Ana, Bill,--and Claudette?

By: Dr. Jeff Masters , 1:52 PM GMT on August 16, 2009

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After one of the slowest starts to hurricane season in the past twenty years, the hurricane season of 2009 has exploded with activity over the past 48 hours. This morning, Tropical Depression Four joined Ana and Bill in the Atlantic, and appears poised to become Tropical Storm Claudette later today. Indeed, this may already be Claudette, as morning's QuickSCAT pass showed top winds of 45 mph. NEXRAD radar animations out of Tallahassee, FL, show a small but well-organized tropical cyclone with plenty of heavy thunderstorm activity, and improving low-level spiral banding. Satellite loops show an area of intense thunderstorms with cold cloud tops expanding near the storm's center.


Figure 1. Current long-range radar out of Tallahassee, FL.

It's pretty amazing (and a little unnerving) how quickly this storm sprang up. TD 4 developed literally overnight, and has the potential to be a strong tropical storm by the time it makes landfall tonight along the Florida Peninsula. TD 4 reminds me of 2007's Hurricane Humberto, which became a hurricane just 24 hours after first appearing as a tropical depression. I don't think TD 4 has time to reach hurricane strength, since wind shear as diagnosed by the SHIPS model was moderate, 10 - 15 knots, but it does have time to strengthen into a 50 - 60 mph tropical storm before landfall. Given that the storm is so small, storm surge flooding should not exceed 3 -5 feet, and will not be the major hazard from TD 4; inland flooding from heavy rain of 3 - 6 inches is likely to be the main threat from the storm.

Tropical Storm Ana continues to struggle
Tropical Storm Ana continues to struggle. Dry air continues to plague the storm, thanks to the large area of Saharan air the storm is embedded in. Ana's heavy thunderstorms are limited to just one small spot near the center. Wind shear appears to have lessened some, though, since yesterday. Thunderstorms were not able to form at all near the center yesterday, since strong wind shear tends to blow a storm's heavy thunderstorms to one side of the storm, exposing the low-level center to view. With heavy thunderstorms building near the center this morning, shear appears to be less of a problem for the storm. Top winds seen by this morning's QuikSCAT pass were about 35 mph. The outer rain showers from Ana should appear on radar out of Martinique today.

Shear is low (5 - 10 knots), and is forecast to remain low for the next two days. SSTs are warm, 28°C, and will warm further over the next two days. However, there is so much dry air around Ana that significant strengthening appears unlikely. Nearly all of the models predict Ana will dissipate sometime in the next three days, though the HWRF and GFDL predict that this will happen because Ana will move over the rugged terrain of Hispaniola. Ana is likely not strong enough to survive an encounter with the big island that the Dominican Republic and Haiti share. At this time, it does not appear that Ana will be moist enough to cause a major flooding disaster on Hispaniola.


Figure 2. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the northwest of Tropical Storm Bill. Image credit: NOAA/SSD

Tropical Storm Bill gathers strength
Tropical Storm Bill is gathering strength in the middle Atlantic Ocean, and appears poised to become a powerful Cape Verdes-type hurricane later this week. QuikSCAT data from this morning shows a large circulation with top winds of 35 - 40 mph. Water vapor imagery (Figure 2) shows that there is some dry air to the northwest of Bill, and this dry air is being drawn into Bill's center, slowing intensification. It will likely take another day before Bill can moisten the atmosphere enough to ward off the dry air, and allow more significant intensification.

Wind shear is low, 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 15 knots, for the next five days. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next four days, then warm substantially as the storm nears the Lesser Antilles Islands. The combination of low wind shear and sufficiently warm SSTs should allow Bill to intensify steadily to hurricane strength by Wednesday.

The big news is that our most reliable computer model from last year--the ECMWF model--appears to have made the right call yesterday, forecasting that a major trough of low pressure would develop along the U.S. East Coast, turning Bill more to the north. All of the other models--with the notable exception of the UKMET model--have now jumped on the ECMWF bandwagon, forecasting that Bill will pass well north of the Lesser Antilles Islands. The UKMET has Bill hitting the islands, but is being discounted since it is an outlier. It currently appears that the trough approaching the U.S. East Coast will be strong enough to recurve Bill before it reaches the U.S., though it is too early to be confident of this. Several of the longer range models show Bill passing near Bermuda or Nova Scotia, Canada.

I'll have an update later today.

Jeff Masters

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Quoting stormpetrol:
Bill trucking westward again for the time being.


:/ i see pretty defined NW movement. Looks like a fish... Smells like a fish... when it passes puerto rico to the north I'll taste the fish. We hope others do to.

anxious for it to come and give us some surf!
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Quoting CaneWarning:


Poof!


LOL...why so serious? :)

And...Here...We...GO!
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2073. SaoFeng
Claudette still at 45kts 50mph... 5pm update
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@2040. I hate to say it but Bill has an eye in that animated loop.
Quoting CycloneOz:


NBC, our current administration's PR firm, is changing the name of The Weather Channel. It is now going to called The Climate Change Channel. When they do it, I'll "change the channel."


You are ridiculous. I might as well put you on ignore before you start spamming about Xtremehurricanes.com or whatever it is again.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2068. JAC737
P451 - great visual of Bill. Thank you StormW. What's the chances of Ah-na getting her spin back?
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2067. jipmg
Quoting stormpetrol:
Bill trucking westward again for the time being.


and its moving at over 20mph so..
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I think that at 5pm Bill will be bumped up to 70mph.
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Quoting southfla:
extreme236 - You are being far more patient today than I would be - good for you.


