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 kmanislander:


Looks like an open wave


Its getting close...still holding on to an ill-defined circulation.
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Quoting extreme236:
Bill looks like a very large cyclone.


GUESS WHAT? IT IS!!!
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1823. jdjnola
Wow Claudette's radar signature is impressive now. Clear CoC, almost closed off: Link
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Quoting seminolesfan:
Nay, it's just west of 270. :)


LOL
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Bill looks like a very large cyclone.
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Quoting blairkiel:
Cat 4 for between Corpus and Houston is a very likely outcome


What is likely?
Member Since: October 21, 2008 Posts: 248 Comments: 3970
Quoting IpswichWeatherCenter:
Ana is a Tropical Depression according to the ADT site.

http://cimss.ssec.wisc.edu/tropic2/real-time/adt/adt.html


Looks like an open wave
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1818. CJ5
It appears those in Guadeloupe will get a wake-up call from Ana.
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1817. flsky
Quoting Weather456:
I think we came to an agreement, Bill is moving west westnorthwest northwest. WWNWNW


Ha - funny!
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DESTIN, FL
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Dr. Masters,

What is your prediction for Ana's entrance into the Gulf of Mexico, and possible strengthening into a major hurricane?
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Quoting jasoniscoolman10:
maybe conn will get hit by hurricane bill..wow.


Based on that, the entirety of the Eastern Seaboard could get hit.
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1813. IKE
Claudette forming a new center?

Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting hurristat:


So if it hits land and kills people, can I hold you responsible?



lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115487
Center of Claudette starting to show itself again SSE of Panama City. Looks like she will come ashore a little west of PCB if trends continue. The slower she goes, the further west she goes as the ridge will continue to build westward with time.
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I'm glad its a fish, hurricanes are too expensive. and if the models are right, this will be fun to watch

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Quoting Weather456:
I think we came to an agreement, Bill is moving west westnorthwest northwest. WWNWNW
Nay, it's just west of 270. :)
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For all of you that are letting your guard down and accepting this northern turn that the models are indicating you are going to be in for a big suprise. It is possible and even probable now that all of the models have jumped on the bandwagon....however there is still a large cone of uncertainty and to write Bill of as a fish storm at this stage is foolish....just remember ole blue told ya so!
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Quoting jipmg:


That is an upper level low, no chance its going to form it takes days for something to spin down in the surface, and its moving too fast for that to happen, and its spinning with dry air.


I am talking about Invest 91 are you saying that is the ULL??
I see the ULL in a different area..
I am talking about this area..


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Ana is a Tropical Depression according to the ADT site.

http://cimss.ssec.wisc.edu/tropic2/real-time/adt/adt.html
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Bill is heading for the fishes.
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I'll check in for the 5 pm updates. Out for now
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Quoting blairkiel:
Cat 4 for between Corpus and Houston is a very likely outcome
Outcome of what???
Member Since: August 25, 2008 Posts: 0 Comments: 17
Quoting Tazmanian:
bill wont be a fish on my watch


So if it hits land and kills people, can I hold you responsible?
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Based upon the Advisory points of Claudette between 2 and 3 - she's been moving at 6 mph.

Any news?
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bill wont be a fish on my watch
Member Since: May 21, 2006 Posts: 5091 Comments: 115487
Quoting Tazmanian:
and bill wont be a fish


I wouldn't think so... He doesn't have gills or fins.
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1796. jipmg
Quoting Weather456:
I think we came to an agreement, Bill is moving west westnorthwest northwest. WWNWNW


yep, but the last too loops it jogs nearly due west, basically WNW-W not NW
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Quoting blairkiel:
Cat 4 for between Corpus and Houston is a very likely outcome
ROFL
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Quoting JAC737:
I really get a kick out of you all. There's all this, "Where's it going? Am I in the clear? Am I going to get hit?" and someone says, yes and someone says no and someone says maybe. And then it's all, "You're not an expert! You're not a meteorologist! Don't you say so and so is in the clear! Don't you say it's heading west! It's a wobble!" So you yell at each other for predicting and you yell at each other for warning each other.


I agree which is exactly why people should start using their head before asking such a question when it has been said millions of times that no one can tell you for sure where a storm will hit until it does. My favorite is when they get the answer that no one knows they accuse all the experts of playing favorites. Love that
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1792. jipmg
Quoting lopaka001:
Looking at the latest sat images is there another system right behind Claud??


