Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 04:17 PM GMT on Αύγουστος 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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If it goes over Cuba/DR its tiny circulation will be done.
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If Bill shifts a little more west then the trough Drak was talking about earlier would actually serve to curve it into Florida not before it! Lots of scenarios to track on these two!
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Quoting WPBHurricane05:
Max Mayfield on long range forecasts.


As I posted earlier, Max seemed more concerned that normal last night. none of the "lots can happen in 5 days" more get prepared over weekend...all models have it on doorstep by Wed.
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people really just need to stop responding to JFV.
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1210. KEEPEROFTHEGATE (Mod)
Quoting WeatherStudent:


This would be my fifth, why? :) Guys, I'm only following Adrian's viewpoints here, OK? Besides, the man's got a B.A. Degree in Tropical Meteorology, meaning that he knows his canes and TS's, alright?
he knows nothing ws except what the book tells him and in reality the book is meant as guidance just like the models
Member Since: Ιούλιος 15, 2006 Posts: 178 Comments: 56059
So ana could be a gulf storm?
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1208. JRRP
hmmmmm...
Link
see you tomorrow
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I say everyone needs to keep an eye on Bill, east coast,carribean, and the GOM....Not that I'm expert of course....
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
Max Mayfield on long range forecasts.
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Highndry:

I do agree with you but models are in good agreement with BILL going north of PR! With sunch good agreement it's hard not to believe it BUT these models are really over doing BILL with the intensity forecast and hence they are futher north!
I don't see BILL rapidly intensifying - YUP I am going against what NHC is saying...not the first time!! HAHA!
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Bill has a 10% chance of being cat4 or 5 within 5 days, as per NHC.
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Quoting IKE:
1180 & 1181.

He got what he wanted.

Thank you IKE!

Quoting atmoaggie:
Y'all know what is more annoying than WS's posts? When he and his comments become a primary topic of conversation. Someone please post a WS drama blog in their own space and take it there. That would be nice.
Addendum: I see the effect worsened as I typed this post. Apropos.
Member Since: Αύγουστος 16, 2007 Posts: 6 Comments: 12463
WOW, good info here.
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1200. java162
Quoting islandblow:
So here I am on Dominica, Lesser Antilles, waiting to be sideswiped by Ana and maybe hit by Bill-to-be if he keeps going west. Will get high seas on the Atlantic coast of the island in any case, so fihermen are being warned to drag up their boats off the beaches.


hey hey!!!! from dominica as well.. what part area do you live?
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Quoting WeatherStudent:
So no longer a SF threater from either system then, Adrian? Yes, we've lucked out yet again.


Nope did not say that in anyway, model consensus has somewhat shifted to our south GFDL/HWRF etc... land interaction now looks like a pretty big issue with this small disturbance.Just watch and see what developes over the next 2-3 days.
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1196. rjla67
Good evening everyone. Living here in Tampa, Florida and this is by far the best place to get up to the minute information on the tropics and I have learned a lot from all of you. Being a photographer, mother nature has a way to not only show her nasty side, but can be quite beautiful as well. While I am far from qualified to provide as much information as most of you, I can show what I am seeing here in the bay area through my viewfinder.

Last year was my first attempt and I will try to capture what it looks like if any storms pass through the area. Here is just one of the many images I captured as Ike took a glancing appearance here in the area. The image was taken on Honeymoon Island, Florida.



Thanks everyone for your valuable insight as well as to Dr. M for a great learning resource.

-robert.
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The whole entire east coast isn't "in the clear". Any of these systems could go anywhere in the CONUS at this point.
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1192. sfla82
With every run it looks better and better for Miami and Ft. Lauderdale! Ana shifted way south and Bill is shifting away from Fl too! I don't know how we do it here in S Fla but we keep getting missed. Don't get me wrong, we need the rain but with Ana and Bill certain to miss us it is for sure a relief!
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1191. sfla82
With every run it looks better and better for Miami and Ft. Lauderdale! Ana shifted way south and Bill is shifting away from Fl too! I don't know how we do it here in S Fla but we keep getting missed. Don't get me wrong, we need the rain but with Ana and Bill certain to miss us it is for sure a relief!
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1190. Patrap
Multiplatform Satellite Surface Wind Analysis,Time of Latest Image: 20090815 1800 UTC
Member Since: Ιούλιος 3, 2005 Posts: 428 Comments: 129841
1189. KEEPEROFTHEGATE (Mod)
Quoting rareaire:


what?
forget raraire hes just being foolish or maybe he is foolish really not sure
Member Since: Ιούλιος 15, 2006 Posts: 178 Comments: 56059
1188. Fshhead
Quoting WeatherStudent:
So no longer a SF threater from either system then, Adrian? Yes, we've lucked out yet again.


