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 just can't believe how quickly it is building and intensifying its thunderstorms.. The core is now building stronger rains to the west of its center, while the northern portion of the center is now also rain-wrapped, and there are at least 3 distinct bands to its south and east.
4-Hour Radar Loop
I'm going to try to catch a quick nap, lol, I'll be back! I don't know about many of you all, but I've just got a bad feeling this could intensify to be a bit stronger than residents of the Panhandle are expecting...
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Morning....

Looks like 91 has surprised us. I expect it to hit between PCB and Destin at about 50 mph sustained winds. Everyone on the Panhandle needs to make preparations. Bring in anything that may blow, etc.... you know the drill!
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4511. Grothar
Quoting stormwatcherCI:
It doesn't look to me like it even caught the area she is in. What are you looking at ?

Morning. It would appear there is a burst of convection slightly to the North of the 8:00 PM position. Would you know if a system as weak as Ana could reform a COC. Each run shows the convection to be bigger and slightly North. In your opinion, could this significantly change to forecast track??
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Time for your morning joke:

Indians ask their new chief whether the winter will be cold or mild. Since the young chief never learned the ways of his ancestors, he tells them to collect firewood, then goes off and calls the National Weather Service.
“Will the winter be bad?”, he asks.
“Looks like it.”, is the answer.
So the chief tells his people to gather more firewood. A week later he calls again. “Are you positive the winter will be very cold?”
“Absolutely.”
The chief tells his people to gather even more firewood, then calls the NWS again: “Are you sure?”
“I’m telling you, it’s going to be the coldest winter on record.”
“How do you know?”
“Because the Indians are gathering firewood like crazy!”
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Quoting Weather456:
Tropical Update


Active Tropics: TD 4; TS Ana; TS Bill



What do you make of the quikscat pass of Ana ?
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Quoting HaboobsRsweet:
It is very cloudy and has that tropical feel down here in southern MS. Look slike NHC forecasted TD4 to be TS before landfal at the panhandle. Looks like a lot of rain for us in the next 48hours.
South MS just like South Al probably won't get more than popcorn showers out of this if it goes to the Big Bend area
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Quoting kmanislander:


We'll see what the NHC do but it sure does not look like a TS to me. I suspect the surface low is pretty much gone and what we are seeing is the 850 vort.


The ASCAT showed west winds, albeit not predominant in the southern semi circle. It is evident in the shortwave imagery.
Member Since: July 19, 2008 Posts: 43 Comments: 4051
there is a major south westward push by the bermuda high taking place right now.

this high is essentially the key player in bill and anna's track. the models are all currently way off with the intensity and oreintation and movement of this high. Bill and Anna may never see the trough 4-5 days out and may very well make landfall in south Florida if the high keeps digging in.


Florida Residents Stay Tuned to the Tropics .....



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Tropical Update


Active Tropics: TD 4; TS Ana; TS Bill

Member Since: July 24, 2005 Posts: 407 Comments: 19076
anyone have any microwave or short wave imagery on TD4?
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Full SAB readings:

16/1145 UTC 28.2N 84.2W T2.0/2.0 04L
16/1145 UTC 12.2N 37.7W T3.0/3.0 BILL
16/1145 UTC 14.5N 54.9W T1.5/2.0 ANA
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Ana is sure tenacious to have lasted this long. Good job really (so far), who knows what she could of done with a bit of time in a toasty environment.
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Quoting fmhurricane2009:
It is possible, it rapidly intensified last night, a 49 MPH TS is not out of the question, I expect a Pensacola landfall


Pensacola is too far west for its current heading.. It'll most likely be between Destin and Panama City, while scraping the coast of Apalachicola.
Personally, this has been intensifying quite impressively over the last hour and a half, and I foresee a strong TS due to its compact size, as not as much energy is needed to strengthen the core of such a small system.
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Quoting HIEXPRESS:

http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html


Looks like the CMC path. Are they the only one holding onto Ana past the Caribbean?
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Good morning!

Bill seems rather large. Bizzarre how impressive it looks compared to all other systems out there, yet its top MPH is not. I think it will survive since Anna kind of took a bullet for it but let's see where it goes. :)
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It is very cloudy and has that tropical feel down here in southern MS. Look slike NHC forecasted TD4 to be TS before landfal at the panhandle. Looks like a lot of rain for us in the next 48hours.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Quoting WxLogic:


Still has a circulation... also Shortwave show the low level circulation too... Shortware with some convection on its center.


We'll see what the NHC does but it sure does not look like a TS to me. I suspect the surface low is pretty much gone and what we are seeing is the 850 vort.
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Quoting kmanislander:


Even that does not look closed to me. No West winds


It has a circulation, and a flare of thunderstorms just occurred over the center.
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Just noticed that the ECMWF has a low going through the Fl. staits at the end of its run. Have to see if it holds on to that in the future.

