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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2414. stormshed
1:41 AM GMT on August 16, 2009
Quoting Skyepony:
Severe Thunderstorm Warning up in N Brevard..weak rotation..


just starting to get my first bit of rain right now. (south of the TiCo Apt) very lilght though
Member Since: August 16, 2006 Posts: 0 Comments: 49
2413. AllStar17
1:41 AM GMT on August 16, 2009
When is was on vacation, I was limited to TV for the most part, so unfortunately I was forced to watch TWC for updates. And I was pleasantly surprised. They did good coverage, at least good enough until I got back today. It is very good to be back on this blog, and being able to check internet on a regular basis, as only about once a day for about 10 mins. was I able to check updates. TWC was not bad, though. Good to be back, and I did have a good vacation. Man, though, talk about active. 456, I hope you weather the storm(s) OK! Glad you are prepared for Ana and Bill.
Member Since: June 29, 2009 Posts: 13 Comments: 5315
2412. thelmores
1:41 AM GMT on August 16, 2009
91L I must confess, may obtain tropical status prior to landfall near Pensacola??

Member Since: September 8, 2005 Posts: 0 Comments: 3805
2411. jpsb
1:41 AM GMT on August 16, 2009
Quoting TexasHurricane:


yeah, kinda does....not sure if it actually is or not though.
Does it have a surface low yet? If it does, then anything can happen. Just depends on how long it stays in the warm gulf waters.
Member Since: June 30, 2009 Posts: 0 Comments: 1197
2410. cyclonekid
1:42 AM GMT on August 16, 2009
Nice Mid-Level Rotation:

Member Since: July 14, 2009 Posts: 51 Comments: 1731
2409. Thundercloud01221991
1:41 AM GMT on August 16, 2009
I think we have a TS in the Gulf by 11 PM
Member Since: August 1, 2006 Posts: 28 Comments: 3716
2408. stormbottom
1:41 AM GMT on August 16, 2009
ps...got a 150 mph rated metal roof..bring it on bill !
Member Since: August 4, 2008 Posts: 0 Comments: 12
2407. RENONV
1:40 AM GMT on August 16, 2009
StormW

I hope you are still on to answer my question. Are you a professional in predicting weather? If your answer is yes, then the blogers on this site should look up the definition of a professional. That should qualify your credentials and your expert analysis. For those who are not professionals by definition are only rendering an opinion and they should qualify their assumptions/predictions as a non-professional analysis. There is a handful of blogers on this site of which I completely value their ability to analyze these storms and make informed analyses that I believe do not carrier the title of a professional meteorologist. There are even a few bloger’s that I believe have a love and god given talent to analysis these system and make educated predictions that I scroll by when seeing their names because of their arrogant attitudes. I feel that’s unfortunate for them in my opinion as their attitude decays their ability to gain the respect from others. There are on lookers here that desire to know what the future may hold for thier safety. These individuals have natural talent and ability to hopefully protect someone who needs to heed their foresight is placed on ignore because of thier arrogances

Back to my hole.
Member Since: July 29, 2008 Posts: 0 Comments: 17
2406. cajunkid
1:40 AM GMT on August 16, 2009


happens this time ever year on here
Member Since: July 10, 2005 Posts: 3 Comments: 1281
2405. Orcasystems
1:40 AM GMT on August 16, 2009


ANA

TD3

91L
Member Since: October 1, 2007 Posts: 81 Comments: 26511
2404. freeroam
1:41 AM GMT on August 16, 2009
Any idea when StormW giving next update? I hate waking up to a weather surprise.
Member Since: September 1, 2007 Posts: 0 Comments: 249
2403. Ameister12
1:39 AM GMT on August 16, 2009
Quoting CaneWarning:
Bill is looking nice tonight.

Quite.
Member Since: August 9, 2009 Posts: 10 Comments: 5075
2402. CaneWarning
1:39 AM GMT on August 16, 2009
Quoting TexasHurricane:


yeah, kinda does....not sure if it actually is or not though.


