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 happybrats3:
Hi all! I have two questions.

1. If TS Ana sweeps S. Fl and heads into the GOM, what is the chance of it becoming a hurricane? I am thinking of the warm waters through there and how that fuels it.

2. If the above does happen, how fast could it develop through the GOM and into "roughly" what strength a hurricane? Thinking distance/heat/time here.

I am just an avid hurricane watcher, no exp WHATSOEVER as evident with my questions.

Thanks!
Tracey


1. It potentially could become a hurricane assuming it misses Cuba and all the other islands.

2. It may be strong, but, as I said, it needs to stay from Cuba, DR, etc...
Member Since: July 10, 2006 Posts: 27 Comments: 1623
1513. Patrap
T S ANA Floater - Funktop Color Infrared Loop
Member Since: July 3, 2005 Posts: 428 Comments: 129796
Claudette?
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Quoting XL:
I'm West Bay also
Hi Stadium effect and StormwatcherCI

WOW SO FOUR WEST BAYERS INCLUDING ME
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Hey y'all....LONNNG time lurker here, from just outside Mobile. I stay glued to this blog daily! Just wanted to say I appreciate all the good info, even if I never post! Some of y'all are pretty hilarious! Keep the info coming--I don't know enough yet to add anything, but your info is very helpful!

First question....what is it about the Hebert Box that is so important? Is it just a persistent pattern among west FL falling hurricanes?
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Dats a lot of isobars for the GFS at 162 hours

Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting chevycanes:
18z GFS showing Bill recurving well east of the Bahamas.

looks like the models are trending more and more to a recurve and missing Puerto Rico and the east coast.
Hope Ana and Bill "listen" to the models and do what they are supposed to do.
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Wind shear doesn't seems to be an issue in the short term for Ana.Link
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1505. JLPR
wave behind Bill looking a little sad =P

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Quoting Halon056:
Very interesting for models.... mm5 and the gfs are both predicting another storm behind Bill. The cmc is predicting another storm in the GOM towards the latter part of the run...


The thing is people on this blog were so impatient for tropical development in June and july. I kept on telling them the tropics will fire up sometime soon. Now we've got what, 4 to perhaps 5 areas that bears watching in the atlantic. Belive me, you think this is a lot just wait till september. We may have a 2004 type season. (not scaring you FL it is when the comparison of when the real season begins.
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Quoting mobilegirl81:
Bill could be a double threat 1-South Florida and 2-somewhere along gulf coast.
oh ok, thanks a lot.
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18Z GFS 120 hrs - still reamining to the north

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18z GFS showing Bill recurving well east of the Bahamas.

looks like the models are trending more and more to a recurve and missing Puerto Rico and the east coast.
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1499. jipmg
Quoting canesrule1:
hmmmm, the Official line in much more northerly than all models, do u think Ana will still be a SFLA storm?


looks like we migth barely be in the cone, if those models continue on there southerly track, if ana gets organized tonight it will move WNW as models were picking up earlier today, really depends on what happens tonight
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Quoting stormwatcherCI:
Hi. Lots of Cayman based folks. At least if we do get anything hopefully we will be able to keep each other up to date on what is happening.


How many of you have a weather station ?. It might be good some time to compare stats if need be.
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Quoting WeatherStudent:
Damn models, go northward!!!!!!!


You just said a week or so ago that you didn't want to see a storm impact you, and yet now you do.

Make up your damn mind.
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Quoting hurricane23:
18z GFS has a recurve....Looks to me the ECMWF might nail this one if the trends continue.


2 others behind Bill.
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I don't know if I'm looking at it right, but the GFS 18Z shows Ana hitting Florida, Bill out to sea, and Claudette and Danny heading for the islands.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
1494. Patrap
.."Okay,Lets get the CIRRUS and STRATUS in High Mode and lets also get another 2 Blade's added to the NHC server..

..and someone Brew up some strong Java,..and get me another Pencil,too"..




Member Since: July 3, 2005 Posts: 428 Comments: 129796
Quoting kmanislander:


Only fitting since we have been dubbed the hurricane capitol of the world LOL
It's funny but other than Gilbert I don't remember that many affecting us before Ivan although I know there were a few close calls but since Ivan it's like every other hurricane heads in our direction.
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Hey XL! Happy hurricane tracking!
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18z GFS on bill has a recurve....Looks to me the ECMWF might nail this one if the trends continue.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
Quoting WeatherStudent:


None, but I've still got hope for Ana to potentially impact us, fingers and toes tightly crossed.


