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 TampaSpin:
Just found a closed low using the National DAta bouy system......its there....Hope you all can figure out how to use this...


Tampa...if this is the link you used...you're looking at ocean current vectors, not atmospheric winds.
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3363. Dan187
Link

Ship at 25.70N 83.10W reporting 8kt winds from 230 degrees.
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I do believe Bill could be a hurricane tomorrow
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So... Bill is going fishing and Ana is about to die. Looks like the only action the US is going to see is from invest 91L. This turned out to be alot hype. Looking on IR 91L looks more impressive than Ana.
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Quoting sfla82:


Its done!!!!
now it's my turn GO AWAY!!!
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Does anybody else think that 91L will be stronger than a weak tropical storm by the time it hits land?
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I see a upper level low headead for Florida. how will this play into the week?
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Quoting DM21Altestic:
TampaMishy never answered my question. : (
It says no.
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ANA

TD3

91L
Member Since: October 1, 2007 Posts: 81 Comments: 26511
3352. sfla82
Quoting weatherblog:
I think if Ana strengthens it will hit South Florida and recurve up the state. If it stays weak, I think it'll hit the DR, Haiti, and Cuba and definitely dissipate. So, it better start intensifying or it's done.



Its done!!!!
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Quoting TampaSpin:


When you get this link up zoom in tight SW of Tampa you can see it then.

Yea I am tracking with you I see it.
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Quoting HaboobsRsweet:

Ok first off there is no buoy anywhere near where I would expect to see a N or W wind at this stage. Also, I would expect offshore flow this time of night up and down the west coast of FL which is what the buoys just offshore are showing. No buoy on the west edge or north edge (out over the water and not right up against the shore line) is giving accurate wind data to show rotation. Just look at radar. You may have your answer.

OK, but shouldn't something be showing a SW wind...to the SE of the "center"? And a S wind somewhere E of center? You telling the landbreeze is overcoming the burgeoning TD-4?
Really, just trying to learn from a real met!
Member Since: August 16, 2007 Posts: 6 Comments: 12461
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dang thing sure seems to be spinning when i lok at it! post 3334
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Quoting TampaSpin:
Just found a closed low using the National DAta bouy system......its there....Hope you all can figure out how to use this...


When you get this link up zoom in tight SW of Tampa you can see it then.
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3345. Felix95
That's right 91L, I need some sleep.
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I think if Ana strengthens it will hit South Florida and recurve up the state. If it stays weak, I think it'll hit the DR, Haiti, and Cuba and definitely dissipate. So, it better start intensifying or it's done.

Member Since: July 10, 2006 Posts: 27 Comments: 1623
3343. Patrap
HH Plan of the Day

000
NOUS42 KNHC 151715
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0115 PM EDT SAT 15 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 16/1100Z TO 17/1100Z AUGUST 2009
TCPOD NUMBER.....09-079

I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM ANA
FLIGHT ONE -- TEAL 70
A. 16/1800Z,17/0000Z
B. AFXXX 0102A ANA
C. 16/1530Z
D. 15.6N 56.3W
E. 16/1700Z TO 17/0000Z
F. SFC TO 10,000 FT

FLIGHT TWO -- TEAL 71
A. 17/0600Z,17/1200Z
B. AFXXX 0202A ANA
C. 17/0330Z
D. 16.7N 60.0W
E. 17/0500Z TO 17/1200Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES.
A G-IV SURVEILLANCE MISSION IS PLANNED FOR 18/0000Z
WITH TAKEOFF AT 17/1730Z. A FOLLOW-ON G-IV MISSION
IS POSSIBLE FOR 18/1200Z WITH TAKEOFF AT 18/0530Z.

3. REMARK: NOAA43 AND THE G-IV WILL FLY FOUR SUCCESSIVE
RESEARCH MISSIONS INTO AND AROUND ANA DEPARTING FROM
TBPB AT 15/2000Z, 16/0800Z, 16/2000Z, AND 17/0800Z.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
SEF

Member Since: July 3, 2005 Posts: 424 Comments: 128314
Quoting TampaSpin:
Just found a closed low using the National DAta bouy system......its there....Hope you all can figure out how to use this...


