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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Things look active tonight across the tropics BUT if the trends continue with Bill it should not be an issue for the U.S.

Next 2 systems....Blah
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3413. code1
Agree stormsurge39 and tropics21. Much ado about something that may or may not be. Now, for those of you new in the last bit? I've been here since blogs started on WU. Want us to take over the main blog again? Nahh, I don't think so.

Be cool, grow up and learn from each other. I am old enough to be your parent or even grandparent to some of you since blog started. Listen and learn from others without the oneupmanship. You will learn far more that way.
I live on the FL panhandle and am in Galveston working. I and others surely don't need to want to wade through the juvenile posts some of you make here to show your cajones. We are NOT sitting in your parents home thinking someone else will protect us. Please think of it from an adult side. You'll be there yourselves before your know it!!
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3412. flsky
Quoting HaboobsRsweet:

While I agree with that quote, each year they do seem to get a little better. I think you can go out to 5 days now but still need some minor adjustments after day 3.


I agree. I've done a lot of personal wishcasting, but it seem like, in the past couple of years, that intelligently-considered models override.
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Quoting DM21Altestic:
Wasn't twinkster a troll from last year, too? Or am I getting him confused with somebody.
I don't remember your name last year on here..Was it something else?
Member Since: July 30, 2007 Posts: 0 Comments: 1474
Quoting TampaMishy:
It's going great! Nice and breezy here tonite for a change. What about you?

We've got a cold front and rain here. I ran in downpours and 54 degree temps this morning. It's normally upper 90's here this time of year, so the cool down has been nice.

Are your winds starting to shift direction there at all?
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3407. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129089
Quoting atmoaggie:

I do too, but it has no east to west winds on the north end...the one type the RUC did see. That is nonsensical. If any part should be there, it is that one.

Oh, and I know why. Turn off the 25 hour average, which I think you can agree is bulls*** for this application and you see nothing at all.

I do agree with you that it is hard to find the support data out there from buoy obs but I just never have been a fan of buoy data anyway. Once you get some good waves going, the buoys are usually under water anyway. I have a hard time overlooking the radar loop. I can look right at it and pick out where I believe the center is and see rotation starting now and def going to be clearer by the morning.
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what about the wave behind bill do models still show development with that???
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Quoting TampaSpin:


You are correct that is ocean SURFACE currents.....which a SURFACE LOW will show up...


Maybe...but there is a lag between current motion and surface wind...and a pre-existing current has some memory...a change in the wind won't immediately change the curent and there is a big difffence in momenntum between moving air and moving water...nevertheless, an interesting way to see the wind field without benefit of direct wind measurements.
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Whats the next name?
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Wasn't twinkster a troll from last year, too? Or am I getting him confused with somebody.
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3401. jipmg
Models take mr Bill out to sea, all of the models everyone of them...

Models take ana to its death over the caribbean.. some shitfting north, oh well im going to sleep im starting to lose interest in these systems
Quoting stormsurge39:
A wise met told me one time, any model more than 3 days out is a crap shoot. weather patterns can change that models cannot predict!!!


yeah, I don't know. It may do the north thing, but I am leary....
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting flsky:

Go away.




ok first of all who are you? second of all you have no right to keep telling someone to go way. this is about the 10th time i have seen you say this.

you are now officialy the first person on my ignore list ever
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Quoting HaboobsRsweet:

Yea I am tracking with you I see it.

I do too, but it has no east to west winds on the north end...the one type the RUC did see. That is nonsensical. If any part should be there, it is that one.

Oh, and I know why. Turn off the 25 hour average, which I think you can agree is bulls*** for this application and you see nothing at all.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting eye:
Ana about to die
Bill is going to be a fish (recurve far away from the CONUS)
Blob in the gulf will just be a rain maker

BOY, the tropics are exciting!!!! *yawn*

Ahhh, I forgot about this epic troll. He's baaaaaaack....
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The bigger the storm the more its influenced. The trough looks to be VERY strong and digging in bigtime. If the models are over doing it could hit the Outerbanks or New England.
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Quoting stormsurge39:
A wise met told me one time, any model more than 3 days out is a crap shoot. weather patterns can change that models cannot predict!!!

