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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they did other 2 bid they for get to do bill??

Link
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Quoting hurristat:




Oh - so basically 2003 Bill = 2009 Claudette, and 2009 Bill = 2003 Claudette (Cat 1 Hurricane, hit Texas)
Member Since: Posts: Comments:
Quoting rwdobson:
Canesrule has been dead-set in favor of bill over S Fl since it was just a wave coming off Africa.
yup
Quoting FloridaDweller:
456-
Can you elaborate on why Bill speeding up would be 'Bad'?


a faster bill feels the weakness at later intervals. It means more west than maybe originally forecast. we have to see if Bill continues to do so over the next couple of days
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting dcoaster:
Well from my calcs using lat/long to distance, Bill is somewhere in the 20-23mph speed range.
wow, if it continues at that speed it will surely blow past the trough and effect SFLA.
1570. jipmg
Quoting canesrule1:
my local news


oh so then the models should be changing.. but they arent so idk whats going on o-O
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Canesrule has been dead-set in favor of bill over S Fl since it was just a wave coming off Africa.
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Quoting IpswichWeatherCenter:


What happened then?


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Quoting dcoaster:
Any scenarios for Bill if he slows down or speeds up?


Read JM's post that you are commenting on right now. Lol. Slower and it gets the weakness in the high that is forecast and gets the trough. Faster and it blows past all that and almost a sure landfall on US, possibly northern islands.
Member Since: July 29, 2006 Posts: 28 Comments: 1777
1566. KEEPEROFTHEGATE (Mod)
Quoting Weather456:
its hard to keep up on the blog. 10 posts a minute
YEAH
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Well from my calcs using lat/long to distance, Bill is somewhere in the 20-23mph speed range.
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Quoting jipmg:


the models say the high wont build and the trough will strengthen and take bill off to sea, were did you get that expectation of yours?
my local news
1563. IKE
Quoting tharpgomex:
Ike do you think Claudette has stalled


Fixing to move on in with a few hours.

Destin,FL. had waterspouts reported.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Product: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 16th day of the month at 18:54Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 300)
Storm Number: 02
Storm Name: Ana (flight originating in the North Atlantic basin)
Mission Number: 1
Observation Number: 08

Mandatory Data...

Observation Time: Sunday, 18:52Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 15.4N 57.8W
Location: 200 miles (323 km) to the NE (37°) from Bridgetown, Barbados.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 330 meters
Flight Level Wind: 5 knots (~ 5.8 mph) (Bearing was unavailable.)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 24°C
Flight Level Dew Point: 18°C
Weather (within 30 nautical miles): Shower(s) (continuous or intermittent precipitation - from cumuliform clouds)
Mean Sea Level Pressure (MSLP): 1009 mb (extrapolated)

Optional Data...

Estimated Surface Wind Direction: Bearing was unavailable.
Estimated Surface Wind Speed: 5 knots (~ 5.8 mph)

Remarks Section...

Surface Wind Speed (likely by SFMR): 11 knots (~ 12.7mph)
Member Since: Posts: Comments:
1561. Michfan
Quoting FloridaDweller:
456-
Can you elaborate on why Bill speeding up would be 'Bad'?


It would result in him not being recurved by the forecasted trough because he would miss it.
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Quoting winter123:
latest ana vis. it's very small and elongated. I don't forsee anything more than a 30mph TD at next update.



Link


that vis is from 6am
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting winter123:
latest ana vis. it's very small and elongated. I don't forsee anything more than a 30mph TD at next update.



Link


I think that would be generous. From this morning it no longer seemed to be even that.
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Quoting AllStar17:
Look what will emerge off Africa soon enough. Another storm?
1557. Lizpr
Quoting Weather456:
its hard to keep up on the blog. 10 posts a minute


tell me about it everytime time I refresh theres 1 or 2 new pages lol
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1556. Michfan
Quoting IpswichWeatherCenter:


It wasn't - it was just a question!


LOL. Shes nowhere near organized enough as of right now form an eye. The center is a little exposed atm.
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456-
Can you elaborate on why Bill speeding up would be 'Bad'?
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1554. jipmg
Quoting canesrule1:
as bill speeds up it will miss the trough and go towards Florida, and the high is expected to build westward and the trough to weaken.


the models say the high wont build and the trough will strengthen and take bill off to sea, were did you get that expectation of yours?
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1552. BA
Quoting Patrap:
One has to click on the Map after the zoom controls for a specific Location to zoom to.


yeah, and mine will never zoom out or pan for some reason
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Quoting Michfan:


Lets not jump the gun now. LOL.


It wasn't - it was just a question!
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Quoting Weather456:


bad


vary bad
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Quoting Weather456:
its hard to keep up on the blog. 10 posts a minute
i agree
Quoting cajunkid:
MississippiWx, you can see its just about stalled. Seen it happen several times the past few years with the WU radar you all look at. This looks too familiar.