Somethings going on there, I'm not going to call it a closed low just yet. But there is some kind of wind shift.
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Quoting HaboobsRsweet:

Ok first off there is no buoy anywhere near where I would expect to see a N or W wind at this stage. Also, I would expect offshore flow this time of night up and down the west coast of FL which is what the buoys just offshore are showing. No buoy on the west edge or north edge (out over the water and not right up against the shore line) is giving accurate wind data to show rotation. Just look at radar. You may have your answer.

On a side note buoy PLSF1 is showing a south wind right where you would expect to see a south wind. Hmm. Rotation at the surface? Probably
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IS there anyone near Jacksonville?
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Quoting ConchHondros:
Quoting iluvjess:
While I don't put to much faith in the insect behaviour theories, marine life does react to tropical weather conditions. The specs shut off today. Been limiting out for two weeks straight. Tonight they disapeared. Got home under a star filled sky and my dog is whining to come inside... Baldwin County, AL
.
We are having a bagworm infestation in OKC...last time that happened we were in a recession durring the mid-late 80's around Hurricane Alan time frame...hmmm

Pensacola here, been noticing more ant mounds in our yard, and my cat has been going nuts the last week or so, not like herself...didn't have her before Ivan so can't compare behavior, and she was just a baby when Dennis came thru so nothing to compare to behavior
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Quoting atmoaggie:

The RUC 925mb wind analysis (after assimilating all available surface obs, of course)



Wrong plot.

Right plot:
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting reedzone:


While that is true, it's still too close for comfort, especially the Carolinas.


Bill's going to have to slow down for any re curvature to occur.
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Quoting homelesswanderer:


I'd agree with that. And just add my local mets said 91l would affect us Monday. And that of the other two we may need to watch Ana. But didn't elaborate farther. O I'm in SE TX.


Me too...
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Welcome to the 2009 Hurricane season, it has finally started.

Convergance of a dead front and a tropical wave, with perfect outflow, should be TD by noon.


Could be hurricane by noon if this RI keeps up


Now time for bed.
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Quoting hurricane23:
00z GFS sharp right turn out to sea similar to EURO.


While that is true, it's still too close for comfort, especially the Carolinas.
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Quoting HaboobsRsweet:

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


whoa, the words free and sex on the same sentence! always an attention catcher

good evening my fellow earthlings... just woke up from my current sick disturbed sleep cycle (ive had roughly less than 5 hours of sleep in the last 40 hours).

yes i will go to the doc... by the way... can some one help me out by pointing what doctors treat sleep diseases? thanks in adv...

ana seems to be having such a hard time. bill on the other hand i think is consolidating its circle on latest imagery. panhandle disturbance looks growing. waiting for cyclones to be much closer to PR to make any assesments.
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3329. code1
Quoting presslord:


not sure what language you speak, pumpkin...but here we speak English...and that ain't at all what she said...


From my mouth to your ears press. Am thinking it time to ask the WU masters for a separate blog for those under and over a certain age for here! Still hold to the first years here I suppose. Not near the crap going on now. Young and old in the mix. Old knows, and young think they know. Makes the world go around for sure, but dang sure makes it hard for those of us not under our parents roof's to read intelligent conversation for the most part. There are a few young folks here, I am happy to follow and learn from. Note....I say few, the others just found a forum for their testosterone outlets. Go and get a date guys and gals!!
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Wind shift at the surface, bouy obs as 91L passes over the FL keys. Pressure didn't get very low, so I won't get to excited, but I think this is a closed low.


