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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It looks like Ana might be completely exposed again.


Member Since: Αύγουστος 9, 2009 Posts: 10 Comments: 5080
Taz, I agree. 91L is much closer to home and is much more important right now. We could have a possible Humberto of 2007 situation. Also to remember that a rapidly intensifying storm is likely to slow down some more.
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2711. snotly
I'm a little concerned about the symmetric semi-circle of convection blowing up all around 91L, let's hope we don't wake up in the morning with a 45kt storm...
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Quoting Tazmanian:
guys for get bill for right not whats talk about 91L its more coloer to home right now then bill is


Bill is intensifying and is a possible threat down the road.
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2709. Drakoen
Bill's center is not in the middle of the deepest convection. It is on the northwestern edge of it.
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30727
Quoting sfla82:
With the new models for Ana and Bill I don't see how S Fla can be in the cone any longer! If not 11pm I would say 5am and we are no longer in the cone. I knew all along neither storm would come this way but its great when all the models agree with your thinking...It gives me peace of mind! With these two storms out of the way I will now focus on the next waves coming off Africa!
They are far from out of the way. Just as easily as the track shifts away it can shift back again. I don't feel good until it is GONE.
Member Since: Οκτώβριος 9, 2008 Posts: 0 Comments: 8436
Quoting Tazmanian:
guys for get bill for right not whats talk about 91L its more coloer to home right now then bill is


I love you man
Member Since: Ιούλιος 14, 2006 Posts: 0 Comments: 1163
2706. jipmg
Quoting Drakoen:
I see a northward shift in the track for Bill.


so bill has the potential to move out of the cone of uncertainty then, since its continuing on a due west movement
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Quoting superweatherman:
91L will be at least orenge or even red at 11pm advisory


There is not an 11 pm TWO, it is a 2 am TWO
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2703. rxse7en
Is it an expected trough that will guide Ana northward eventually? Will this be the same trough that's to interact with Bill. Weather analysis--for me-- is like doing a Rubik's Cube--one-handed and half-blind. At least for me it is. God bless you guys that can keep a handle on all of the chaos and work out a coherent and effective forecast model. Just seems like there are way too many uncontrollable factors to keep up on. You'll rarely see me/if ever/try to forecast a cyclonic system. I just let you guys do your vooddoo and learn as we go on year after year.
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Quoting canesrule1:
Im going to put the advisories up, that way we have no double posts.

How about no one does?
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2701. sfla82
With the new models for Ana and Bill I don't see how S Fla can be in the cone any longer! If not 11pm I would say 5am and we are no longer in the cone. I knew all along neither storm would come this way but its great when all the models agree with your thinking...It gives me peace of mind! With these two storms out of the way I will now focus on the next waves coming off Africa!
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2700. Relix
Ana is confusing me. Just where is she moving
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Hey Biloxi Saint how's it going? Just got done a little while ago getting the yard completely done before we get whatever this is that is coming our way...You doing ok tonight?
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just reading stormws update it sure sounds and looks like the secnario he described

http://www.news4jax.com/hurricanetracker/index.html
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Quoting viman:


Just keeping an eye on Ana, doing some preparations, fill the truck with gas, buy water, check generator, etc. What do you think, looks like were gonna get blown, seems like its fast moving though. NWS outa PR is talking about Monday afternoon, looks like some kinda a weather is in front of Ana? Thoughts.


its Ana and shes currently moving at a pretty fast clip so Monday night seems reasonable.
Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
guys for get bill for right not whats talk about 91L its more coloer to home right now then bill is
Member Since: Μάιος 21, 2006 Posts: 5091 Comments: 115437
2695. Skylink
Quoting Skylink:


no doubt about it, we need the rain so bad, lakes are less than 50% full, and they just closed the last boat ramp on Lake Travis, I think we will need 3 tropical systems here to end the drought. But there's always hope.


Sorry, all I was just trying to say is that El Nino is having 0 affect on the Atlantic Hurricane season being so slow to develop this year.
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This advisory is going to be interesting!
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2693. Drakoen
Quoting Weather456:
Sometimes its not your age but the way one acts which make them appear younger than they truly are. Its something we call immaturity.


How erudite you are!
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30727
Hi everyone. It's been a while since my last comments on these blogs. I'm an amateur weather enthusiast and this blog really helps me out to get a better picture on how tropical cyclones work so thanks a lot to everyone!
Anywho, what are the odds for Ana getting into the caribbean and into the GOM afterwards?
Thanks a lot and keep it up, this season is popping out really quickly!
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keeyaw, the blog moves fast now-a-days
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2690. Drakoen
I see a northward shift in the track for Bill.
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30727
Sometimes its not your age but the way one acts which make them appear younger than they truly are. Its something we call immaturity.
Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
Quoting DestinJeff:


no apparent northerly component to Ana's fwd motion. central moisture most significant near 15N, even south of there. dry air still getting the squeeze

well look it has a good enough shield in front of TS ANA and if you look very close you see that on the southeastern side it is trying to push the dry air out
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Quoting mynameispaul:
Probably old news re 91L



A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS OVER THE SOUTHEASTERN
GULF OF MEXICO IS PRIMARILY ASSOCIATED WITH A TROPICAL WAVE
INTERACTING WITH A MID- TO UPPER-LEVEL TROUGH. THIS ACTIVITY HAS
BECOME A LITTLE MORE CONCENTRATED OVER THE SOUTHEASTERN GULF OF
MEXICO WHERE SURFACE PRESSURES ARE BEGINNING TO FALL. THERE ARE NO
SIGNS OF A SURFACE CIRCULATION AT THIS TIME AND ANY ADDITIONAL
DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR. THIS SYSTEM SHOULD
MOVES TOWARD THE NORTHWEST OVER THE EASTERN GULF OF MEXICO ON
SUNDAY. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

http://www.nhc.noaa.gov
/gtwo/gtwo_atl_sub.shtml?area1#contents




yes that is old
Member Since: Μάιος 21, 2006 Posts: 5091 Comments: 115437
2685. Drakoen
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30727
Probably old news re 91L



