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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I'm gonna go with a direct Bermuda hit no less than a glancing blow/brush. JMHO but U.S. is clear and Bermuda should watch and give their attention to Bill.
Member Since: June 27, 2009 Posts: 0 Comments: 152
Quoting KEEPEROFTHEGATE:
618

URNT12 KNHC 161655

VORTEX DATA MESSAGE AL042009

A. 16/16:43:20Z

B. 29 deg 04 min N

084 deg 56 min W

C. 925 mb 754 m

D. 35 kt

E. 285 deg 11 nm

F. 072 deg 28 kt

G. 302 deg 25 nm

H. EXTRAP 1008 mb

I. 20 C / 767 m

J. 23 C / 766 m

K. 9 C / NA

L. NA

M. NA

N. 1345 / 9

O. 0.02 / 1.5 nm

P. AF304 0104A CYCLONE OB 02

MAX FL WIND 28 KT NW QUAD 16:34:30Z

MAX OUTBOUND FL WIND 54 KT NE QUAD 16:44:40Z

SLP EXTRAP FROM 925 MB


Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 16th day of the month at 16:55Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 304)
Tropical Depression: Number 4 (flight originating in the North Atlantic basin)
Mission Number: 1
Observation Number: 02
A. Time of Center Fix: 16th day of the month at 16:43:20Z
B. Center Fix Coordinates: 29°04'N 84°56'W (29.0667N 84.9333W)
B. Center Fix Location: 88 miles (142 km) to the SSE (150°) from Panama City, FL, USA.
C. Minimum Height at Standard Level: 754m (2,474ft) at 925mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 35kts (~ 40.3mph)
E. Location of the Estimated Maximum Surface Wind: 11 nautical miles (13 statute miles) to the WNW (285°) of center fix
F. Maximum Flight Level Wind Inbound: From 72° at 28kts (From the ENE at ~ 32.2mph)
G. Location of Maximum Flight Level Wind Inbound: 25 nautical miles (29 statute miles) to the WNW (302°) of center fix
H. Minimum Sea Level Pressure: 1008mb (29.77 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 20°C (68°F) at a pressure alt. of 767m (2,516ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 23°C (73°F) at a pressure alt. of 766m (2,513ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 9°C (48°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 925mb (If this vortex is from mid 1990's or earlier 925mb might be incorrect. See note.)
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1.5 nautical miles
Remarks Section:
Maximum Flight Level Wind: 28kts (~ 32.2mph) in the northwest quadrant at 16:34:30Z
Maximum Flight Level Wind Outbound: 54kts (~ 62.1mph) in the northeast quadrant at 16:44:40Z
Sea Level Pressure Extrapolation From: 925mb

Special Notes:
- If this vortex is from approximately the mid 1990's or earlier, the "fix level" is properly decoded as "Other". Meaning, the level is not 1500ft, 850mb, 700mb, 500mb, 400mb, 300mb, or 200mb, but might not necessarily be 925mb. In vortex messages since approximately the mid 1990's, the number "9" in the vortex for this section explicitly decodes as 925mb and "NA" means "Other".
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The hot waters of the GOM will help claudette strengthen some. Probably a CAT 1.
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Quoting WeatherBubba:
Looks to a long-time stormwatcher in Tallahassee like Claudette will go ashore around Apalachicola. The Great Panhandle Hump (named after a former UF Cheerleader) that protrudes into the GOM should break up the bad stuff in the NE Quad before it reaches any major population. Let's hope...
--Bubba


Hey - I'm in that "hump"
Member Since: July 9, 2005 Posts: 0 Comments: 387
921. jpsb
Quoting CycloneOz:
"Hardly anyone wanted to even acknowledge the Key West disturbance yesterday..."
Speak for yopurself, I was all over that blob yesterday and the evening before.
Member Since: June 30, 2009 Posts: 0 Comments: 1275
Quoting reedzone:
My gut feeling is the Bill clips or even hits New England, It's a close call recurvature.