08 15 11:00 pm WSW 13 15 - - - - 30.09 +0.05 77.4 85.6 - 35.98 - -
08 15 9:00 pm S 3 4 - - - - 30.05 +0.03 79.9 85.8 - 35.87 - -
08 15 8:00 pm W 1 3 - - - - 30.04 +0.03 77.9 86.0 - 35.93 - -
08 15 7:00 pm WSW 9 12 - - - - 30.03 +0.00 77.2 85.8 - 35.84 - -
08 15 6:00 pm W 8 9 - - - - 30.01 +0.03 74.8 85.8 - 35.87 - -
08 15 5:00 pm N 9 10 - - - - 30.01 +0.02 73.9 85.8 - 35.75 - -
08 15 4:00 pm WNW 12 14 - - - - 30.02 -0.01 76.8 86.0 - 36.03 - -
08 15 3:00 pm W 26 29 - - - - 29.99 -0.05 78.4 86.2 - 36.04 - -
08 15 2:00 pm SSW 23 26 - - - - 29.99 -0.04 77.5 86.2 - 36.04 - -
08 15 1:00 pm SW 12 - - - - - 30.03 +0.02 79.2 - - - - -
08 15 12:00 pm SW 12 13 - - - - 30.03 +0.03 80.4 86.5 - 36.18 - -
08 15 11:00 am SSW 21 23 - - - - 30.03 +0.04 78.1 86.5 - 36.22 - -
08 15 10:00 am SSW 15 16 - - - - 30.01 +0.04 77.7 86.4 - 36.14 - -
08 15 9:00 am S 16 18 - - - - 30.00 +0.05 78.1 86.4 - 36.13 - -
08 15 8:00 am SSE 5 6 - - - - 29.99 +0.04 76.5 86.2 - 33.81 - -
08 15 7:00 am SSE 6 6 - - - - 29.97 +0.01 77.9 86.4 - 36.15 - -
08 15 6:00 am SSE 9 10 - - - - 29.95 -0.01 81.1 86.2 - 36.15 - -
08 15 5:00 am SE 18 20 - - - - 29.95 -0.04 81.1 86.2 - 36.12 - -
08 15 4:00 am ESE 17 18 - - - - 29.96 -0.05 84.0 86.4 - 36.14 - -
08 15 3:00 am SE 18 19 - - - - 29.96 -0.06 83.8 86.4 - 36.15 - -
08 15 2:00 am SE 19 20 - - - - 29.98 -0.04 84.6 86.4 - 36.13 - -
08 15 1:00 am ESE 13 14 - - - - 30.01 -0.04 82.4 86.4 - 36.13 - -
08 15 12:00 am E 10 12 - - - - 30.02 +0.00 82.4 86.4 - 36.12 - -
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Quoting TexasHurricane:


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


I'd agree with that. And just add my local mets said 91l would affect us Monday. And that of the other two we may need to watch Ana. But didn't elaborate farther. O I'm in SE TX.
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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).

Ok first off there is no buoy anywhere near where I would expect to see a N or W wind at this stage. Also, I would expect offshore flow this time of night up and down the west coast of FL which is what the buoys just offshore are showing. No buoy on the west edge or north edge (out over the water and not right up against the shore line) is giving accurate wind data to show rotation. Just look at radar. You may have your answer.
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Yes I know. I have been waiting since Thursday for this to happen. I really expeted her to be born a little further south. Hopefully she will hurry up and get here before she picks up to much steam. We need some rain but I sure hate she going to mees up some great fishing. Pat, is there a plane headed into her tomo?

Quoting Skyepony:
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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guys guys guys


90L is now TD 3/Bill

WU has not got in a ch to re move 90L yet from there page
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00z GFS sharp right turn out to sea similar to EURO.
Member Since: May 14, 2006 Posts: 8 Comments: 13792
00Z GFS is out to sea BUT too close for comfort on the East Coast. This track could verify in reality, I can see that happening.
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The RUC 925mb wind analysis (after assimilating all available surface obs, of course)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting Felix95:
So right now we have 90L, Ana, and Bill. Are the models still predicting something to form behind Bill?


91L not 90L.
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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
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

reported 2 hours ago...
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3315. Felix95
So right now we have 90L, Ana, and Bill. Are the models still predicting something to form behind Bill?
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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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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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