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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1314. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 128240
Quoting stormpetrol:

You know what you are, I'll give you a hint, Its looks just your avatar!!!
ROFLMAO
Member Since: Posts: Comments:
Hello y'all. I've been lurking here for over a year now, and thought I'd finally log in. I've grown so e-fond of some of you... Storm, Weather Student, Keeper of the Gate, etc. I've learned a lot, and appreciate it. Definitely gives me an edge here in New Orleans. Should be an interesting week.
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1311. BrandiQ
Can some please post the link to the GFS model.
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Quoting RescueAFR:
Good evening...From South Fla..
Do I read the GFS and GDL correct, South Fla appears out of the woods?....at the moment for both of these storms?
You said it. At the moment. Time will tell.
Member Since: Posts: Comments:
Quoting ssmate:
Poll Time:

1) A
2) B
3) C
4) D

I'll tally up all the votes in 20 minutes.


best poll ever....
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Quoting RescueAFR:
Good evening...From South Fla..
Do I read the GFS and GDL correct, South Fla appears out of the woods?....at the moment for both of these storms?


Not at all. There is no such thing as out of the woods if you're in the cone.
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Quoting 92Andrew:


No. I am not tempered. It is just the sort of homophobia that makes such people an outdated person living in a 21st century western country.


2nd time youve mentioned homophobia out of that entire rant.?? can we please quit quoting it and move on!
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Quoting RescueAFR:
Good evening...From South Fla..
Do I read the GFS and GDL correct, South Fla appears out of the woods?....at the moment for both of these storms?


Ummm...NO!
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NOAA 49 has sent its first sonde back..
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Good evening...From South Fla..
Do I read the GFS and GDL correct, South Fla appears out of the woods?....at the moment for both of these storms?
Member Since: Posts: Comments:
1300. java162
Quoting Weather456:


I dont do intensity forecasts. I said at the current rate Bill could become a hurricane as early as Sunday night.

The other intensity forecasts are the opinions of models and that of Weather456, lol

But has I said before the models maybe off a bit taking Bill that far north. Some like the UKMET and NOGAPS have been in line with the official forecast which takes the system over Anguilla.

The track will shift many times over the next 5 days, but basically I'm leaning more towards west, base on where Bill developed, current location and speed of motion.


i think bill is way too south for it to go all the way to the north( ignoring steering paterns)
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Quoting ssmate:
Poll Time:

1) A
2) B
3) C
4) D

I'll tally up all the votes in 20 minutes.



Umm... B?
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1298. afj3
Quoting stormhank:
does anyone have a link to the UKMET model page and the NOGAPS model page/ thanks for any links

Will this work? http://moe.met.fsu.edu/tcgengifs/
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1297. ssmate
Poll Time:

1) A
2) B
3) C
4) D

I'll tally up all the votes in 20 minutes.
Member Since: Posts: Comments:
what go on with this
Decoded recon data in the last 30 minutes:

No decoded data could be found.
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imo, the faster these storms move the less likely they are to pull wnw, if they keep at this pace ,I suspect both of them will enter the Caribbean and God knows thats the last thing we need to happen.
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Quoting JAC737:
1241. SavannahStorm 9:11 PM GMT on August 15, 2009 That animated graphic is amazing. Where did you find it?


It is one of many graphics found on the CIMSS Site.
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Quoting KEEPEROFTHEGATE:
Quoting kingzfan104

Do No Harm

I will not attack, embarrass, humiliate, or make others fear for their safety

I will respect my readers, critics, and subjects of my posts. I will discuss and answer all people with respect, regardless of age, sex, race, religion, nationality, ability, attractiveness, and social or economic status or mental state
Amen.
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1290. KEEPEROFTHEGATE (Mod)
kingzfan104

has been replaced with empty space
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Quoting weathersp:


NOAA 43 is the P-3...

So it should be under NOAA products..

ok thanks
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Quoting forestwedder:
456 as a fellow islander, are you confident in the models at this time taking Bill N of us? I see you seem to be predicting faster intentisfying than the models. What is your educated gut feeling on direction ;-)


I dont do intensity forecasts. I said at the current rate Bill could become a hurricane as early as Sunday night.