Your kiddin' right??? Waaay to early to say that!
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I have been seeing a more organized pattern develop within Bill today. The eastern band continues to wrap around the eastern side of the circulation cutting off the dry air intrusions that have been haunting the coc. More convective activity continues to occur around the circulation indicative of a more moist environment for Bill. This is also indicative of less wind shear and warmer SSTs. Ana is more on life support as her circulation is still well west of the convection. The tropical wave/LLC around Florida is going through a cycle of convection, but I expect it to redevelop as a more definitive circulation is evident on visible satellite imagery. Bill's coc is now able to develop is own more intense convection now that the atmosphere is more moist and secluded from the dry air source. I expect him to look a lot better later this afternoon and evening. Ana is fighting a lot of dry air and wind shear today. I don't expect her to look better until tomorrow.
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1186. IKE
1180 & 1181.

He got what he wanted.
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roflmao at southfla43yrs
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1184. JLPR
Quoting WeatherStudent:


No exsageres tampoco. Lo mas probable seria que ella termine crusando directamente por encima y por el centro de la isla.


wow gracias por el mensaje de esperanza =\
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1183. Relix
Quoting JRRP:

oh.... i do not like that track


I am 80% certain it'll drop south. Or at least I hope.
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Quoting Chiggy007:
TExas:

That picture you just posted - the white spaghetti line is the UKMET model...


It wouldn't surprise me...
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
Quoting WeatherStudent:
So no longer a SF threater from either system then, Adrian? Yes, we've lucked out yet again.


Why do you ask such a question? You could see very well that Florida remains in the cone of uncertainty. How many hurricane seasons have you been through again?
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Quoting WeatherStudent:
So no longer a SF threater from either system then, Adrian? Yes, we've lucked out yet again.


what?
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Quoting Chiggy007:
TExas:

That picture you just posted - the white spaghetti line is the UKMET model...


OH MY GOSH...how funny...sorry I am new here this year and I don't know all the names of the models and such.
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
Quoting WeatherStudent:
So no longer a SF threater from either system then, Adrian? Yes, we've lucked out yet again.


Stop spreading disinfo. Bill is too far out from Florida to know if its an immediate threat.
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Oh, hello. THanks WBP
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1175. JRRP
Quoting WPBHurricane05:


Its on this website.


oh.... i do not like that track
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Quoting ralphfurley:
I wonder if Max Mayfield will be working tonight...

futuremet is filling in for him.
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TExas:

That picture you just posted - the white spaghetti line is the UKMET model...
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Chiggy:


The east and northeast side seem to be of marginal import currently as Bil is chugging westward like a bat out of hell and the west side is looking pretty damn good. I think the east side is the result of the shear but that'll stop by the beginning of the workweek, ad after that it's pretty much a straight shot to the islands with nothing around but wet, warm, dead air around the TS, no shear to speak of, and plenty of warm, deep water below it for Bill to suck up.
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Quoting StormW:


That may have been Humberto...he was close to the TX coast, and before he developed, it was almost dead, then the upper pattern reversed, and bang!

And was a classic example of THCP in shallow waters being underestimated as there is no 26C isotherm...hot all the way to the bottom.
Member Since: Αύγουστος 16, 2007 Posts: 6 Comments: 12463
Quoting FloridaTigers:
It'll be interesting to see if the next run of models keep shifting Ana south.


And Bill for that matter...
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
Quoting Chiggy007:
TexasHurricane:

I am believing the 12Z UKMET right now...what say you?


can you give me that link please....
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
Quoting jdjnola:


I think her bigger problem is the dry air. Depends on how moisture much Bill gives or takes.


Agree. Wind shear is favorable for Ana.
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1164. KEEPEROFTHEGATE (Mod)
Quoting SOUTHFL43YRS:
OMG! I'M EVACING TONIGHT.
just calm down follow guidance from NHC listen to local officials we got a couple days before anything starts to affect people first in line are my friends in northern leewards lets keep things flowing smoothly for them
Member Since: Ιούλιος 15, 2006 Posts: 178 Comments: 56059

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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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