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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3314. TXEER
Quoting TexasHurricane:


As of right now, I would say no, but you should always keep an eye out, because things can change.


Thank you!
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Good night all. Will Check in tomorrow. Definitely know what some of you are saying about the "feel" of the air. I've experienced it also. It's hard to describe though. More like a sixth sense kinda thingy. Nite.
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Quoting atmoaggie:

Yeah, yeah, yeah. I know what little I have picked up about lift, buoyancy, CAPE, CINH, etc. just being a bump on a log. Some convergence, clearly, but I wouldn't write home to momma about it. But maybe I just am not as good as you mets.
So you keep looking a 1/2 mile in the sky at your surface low:

and I will look for surface obs with sustained wind directions that support it (not the wind shift from the cold pool of a nearby cell).


Member Since: October 1, 2007 Posts: 81 Comments: 26511
3310. KEEPEROFTHEGATE (Mod)
its almost time to create some empty space


yakkusa if ya there make em disappear
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Here's 3 possible scenarios for Tropical Storm Bill

1. Catches the trough early and steers out to sea, maybe affecting Bermuda.

2. Heads more westward then feels the weakness of the trough but doesn't get pulled out to sea, instead it heads north, off the coastline of the Carolinas and then makes a historic landfall in the Northeast.

3. Trough is weaker then forecasted and Bill does a Frances (2004), heads west into Florida, then GOM *slight chance of this happening*
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Quoting rareaire:
no my bud Tampa got me! bouey is not working. and i will never wear mandals!


Crocs will get those piggies nice and sweaty for your boy though...
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91L looks like it may be a tropical depression just before landfall; maybe, at most, it'll attain weak tropical storm status. Nothing to worry about with this system.

Ana looks weak still which is the reason the models and the NHC are showing it heading west. This certainly won't survive Haiti, DR, and Cuba. This may regerenerate in the GOM, but I say little to no chance since this is a very weak, vulnerable storm. Perhaps if it organizes before the islands, it will go on the north side of the cone and hit South Florida which is the worst case scenario since it would tap into the hot Bahama waters.

Bill, on the other hand, while shown to be a fish storm, looks like it's too early to really tell. I still think this is a big threat for the Leewards and Puerto Rico. After that, it could go out to sea, hit the east coast, or make a landfall in Florida and recurve up the state. Right now those are all in the realm of possibilities, and until we have a more consistent model agreement, I'm thinking the whole eastern seaboard is still in major risk.

Behind Bill there is a new tropical wave that needs to be monitored for it can be Claudette or Danny soon and be the next threat down the road.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
Quoting HaboobsRsweet:

Whatever dude, I have been a met for a long time. Lets go back to basics shall we? First off to even have a thunderstorm, you must have convergence. That is how you get lift and an updraft. Make sense? Even if it is small scale you still have convergence. Ok if you look at radar you can see cyclonic rotation. i do not need buoy data that is spread out over hundreds of miles when I can see an updated image every 5 minutes and watch it spin.

Yeah, yeah, yeah. I know what little I have picked up about lift, buoyancy, CAPE, CINH, etc. just being a bump on a log. Some convergence, clearly, but I wouldn't write home to momma about it. But maybe I just am not as good as you mets.
So you keep looking a 1/2 mile in the sky at your surface low:

and I will look for surface obs with sustained wind directions that support it (not the wind shift from the cold pool of a nearby cell).
Member Since: August 16, 2007 Posts: 6 Comments: 12461
no my bud Tampa got me! bouey is not working. and i will never wear mandals!
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3250. flsky 4:31 AM GMT on August 16, 2009
Quoting WeatherStudent:


i already did

Go away.
-----
thats all i have seen you post this evening. now u are going away from my screen. its a shame, but ive had to add 7 names to my ignore list JUST today. but reading the blog is sooo much easier once you get rid of all the irrelevant junk.

on a weather note, since this is what this blog is about (not roaches or bathrooms), 91L seems to be organizing pretty well and i think it has time to get to weak TS strength by tomorrow afternoon.
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Quoting WeatherStudent:


Hey there, Mishy, good to see ya again.
Hi
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10 - Navy-2 (42013)
Local Time: 12:35 AM EDT on August 16, 2009 Location: 27.16 North -82.95 West | Google Maps
Buoy Type: Offshore Buoy
Windspeed measured by: anemometer
Current Weather/Wave Observations
Updated: 10:40 PM EDT on August 15, 2009
Air Temperature: ° F
Wind direction (W Dir): East (95 - 104 Degrees)
Wind Speed (W Spd): 21.4 kts (24.6 mph)
Wind Gust (W Spd): 23.3 kts (26.8 mph)
Atmospheric Pressure (AP): 29.99 in
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Quoting TampaSpin:
Amazing the Dam bouys where the surface low is forming is not working......if you look at the wind directions a Low is just above the surface if not there......it may not be completely closed as Stormchaser just showed in his graphic but its coming very quickly.