I don't think its an eye it just looks like it. Has a very nice center on it.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
2401. stormbottom
1:39 AM GMT on August 16, 2009
before the storms get any closer- i dont post at all normally..just listen...let me thank you all in advance for your expertise and advice...most of you were here during my roof lift off during frances..and kept me from freaking out during jeanne and wilma and the rest...talking about the storms takes alot of the fear out...so thanks -glad you're here for everyone as we enter another exciting season of dodge the bullet !
Member Since: August 4, 2008 Posts: 0 Comments: 12
Quoting PBG00:


August 18th in Palm Beach County
Why would you wishcast a major hurricane at yourself?
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2399. KEEPEROFTHEGATE (Mod)
02L/TS/ANA
MARK
14.4N/49.7W


03L/TS/BILL
MARK
10.9N/35.7W


AOI/INV/91L
MARK
25.1N/82.3W
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Michfan 1:24 AM GMT on August 16, 2009

PcolaDan 1:27 AM GMT on August 16, 2009

thanks to the both of you for answering my questions.. very helpful :)

and i do agree going to war with a season vet is makes you feel so much more safer then doing it with a rookie!

i have nothing intelligent to say about the weather and storms other then it rained like crazy earlier here due to 91L i'm hoping that it doesn't blow up more and is only a heavy rain producer where ever it may go good luck and godspeed to anyone in the path of any of these storms!
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Quoting CaneWarning:
It almost looks like 91L has an eye.


yeah, kinda does....not sure if it actually is or not though.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
2395. 10Speed
Quoting CaneWarning:
It almost looks like 91L has an eye.


This is a TD, at least.
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Quoting Grothar:
Hi Weather456, Grothar here. In a previous blog I mentioned a friend (in the profession) had just informed me that the Center of Circulation of Bill may be further South than had been established by the NHC. I received a reply from jipmq. Since you have been informative before, could you please share your opinion. By the way, does this bickering (is this the correct word) currently going on distract from the rest of you discussing matters of such importance? I speak 5 languages and I am sure I do not speak them all correctly.


its rather a waste of blog space it such a time info needs to be communicated.

IMO, I have been saying this since Bill was 90L. Tracks are going to shift as along as it does two things:

continue west

speed up


Bill is now moving wsw or 260.

Now recurve the storm as the models do, it still leaves about 1-2 degrees lat which when extrapolated 5 days out is a very large error. I dont buy some of the models since they had Bill moving west northwest (where it is suppose to be). I'm still not a 100 percent sure on this, so it remains a watch and see but so far Bill has not turn north.
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2393. Skyepony (Mod)
Severe Thunderstorm Warning up in N Brevard..weak rotation..
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really nice show going on outside my house! man the lightning is close!
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Quoting TexasHurricane:


I think Northwest, bringing it to the Florida panhandle area I believe.
Thanks.
Member Since: July 14, 2009 Posts: 51 Comments: 1731
Does anyone else think Bill will be a hurricane tomorrow?
2388. Skyepony (Mod)
Quoting BiloxiGirl:
Within reason how strong can 91L get? I know anything is possible and all that stuff.... but what is the best educated guess based on odds and stats? How strong will it get?


For a few days I've stuck with a TD or TS wouldn't suprise me. This lightning..I'll go outside chance of a Cat 1.
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It almost looks like 91L has an eye.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Could Bill possibly be a cat 1 by tomorrow?
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2385. beeber
As a Red Cross Emergency Services Director on the Mississippi Gulf Coast, I watch these blogs with great interest. Everyone, please keep up the great job that you are doing for my planning for storms. Thanks.
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Quoting cyclonekid:
91L:


1. 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.


Which way is 91L moving?


I think Northwest, bringing it to the Florida panhandle area I believe.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
We're have a nice evening in Tampa.
Member Since: April 26, 2009 Posts: 3 Comments: 3667


91L is rotating nicely...
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2380. Relix
I forgot to add... that misinfo will cause disasters if something abd does happen!
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Quoting CaneWarning:


Are you making any preps?