While I agree with that quote, each year they do seem to get a little better. I think you can go out to 5 days now but still need some minor adjustments after day 3.
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Ana's lost all her convergence.
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Quoting CatastrophicDL:
Hey Mishy - you ought to tell him you didn't need your magic 8ball for that! How's it going?
It's going great! Nice and breezy here tonite for a change. What about you?
Member Since: July 30, 2007 Posts: 0 Comments: 1474
3388. eye
Ana about to die
Bill is going to be a fish (recurve far away from the CONUS)
Blob in the gulf will just be a rain maker

BOY, the tropics are exciting!!!! *yawn*
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WEAKENING FLAG: ON?

Give me a break. Please.
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Quoting Progster:


Tampa...if this is the link you used...you're looking at ocean current vectors, not atmospheric winds.


You are correct that is ocean SURFACE currents.....which a SURFACE LOW will show up...
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Quoting code1:


From my mouth to your ears press. Am thinking it time to ask the WU masters for a separate blog for those under and over a certain age for here! Still hold to the first years here I suppose. Not near the crap going on now. Young and old in the mix. Old knows, and young think they know. Makes the world go around for sure, but dang sure makes it hard for those of us not under our parents roof's to read intelligent conversation for the most part. There are a few young folks here, I am happy to follow and learn from. Note....I say few, the others just found a forum for their testosterone outlets. Go and get a date guys and gals!!
yup romper room
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A wise met told me one time, any model more than 3 days out is a crap shoot. weather patterns can change that models cannot predict!!!
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Quoting Tazmanian:
no way bill will be a fish its too big too make that turn andits moveing too fast

See? Taz may not have gotten an "A" in his BCIS class, but he sure knows his tropical weather.
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Drak is bill going to get the wave you were talking about yesterday if it keeps growing at its current pace?
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Quoting rareaire:
dang thing sure seems to be spinning when i lok at it! post 3334


maybe its you who's spinning!
(takes out breathalyzer)
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Quoting WeatherStudent:


Plz do. Thanks for your assistance.

once again thank you nows he's now my list now i feel good :)
Member Since: July 13, 2008 Posts: 6 Comments: 10796
Quoting atmoaggie:

OK, but shouldn't something be showing a SW wind...to the SE of the "center"? And a S wind somewhere E of center? You telling the landbreeze is overcoming the burgeoning TD-4?
Really, just trying to learn from a real met!

The rotation is really tight. It is in its really early stage. Those east winds to the east of the storm is kinda feeding your convergence zone. There is a south wind to the south as well feeding into the center of where the circulation is forming. That is just my opinion. It also is hard to overlook rotation that you can see on radar. You can see the tight spin around where I would expect the center to be. Winds are too light for TD status at the moment. I would expect the next surface anal to have a low there.
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Quoting sfla82:


Its done!!!!


Possibly. It doesn't look to be intensifying.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
I would not call out ana any time soon she's already served crow to many of us on here!!
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Quoting audioslave8:
So... Bill is going fishing and Ana is about to die. Looks like the only action the US is going to see is from invest 91L. This turned out to be alot hype. Looking on IR 91L looks more impressive than Ana.

Bill isn't going fishing.
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3373. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129089
Quoting extreme236:
I do believe Bill could be a hurricane tomorrow


I agree.
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3371. Drakoen
Bill is getting a lot better organized.
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winds at 20-25mph here in sarasota a rain band its the 2nd one in a hour and 4th today,TD4 5am,IMO
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Hey Mishy - you ought to tell him you didn't need your magic 8ball for that! How's it going?
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Quoting TampaMishy:
It says no.

That sucks. Ah well, I guess I'll have to date Alyssa, who's my own age...


Also, am I the only person on this blog who has zero people on their ignore list? I'm old enough to handle the heat.
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3366. code1
serialteg? If you have to ask that. You are one whom I was just speaking of in my last post.

Tropics anyone without hyperbole or me antics?

Dr. M, do you hear us?
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Well I am out...predictions from the Conch...Bill starts a more northerly track...Ana continues to mystify Rare...91L swells up like a tick on its way to Al/La...and JFV moves out of his moms basement...but keeps the shower curtain...
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Quoting TampaSpin:
Just found a closed low using the National DAta bouy system......its there....Hope you all can figure out how to use this...


Tampa...if this is the link you used...you're looking at ocean current vectors, not atmospheric winds.
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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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