OOZ GEM regional run indicates weak surface low development this morning ...as bullish as it has ever been.
Link
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PatRap 90L could very well be a very strong Tropical Depression by the time it gets in your neighborhood.....Alot of flooding rain coming at you all.
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Quoting WeatherStudent:
Anyways, back to the tropics before the admin decides to kick all three of us out of here.
The Blog allready did JFV Lmao
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3292. Skyepony (Mod)
iluvjess~ Many of the models have been forcasting 91L if you look at the 850 vorticy for days. Most take it in somewhere from panhandle to LA. It doesn't seem to matter much where they land it, most have eventually tracked it across AL after the landfall..
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3291. flsky
Quoting TXEER:
OK...allow me to try again...do you have to be a regular to get a question answered?

I live in Houston...survived Ike and I'm asking once again...does anyone think either of these three will make it to Houston?

THANKS!


Hard to say. I recommend that you access WU often and monitor the updates. It can really be a crapshoot.
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Quoting TXEER:
Any of these three coming to Houston?

My natural gas generator won't be installed until the 26th...if I'm going to spend $8,000 on one of those things I want it in before we get hit again!


Yep! Eventually, you just hope it won't get a good workout for a few...a lot of years!!
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3289. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127804
Quoting WeatherStudent:
Anyways, back to the tropics before the admin decides to kick all three of us out of here.


LMAO Is that Finding Nemo???
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Quoting jaevortex:


wow i didn't know such a professional long time met would call someone (a woman professional) a dude

I use the word dude freely regardless of sex. Just a figure of speech.
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Quoting sfla82:


Ok...LOL
some people never learn...it ain't ove till it's COMPLETELY gone!!!!and that's a fact...going to be on that note...
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Quoting TXEER:
OK...allow me to try again...do you have to be a regular to get a question answered?

I live in Houston...survived Ike and I'm asking once again...does anyone think either of these three will make it to Houston?

THANKS!


As of right now, I would say no, but you should always keep an eye out, because things can change.
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3283. sky1989
I just got back on after getting off work, and I see that the models have shifted dramatically northward with Bill. The ECMMF (or whatever it's called, you know what I'm talking about) was the first to show this, and Dr. Masters said it performed the best trackwise, on most of the storms last year. Does anyone think that the models will shift back toward the south? I am a little skeptical since I see that Bill has been moving WSW recently and has not gained much latitude.
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3282. kachina
Quoting TXEER:
OK...allow me to try again...do you have to be a regular to get a question answered?

I live in Houston...survived Ike and I'm asking once again...does anyone think either of these three will make it to Houston?

THANKS!


Answer: We don't know. We don't even know if any of them will hit land at all yet. They're too far out at sea.
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Gas prices will be going up again... along the Gulf Coast.
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post 3226 - LMAO - did he really say that?
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Finally an impressive system in the Atlantic.

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Rare...I think you were smooth ass ignored...maybe if you had on open toe sandals...
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Quoting sfla82:


Ok...LOL


Sorry bud, there's also a decent chance it will go up the East Coast, maybe hit New England. Not every storm that turns north goes out to sea, some trough will weaken and the storm will move northwest. Just because models show it, doesn't mean it's happen, besides, it's still moving west when models have it moving WNW already.
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What do yall think the impacts of 91L will be?
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3272. TXEER
OK...allow me to try again...do you have to be a regular to get a question answered?

I live in Houston...survived Ike and I'm asking once again...does anyone think either of these three will make it to Houston?

THANKS!
Member Since: Posts: Comments:
3271. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127804
Quoting HaboobsRsweet:

Whatever dude, I have been a met for a long time. Lets go back to basics shall we? First off to even have a thunderstorm, you must have convergence. That is how you get lift and an updraft. Make sense? Even if it is small scale you still have convergence. Ok if you look at radar you can see cyclonic rotation. i do not need buoy data that is spread out over hundreds of miles when I can see an updated image every 5 minutes and watch it spin.


wow i didn't know such a professional long time met would call someone (a woman professional) a dude
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Quoting DM21Altestic:
Let's take a vote: Who's been the #1 Successful Troll of the 2009 Hurricane Season on WU?


WeatherStudent by far.
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Quoting jaxairportman:
I miss being in tampa and sarasota. Do you think you will get some rain from 91L?
My magic 8ball says, "Most definately"!
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Member Since: October 1, 2007 Posts: 81 Comments: 26511
3264. sfla82
Quoting reedzone:
Bye bye Bill? You guys are being very premature, you'll see things change with Bill, he's not going anywhere yet.


Ok...LOL
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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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