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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that's a big longwave trough though.

i'm not convinced it will dig that deep but i guess we'll see.
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Quoting IKE:


Both systems are struggling.


One system is struggling, TD3's doing alright according to Dr. Masters. Convection dying over the COC somewhat but its increasing in the bands, that will feed it more moister.
Member Since: August 10, 2009 Posts: 3 Comments: 672
TD3's finally on the ADT page.

Link

And for Ana:

Link
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110. IKE
Quoting futuremet:
Out-to-sea



What happened to the post claiming an east Florida hit?
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Quoting chevycanes:

no it doesn't.

current 12z run curves it just east of FL.



Yup...I posted yesterdays GFS by mistake.

The new GFS takes it over far eastern Bahamas and out to sea.
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Quoting IKE:


12Z GFS picks up on that and moves it into the north-central GOM coast on the beginning of the run.


Ike, does it bring it in as a mere rain maker or something more??
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107. JLPR
Quoting IKE:


Both systems are struggling.


yep they may have good circulation but they are lacking in the convection department xD

The funny part is that Ana is forecasted to make landfall in extreme eastern PR and Td 3 is forcasted to pass close to our northeast,
I do hope they continue like this and dissipate xD
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Quoting WindynEYW:


is that a recent (like today) pic?
Member Since: September 4, 2007 Posts: 0 Comments: 490
Quoting futuremet:
NOGAPS is overdoing Ana


Can you give me an idea of what the steering,high, or what ever will be next week.

Thanks
Brandy
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Quoting BrockBerlin:
anyone here from louisiana remember Bill from the last cycle it was quite weak but delivered a lot of rain and showed up without much warning.

THats what i am worried about with the spin by the keys.
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Quoting FLHurricaneChaser:
Drak.. GFS takes it west into Florida

no it doesn't.

current 12z run curves it just east of FL.

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Quoting hurricanelover236:
Mark my words. Anna wont survive and wont cause florida or the islands any problems. Td 3 may become stronger but i dont c that hitting the us either. We are in the clear. Time to celebrate.


I heard that yesterday when it was TD2
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78. Doove4cane 4:36 PM GMT on August 15, 2009
Let's not forget instant hurricane humberto


exactly...don't forget about these pop up storms that we have had in these past few years...expect the unxpected sometimes...

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Out-to-sea



Member Since: July 19, 2008 Posts: 43 Comments: 4051

NEXRAD Radar
Key West, Echo Tops Range 124 NMI


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Quoting Doove4cane:
Let's not forget instant hurricane humberto

Link


Yep, went to bed with a tropical storm warning - woke up in the middle of the night to a cat 1 .....
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Quoting floridafisherman:
52. AussieStorm 4:30 PM GMT on August 15, 2009 Proof plz
------------

dont quote the trolls. just poof them and let them essentially talk to themselves. quoting them only emboldens them to make more outragous statements. and yes, hurricanelover is a troll. hes only posting to get reactions from ppl like you who actually know the science behind tropical development.




That's Hurricanelover not CaneLover....I'm not a troll, just an observer with questions! :)
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Any thoughts on the AOI's in the Gulf?? Drak, StormW? Interesting...
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88. IKE
Quoting JLPR:
I noticed no one is mentioning the fact that Td3's convection is dissipating?



whats up with that?


Both systems are struggling.
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I have a friend who doesn't have their hurricane kit together...can someone send me a link to a place that has a list of everything you need in one? I will link it up and forward it to her.

Thanks, Melissa
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Quoting jpsb:
Yea, that is what I am watching. I've been told not to worry about it since it does not have a surface low, but I am still watching it. lol.


In the last blog, I included a link to a Florida Key's buoy that indicated continuous nearly 30 knots/hour west shifting winds on the southern end of circulation which although I am not an expert would indicate to me a surface low. No-one on this blog responded to my post which indicated to me that perhaps the buoy readings were not meaningful. Perhap everyone was too busy commenting on a sometimes annoying blogging who I will not name. Sorry if I offend, it is not my intention just wanted some expert analysis regarding the buoy readings I linked and posted.
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Quoting Michfan:


DMIN. Quite normal for this time of day.


More than just Dmin it looks like.

Some easterly shear of around 10-20 kts, as well as dry air to the north of the TD.

Same sort of scenario as Ana, though not quite as bad (or good, one could say.)

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83. JLPR
If it is D-min then Td 3 is having problems of maintaining convection just like Ana
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Quoting HurricaneKyle:


From what I read that Dr. Masters posted, the models calling for a more northerly path were probably incorrect because TD3's convection came together more south than expected. So we'll have to watch it right now, but it's going to be hard for it to curve out to see IMO.


All the models take it around the northern islands or north of there which would put it in a position vulnerable to recurvature
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I think people need to focus on flooding scenarios. Idk about current florida rainfall conditions and of the past weeks, but if its already raining a lot as some blogger pointed out - the sediment will get much more rain and water from coastel flooding. Given that in some areas there will pass at least 2 systems.
You need to take into account that these sums up the overall effect.

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Quoting foggymyst:
FLHurricanechaser..in what part of florida do you live?


West Palm area
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That would be one run of bad luck if TS Ana hit S FL and then Bill followed close behind a few days later. Ughhh....
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Let's not forget instant hurricane humberto
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77. IKE
Quoting GetReal:
I was just going to mention that radar loop Auburn... There is definately a cyclonic circulation centered just north of a Key West... The convection is also increasing and getting better organized... IMO


12Z GFS picks up on that and moves it into the north-central GOM coast on the beginning of the run.
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76. JLPR
Quoting Michfan:


DMIN. Quite normal for this time of day.


It isnt D-minimum yet over there
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52. AussieStorm 4:30 PM GMT on August 15, 2009 Proof plz
------------

dont quote the trolls. just poof them and let them essentially talk to themselves. quoting them only emboldens them to make more outragous statements. and yes, hurricanelover is a troll. hes only posting to get reactions from ppl like you who actually know the science behind tropical development.

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Quoting JLPR:
I noticed no one is mentioning the fact that Td3's convection is dissipating?



whats up with that?


DMIN...
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patrap...the thing below the keys is getting interesting...
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Quoting JLPR:
I noticed no one is mentioning the fact that Td3's convection is dissipating?



whats up with that?


DMIN. Quite normal for this time of day.
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Navy Page
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I thought you had good news...thanks for the update

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.
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Quoting Drakoen:


A strong trough grabs this thing and takes it out to sea or it parallels the eastern seaboard
could 03L go onshore through SFLA, and make the turn over Florida?
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67. JLPR
I noticed no one is mentioning the fact that Td3's convection is dissipating?



whats up with that?
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Drak.. GFS takes it west into Florida
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Quoting Drakoen:


A strong trough grabs this thing and takes it out to sea or it parallels the eastern seaboard


Do you agree with that scenario???
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The only proof you need is the satellite. The enviornment is extremely hostile with the dry air and shear. ana is a small circulation and will get torn up. I have been saying from the beginning nothing will amount too much so in the end we shall see who is right.
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About JeffMasters

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