Patience is a virtue I wish I had a lot more of sometimes :)
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Michfan:


I feel sorry for you then.


We could all use the entertainment. Oh yeah, POOF!
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hello all just wondering if bills gets very strong could it eat thru any influence that would make it curve out to seas and do its own thing
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Quoting winter123:
Claud. has had a definite WNW movement for most of the day. If this keeps up it may even hit al, miss., or LA


Link


shes grazing the coast... hmmmmmmmmmmm

not that good.
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Quoting CycloneOz:


NBC, our current administration's PR firm, is changing the name of The Weather Channel. It is now going to called The Climate Change Channel. When they do it, I'll "change the channel."


Poof!
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2060. Michfan
Quoting CaneWarning:


Hey may not be an expert, but I sure do enjoy his opinion.


I feel sorry for you then.
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2058. TXEER
Quoting tiggeriffic:
TXEER,

Veterans of storms have noticed that animals and bugs know when a storm is coming... ants begin to march and then disappear a few days b4 a storm hits, birds and squirls for days will frenzy feed and then disappear, even dogs, horses, etc, start to pace and get very nervous...animals can sense the pressure change days b4 humans can...and in my opinion, b4 computers


Thanks...I noticed that with my dogs but never with ants.
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Quoting HurricaneFCast:
If you want to be completely honest, the only true "Expert" here is Dr. Masters...
I also value StormW's opinion, and he is probably the closest one to an expert who comments on this blog.

I agree.
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why can't everyone just be glad that we have the technology to be able to even watch them and make an educated decision based on what we see? 50 years ago...we wouldn't have even known they were coming b4 it was too late unless a ship happened thru or near one...
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2054. JAC737
It hurts pretty bad to be hit with the TWC at 30 mph.
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Bill trucking westward again for the time being.
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Claudette is pushing a lot of moisture to us in south-central Louisiana. Yay for rain all week. :p
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2050. Dakster
Stormw - Thanks for the update! Now I can sleep easy tonight.
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Quoting eyesontheweather:
NBC bought a nice product in TWC now they are sinking it with changes they have implemented especially wake up with "annoying" Al, very little value and a great loss in credibillity


NBC, our current administration's PR firm, is changing the name of The Weather Channel. It is now going to called The Climate Change Channel. When they do it, I'll "change the channel."
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Quoting Tazmanian:
your jokeing aret you why Category5HitsNY i have nevere seen him on the blogs befor other then a few days ago and i have not seen him


Yes, I am joking. He is often in chat and last night he said Ana would hit Miami, Tampa, Mobile, New Orleans and then NYC.
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If you want to be completely honest, the only true "Expert" here is Dr. Masters...
I also value StormW's opinion, and he is probably the closest one to an expert who comments on this blog.
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I think it's slightly amusing how people like to add an extra n into "Ana." It's not supposed to be there, folks. It's either a spanish or french name.

Also, other culprits are Edouard, Hanna, Erica, Hilary, and a bunch more.
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Thanks StormW, always appreciated! :-)
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extreme236 - You are being far more patient today than I would be - good for you.
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your jokeing aret you why Category5HitsNY i have nevere seen him on the blogs befor other then a few days ago and i have not seen him
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Cloudy but dry here (for the moment)
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Quoting pcolasky:


Good down pour here!


By the sounds outside, it will be doing the same here soon...
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Quoting druseljic:
A few rumbles of thunder in Pcola...


Good down pour here!
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and has for you ANNA you be RIP at the 5pm update
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We just had a heavy rain shower pass through Tampa. Lots of thunder and gusty winds.
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Quoting jipmg:


epic fail LOL


Not an epic fail, an epic win, for figuring out something!
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2034. CJ5
Quoting Tazmanian:



and commets may be lol


I think it is still there.
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2033. jdjnola
Speaking of the basics, it seems as if someone does not understand the limitations of radar data!

I understand the limitations of radar data well, but a well defined storm will traditionally have completely closed off convection in the radar signature over the CoC. It may not be perfectly over the CoC, but it is closed. Example: Link
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Quoting P451:
African Wave Train



Danny, Ericka, etc....?
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Quoting BiloxiIsle:

Weatherstudent is not an expert.


Hey may not be an expert, but I sure do enjoy his opinion.
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Quoting CaneWarning:


They give Dr. Lyons like 2 minutes for a tropical update...its crazy. I hate what TWC has become.
NBC bought a nice product in TWC now they are sinking it with changes they have implemented especially wake up with "annoying" Al, very little value and a great loss in credibillity
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Quoting P451:
African Wave Train



where do you get these gifs?
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TXEER,

Veterans of storms have noticed that animals and bugs know when a storm is coming... ants begin to march and then disappear a few days b4 a storm hits, birds and squirls for days will frenzy feed and then disappear, even dogs, horses, etc, start to pace and get very nervous...animals can sense the pressure change days b4 humans can...and in my opinion, b4 computers
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A few rumbles of thunder in Pcola...
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Quoting StormW:
Good afternoon,

Hot off the press!

Thanks!

SPECIAL TROPICAL UPDATE AUG 16, 2009 ISSUED 4:25 P.M. EDT


Of all the so called mets on this site..StormW is the man..when he talks I listen
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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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