Nope.
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Quoting AussieStorm:
Do we have Claudette yet or is everyone jumping the gun again?
special statement issued 1215 pm aug 16 2009 td04l rename 04l TS CLAUDETTE
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My gut feeling is the Bill clips or even hits New England, It's a close call recurvature.
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Quoting AussieStorm:
Do we have Claudette yet or is everyone jumping the gun again?


Claudette was named at 12:15 p.m. EDT by the NHC. The question is what her winds will be at the 2 p.m. intermediate.
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Ana may come over the northern Lesser Antilles with it's current motion. If it can avoid Hispaniola she will be a player
Member Since: October 28, 2006 Posts: 57 Comments: 30814
Hard to believe Caludette popped up.Hope all of my fellow Floridians in the Panhandle are prepared for some more rain. Be safe!
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Bill is more and more likely to recurve. U.S. landfall is very unlikely.
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GFS run shows a powerful Bill moving east of the US coast
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting rareaire:
so claudettes is close to cat 1 speed?


Not quite. It may strengthen some, and it could be a strong TS to perhaps a hurricane if it slows down some. Right now it is 45-50 mph winds which is a rather weak TS.
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So Claudette is here...She is looking good might I add. Who would have thought we would have something form in the GOM that quick. But then, I quess it shouldn't be a surprise since the GOM waters are HOT!!

So the models for Bill are still looking to be a fish storm. Who is not agreeing with that? What are your thoughts?
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http://www.ndbc.noaa.gov/station_page.php?station=sgof1
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Quoting amd:


cyclone, I need a crow recipe. I thought for sure Claudette would not develop. I guess I learned a weather lesson. NEVER underestimate the ability of the gulf's waters to spin up systems


There are several of us who lived along the Gulf Coast for many many years.

We know...I can tell you first hand, I've watched the dang things spin up right above my head. Most awesome...
Member Since: August 26, 2006 Posts: 10 Comments: 4101
906. jpsb
Quoting Drakoen:
Impressive gain in size captured there. Thanks. Well if Claudette han't gown so big so fast she might have had a longer life drifting West. Sure hope Texas get some rain soon, maybe those blobs off to Cluadette left will get here.
Member Since: June 30, 2009 Posts: 0 Comments: 1275
Quoting AussieStorm:
Do we have Claudette yet or is everyone jumping the gun again?


It is officially Claudette. Look at the NHC site.
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Quoting futuremet:
Out-to-sea


Not good for Bermuda.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting CycloneOz:
Hardly anyone wanted to even acknowledge the Key West disturbance yesterday...

Now, hardly anyone can resist talking about the fruition of that disturbance today.

LOL!
Yep...but it could have just as easily fizzled. Can't write these storms off until they're completely gone.
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Quoting extreme236:


Outbound means they got those winds when they were leaving the vortex on that pass. Flight level winds are almost always higher on the NE side than the NW side which explains the difference.


ty
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Very impressive how fast Claudette formed.
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Seems maybe the old core,albeit small,may be giving way to a newer one thats forming around it..

Member Since: July 3, 2005 Posts: 428 Comments: 129795
618

URNT12 KNHC 161655

VORTEX DATA MESSAGE AL042009

A. 16/16:43:20Z

B. 29 deg 04 min N

084 deg 56 min W

C. 925 mb 754 m

D. 35 kt

E. 285 deg 11 nm

F. 072 deg 28 kt

G. 302 deg 25 nm

H. EXTRAP 1008 mb

I. 20 C / 767 m

J. 23 C / 766 m

K. 9 C / NA

L. NA

M. NA

N. 1345 / 9

O. 0.02 / 1.5 nm

P. AF304 0104A CYCLONE OB 02

MAX FL WIND 28 KT NW QUAD 16:34:30Z

MAX OUTBOUND FL WIND 54 KT NE QUAD 16:44:40Z

SLP EXTRAP FROM 925 MB
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Surface winds around 50mph in Claudette right now, hopefully recon hangs around for a while to see what happens.
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Quoting canesrule1:
Recon has found 62MPH winds at the surface in the COC of Claudette.


