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 DM21Altestic:
I believe it was Drak himself that got banned for fishcasting last year during Hurricane Bertha. He correctly predicted that Bertha was going to be a fish storm, and to express that, he posted a fish.


Bertha effected Bremuda. Bertha wasn't a fish.
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Quoting HaboobsRsweet:

I do agree with you that it is hard to find the support data out there from buoy obs but I just never have been a fan of buoy data anyway. Once you get some good waves going, the buoys are usually under water anyway. I have a hard time overlooking the radar loop. I can look right at it and pick out where I believe the center is and see rotation starting now and def going to be clearer by the morning.

Buoys are quite capable of measuring 84 mph winds in 56 foot waves. I know most of the moored ones have a 50-foot tether.





And I want to fess up. I have been holding out on you. I am a met. My job is to build hurricane wind fields based on all available observations for the sake of storm surge modeling. I, and my office, have done this for about 8 years and have done so for USACE, NASA, NOAA, coastal engineers, forensic studies.
We use a fair bit of analysis when there are no surface obs and I agree that the radar is showing some nice mid-level turning...but that does not always mean surface low. Maybe it is and maybe it is not there right now, but will be soon. Still a possibility it doesn't do much, if any, development.

Hey, anyone know what model was supposed to get assimilation of the WSR-88D data? Was that starting this year?
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Whats got most models shifting N on Bill?
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Quoting weatherman113:
what about the wave behind bill has it riped yet??? does it still have a chance??

ECMWF develops it
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Quoting CatastrophicDL:

Yep
Not much of a summer when the weather is like that.
Member Since: July 30, 2007 Posts: 0 Comments: 1474
Quoting Orcasystems:
The models are definitely starting to show the Northern shift in track





you can have your mode runs lol



the mode runs are trash at this time way too soon to tell what bill will do
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Quoting btwntx08:
wow adrian bill will not be a fish storm its still ways out and its too far low to be pick up i believe bill will probably go to the gom


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.
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Quoting iluvjess:
Pat and Orca. Challenge Question. How many named tropical systems have ever been born and reached atleast TS status while never leaving the shelf? Could 91L be the first ever if it reaches storm status?


Pat wins.. I have no idea
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Pat and Orca. Challenge Question. How many named tropical systems have ever been born and reached atleast TS status while never leaving the shelf? Could 91L be the first ever if it reaches storm status?
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3452. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127950
what about the wave behind bill has it riped yet??? does it still have a chance??
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Quoting serialteg:


that pretty much sums 90% of the message board.

which is why crow is being declared an endangered species all around the GOM, CONUS, and CARIB.




i see your looking for a 24hr ban???


some one was posting photos a fish and they got ban last year for 24hrs so if i where you i would re move it
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Quoting KerryInNOLA:
???? Has there ever been a hurricane to get into the Chesapeake Bay and then head to Washington giving it hurricane winds? How likely is this?

Well usually what happens is the shape of NC and the Outer Banks puts that in harms way first before it could reach the mouth of the Chesapeake or eastern VA. I guess it could happen but the Outer Banks would take a beating first.
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Waiting for the 1 AM updates on 91L. Even if it
doesn't develop, looks like higher than normal
tides for us in SE Louisiana along with heavy rainfall.
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Quoting TampaMishy:
Are you in Utah?

Yep
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The models are definitely starting to show the Northern shift in track


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Quoting rareaire:
That pic patrap posted looks to be spinning am i correct Tampa?


Ya but radars can be very deceving with Tropical systems....that spin your seeing could be mid level on radar and not at the surface.....but, i believe there is a Surface Low that has just formed......
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Tampa spin does 91L look like its going more N?
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3440. Patrap
Quoting HaboobsRsweet:
What do you think Patrap? Surface Low?


Watching that CoC tighten up,..Id say were getting there,78% or better chance there's a Low spinning up at the surface now. Its in the Tounge of very warms SST's,venting is good,..Shear Nada,..

The flue is open,the match is Lit I'd say.



Member Since: July 3, 2005 Posts: 423 Comments: 127950
91L seems to be consolidating around 26.7N, 83.8W....
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Quoting DM21Altestic:


I'm really liking the looks of this system.



yup now bill is starting to look more like a hurricane
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Quoting HurricaneKyle:


AGAIN I repeat rofl. They had Bill in the Caribbean yesterday, these WILL change. I guarantee you, and if anyone calls a system 7 days out a fish is either making a joke, being a troll, or doesn't know about the tropics. Same with those who guarantee a US landfall.


that pretty much sums 90% of the message board.

which is why crow is being declared an endangered species all around the GOM, CONUS, and CARIB.

