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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Just got a tornado in Cape Coral. Claudette's presence felt, even though it's a ways off now.
Member Since: Posts: Comments:
2124. Dakster
Quoting TXEER:
I have a serious question.

What is it that causes these bands of clouds to come Wstward across Africa on a regular basis from August to October?

Thank you!


Trade winds.. Climatology and of course, Mother Nature has setup the Earth to do this during this time of year.

Member Since: March 10, 2006 Posts: 0 Comments: 10313
tornado warning in norther lee/southern charlotte county florida. looks like a band from claudette is moving in.
Member Since: August 28, 2005 Posts: 0 Comments: 551
Quoting StormW:
Good afternoon,

Hot off the press!

Thanks!

SPECIAL TROPICAL UPDATE AUG 16, 2009 ISSUED 4:25 P.M. EDT
Quoting F1or1d1an:
Cloudy but dry here (for the moment)
for the ones reporting live conditions for claudette, please list you location so we know the exact spot you are at please. i am 8 miles east of defuniak springs in walton county in nw florida.
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Poor Ana.
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2120. jipmg
Bill did not speed up according to the NHC, despite satellite saying otherwise
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2119. Relix
Hey Ana is a depression =P
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2118. TXEER
I have a serious question.

What is it that causes these bands of clouds to come Wstward across Africa on a regular basis from August to October?

Thank you!
Member Since: Posts: Comments:
2117. Dakster
Quoting DestinJeff:
need to hit the Midget Roman Emperor ... $5, Hot-N-Ready ... just in case power gets knocked later. cold pizza good for 24 hours.


LOL
Member Since: March 10, 2006 Posts: 0 Comments: 10313
Hi again
News from NHC about Ana:

000
WTNT32 KNHC 162041
TCPAT2
BULLETIN
TROPICAL DEPRESSION ANA ADVISORY NUMBER 19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
500 PM AST SUN AUG 16 2009

...ANA WEAKENS TO A TROPICAL DEPRESSION...

AT 500 PM AST...2100 UTC...A TROPICAL STORM WATCH IS IN EFFECT FOR
THE DOMINICAN REPUBLIC FROM CABO ENGANO WESTWARD TO CABO BEATA. A
TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

A TROPICAL STORM WATCH ALSO REMAINS IN EFFECT FOR PUERTO RICO...THE
U.S. VIRGIN ISLANDS...THE BRITISH VIRGIN ISLANDS...MONTSERRAT...
ANTIGUA...BARBUDA...ST.KITTS...NEVIS...ANGUILLA...ST.MAARTEN...ST.
MARTIN...SABA...ST. EUSTATIUS...GUADELOUPE...AND ST. BARTHELEMY.

A TROPICAL STORM WATCH REMAINS IN EFFECT FOR PUERTO RICO...THE
U.S. VIRGIN ISLANDS...THE BRITISH VIRGIN ISLANDS...MONTSERRAT...
ANTIGUA...BARBUDA...ST.KITTS...NEVIS...ANGUILLA...ST.MAARTEN...ST.
MARTIN...SABA...ST. EUSTATIUS...GUADELOUPE...AND ST. BARTHELEMY. A
TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

INTERESTS ELSEWHERE IN THE LEEWARD ISLANDS AND THE NORTHEASTERN
CARIBBEAN SEA SHOULD MONITOR THE PROGRESS OF ANA. ADDITIONAL
WATCHES AND WARNINGS MAY BE REQUIRED FOR PORTIONS OF THESE AREAS
LATER TODAY.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA
OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR NATIONAL METEOROLOGICAL SERVICE.

AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL DEPRESSION ANA WAS
LOCATED NEAR LATITUDE 15.1 NORTH...LONGITUDE 58.8 WEST OR ABOUT 170
MILES...270 KM...EAST OF DOMINICA.

THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 23 MPH...37 KM/HR. A
TURN TOWARD THE WEST-NORTHWEST IS EXPECTED TONIGHT AND TOMORROW. ON
THIS TRACK THE DEPRESSION WILL CROSS THE NORTHERN LEEWARD ISLANDS
TONIGHT AND ENTER THE NORTHEASTERN CARIBBEAN SEA ON MONDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24
HOURS. DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
SHOWS THAT THE CIRCULATION OF ANA HAS BECOME LESS ORGANIZED TODAY.
IF THIS TREND CONTINUES...ANA COULD DEGENERATE INTO A TROPICAL WAVE
TONIGHT.

THE MINIMUM CENTRAL PRESSURE RECENTLY REPORTED BY AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT WAS 1008 MB...29.77 INCHES.

ANA IS EXPECTED TO PRODUCE RAINFALL AMOUNTS OF 2 TO 4 INCHES OVER
THE LEEWARD ISLANDS...INCLUDING PUERTO RICO...AND THE U.S. AND
BRITISH VIRGIN ISLANDS...WITH ISOLATED MAXIMUM AMOUNTS OF 6 INCHES
OVER MOUNTAINOUS TERRAIN.

...SUMMARY OF 500 PM AST INFORMATION...
LOCATION...15.1N 58.8W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...WEST OR 280 DEGREES AT 23 MPH
MINIMUM CENTRAL PRESSURE...1008 MB

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 800 PM AST FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 1100
PM AST.

$$
FORECASTER BRENNAN/ROBERTS
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So how likely is it that Bill will miss the northern leeward islands? The storm is pretty far south... and in the last three weeks computer models have not been doing well.. so are the steering currents still relatively unpredictable?
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2113. jipmg
Quoting bluehaze27:
What happens if Bill outruns the upper-level trough or the trough flattens out?


It continues W-WNW

@weather456

stop being a fishcaster
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Quoting Tazmanian:



i was right a a long


You normally are right!
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Quoting ssmate:

Why is that a poof? TWC has clearly stated that they have moved their focus to bringing climate change to it's forefront. The Admin. part could have been left out, but TWC agenda is clear.


