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 think people are being deceived by Bill's motion because it is wrapping that big band of convection to the north around its center, thus causing uncertainty in the motion
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Bill looks like due W to me right now. those long range forecast models past 3 day are iffy. They usually are. Thats what any good met will tell you.
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Quoting Walshy:



No update on Sunday. I think it is because of church or something...


No - "I'll have an update Sunday. Jeff Masters "
See Saturday's update (at the end)
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Simple, the UK Met might actually be right.

At this stage no one 'knows' where the storm is going.

The only 'virtual' certainty is that it will be a major hurricane with serious destruction on whatever comes into its path.
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Quoting Walshy:



No update on Sunday. I think it is because of church or something...


I forget some people go to church these days. I don't know a single person who goes unless there is a wedding or funeral!
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4707. java162
Quoting bajelayman2:


Unfortunately, Bill may be this year's Katrina or Andrew, in damage terms.

He definitely looks impressive already and covers a large area.


i don't think so.... it appears bill will be a fish storm.. it is already moving nothward..
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Good Morning everyone,

I live in the Tampa Bay area. Does anyone have the latest info on TD 04? Thanks.

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Foxx- I was thinking Alberto too. Doubt we get much of anything (I'll be happy with an inch of rain!) but we are under a flood watch and in Tallahassee the flood is as bad as the wind could be. If nothing else this is a "gentle" reminder that it is mid-August and nothing is off limits!
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Unfortunatley it is still too early to tell what is going to happen with these systems. Let's just hope Ana fizzles completely and Bill curves out to sea without affecting any land.
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Claudette will strengthen rapidly after reaching 50MPH. A well defined anticyclone is currently over, providing good upper level divergence.
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Quoting CaneWarning:
Folks in the panhandle prepare now for something that will be weaker than a typical afternoon t-storm! My goodness some people on here like to hype. I woke up to an email from a blogger about rapidly strengthening Claudette. We don't even have a Claudette to rapidly strengthen.


Exactly..when you get that feeling in the pit of your stomach you know..just as well as any experienced met-you just can feel it when you've been around long enough
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Quoting HurricaneKyle:

I don't have it. Either its on the backup site or he was making it up to mess with us.

i've had a look at both sites and still has 04L .Four
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4700. sfla82
I wake up this morning and S. Fla is in the clear again! RIP Ana..... If she makes it she is going way south and with Bill everyone thought this ridge would build in and push Bill west....well Bill is already moving NW and is already north of the NHC projected track. So everyone thought i was crazy for calling S Fla in the clear and 24 hours later we are still in the clear!!!
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4699. IKE
Ana looks likely to be downgraded to me. Just not much circulation left. Looks like a large, impressive tropical wave, moving west.

Bill looks like it will go NE of the islands and be a threat to Bermuda.

TD4/Claudette ?, looks like a rainmaker for the panhandle. Maybe some gusty winds.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Walshy:



No update on Sunday. I think it is because of church or something...


I'll have an update Sunday.

Jeff Masters
Member Since: August 10, 2009 Posts: 3 Comments: 672
Quoting AussieStorm:

Link plz
I saw it there earlier too but not there now.
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4695. Walshy
Quoting AllStar17:
Dr. Masters' update shall be interesting to say the least!



No update on Sunday. I think it is because of church or something...
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4693. jdjnola
Quoting A4Guy:
looks like Bill's COC relocated north under the deeper convection...tough to be certain, tho.


That's what I'm thinking. Trochoidal motions. "Because of this effect, forecasters use a longer term (6 to 24 hours) motion to help forecast tropical cyclones, which acts to smooth out such wobbles." (see link for source)
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Quoting WPBHurricane05:


Interesting. Bill is still one to watch for the Leeward Islands, Bahamas, and the East Coast.


Unfortunately, Bill may be this year's Katrina or Andrew, in damage terms.

He definitely looks impressive already and covers a large area.
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Quoting Cotillion:


Link


Thanks.=
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Quoting AussieStorm:

Link plz

I don't have it. Either its on the backup site or he was making it up to mess with us.
Member Since: August 10, 2009 Posts: 3 Comments: 672
Member Since: July 19, 2008 Posts: 43 Comments: 4051
Dr. Masters' update shall be interesting to say the least!
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Quoting jdjnola:


Let the turn vs wobble debate begin!



GOOD WARNING!
X2 It must be on that path for 3 hour for it to even be considered a change in direction. I am staying off the blogg till tonight. Let the battle begin!
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looks like the islands and florida are in the clear. Why it the ukmet being so persistent with a wnw track though?
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Quoting HurricaneKyle:
I think its Claudette on the backup navy site.

Link plz
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Quoting CaneWarning:
Folks in the panhandle prepare now for something that will be weaker than a typical afternoon t-storm! My goodness some people on here like to hype. I woke up to an email from a blogger about rapidly strengthening Claudette. We don't even have a Claudette to rapidly strengthen.


Cane, those waters are HOT and I mean HOT, and TD4 is small. We could see a Humberto. They thought it was going to be 'nothing more than a thunderstorm'. Than wack! Category 1 landfall.
Member Since: August 10, 2009 Posts: 3 Comments: 672
4683. java162
Quoting islandblow:
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.



where you from?
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Quoting CaneWarning:


Yeah, this one is for the fishes.


Don't jump to conclusions that quickly
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4679. A4Guy
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.

Cat5 Bill in 120 hours might be a watcher.




Ummm...wouldn't the meteorologists at the NHC...you know, the ones with the Doctorate in meteorology...pick up on that and reflect it in their forecast and/or discussion?
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TD4..soon to be Claudette(?)...not causing impact to commercial aviation at this time due to low cloud tops. PIREPS are only a few tops above FL300, typical of tropical activity. No major disruption planned for panhandle at this time, mostly due to location of landfall with no major airports in vcnty and slow Sunday traffic
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Good morning everyone. It looks like the wave we were watching developed into troopical storm 4.
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Watch out Bermuda.

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Quoting theshepherd:
Yup...That's what happens when too many spend too much time in an armchair and like to include "cool" words in their vocabulary.
Well if you're insinuating, I'm acting highbrow or mindful, well I reckon I'll take that as a compliment. Sorry your fishing yesterday was washed-out. Looks like clear skies for the Keys today.
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4674. jdjnola
Quoting LightningCharmer:
Several bloggers here were tracking it for over two days. That's why I read this blog. It give me an extra day or two to prepare just in case.


I said yesterday the GoM was making me uneasy and I wasn't lying. I was wrong with almost every prediction last year, but have so far been right with almost every prediction this year.
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Beachfoxx...you've got mail
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Quoting WPBHurricane05:
Bill well to the north of the forecast dots.


Yeah, this one is for the fishes.
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I think its Claudette on the backup navy site.
Member Since: August 10, 2009 Posts: 3 Comments: 672
The Leeward Islands and points NW should not let their guard down with Bill, as things are bound to change, like always
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Hey Buddy,

Long time no see! Glad you are home to help the family. Really don't expect too much, but I'd rather be READY than to be caught off guard.
Quoting F1or1d1an:
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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4667. A4Guy
looks like Bill's COC relocated north under the deeper convection...tough to be certain, tho.
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Folks in the panhandle prepare now for something that will be weaker than a typical afternoon t-storm! My goodness some people on here like to hype. I woke up to an email from a blogger about rapidly strengthening Claudette. We don't even have a Claudette to rapidly strengthen.
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Quoting AllStar17:
You could argue Ana looks better now than earlier

I know, theres a big burst of convection that formed where the exposed center was.


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


Link
Member Since: August 23, 2008 Posts: 7 Comments: 5300

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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.