At flight level not the surface
Member Since: October 28, 2006 Posts: 57 Comments: 30814
Do we have Claudette yet or is everyone jumping the gun again?
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Out-to-sea
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Quoting ConchHondros:


Drak would have to log off...


Ridiculous.
Besides, why are you wearing a sweater under your Tommy Bahama shirt?
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893. amd
Quoting CycloneOz:
Hardly anyone wanted to even acknowledge the Key West disturbance yesterday...

Now, hardly anyone can resist talking about the fruition of that disturbance today.

LOL!


cyclone, I need a crow recipe. I thought for sure Claudette would not develop. I guess I learned a weather lesson. NEVER underestimate the ability of the gulf's waters to spin up systems
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What a difference that 24 hours makes.....good to see that Ana is still weak and Bill is looking more like a non issue for the U.S.....
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Recon has found 62MPH winds at the surface in the COC of Claudette.
Nice image, Pat - looks like if you live in the panhandle, you're gonna get wet...
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Quoting serialteg:


ty, why is it outbound though? why is it different from max flight level wind of 28knot...

i guess we should be concerned with sealevel winds more, but anyway its a valid question


Outbound means they got those winds when they were leaving the vortex on that pass. Flight level winds are almost always higher on the NE side than the NW side which explains the difference.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Best I can see is the 47 mph SFMR Sfc wind on the 16:51Z reading. Observation No. 3 calling it 38mph Sfc.
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It's stuck in that spot Patrap
Member Since: October 28, 2006 Posts: 57 Comments: 30814
Looks to a long-time stormwatcher in Tallahassee like Claudette will go ashore around Apalachicola. The Great Panhandle Hump (named after a former UF Cheerleader) that protrudes into the GOM should break up the bad stuff in the NE Quad before it reaches any major population. Let's hope...
--Bubba
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45 knot surface winds 50mph storm
Member Since: October 28, 2006 Posts: 57 Comments: 30814
Entire Caribbean is under the gun from these storms, from Alabama to the leeward islands



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Member Since: July 3, 2005 Posts: 428 Comments: 129795
Hardly anyone wanted to even acknowledge the Key West disturbance yesterday...

Now, hardly anyone can resist talking about the fruition of that disturbance today.

LOL!
Member Since: August 26, 2006 Posts: 10 Comments: 4101
Quoting CycloneOz:
Claudette is showing us all just how dangerous the GoM is right now in regards to TC development.

Ana is supposed to be in the GoM come Tuesday as a depression?

That won't last for long. She could blow up into a monster by the time she makes landfall!!!!


That's what I've been thinking.
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Time: 16:56:30Z
Coordinates: 29.5667N 84.35W
Acft. Static Air Press: 926.0 mb (~ 27.34 inHg)
Acft. Geopotential Hgt: 812 meters (~ 2,664 feet)
Extrap. Sfc. Press: 1017.6 mb (~ 30.05 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 142° at 38 knots (From the SE at ~ 43.7 mph)
Air Temp: 17.4°C (~ 63.3°F)
Dew Pt: 7.7°C (~ 45.9°F)
Peak (10s) Flt. Lvl. Wind: 40 knots (~ 46.0 mph)
SFMR Peak (10s) Sfc. Wind: 36 knots (~ 41.4 mph)
SFMR Rain Rate: 8 mm/hr (~ 0.31 in/hr
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Quoting extreme236:


Its on the vortex message...


ty, why is it outbound though? why is it different from max flight level wind of 28knot...

i guess we should be concerned with sealevel winds more, but anyway its a valid question
Member Since: August 22, 2006 Posts: 2 Comments: 1988
I wouldn't wanna be a HH flying into Ana. They must be bored out of there mind. Guess its better than flying into a rapidly strengthening hurricane.
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so claudettes is close to cat 1 speed?
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Member Since: October 28, 2006 Posts: 57 Comments: 30814
Quoting TideWaterWeather:


54 is flight level


I know. But if you reduce those down its at least around 45 knots.
Member Since: August 2, 2007 Posts: 19 Comments: 19234

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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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