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 IpswichWeatherCenter:
Whats TD 04's TCGM? (Tropical Cyclone Guidance Message)


Link
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4663. jdjnola
Quoting WPBHurricane05:
Bill well to the north of the forecast dots.


Let the turn vs wobble debate begin!
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Quoting LightningCharmer:
"Fish" storms as some of you folks call them are not meaningless. They have a profound effect on maritime interest. I was always told they where "ship" storms until I started reading this blog.
Yup...That's what happens when too many spend too much time in an armchair and like to include "cool" words in their vocabulary.
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Quoting HurricaneKyle:
TD4 That wasn't expected. Wow that was fast, on track to be Claudette.
Several bloggers here were tracking it for over two days. That's why I read this blog. It gives me an extra day or two to prepare just in case.
Member Since: September 1, 2007 Posts: 0 Comments: 1269
Ana is about to pass through, or just north of, a pocket of notably higher oceanic heat content.

OHC (from yesterday)
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4659. Thaale
Quoting Relix:
Bill is moving WNW... but even then he's south of forecast points. He will have to do that NNW turn which I don't see happening soon.
What are you talking about? He's N of the forecast points, at least as far as the major models and certainly the NHC forecast track. Last night they projected him to dip from 11.3 to 11.2. Instead he was at 11.4 at the next advisory. And he keeps turning more N.

As for NNW, please. No model had him moving NNW until five-seven days from now.
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I know what Steve Lyons said, but I am seeing bands wrapping into its center from the west, east and south. Also the northern side of circulation could be small as well.
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Quoting AussieStorm:

I had a look... no Claudette yet
It was there at 8:30, but you are right, not there now.

@8:30am Eastern

2009 Storms
All Active Year

Atlantic
green ball04L.CLAUDETTE
green ball03L.BILL
green ball02L.ANA

East Pacific
green ball10E.GUILLERMO

Central Pacific

West Pacific
green ball95W.INVEST
green ball94W.INVEST
green ball01C.MAKA

Indian Ocean

Southern Hemisphere
Member Since: Posts: Comments:
Heya Foxx - for once, I'm in position. Just gonna have to wait and see if I need to call the office and tell them I won't be in NOLA on Monday morning.
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Whats TD 04's TCGM? (Tropical Cyclone Guidance Message)
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Quoting P451:
4606. I don't understand it either but the pressure are high and actually rising throughout the region. This could change but this system doesn't have all that much room. If all goes great for the system what could we possibly get here? 70mph TS? Given the high and rising pressures and the lack of real estate could we get more than a 55mph TS realistically?

I know there's a lot of fuel out there but something isn't right overall. That pressure situation is confusing at best.

Claudette - RGB Enhanced Day/Night Visible




..and again, the current pressure:



3HR Pressure Changes (scale: lightest blue is still a 0-1MB rise in 3 hours.)



Surface Wind Streamlines:


TD4 hasn't been named Claudette yet
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting TropicalNonsense:
HWRF Makes Bill a Super Cat5 at 120 hrs out.

just before making the over predicted Northward recurvature
which may not take place at all without help from HAARP.
The Highs orientation is wrong and the troughs movement is
over done in virtually every model so far.

if the highs were to bridge on the backside of the trough
bill may get trapped which could
make for a slightly different forecast.

in other news Anna is dead but Cat5 Bill in
120 hours might be a watcher.




Interesting. Bill is still one to watch for the Leeward Islands, Bahamas, and the East Coast.
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Bill well to the north of the forecast dots.
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You could argue Ana looks better now than earlier
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{{{Mandy}}} Yep, better to be safe, ready and alert than SORRY!
Alberto always come in mind when someone "blows off" a storm... the GOM turned blood red.... it was freakish!
Quoting MandyFSU:
{{{Foxx}}} Well said- I'm not worried about TD4 too much- but it only takes one good rain band to knock over patio furniture and ruin a window. Hope all stays above the status quo over your way :)
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HWRF Makes Bill a Super Cat5 at 120 hrs out.

just before making the over predicted Northward recurvature
which may not take place at all without help from HAARP.
The Highs orientation is wrong and the troughs movement is
over done in virtually every model so far.

if the highs were to bridge on the backside of the trough
bill may get trapped which could make for a slightly different
forecast late next week

Cat5 Bill in 120 hours might be a watcher.


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TD4 That wasn't expected. Wow that was fast, on track to be Claudette.
Member Since: August 10, 2009 Posts: 3 Comments: 672
Yachts and other small craft are sailing past Dominica southwards since yesterday to be out of harms way. The harbour of Prince Rupert bay here is empty of yachts this morning.
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Quoting eddye:
billl going to fl due to the bermuda high breaking news bill going to florida


lol
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Subtropical ridge (Wikipedia)
...The ENSO climate cycle can displace the subtropical ridge, with La Niñas allowing for a more northerly axis for the ridge, while El Niños show flatter, more southerly ridges....
...In the Atlantic basin, the subtropical ridge position tends to lie about 5 degrees farther south during El Niño years, which leads to a more southerly recurvature for tropical cyclones during those years....