The other intensity forecasts are the opinions of models and that of Weather456, lol

But as I said before the models maybe off a bit taking Bill that far north. Some like the UKMET and NOGAPS have been in line with the official forecast which takes the system over Anguilla.

The track will shift many times over the next 5 days, but basically I'm leaning more towards west, base on where Bill developed, current location and speed of motion.
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Everything keeps shifting southward. For Florida, thats good that Ana might so south. For Bill, thats not so good.
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WS doesn't deserve those comments in any way. That pest that said that to him needs to grow up big time.
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Quoting wunderkidcayman:
ok guys which one is for NOAA43
Main Air Force Products (KNHC):
Main NOAA Products (KWBC):
Air Force Backup Products (KBIX):


NOAA 43 is the P-3...

So it should be under NOAA products..
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Explain please.
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So what is the GOM interest looking like now?
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ok guys which one is for NOAA43
Main Air Force Products (KNHC):
Main NOAA Products (KWBC):
Air Force Backup Products (KBIX):
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I have a feeling the track for Bill will continue to shift a little more south due to the center being more south and the current movement which is just south of due west.
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1276. JAC737
1241. SavannahStorm 9:11 PM GMT on August 15, 2009 That animated graphic is amazing. Where did you find it?
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1275. Relix
The problem is 456.... that track is too far to the N, IMO.. for this system. I am gonna take a break from system tracking hahha
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456 as a fellow islander, are you confident in the models at this time taking Bill N of us? I see you seem to be predicting faster intentisfying than the models. What is your educated gut feeling on direction ;-)
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1273. java162
Quoting forestwedder:
Here's hoping the models are right & Bill will pass N of us here in the islands. Lots of people have been laid off in the last few weeks so rebounding from a hurricane will not be easy in these very vunerable islands.
Recently the natural curve N by systems tracking our way has been false hope with the two big ones defying the norm. Ivan decided to track S & destroyed Grenada & more recently Dean levelled off & blasted Martinique & Dominica. To be honest I don't see Bill curving fast enough to miss us unless strengthening occurs rapidly in the next 2 days. I see rapid strengthening occuring much closer to the chain by which time a target will be locked on. GOOD LUCK fellow islanders!!



a bit of exageration there i must say!!!
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HWRF brings bill to cat 4

940 mb and 120 knots - I'm glad he's north of I.



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1270. KEEPEROFTHEGATE (Mod)
Quoting Weather456:
Bill has a 19% chance of becoming a cat 3 in 5 days, that is pretty high for a cat three at 5 days.

Most storms settle with less than 1 and 5 percent while others that surprisingly became majors quickly (Charley) had less than 15%.
bill movin along right on cue with dmax commencing tonight at 11 pm should get some good convection going and yes could become a min. cat 1 by late morning tomorrow its fate is in the hands of the dmax tonight
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Pat do you have a link for the long range model guidance?
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TY, JlPR,,very nice sight..!
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Quoting PensacolaDoug:
Lifted from Joe Bastardi's blog this afternoon...

Thanx! While I am not "wishcasting" I do believe it is worthy of watching.
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1266. juniort
Quoting forestwedder:
Here's hoping the models are right & Bill will pass N of us here in the islands. Lots of people have been laid off in the last few weeks so rebounding from a hurricane will not be easy in these very vunerable islands.
Recently the natural curve N by systems tracking our way has been false hope with the two big ones defying the norm. Ivan decided to track S & destroyed Grenada & more recently Dean levelled off & blasted Martinique & Dominica. To be honest I don't see Bill curving fast enough to miss us unless strengthening occurs rapidly in the next 2 days. I see rapid strengthening occuring much closer to the chain by which time a target will be locked on. GOOD LUCK fellow islanders!!


I agree with that a huricane in these lands would be tragic... I wish you luck as well
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Quoting wunderkidcayman:
guys the recon aircrafts are out
Decoded recon data in the last 30 minutes:

Non-Tasked Mission Data (for at least one product)
Updated on our site 19 minutes ago
08/15 Td2 NOAA N49RF UZNT13


is this data part of the 18z?
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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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