A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS OVER THE SOUTHEASTERN
GULF OF MEXICO IS PRIMARILY ASSOCIATED WITH A TROPICAL WAVE
INTERACTING WITH A MID- TO UPPER-LEVEL TROUGH. THIS ACTIVITY HAS
BECOME A LITTLE MORE CONCENTRATED OVER THE SOUTHEASTERN GULF OF
MEXICO WHERE SURFACE PRESSURES ARE BEGINNING TO FALL. THERE ARE NO
SIGNS OF A SURFACE CIRCULATION AT THIS TIME AND ANY ADDITIONAL
DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR. THIS SYSTEM SHOULD
MOVES TOWARD THE NORTHWEST OVER THE EASTERN GULF OF MEXICO ON
SUNDAY. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

http://www.nhc.noaa.gov/gtwo/gtwo_atl_sub.shtml?area1#contents
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Im going to put the advisories up, that way we have no double posts.
Quoting Drakoen:


Do you really believe that? LOL!


I started to fall for it too, but then I decided that I didn't care if you were 108 or 2 (albeit a freakishly smart 2 yr old,) that as long as you were informed and knowledgeable I just didn't care. lol

Evening all. Gonna be a busy night.

Evening StormW. Thanks for keeping those updates coming. Much appreciate it.
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91L will be at least orenge or even red at 11pm advisory
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2680. Skylink
Quoting cajunkid:
I'd like to see 91L come up through Corpus as a depression and sit on Austin for a few days. Never seen it that dry in that area.


no doubt about it, we need the rain so bad, lakes are less than 50% full, and they just closed the last boat ramp on Lake Travis, I think we will need 3 tropical systems here to end the drought. But there's always hope.
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2679. viman
Quoting Weather456:


everything is alright, you


Just keeping an eye on Ana, doing some preparations, fill the truck with gas, buy water, check generator, etc. What do you think, looks like were gonna get blown, seems like its fast moving though. NWS outa PR is talking about Monday afternoon, looks like some kinda a weather is in front of Ana? Thoughts.
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2678. aquak9
heres my question :doesnt bills track resemble hurricane dora 1964 ??

Bite your tongue!! That was the last hurricane to hit this area from the east. And let's keep it that way!
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Quoting Skylink:



Please see the following link, http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf

A forecast of Nino saying it may last through next winter means a couple of years to you? And that is a forecast statement based on obs through July.

Barely Nino now and there has been some indications that it is not strengthening further.

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41041 windspeed holding currently @ 17.5 knots...
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2675. flsky
Quoting stormshed:
flsky,

I believe you are right. The radar makes it look like your town is up in the next 30 minutes to an hour. Since it will be raining cats and dogs for you soon, if you see my dog will you tell it to go back home? :)


Ha! Will do!
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Ana is developing storms on her southern side. Interesting. Maybe the shear and dry air are subsiding or leaving. Just something to watch. Bill is looking very intense right now. I would say they would update Bill to 45 or 50mph winds Taz, not 60mph.
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2673. Patrap


91L Short Floater - Rainbow Color Infrared Loop
Member Since: Ιούλιος 3, 2005 Posts: 427 Comments: 129439
Quoting Weather456:


Dean,


Which went over Jamaica and south of Grand Cayman as a Cat 4(I think)
Member Since: Οκτώβριος 9, 2008 Posts: 0 Comments: 8436
Quoting Drakoen:


Do you really believe that? LOL!


my image of Drak is that he's in diapers.....

Depends...
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Quoting StormW:
Regarding 91L:

Just to show you how fast things change.

A well established upper level anticyclone is over 91L...this is now forecast by the GFS wind shear to move in tandem. Doesn't look like it's at the surface quite yet. However, if it works down before getting to the coast...the possibility MAY exist for this to begin to spin up quicker. This could, if it works to the surface, become a depression. Based on current flow and forecast steering, right now it looks as if it could come ashore bewteen MS/LA. I may no be able to be on in the morning, so I recommend staying tuned to local wx. Fortunately, it mst likely will run out of time forany significant development.




thanks stormW. we appreciate it!
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91L is looking interesting. Radar has a closed circulation in the last few frames.

Didn't we have a storm like this 2 years ago that there was a massive debate about naming a subtropical that NHC finally named as tropical and it flopped along the north gulf coast for a few days? Looks oddly similar.
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Quoting Weather456:


Dean,


new here to posting but i have been lurking since frances jeane and charleys day i have obtained quite a bit from this site i have also been quite entertained at times

heres my question :doesnt bills track resemble hurricane dora 1964 ??
any thoughts
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I'd like to see 91L come up through Corpus as a depression and sit on Austin for a few days. Never seen it that dry in that area.
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Quoting FloridaTigers:
When did NHC do away with the line in the cone? I remember Max Mayfield for years wanted to get rid of it.


They did not do away with it. It is still there, but you just have to click on a link above the map.
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Quoting Chucktown:
What up Press? Little sigh of relief with the current thinking on Bill. Not set in stone, but nice to see 95% of the models keep Bill well offshore and out to sea. Still not out of the woods with all the other waves exiting Africa so we'll have to sea (get the pun?)



yea...I feel better...
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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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