You are definitely not the sharpest knife in the drawer are you...
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting WeatherStudent:


None, but I've still got hope for Ana to potentially impact us, fingers and toes tightly crossed.


dude, something is wrong with you..... who would wish a hurricane on themselves ????
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Quoting Patrap:
T S ANA

hmmmm, the Official line in much more northerly than all models, do u think Ana will still be a SFLA storm?
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Kori, AIM
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Quoting XL:
I'm West Bay also
Hi Stadium effect and StormwatcherCI
Hi. Lots of Cayman based folks. At least if we do get anything hopefully we will be able to keep each other up to date on what is happening.
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Bill could be a double threat 1-South Florida and 2-somewhere along gulf coast.
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Quoting stormwatcherCI:
1 in East End and I know of 1 in Red Bay and 1 in the Brac. We are well represented for such a small island.


Only fitting since we have been dubbed the hurricane capitol of the world LOL
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Quoting stormwatcherCI:
Is that Ana ?
yes
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Hi all! I have two questions.

1. If TS Ana sweeps S. Fl and heads into the GOM, what is the chance of it becoming a hurricane? I am thinking of the warm waters through there and how that fuels it.

2. If the above does happen, how fast could it develop through the GOM and into "roughly" what strength a hurricane? Thinking distance/heat/time here.

I am just an avid hurricane watcher, no exp WHATSOEVER as evident with my questions.

Thanks!
Tracey
Member Since: Posts: Comments:
Quoting wunderkidcayman:

SHOW ME HOW YOU GOT THAT IS IT ON TROPICAL ATLANTIC RECON IF IT IS WHERE
I got it from an "anonymous software" but it was located at 1000MB, and please take odd ur caps, lol.
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Quoting tropicfreak:
Funny thing is, a few days ago on TWC i was watching it could happen tomorrow. They were saying that a major hurricane will hit Georgia. Could it happen with bill, or will it turn at the last minute bounding for the carolinas. Not to scare anybody in GA.


Silence! The 20th century was very quiet here, and we hope to keep it that way in the 21st.
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Quoting WeatherStudent:


None, but I've still got hope for Ana to potentially impact us, fingers and toes tightly crossed.


...Wow.
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Quoting jipmg:
convection blows up over ana's center


The center is still totally exposed. Follow it on this loop in which the last frame is under night vis imagery.
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Very interesting for models.... mm5 and the gfs are both predicting another storm behind Bill. The cmc is predicting another storm in the GOM towards the latter part of the run...
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Quoting kmanislander:


Two in West Bay and two in South Sound !
1 in East End and I know of 1 in Red Bay and 1 in the Brac. We are well represented for such a small island.
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1474. Patrap
T S ANA

Member Since: July 3, 2005 Posts: 428 Comments: 129796
Quoting tropicfreak:


I don't know about that. I think it is going to be an east coast storm. FL GA, SC and perhaps NC bears watching with bill. Fl mostly with ana.

agreed.
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1472. jpsb
Quoting Patrap:
Happy someone is still watching the blob. lol, I think we will know what the blob is going to do (or not do) by tomorrow AM.
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Quoting canesrule1:
The highest winds Recon has picked up is 44 knots.
Is that Ana ?
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In case anyone forgot, the 18Z GFS is running (and I swear this time it is todays!).
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Funny thing is, a few days ago on TWC i was watching it could happen tomorrow. They were saying that a major hurricane will hit Georgia. Could it happen with bill, or will it turn at the last minute bounding for the carolinas. Not to scare anybody in GA.
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New dropsodne from NOAA 49 shows winds at 40 mph just above the surface..

MB alt: 1000mb
Above sea level: 38m (125 ft)
Temp: 25.0C (77.0F)
Dew Pt: 24.9C (76.8F)
Winds at : 160 (from the SSE)
Wind Speed: 34 knots (39 mph)

Raw Data.
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Quoting stormpetrol:

Not really, its actually spot on, you're looking at the convection which is slightly removed north of COC.
That's what I was seeing also. Convection moved to the North bot not the CoC
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1466. XL
I'm West Bay also
Hi Stadium effect and StormwatcherCI
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Yes, West Bayers are well represented on this blog for sure. lol. Fingers crossed for a clear season guys!
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Quoting canesrule1:
The highest winds Recon has picked up is 44 knots.

SHOW ME HOW YOU GOT THAT IS IT ON TROPICAL ATLANTIC RECON IF IT IS WHERE
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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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