ECMWF
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Quoting kmanislander:


Isn't 2 a TD ?. I don't see Ana holding on to a TS classification in the face of the QS pass.

Yep.

Ana's had that classification for a bit now.
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Quoting Cotillion:
First SAB reading:

DATE/TIME LAT LON CLASSIFICATION STORM
16/1145 UTC 14.5N 54.9W T1.5/2.0 ANA -- Atlantic


Isn't 2 a TD ?. I don't see Ana holding on to a TS classification in the face of the QS pass.
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As usual, great images P451!
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting canehater1:
This Trop season reminds me about a description of
working at sea I overheard once.."days upon days of pure boredom, interupted by moments of sheer panic" lol


Lol. Perfect!
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4488. WxLogic
Quoting futuremet:


ASCAT


Still has a circulation... also Shortwave show the low level circulation too... Shortware with some convection on its center.
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Would somone tell me what the models are seeing that take bill on this more northerly path and possibly recurving
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First SAB reading:

DATE/TIME LAT LON CLASSIFICATION STORM
16/1145 UTC 14.5N 54.9W T1.5/2.0 ANA -- Atlantic
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Quoting WxLogic:
NAM did a pretty good job handling this weak disturbance... on Friday it was depicting the TW and/or a piece of energy moving up along the FL W coast over the weekend.

Interesting to note... you'll notice that is handling TS ANA in different fashion than other models... since it will be soon within its domain... should be interesting how is depicted @ 12Z.

http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html
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This Trop season reminds me about a description of
working at sea I overheard once.."days upon days of pure boredom, interupted by moments of sheer panic" lol
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Actually, the "centre" is momentarily under convection. How long that will last, who knows.
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Quoting futuremet:


ASCAT


Even that does not look closed to me. No West winds
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Good Morning,

Tropical Update


Active Tropics: TD 4; TS Ana; TS Bill

Member Since: July 24, 2005 Posts: 407 Comments: 19076
4479. Relix
Ana should strengthen after 55W. Hotter waters, better enviroment!
Member Since: August 3, 2006 Posts: 0 Comments: 2741
Quoting kmanislander:
Good morning all

I just took a look at quikscat and can no longer find a closed circulation with Ana. In fact all I see is a wind shift and this tells me that Ana has degraded to an open wave and will likely be declassified later today unless it regenerates once more.

This has not surprised me as I have been saying from yesterday morning it would likely be downgraded or dissipate before reaching the Islands.



ASCAT
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Quoting stormwatcherCI:
It doesn't look to me like it even caught the area she is in. What are you looking at ?


The centre would be around 54W, 14N.

Nothing there.

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Quoting stormwatcherCI:
It doesn't look to me like it even caught the area she is in. What are you looking at ?


Yes it did. Ana was at 14.6n 54.7W at 5 am. Only a wind shift there now
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4475. WxLogic
NOTE: If Bill does not organize better and get stronger soon then a track like ANA won't be surprising... as it won't have enough depth to feel the trough.
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Quoting fmhurricane2009:
It is possible, it rapidly intensified last night, a 49 MPH TS is not out of the question, I expect a Pensacola landfall
which storm was 49 mph last night?
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Do any of u think Ana will survive a trip over Greater antillies?
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4472. Relix
G'Morning WU!!

Ana looks pathetic and near dead. She also seems to be missing PR for sure this time, I always said she was not gonna make the turn. Bill is interesting but it's still too far out. Should pass a couple hundred miles from the antilles... and for you guys in 4's path... take care!
Member Since: August 3, 2006 Posts: 0 Comments: 2741
Quoting kmanislander:
Good morning all

I just took a look at quikscat and can no longer find a closed circulation with Ana. In fact all I see is a wind shift and this tells me that Ana has degraded to an open wave and will likely be declassified later today unless it regenerates once more.

This has not surprised me as I have been saying from yesterday morning it would likely be downgraded or dissipate before reaching the Islands.

It doesn't look to me like it even caught the area she is in. What are you looking at ?
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Quoting caneluver:
When do the next model runs come out?


6z should be out.

12z won't be out for another couple of hours yet.
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The TWC has sent Jeff Morrow to the Florida panhandle. Look out!
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It is possible, it rapidly intensified last night, a 49 MPH TS is not out of the question, I expect a Pensacola landfall
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Thanks Cotillion and jdjnola. :)
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It appears a half eyewall is forming looking the Tampa, FL radar. Intense convection wrapping around its center and bands are intensifying.
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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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