Yeah, I agree with Claudette being nearly stalled. What worries me is if she stays stalled/slow moving long enough, she will allow the subtropical ridge to build further in from the Atlantic, forcing her further west. Thus, she would have more time over water.
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Look what will emerge off Africa soon enough. Another storm?
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latest ana vis. it's very small and elongated. I don't forsee anything more than a 30mph TD at next update.



Link
Member Since: July 29, 2006 Posts: 28 Comments: 1777
1544. Fshhead
Quoting code1:


Ahh, let him take camera and have a coffin waiting on him as well. How old is this child?


MAN, AGREED!!!! I have been through a cat.5 & let me tell you there is NO way I was going outside for it. I did go outside in Wilma albeit in a very sheltered spot.. ;)
Member Since: Posts: Comments:
Quoting MississippiWx:


What satellite loops are you looking at to get this idea? The center is almost due south of Apalachicola and that is very evident on radar. The big blow up of convection to the south on IR loops is just in the moisture influx.


I am looking at the water vapor loop of Claudette on the NHC website. Also, the COC relocation is giving the impression that she has stalled. She hasn't really stalled. I am anxious for the next advisory to prove this.
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Quoting dcoaster:
Any scenarios for Bill if he slows down or speeds up?
as bill speeds up it will miss the trough and go towards Florida, and the high is expected to build westward and the trough to weaken.
1541. Patrap
One has to click on the Map after the zoom controls for a specific Location to zoom to.
Member Since: July 3, 2005 Posts: 420 Comments: 127543
They're only voluntary evacuations... nothing major.
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1539. Michfan
Quoting IpswichWeatherCenter:


Based on that - I would say that Claudette is trying to look like a decent system instead of some weird boot.

Shes slowly developing Convection in the NW and SW quadrants, to give a more round appearance - so maybe an eye as well?


Lets not jump the gun now. LOL.
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Quoting Funkadelic:
Here, take a look at this:
http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

You can clearly see that Ana is well north of the forcast point... Why did they not change the track at 2:00pm??


Because the hunter flew through the COC at 58W 15N. i.e. the south end of what had been the model cluster
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Quoting HurricaneKyle:


Wow. This is certainly more impressive than 2003's Bill.


What happened then?
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Wow, the tropics are amazingly dynamic right now. High pressure to the north is pushing on Claudette which is also being influenced by the massive upper level low to the east. Mositure from the system is starting to rotate around an axis in the SW GOM. Have a suspicion that we may be seeing a little more of Claudette than we had expected. Just a hunch. ULL east of interacting with all three stroms. Doesn't get any better than this. Grab the popcorn!
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1535. mkmand
Claudette strenghening by every minute

Bill is nearly a hurricane and moving more north

Ana is dying
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Quoting 996tt:
Seriatag:

Going back later. Got tired of catching small waves on long board after 3 hours. Fun but I am getting old . . . and saving energy hopefully for some overhead stuff.


thats what im talking about!

which reminds me...

thank you! im heading out to see if i can find a better wetsuit. I'm getting bad rash from my board and it looks like its gonna be a busy surfing week for me :D
Member Since: August 22, 2006 Posts: 2 Comments: 1975
Quoting canesrule1:
Lots of wow factor with Bill:



Claudette really strengthening:




Based on that - I would say that Claudette is trying to look like a decent system instead of some weird boot.

Shes slowly developing Convection in the NW and SW quadrants, to give a more round appearance - so maybe an eye as well?
Member Since: Posts: Comments:
its hard to keep up on the blog. 10 posts a minute
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1531. BA
Quoting FLHurricaneChaser:


Evacuations! Are you serious? If you have to evacuate for a tiny weak TS then that place shouldn't be inhabited.


they just passed a law here (south texas) that they can arrest you if you don't evacuate, "choice" is no longer an option
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Wow. This is certainly more impressive than 2003's Bill.
Member Since: August 10, 2009 Posts: 3 Comments: 672
I don't know why everyone is freaking out about Claudette. I am no expert, and it is amazing how fast she spun up, but she is too close to land to have enough time to develop.

I am from Houston and saw what stalled Tropical Storm Allison did, but I don't see the conditions for that....again I am no expert, but none of the experts seem as concerned about Claudette as a vocal few on this blog do. I don't intend to offend, but its just my observation.
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Bill is such a beautiful looking storm! its massive as well! Wouldn't want that thing anywhere near me. If bill hit central fl, cloud cover would spread from north carolina to cuba!!!
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thanks Patrap
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1526. nolajet
Quoting HurricaneJoe:


That storm made me angry. The center was supposed to come across BR, and since it was a weaker storm, I figured it would be fun to watch. Turns out it had other plans. haha


It wasn't too fun when a tree fell into my kitchen while Cindy was coming through. Just because it is a strong tropical storm or weak Cat 1 does not mean it is harmless. Just sayin'.

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Any scenarios for Bill if he slows down or speeds up?
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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.