A sequence of events as Tropical Depression Four/Claudette formed

August 16, 2009

(all times Eastern Daylight)

11:48 AM Alan Sullivan posts:

At 11 AM EDT, NHC designated TD #3 as expected, far out in the Atlantic. But the tropical wave currently over South Florida may also be spawning a depression. I see rotation and banding on the radar. The rotation is associated with a knot of intense thunderstorms near and over Key West. Surface pressure has not yet begun to fall, but banding is seen in other echoes over South Florida and adjacent waters. I would not be surprised if we get a designation of TD #4 tonight or tomorrow over the Gulf, if this convective pattern can persist.

1:15 PM Flight Plan for the Hurricane Hunters posted, all flights scheduled pertain to Ana,  by forward positioned assets:

NOUS42 KNHC 151715
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0115 PM EDT SAT 15 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
         VALID 16/1100Z TO 17/1100Z AUGUST 2009
         TCPOD NUMBER.....09-079

I.  ATLANTIC REQUIREMENTS
    1. TROPICAL STORM ANA
       FLIGHT ONE -- TEAL 70
       A. 16/1800Z,17/0000Z
       B. AFXXX 0102A ANA
       C. 16/1530Z
       D. 15.6N 56.3W
       E. 16/1700Z TO 17/0000Z
       F. SFC TO 10,000 FT

       FLIGHT TWO -- TEAL 71
       A. 17/0600Z,17/1200Z
       B. AFXXX 0202A ANA
       C. 17/0330Z
       D. 16.7N 60.0W
       E. 17/0500Z TO 17/1200Z
       F. SFC TO 10,000 FT

    2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES.
       A G-IV SURVEILLANCE MISSION IS PLANNED FOR 18/0000Z
       WITH TAKEOFF AT 17/1730Z.  A FOLLOW-ON G-IV MISSION
       IS POSSIBLE FOR 18/1200Z WITH TAKEOFF AT 18/0530Z.

    3. REMARK: NOAA43 AND THE G-IV WILL FLY FOUR SUCCESSIVE
       RESEARCH MISSIONS INTO AND AROUND ANA DEPARTING FROM
       TBPB AT 15/2000Z, 16/0800Z, 16/2000Z, AND 17/0800Z.

II. PACIFIC REQUIREMENTS
    1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
    2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
                      SEF

1:39 PM Tropical Weather Outlook

THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE HAS BECOME
MORE CONCENTRATED TODAY OVER THE FLORIDA KEYS AND THE ADJACENT
SOUTHEASTERN GULF OF MEXICO.  PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

7:31 PM Tropical Weather Outlook

A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS OVER THE SOUTHEASTERN
GULF OF MEXICO IS PRIMARILY ASSOCIATED WITH A TROPICAL WAVE
INTERACTING WITH A MID- TO UPPER-LEVEL TROUGH. THIS ACTIVITY HAS
BECOME A LITTLE MORE CONCENTRATED OVER THE SOUTHEASTERN GULF OF
MEXICO WHERE SURFACE PRESSURES ARE BEGINNING TO FALL. THERE ARE NO
SIGNS OF A SURFACE CIRCULATION AT THIS TIME AND ANY ADDITIONAL
DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR.  THIS SYSTEM SHOULD
MOVES TOWARD THE NORTHWEST OVER THE EASTERN GULF OF MEXICO ON
SUNDAY. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.  

8:37 PM Area of distrubed weather is designated as Invest 91L. Satellite Analysis Branch gives intensity estimate as minimal tropical depression (assuming that there’s a surface circulation, which there was no evidence of at that time).

1:42 AM Tropical Weather Outlook

SATELLITE AND RADAR DATA INDICATE THAT A SMALL AREA OF LOW PRESSURE
IN THE EASTERN GULF OF MEXICO...CENTERED ABOUT 80 MILES SOUTHWEST
OF TAMPA...IS BECOMING BETTER ORGANIZED AND MAY BE DEVELOPING A
CLOSED SURFACE CIRCULATION.  ENVIRONMENTAL CONDITIONS ARE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AND THERE IS A HIGH CHANCE...GREATER
THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
SOMETIME TODAY.  THIS SYSTEM IS EXPECTED TO MOVE NORTHWESTWARD OR
NORTH-NORTHWESTWARD AT ABOUT 15 MPH TODAY.  INTERESTS ALONG THE GULF
COAST OF FLORIDA SHOULD CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.   

5:00  AM Advisories initiated on Tropical Depression Four with Tropical Storm Warnings issued.

9:45 AM Plan of the day released with a “resources permitting” flight scheduled, (which, IIRC, means that the Air Force Reserve squadron is not olbigated to fly). Note how they’ve lost track of which storm we’re on:

3. REMARKS: A RESOURCES PERMITTING TASKING ON TROPICAL
       DEPRESSION 2 IN THE GULF OF MEXICO WILL BE LAUNCHED
       TODAY AT 16/1500Z.

12:15 PM Tallahassee Doppler Radar shows tropical storm force winds, Claudette is born.

12:43 PM Recon find 54 knot flight level winds, which are adjusted to 45 knots (50 mph) at the surface.

And here we are this afternoon:

Tallahassee Radar

Tallahassee Radar

http://weather.cod.edu/analysis/paulradar.pl?TLH

Tropical Storm Claudette

Tropical Storm Claudette

http://www.ssd.noaa.gov/PS/TROP/float3.html

Residents of the Big Bend/eastern Panhandle are advised to consult the National Weather Service offices of Tallahassee for the latest on local effects from Claudette.

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