Since: July 24, 2005 Posts: 407 Comments: 19076
African coast..

Member Since: September 1, 2007 Posts: 0 Comments: 1979
something new here...IR animation of bill.

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2590. jipmg
Quoting InTheCone:
Little Ana...




the center is somewhat exposed though..
The best one yet LOL ROFLMAO
Quoting hurricanehanna:

He was looking for the circulation! lol j/k
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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
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2587. DDR
Quoting Weather456:


slightly south of due west based on microwave imagery past plots and the XTRAP model.

456
I Don't recall but Wasn't ivan forcasted to take a path out to sea.Do you remember?
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2586. flsky
Quoting stormshed:
oh yeah the boomers have started. where you at in brevard?


I can see the flashes of lightning now from DB Shores. Guess it's coming my way.
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models are off right now untill new data is loaded and a new run is done, ithink all will be suprised at new forcast tracks.
Member Since: August 14, 2008 Posts: 0 Comments: 1002
Quoting mossyhead:

just to let you know that with all those straps, etc. your house is more liable to be struck by lightning. was told this by a captain for a fire dept. number one cause of lightning strikes on houses.
6 of one and 1/2 doz of the other.
Member Since: October 9, 2008 Posts: 0 Comments: 8322
Quoting szqrn1:
Okay... help me out.. .is Bill going NW or SW?


Looks like due west to me
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Quoting mossyhead:

just to let you know that with all those straps, etc. your house is more liable to be struck by lightning. was told this by a captain for a fire dept. number one cause of lightning strikes on houses.

great...just what i needed..a big HIT HERE sign on my roof !
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Ana's center still exposed. I think I'm gonna focus my attention on Bill for now.
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Quoting stormdude77:
Can anyone give me an updated satellite image (link) of the African coast?

TIA


Link
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I am very hesitant to rely on models that cannot properly initialize the current movement of a storm....

notice the extremely wide spread between xtrap, and also notice that not a single model shows the current WSW motion.....

Member Since: September 8, 2005 Posts: 0 Comments: 3805
i go with the XTRAP
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An F5 spree is going to start in the next 30 to 40 minutes.
Member Since: August 9, 2009 Posts: 10 Comments: 4939
2575. jipmg
Quoting leftovers:
could ana kind of pull bill west?


no ana is way too far from bill to affect it
Little Ana...


Member Since: September 1, 2007 Posts: 0 Comments: 1979
2573. szqrn1
Okay... help me out.. .is Bill going NW or SW?
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sarasota,tampa ,bradenton getting a lot of rain plus lighting ,you can smell air very wet,,,is 91L in progrees ??
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2571. bjdsrq
Put up some images to WU that I shot from 91L as it moved through lower keys today. Photos are frame grabs from HD video camera.
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Can anyone give me an updated satellite image (link) of the African coast?

TIA
Quoting HURRICANECAT5:
I THINK MODELS WILL SHIFT A IT MORE TO THE SW WITH BILL. HE IS MOVING RIGHT KNOW JUST SOUTH OF DUE WEST AND HIS POSITION IS A VERY DANGEROUS ONE FOR PUERTO RICO AND SOUTH FLORIDA. I AM NOT BUYING THE SOLUTION OF IT GOING OUT TO SEA.


Neither am I.
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2568. jpsb
Quoting IKE:
Looks like it's moving more NW to me(91L).

not looking bad...
A lot will depend on where the surface low formws, if it forms.
Member Since: June 30, 2009 Posts: 0 Comments: 1190
Quoting DDR:

It's not going west? is it wsw?


slightly south of due west based on microwave imagery, past plots and the XTRAP model.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Never trust a storm that smiles back at you!
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2564. jipmg
Quoting Relix:
What's Ana's current movement? W? Or WNW?


In between , just north of due west

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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.