I poofed him because he's not adding anything to the blog. I'm also tired of him advertising his crappy site here.
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2110. Dakster
Can someone please hit the nail on the head of Ana's coffin this time. She keeps coming back to life...

Member Since: March 10, 2006 Posts: 0 Comments: 10313
Quoting Tazmanian:
Last NHC advisory issued on GUILLERMO


CPHC starts issuing at 11pm advisory.
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2107. jipmg
Quoting serialteg:


i "think" the only thing that would make bill veer west again is de-intensification like ana, which is unlikely to happen anytime soon, and a big ol' ridge or sometin. dominant hi-pres area.


there is a dominant high already in place.. and its strengthening, its pushing our gulf storm WNW
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2106. Michfan
Quoting Orcasystems:

ANA

Bill

Claudette


Took ya long enough Orca!
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Bermuda watch out

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Quoting jipmg:


and its moving at over 20mph so..


so, then wouldn't that make Bill less likely to turn north?
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What happens if Bill outruns the upper-level trough or the trough flattens out?
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Claudette turning west makes sense, since the high will be building in from the east.
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Quoting IceSlater:
BILL

REPEAT...CENTER LOCATED NEAR 12.8N 40.0W AT 16/2100Z
AT 16/1800Z CENTER WAS LOCATED NEAR 12.5N 39.2W

65MPH 994MB



i was right a a long
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Quoting weathercrazy40:
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


i "think" the only thing that would make bill veer west again is de-intensification like ana, which is unlikely to happen anytime soon, and a big ol' ridge or sometin. dominant hi-pres area.
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Quoting P451:
Not the most impressive radar signature for Claudette.



Does it seem like her center keeps re-locating towards the end of the loop?


Go west. Watching from NOLA
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Quoting lopaka001:


IKE do you see another system just south of Claud aka Invest 91??
I was asking the same question 20 mins ago but no one answered..
Maybe I am looking too much into the latest sat images but it looks like something trying to form just south of Claud..



everything in that image is one system....not 2...
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2096. ssmate
Quoting CaneWarning:


Poof!

Why is that a poof? TWC has clearly stated that they have moved their focus to bringing climate change to it's forefront. The Admin. part could have been left out, but TWC agenda is clear.
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Last NHC advisory issued on GUILLERMO
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I belive the weather reports on here are so good because many people participate. Ofc not everything is on topic or correct, but overall a decent source for information on current weather outlooks and coverage.
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Quoting extreme236:


You are ridiculous. I might as well put you on ignore before you start spamming about Xtremehurricanes.com or whatever it is again.


You have no idea what you're even talking about. Ever wonder why I can mention that site in here and not get banned?

{Was that a poof I heard just now?}
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Quoting P451:
Not the most impressive radar signature for Claudette.



Does it seem like her center keeps re-locating towards the end of the loop?

Radar images can be decieving, but C is going to be further west before landfall - if you're in Pensacola, just put on your galoshes...
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2091. jdjnola
Quoting jlp09550:
Claudette is pushing a lot of moisture to us in south-central Louisiana. Yay for rain all week. :p


Is that anything abnormal for us lately? But yes, Claudette is sure to bring some (more) rain.
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BILL

REPEAT...CENTER LOCATED NEAR 12.8N 40.0W AT 16/2100Z
AT 16/1800Z CENTER WAS LOCATED NEAR 12.5N 39.2W

65MPH 994MB
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2089. jipmg
Quoting CaneWarning:


She's trying to miss the coast by reforming an LLC to the west.


she's trying to miss the coast? So now they can think?
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2088. pcola57
Hello All...Just now getting a storm in pensacola from Claudette leading flow...been a lurker here for a couple of years and never posted...this might be the year i break out of my shell...hats off to all here as i have really learned alot and have found this blog an invaluable tool...i hope "some" of the bloggers can take a step back and look at all the truely unique and and talented pepole who contribute...will post from time to time...gonna head out to the porch and watch for awhile...bye for now...
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5 PM out
No change in Claudette.
Bill up to 65.
Member Since: August 10, 2009 Posts: 3 Comments: 672
2086. Michfan
Recon is headed out of barbados.
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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


it was a wobble....she will wobble off and on....shes being bumped by the high....but the main general direction has stayed just north of nw...cmon...def a panhandle landfall of a strong tropical storm..
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Quoting DestinJeff:
TWC: "we think Claudette will go in somewhere between Mobile and Tallahassee area"

in related news, the high for today will be between 20 degrees and 100 degress. just hard to nail down right now.


LOL
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2082. Relix
Quoting serialteg:


:/ 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!

I think that's convection.
Ana won't make the 5PM cut I guess.
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Quoting DestinJeff:
TWC: "we think Claudette will go in somewhere between Mobile and Tallahassee area"

in related news, the high for today will be between 20 degrees and 100 degress. just hard to nail down right now.


LMAO...TWC is so awful.

As the day goes on, I'm becoming more of a Mobile/Pcola believer. Claudette won't be able to strengthen much more until she consolidates that inner core, though. Currently, she is having trouble doing that.
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Quoting P451:
Not the most impressive radar signature for Claudette.



Does it seem like her center keeps re-locating towards the end of the loop?


She's trying to miss the coast by reforming an LLC to the west.
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ANA

Bill

Claudette
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting extreme236:


You are ridiculous. I might as well put you on ignore before you start spamming about Xtremehurricanes.com or whatever it is again.


Yeah, I just did.
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No problem TXEER...

Heya StormW...glad to see you here today... and to those who do not know...StormW is an expert...took and passed the test and all... even does the climatology for the military... i trust StormW emphatically!
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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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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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