All I had to do was update my hurricane kit and make sure I had a plan. I still dont have a wireless radio though.
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2378. Grothar
Hi Weather456, Grothar here. In a previous blog I mentioned a friend (in the profession) had just informed me that the Center of Circulation of Bill may be further South than had been established by the NHC. I received a reply from jipmq. Since you have been informative before, could you please share your opinion. By the way, does this bickering (is this the correct word) currently going on distract from the rest of you discussing matters of such importance? I speak 5 languages and I am sure I do not speak them all correctly.
Member Since: July 17, 2009 Posts: 71 Comments: 26889
2377. PBG00
Quoting jipmg:


August 24 , if bill hits, it hits August 23


August 18th in Palm Beach County
Member Since: October 20, 2005 Posts: 14 Comments: 6650
wow...thunder is pretty loud here in west palm...i guess i can turn off the automatic sprinklers for a while...
Member Since: August 4, 2008 Posts: 0 Comments: 12
2375. Relix
News here are disregarding Ana. They said it's probably gonna stick to the south and since its so small it will only bring minor rains to PR. They also showed the models and how most of them showed Ana passing south of PR. Now they said they were mostly worried about Bill... but that as of now Ana poses minor threat to PR as it's still moving W.

OH well... we'll know tomorrow.
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2364. Skyepony
It is getting really nasty around us Skye....wasn't anticipating this weather tonight.
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I think this is gonna suck here in Louisiana...but at least its different than listining to people vet health care
Member Since: July 10, 2005 Posts: 3 Comments: 1281
Goerges 1998 is an analog storm to Bill, Also Donna 1960



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Guys and Gals, all this talk of who is trained where is so not related to this blog. If you dont like the creds of a poster then just ignore the information. As for StormW, this is my third year on this blog and to my knowledge he has provided complete accurate information and backs it up with notations

Personally, I would rather go to war with a battle tested Sgt Major then a 1st LT fresh out of West Point. My cred for that comment. My father served 26 yrs US Army. Served two tours in Korea one in Nam, Ran two Platoons in Europe During the Cold War and Taught at West Point.

So please stick to the weather.
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2370. jipmg
Quoting jrweatherman:
When does High School start?


August 24 , if bill hits, it hits August 23
Bill is looking nice tonight.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
2368. IKE
Quoting BiloxiGirl:
Within reason how strong can 91L get? I know anything is possible and all that stuff.... but what is the best educated guess based on odds and stats? How strong will it get?


I would say a low tropical storm....it could be more or less.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Ana and Bill continue to do the Fujiwhara effect.
Member Since: August 9, 2009 Posts: 10 Comments: 5075
91L:


1. 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.


Which way is 91L moving?
Member Since: July 14, 2009 Posts: 51 Comments: 1731
2364. Skyepony (Mod)
Can see the shear on Ana, south just outside her.

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1012mb (29.88 inHg) Sea Level (Surface) 28.6°C (83.5°F) Approximately 23°C (73°F) 215° (from the SW) 5 knots (6 mph)
1000mb 108m (354 ft) 27.6°C (81.7°F) Approximately 23°C (73°F) 235° (from the SW) 6 knots (7 mph)
925mb 794m (2,605 ft) 21.4°C (70.5°F) 19.3°C (66.7°F) 240° (from the WSW) 7 knots (8 mph)
850mb 1,524m (5,000 ft) 18.0°C (64.4°F) Approximately 13°C (55°F) 225° (from the SW) 9 knots (10 mph)
700mb 3,165m (10,384 ft) 9.8°C (49.6°F) Approximately -4°C (25°F) 85° (from the E) 18 knots (21 mph)
500mb 5,880m (19,291 ft) -4.1°C (24.6°F) Approximately -22°C (-8°F) 30° (from the NNE) 8 knots (9 mph)
400mb 7,600m (24,934 ft) -14.9°C (5.2°F) Approximately -36°C (-33°F) 45° (from the NE) 9 knots (10 mph)
300mb 9,710m (31,857 ft) -30.9°C (-23.6°F) Approximately -51°C (-60°F) 95° (from the E) 11 knots (13 mph)
250mb 10,980m (36,024 ft) -40.9°C (-41.6°F) Approximately -57°C (-71°F) 135° (from the SE) 18 knots (21 mph)
200mb 12,460m (40,879 ft) -53.1°C (-63.6°F) Approximately -70°C (-94°F) 100° (from the E) 27 knots (31 mph)
150mb 14,260m (46,785 ft) -65.3°C (-85.5°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 130° (from the SE) 24 knots (28 mph)

Hope they fly 91L soon, it's moved enough away from shore I don't have the surface obs I've had for 2 days.

Lightning here is shakin the house..

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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.