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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I hate to say this but I hope Ana clips south FL because if it does it will just be a TS and that is usually nothing more than a bad thunderstorm with a bunch of rain. If it makes it to the Gulf then things get more interesting and more dangerous.
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TD 3 Storm Relative 1km Geostationary Visible Imagery

Time of Latest Image: 200908151615



Storm Relative 1km Geostationary Visible Imagery

The current suite of geostationary satellites provides visible imagery during daylight hours at higher resolution than many of the infrared channels. Such imagery is useful, especially when animated, for position estimation and monitoring the degree of convective organization. The native visible imagery has been remapped to a one-km Mercator projection and the digital data has been stretched over its full range - allowing a more esthetically pleasing appearance. The center location is based on the last operational position estimate and the previous 12-hr motion
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The CFS is still not fixed!
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Quoting Weather456:


Saint Kitts


I used to date a girl from Saint Kitts...which is probably about all of that story any of you wanna hear...
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raining to beat the band here in grassy key right now. But still only a slight breeze. radar shows that circulation over us. maybe the birth of a system is happening right over the top of me. glad it's just starting here and not ending up here something worse
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alright im off . I have to get the 51 merc sanded some more so you play nice!
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307. amd
Quoting dcoaster:
Anyone else seeing that Ana's CoC seems to be moving MUCH faster now? Basing on very rough lat/long to distance calcs, maybe around 17-18mph?

Look at the last 8-10 frames: TS Ana Visible Satellite


yes, and it is beginning to move north of due west (could just be a wobble though)
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Quoting jipmg:
ANA looking like its about to start a WNW movement

It sure looks like it.
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Quoting Weather456:


Nope, the tropical near the Florida Keys is an exmaple of where Ana and Bill will be going.


there isnt much room for Ana to go noth as every advisory the track keeps shfiting sotuh.

Excellent point.
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have the complete nhc hurricane statement on my blog issued for pr
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Quoting NOSinger:
456......Do you think NOGAPS is a little too bullish? Or do you think this could possibly be a reasonable scenario?


Nope, the tropical near the Florida Keys is an exmaple of where Ana and Bill will be going.


there isnt much room for Ana to go noth as every advisory the track keeps shfiting sotuh.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
from NHC
PR HURRICANE STATEMENT NHC...
SITUATION OVERVIEW...
AT THE PRESENT MOMENT...TROPICAL STORM ANA IS NOT WELL ORGANIZED
BUT THE FORECAST IS FOR THE STORM TO SLOWLY INTENSIFY DURING THE
NEXT TWO DAYS AS IT MOVES TOWARDS THE ISLANDS OF THE NORTHEAST
CARIBBEAN. AT THIS TIME...IT IS TOO EARLY TO PROVIDE EXACT
WIND...RAINFALL...AND SURGE FORECAST VALUES FOR SPECIFIC
LOCATIONS. A GENERAL CONCERN SHOULD BE FOR THE POSSIBILITY OF AT
LEAST DAMAGING WINDS AND LOCALIZED FLOODING SOMEWHERE WITHIN
PUERTO RICO AND THE U.S. VIRGIN ISLANDS.
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The exact center of TD3 is still broad and hence little ambiguous - but generally fluctuating around WSW to W....
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Quoting cg2916:

I think it's likely.
Also, I'm not sure if you read my comment earlier, but what island are you on? Isn't it Antigua?


Saint Kitts
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting rareaire:
What you eat Pat would kill a non Louisianaian! (politically correct term)


Making some Shrimp Creole today later..the Shrimps are fantastic right now,gonna go Pick up some White Shrimp also to Grill as that season opened here Monday
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Anyone else seeing that Ana's CoC seems to be moving MUCH faster now? Basing on very rough lat/long to distance calcs, maybe around 17-18mph?

Look at the last 8-10 frames: TS Ana Visible Satellite
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Quoting NOSinger:
456......Do you think NOGAPS is a little too bullish? Or do you think this could possibly be a reasonable scenario?

I am not 456 of course but would like to get into this converstation. I think it is not too bullish as the trend for most waves this year is the models adjust to a south track. It all depends on what the models do with a forecasted Trough to move across Conus. Timing of the trough combined with the amplitude is going to determine where both storms end up.
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296. CJ5
Fox news just showed the Ana long term point in Miami. That should generate some buzz.
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"Just follow my nooose!"
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294. CJ5
Quoting WeatherStudent:


Really? No it's not.


