Ana and TD 3 take aim at the Lesser Antilles
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
Reader Comments
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You can educate yourself by reading a NHC TWO. "Surface pressures remain high in the area." Boom...now I know you need low surface pressures for a cyclone to form.
you weren't ignored. i got a laugh out of it!
haha hmm, maybe they'll teach me that at Purdue
Maybe they can't decide what to set for the initial intensities?
Im just a watching the wheels go round and round..
But in that area,..well..seen screwier things happen.
The Sky here has High curved,banded cirrus,and low scud rolling east to west.
If the engine stars and the flue is open.
Da voodoo man gonna be busy...
Is it me or does there seem to be more banding going on with it?
08/15/2009 M46.00 MPH GMZ052 FL C-MAN STATION
A SOUTH-SOUTHWESTERLY WIND GUST OF 40 KTS...OR 46
MPH...WAS RECORDED BY THE C-MAN STATION ON MOLASSES REEF
LIGHT AT 145 PM EDT. THIS GUST WAS FROM A HEAVY
SHOWER...ASSOCIATED WITH A PASSING TROPICAL WAVE.
&&
$$
ROSS
It's pouring right now in Fort Myers. Looks to be headed your way soon.
I totally understand your point. I don't think his posts are too dangerous because he always exaggerates on the high side. I would rather have someone do that then the ones who come on and say "nothing to worry about". (EYE) At least if someone takes it seriously they will be more prepared instead of less. His ridiculous posts before Katrina might have actually saved some people. I just think they are kinda funny.
Bill is getting more near to Ana. There is just 1 qudrant between them.
starting to develop some convection
by the way the convection looks I think we wont have Bill at 5pm unless it explodes soon
On every storm, Atlantic and Pacific? Maybe communications problem? I was wondering myself why no 18Z guidance.
I would be surprised if a 00Z CMC/ECMWF blend were to succeed.
Evaluating the sigma levels I do not see where these models are deriving their impetus in causing that much beta motion between 72 and 120 hours, particularly when the steering field remains so longitudinal in orientation. Beginning at this latitude and having virtually no weakness in the ridge modeled out through 144 or so hours, I don't see where that much polar-ward motion is actually going to come from.
I'm considering these models the less likely outliers until I find a reason that fits.
That said, the 12Z CMC did come a tad further west of the 00Z fixes.
I believe everyone from the northern Gulf Coast to Maine needs to be paying attention to the tropics/outlooks over the course of the next week to 10 days.
Ana is tough one to call. I am wondering if her small size has the models only vaguely aware of the system's presence. The U/A wind shows a relaxed shear, yet convection struggles at the current hour. WV imagery suggest pretty strongly that the culprit is a few gulps of dry air. This may continue (...and continue to baffle the models) until she grows (if and when) in size and contains her own environment at the core. She's just not big enough to produce that inward environment just yet.
I believe the difference in the track guidance in why Ana winds up in the Gulf and "Bill" ends up along the East Coast or headed for England is because of scale of development - the weaker systems are reliant on lower level steering.
Kid, you really need to get laid rather than hanging out 24/7 on a weather blog site being nerdy.
Yep, several times and didn't find a single one below 30.
Ah-nah.....TS?
Haven't seen one drop of rain in Ft Myers yet although seems like that will change very shortly. Very overcast and breezy
I agree; they both still look pretty good. Of course TD3 is the largest and best looking right now.
time will tell.
Stormtop was funny in 2005; just go read some of those archive blogs! LOL
and he did "nail" Katrina before anyone else.. but then again, he called EVERY STORM to follow that course and hit New Orleans ,, Eventually one did.
that's better! :D :D :D :D
rainin here now in puerto rico... hope to have my electric generator here soon to be able to report live while storm passes if comes to that. and obviously if internet holds
well that would be a great D-max xD
Possibly. Pacific has the same problem?
I know Ana (and maybe Guillermo by now, haven't really checked SSD or ADT for that) is weakening and TD3 is just chugging along.. maybe hard to get a handle. But wouldn't of thought it'd take over an hour.
Must be something technical, you're probably right.
we do try our best, huh?
Hey FLfishy -
Welcome to the Blog. Me & my wife are up here in Lantana. Guess it finally got interesting out there, uh?
AL 03 2009081518 BEST 0 113N 345W 35 1006 TS
The southerly tracks, unfortnunately seems more reasonable for several reasons:
where TD 3 formed, more south than expected
its forward speed, fast=more west, slower=more pull north. TD 3 has speed up today since it became more organize
its motion and located, at 11.5N moving off towards the west, that very low, especially since the models had this at 14N at that very same latitude
Thanks I was looking for that
AL, 03, 2009081518, , BEST, 0, 113N, 345W, 35, 1006, TS, 34, NEQ, 25, 25, 0, 25,
ANA
Bill
AOI
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