That is an upper level low, no chance its going to form it takes days for something to spin down in the surface, and its moving too fast for that to happen, and its spinning with dry air.
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1791. GatorWX
Quoting WPBHurricane05:


Though considered by some, California is not out of this country....LOL


I know Taz is from Caly, but I wondered if he/she is originally from another country. USA, characters welcome! I love that station!
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Cat 4 for between Corpus and Houston is a very likely outcome
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1789. IKE
Quoting bayoucat:
I live on Parker Bayou just a few miles east of Panama City. Just walked down to the dock. Low fast moving clouds to the east and south. Some wind up in the trees, but mostly just a light breeze. Blue sky directly overhead. We just finished putting up lawn chairs, etc. and will add extra anchors to keep the boats away from the dock (we have a small boatyard) but are not moving and anchoring boats in deeper water. With the storm approaching from the southeast we should have no problem with storm surge--in fact wind should drive water out of the bay. Storm seems to have slowed down which may give it more time over water, but I don't think enough time to become seriously dangerous. Mainly will have limbs, moss, leaves etc. and probably lose power. We have big live oaks and unless one of those limbs goes through the roof we should have no real problems. Will give you an update later.


Good luck....Just had wind gusts to 20-25 mph. First band of rain moved through.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting 996tt:


Haha, one thing I have learned is this is a bunch of conjecture regardless how many big words you try and use to support the conjecture and Steve Lyons and those with a bunch of fancy equipment don't do much better than mua whose degrees have nothing to do with weather.


WHY are many individuals SO NASTY on this forum when a newbie posts something?!? Everyone is contributing to the activity we face TOGETHER. Blogger 996tt ought to refresh "Rules Of The Road" at this Website.
Quoting Michfan:


Thats pretty much how this blog goes on a daily basis during the active part of the season. It will never change.


Wow, what a real shame. There is so much expertise on here that WANTS to say something, but too much potential abuse. For everyone reading this, WHY can't we all get along, meteorologists or non-meteorologists. Everyone will be more better off if we learn from each other and don't take comments personally.
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I think we came to an agreement, Bill is moving west westnorthwest northwest. WWNWNW
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and bill wont be a fish
Member Since: May 21, 2006 Posts: 5091 Comments: 115487
Quoting Vortex1094:


lol but check out the size of the cone


Yes the cone is big, but that is why they stress to pay attention to the cone, not the line down the middle. Heck, that is why they took the line out of the middle of the graphs unless you click to see it.

I am just not sure why people seem to think the fact Bill moving west right now works against the NHC forecast. The truth is we will not know until Wednesday.

If Bill is still under 15N after 8am Wednesday, which would put it outside of the current 3 day cone, then it is time to really rethink the forecast. But to postulate, and say that Bill is not adhering to the forecast already is to go against the NHC and the models.
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Quoting Drakoen:


The dynamic models take it out to sea as well.
This mornings run did. We are still in the lead time for the global dynamical models changing the trough/ridge interaction run to run. Especially since this is VERY much a timing AND trough strength interaction situation the models will be second guessing themselves frequently. IMO, the early models are of little use in such a highly upstream dependent environment.
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Looking at the latest sat images is there another system right behind Claud??


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Well with Bill obviously intensifying and all indications are that he will continue to identify, how would he possibly miss the trough that is forecast to sweep down?
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1780. 996tt
Quoting CatastrophicDL:

I don't think they are close enough to effect each other. I think they have to be within 600 miles of each other. Anyone else remeber how close they have to be?


Looks pretty cool though.
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1779. Michfan
Quoting Michfan:


If i remember right its more like 500 miles or less.


Here we go:

When the cyclones approach each other, their centers will begin orbiting cyclonically about a point between the two systems. The two vortices will be attracted to each other, and eventually spiral into the center point and merge. When the two vortices are of unequal size, the larger vortex will tend to dominate the interaction, and the smaller vortex will orbit around it.

The effect is often mentioned in relation to the motion of tropical cyclones, although the final merging of the two storms is uncommon. The effect becomes pronounced in these storms when they approach within about 1,450 km (900 mi) of each other and are at tropical storm strength or stronger.

http://en.wikipedia.org/wiki/Fujiwhara_effect
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Quoting louisianaboy444:
lolz, why is Drak getting attacked for stating what the models are indicating?

Because if you state that the storm is going anywhere but right at someones door step they call you a downcaster...you gotta learn to just ignore it


And it works vice versa too, people that think its possible that it will go more west than what the models think get called 'wishcasters'
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Quoting Weather456:
where's Hilary when you need her



She's writing under the pseudonym of Claudette today...
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Quoting Tazmanian:



huh???? what are you talking about???


Could be cuz your english is a little "different" sometimes
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Quoting Skyepony:


I think it has helped keep her pulled south & has kept her alive when her convection gets blown off.


So Bill has an umbilical cord?

?_?
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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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