Really...well thats easy to solve, post the data.
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293. jipmg
Quoting Funkadelic:
TD3 starting to look a little bit tighter on Visible satelite.. Still moving south of due west, models will probabley flip back west again later tonight due to the fact that it is rather weak.

Here you can see it slowly organizing and moving WSW:



Link


I think it stopped moving WSW based on the latest images, looking more due west now
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Quoting WeatherStudent:


Really? No it's not.



Well! I guess you've been told!!!!!
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456......Do you think NOGAPS is a little too bullish? Or do you think this could possibly be a reasonable scenario?
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What you eat Pat would kill a non Louisianaian! (politically correct term)
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Quoting futuremet:


lol it's ok. It is hard to know you are being mistaken for JFV.



LOL,,"You Betcha"
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288. jipmg
ANA looking like its about to start a WNW movement
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Somebody better check Joe Bastardi's BP as Im sure his Cage is rattling over the 06 GFS run.
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Quoting Patrap:
Sorry FutrueMet,Im not awake yet,and i didnt realize the post error.
I owe ya Lunch


lol it's ok. It is hard to know you are being mistaken for JFV.
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Quoting jipmg:


convection is trying to blow near the center, well to the east of it, its not being blown off too much, slight to moderate shear blowing over head keeping it from organizing, I suspect at DMAX it will come back

I see it now, but it's still exposed.
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Afternoon all,
Well Well Well... so for us in the Turks and Caicos the worst case scenario would be as follows :Tuesday : Ana....Friday soon to be Bill and the following Monday maybe Claudette???? is that real ?
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Quoting Patrap:
Sorry FutrueMet,Im not awake yet,and i didnt realize the post error.
I owe ya Lunch

You're definitly not awake yet. LOL.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
My other question for the day - after the past couple of years, when people have had to evacuate, it's been a wait and see to when they come back, where they are etc...

Is there anyone who is taking a private list of where people are going and their contact numbers to make sure they are okay?
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Quoting MississippiWx:
TD3 will have to start gaining some latitude now if it's going to make it north of the island chain. The current trend for TD3 appears to be a weakening one, as far as thunderstorms go. DMIN seems to be affecting it. The weaker it is, the further west it will go.


I agree.... If it stays a Tropical Low it does go further west..... So on that note I wish Bill and Ana go out to Sea and not hit anything....

taco :0)
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Quoting Catfish57:
Anyone seeing a semblence of a GOM circulation at 28N 91W?

Thats a big yes.
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Quoting Weather456:
well the weather channel is reporting the wave behind TD 3 will likely become claudette

I think it's likely.
Also, I'm not sure if you read my comment earlier, but what island are you on? Isn't it Antigua?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
CMC and GFS are on board in developing the African wave now.
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Sorry FutrueMet,Im not awake yet,and i didnt realize the post error.
I owe ya Lunch
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What do you think the strengh of Ana will be passing the northern islands?
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273. CJ5
Quoting Patrap:
Dont become too focused on any particular Model run as they will change from Run to Run.


True...in your case we will lean towards the GFDL which has Ana going S of Hispaniola..lol
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Quoting Patrap:
Anyone seeing a semblence of a GOM circulation at 28N 91W?
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Quoting Category5hitsNewYork:

It is all a wait and see game. Nothing is for certain now. Just be prepared.



your handle looks like a bad word...
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well the weather channel is reporting the wave behind TD 3 will likely become claudette
Member Since: July 24, 2005 Posts: 407 Comments: 19076
If that thing does what the models say, i might need to get prepared as well and I live in the middle of the US
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Quoting srada:
Good Morning everyone!

Tropical Storm Ana has finally formed! Does anyone know or can provide when the first recon flight will be? Many thanks in advance

THey went yesterday
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Quoting futuremet:


I am not WS....


LMAO... hes def not awake yet!
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Quoting futuremet:


I am not WS....


Dude!!! We ALL know that! 'specially Pat...I think he was just making a funny...
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Member Since: July 24, 2005 Posts: 407 Comments: 19076

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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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