MJO
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IMHO on 11am advisory's 5 day map they will show Bill making his turn & going out to sea. I just see me myself Bill as a fish storm. Sorry not trying to leave out the islanders I hope the best for ya'll but Bill won't be effecting the lower 48.Ya'll can hold me to my forecast and I'm willing to eat crow but I doubt It'll be on MY menu.
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"Fish" storms as some of you folks call them are not meaningless. They have a profound effect on maritime interest. I was always told they where "ship" storms until I started reading this blog.
Member Since: September 1, 2007 Posts: 0 Comments: 1269

Closest buoy to TD4. The low is about a 1012 mb. Strongest winds (25 kt) displaced to the NW of the centre by about 50 mi. Link
Member Since: September 4, 2007 Posts: 0 Comments: 490
Quoting Beachfoxx:
4541. theshepherd

Shep, my friend, gonna be a busy day here on the panhandle! Boats to secure, and preparations to make! I do believe that TS will be knocking on my door. Expect landfall between PCB and Destin tonight...
Yup. It mucked up Sugarloaf yesterday. Fishing sucks. Kayak still on the floor in the motel room. Power sleeping with A/C on high. Heading to the back country in a bit.
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Steve Lyons on TWC just pointed out that the thunderstorms in the north of TD4 are racing off to the north faster than the center. He said that this is a sign that TD4 is NOT consolidating. Interesting.
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Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?

M = Major Hurricane
Member Since: August 9, 2009 Posts: 10 Comments: 4939
{{{Foxx}}} Well said- I'm not worried about TD4 too much- but it only takes one good rain band to knock over patio furniture and ruin a window. Hope all stays above the status quo over your way :)
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4636. Relix
Ana is also moving entirely to the west, no WNW turn at all.
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4635. srada
Thanks everyone!
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4633. eddye
billl going to fl due to the bermuda high breaking news bill going to florida
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Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?
I think it is for major hurricane.
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Quoting homegirl:
Bouy data from earlier, as 91L passed over the FL Keys, showed a wind shift (with W winds) consistent with a passing low.

Since then the radar, CIMSS vort maps, SSTs, anticyclone forming overhead, all lead me to believe we could see TD04 by 5am.


Claudette by 11am
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4630. cg2916
There seems to be a burst of convection in front of Ana. Maybe an attempt to moisten the air? http://www.ssd.noaa.gov/goes/flt/t1/loop-avn.html
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4629. srada
Quoting BenBIogger:


Major Hurricane


this will be the one I will be watching..that cone dosent look like a recurve to me..in fact it look like it dropped south since the 11:00 advisory last night
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Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?

I guess the "M" means Major Hurricane
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Looks like Ana will miss the next tropical forecast point to the south. Mabey will traverse through the caribbean and wont interact with land after all.
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000
WHXX01 KWBC 161309
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1309 UTC SUN AUG 16 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

TROPICAL CYCLONE BILL (AL032009) 20090816 1200 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090816 1200 090817 0000 090817 1200 090818 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 11.9N 37.7W 12.8N 40.8W 13.6N 44.0W 14.2N 46.9W
BAMD 11.9N 37.7W 12.8N 40.4W 13.8N 43.2W 14.9N 45.9W
BAMM 11.9N 37.7W 12.6N 40.9W 13.2N 44.1W 13.9N 47.0W
LBAR 11.9N 37.7W 12.5N 40.4W 13.3N 43.6W 14.0N 46.8W
SHIP 50KTS 59KTS 69KTS 77KTS
DSHP 50KTS 59KTS 69KTS 77KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090818 1200 090819 1200 090820 1200 090821 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 14.7N 49.6W 16.7N 54.4W 20.3N 59.9W 23.5N 64.4W
BAMD 15.9N 48.6W 18.5N 53.7W 21.8N 58.6W 25.9N 62.6W
BAMM 14.5N 49.6W 16.6N 54.1W 20.3N 58.9W 24.1N 63.2W
LBAR 14.4N 50.1W 16.0N 56.2W 19.7N 60.2W 23.7N 63.5W
SHIP 85KTS 98KTS 97KTS 91KTS
DSHP 85KTS 98KTS 97KTS 91KTS

...INITIAL CONDITIONS...
LATCUR = 11.9N LONCUR = 37.7W DIRCUR = 285DEG SPDCUR = 11KT
LATM12 = 11.2N LONM12 = 35.5W DIRM12 = 279DEG SPDM12 = 10KT
LATM24 = 11.5N LONM24 = 33.3W
WNDCUR = 50KT RMAXWD = 60NM WNDM12 = 35KT
CENPRS = 997MB OUTPRS = 1011MB OUTRAD = 200NM SDEPTH = D
RD34NE = 120NM RD34SE = 120NM RD34SW = 60NM RD34NW = 90NM

$$
NNNN

Bill strengthens. Around 55mph.

Also dropped 5mb.

It's on the path...
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4625. Relix
Bill is moving WNW... but even then he's south of forecast points. He will have to do that NNW turn which I don't see happening soon.
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Yeah right!??? LOL Live in the panhandle long enough and you prepare for the worst and hope for the best! I remember too many times when folks were caught off guard!
Quoting fldude99:
Anybody thats lived in the FL panhandle for more than 20 years give Claudette nothing more than a passing glance
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4623. jdjnola
Quoting DestinJeff:


Bill looks headed NNW


I would say WNW, just looks like he's becoming more symmetric to the north. He's had a flattop the last couple days.
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Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?


Major Hurricane
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Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?


The key tells you it means Major Hurricane
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Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?


Major hurricane
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?


Wind speed is greater than 110 - see the table describing the chart
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Major
Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?
Member Since: Posts: Comments:
4617. cg2916
Quoting srada:
Link

Good morning everyone..

What does the "M" mean on the tracking from NHC?

Major hurricane.
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Monster... lol
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Anybody thats lived in the FL panhandle for more than 20 years give Claudette nothing more than a passing glance
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Quoting CaribBoy:
looks like Bill is now moving WNW


Yup.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.