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Quoting code1:
Ahh Tazz. You are wise beyond your years at times. Does WU allow multiple ignores though? Can't watch Dr. M's blog except early in the morns when the teens are sleeping it off for the most part. Am really sorry I was here tonight.


I mean heck this thing is 7 days out, we haven't a clue were its going. Mexico to Maine is in the cone IMO.
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Quoting TampaSpin:


I know it is strange but, i have used that before and it works.....thats why i went there..LOL.....I could be wrong.


it may very well work...we'll see when 91L gets a quickscat pass or gets near several bouys. IMHO i think a TD is a sure thing.
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Even if 91L doesn't have surface low right now I think it's a safe bet that it will soon.
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3431. Walshy
Quoting KerryInNOLA:
???? Has there ever been a hurricane to get into the Chesapeake Bay and then head to Washington giving it hurricane winds? How likely is this?



Depends on the administration at the white house at that time.
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Quoting DM21Altestic:
Bill keeps chugging westward at a rather brisk pace, ala Dean.




yup


no fish storm
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3429. 2ifbyC
Quoting stillwaiting:
winds at 20-25mph here in sarasota a rain band its the 2nd one in a hour and 4th today,TD4 5am,IMO


Every thing is peeling off the beaches as it approaches Bradenton. It's almost dead calm just east of the ICW.

Sure could use some more rain. Bedtime...
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I am not a troll and never have been a troll. I used to post my own blog on this website regularly but i don't post much here any more because of all the bickering.

Before i go out for the night i don't see trough being so strong and ridge weakening as much as forecast by models so florida might be out of the question but the carolinas northward could still have a problem, not saying a florida landfall is not possible
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Quoting CatastrophicDL:

We've got a cold front and rain here. I ran in downpours and 54 degree temps this morning. It's normally upper 90's here this time of year, so the cool down has been nice.

Are your winds starting to shift direction there at all?
Are you in Utah?
Member Since: July 30, 2007 Posts: 0 Comments: 1474
3425. code1
Ahh Tazz. You are wise beyond your years at times. Does WU allow multiple ignores though? Can't watch Dr. M's blog except early in the morns when the teens are sleeping it off for the most part. Am really sorry I was here tonight.
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Quoting code1:
serialteg? If you have to ask that. You are one whom I was just speaking of in my last post.

Tropics anyone without hyperbole or me antics?

Dr. M, do you hear us?


im sorry. what?
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Quoting jipmg:
Models take mr Bill out to sea, all of the models everyone of them...

Models take ana to its death over the caribbean.. some shitfting north, oh well im going to sleep im starting to lose interest in these systems


They had Bill in the Caribbean yesterday, these WILL change. I guarantee you, and if anyone calls a system 7 days out a fish is either making a joke, being a troll, or doesn't know about the tropics. Same with those who guarantee a US landfall.
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3421. flsky
Quoting code1:
Agree stormsurge39 and tropics21. Much ado about something that may or may not be. Now, for those of you new in the last bit? I've been here since blogs started on WU. Want us to take over the main blog again? Nahh, I don't think so.

Be cool, grow up and learn from each other. I am old enough to be your parent or even grandparent to some of you since blog started. Listen and learn from others without the oneupmanship. You will learn far more that way.
I live on the FL panhandle and am in Galveston working. I and others surely don't need to want to wade through the juvenile posts some of you make here to show your cajones. We are NOT sitting in your parents home thinking someone else will protect us. Please think of it from an adult side. You'll be there yourselves before your know it!!

Hey! Concur!
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Quoting Progster:


Maybe...but there is a lag between current motion and surface wind...and a pre-existing current has some memory...a change in the wind won't immediately change the curent and there is a big difffence in momenntum between moving air and moving water...nevertheless, an interesting way to see the wind field without benefit of direct wind measurements.


I know it is strange but, i have used that before and it works.....thats why i went there..LOL.....I could be wrong.
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What do you think Patrap? Surface Low?
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That pic patrap posted looks to be spinning am i correct Tampa?
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Things look active tonight across the tropics BUT if the trends continue with Bill it should not be an issue for the U.S.

Next 2 systems....Blah
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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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