Tropical Storm IDA

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TROPICAL STORM IDA DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
300 AM CST TUE NOV 10 2009
 
THE CENTER OF IDA IS NOW DEVOID OF DEEP CONVECTION...AS THE COLDEST
CLOUD TOPS HAVE CONTINUED TO SHEAR OFF TOWARD THE NORTH AND EAST
OVER THE PAST SEVERAL HOURS. DATA FROM AIRCRAFT RECONNAISSANCE SHOW
THAT THE CENTRAL PRESSURE HAS SLOWLY RISEN TO 999 MB.  THE HIGHEST
850-MB FLIGHT LEVEL WIND REPORTED BY THE HURRICANE HUNTER AIRCRAFT
WAS 53 KT AT 0733 UTC...AND THE HIGHEST RELIABLE SFMR WINDS WERE
AROUND 40 KT.  WINDS AT THE NUMEROUS MARINE PLATFORMS ALONG THE
GULF COAST HAVE ALSO BEEN SLOWLY DECREASING OVER THE PAST FEW HOURS.
BASED ON ALL THIS...THE INITIAL INTENSITY IS LOWERED TO 45 KT FOR
THIS ADVISORY. A GRADUAL SPIN DOWN OF THE SYSTEM IS FORECAST...
ALTHOUGH IDA IS STILL EXPECTED TO BE AT TROPICAL STORM INTENSITY
WHEN IT COMPLETES EXTRATROPICAL TRANSITION LATER TODAY. MOST OF THE
GUIDANCE SHOWS THE LOW-LEVEL CIRCULATION OF IDA BEING ABSORBED INTO
A FRONTAL ZONE ASSOCIATED WITH A BAROCLINIC LOW THAT DEVELOPS OFF
THE SOUTHEAST U.S. COAST IN ABOUT 48 HOURS.
 
AIRCRAFT FIXES AND SATELLITE IMAGERY OVERNIGHT INDICATED THAT IDA
WAS MOVING ONLY VERY SLOWLY NORTHWARD FOR SEVERAL HOURS. HOWEVER
THE LAST COUPLE OF AIRCRAFT FIXES AND MULTI-CHANNEL SATELLITE
IMAGERY SUGGEST THAT A FASTER MOTION JUST EAST OF DUE NORTH MAY
HAVE BEGUN...AND THE INITIAL MOTION ESTIMATE IS 005/08. DATA FROM
THE AIRCRAFT AND SATELLITE IMAGERY ALSO SUGGEST THAT THE LOW-LEVEL
CENTER IS BECOMING ELONGATED AND LESS WELL-DEFINED. THE DYNAMICAL
GUIDANCE IS INSISTENT ON A TURN TOWARD THE NORTHEAST WHICH COULD BE
BEGINNING NOW AND FINALLY WOULD BRING THE CENTER INLAND LATER
TODAY. THE OFFICIAL FORECAST IS SLOWER AND FARTHER SOUTH THAN THE
PREVIOUS PACKAGE DUE TO THE SLOWER INITIAL MOTION AND MORE WESTERLY
INITIAL POSITION AND A SOUTHWARD TREND IN THE MODEL GUIDANCE. 
 
THE FACT THAT THE LANDFALL OF IDA HAS BEEN DELAYED HAS LITTLE
SIGNIFICANCE SINCE THE TROPICAL STORM FORCE WINDS COVER A LARGE
AREA AWAY FROM THE CENTER AND MOST OF THE HEAVY RAINFALL HAS
ALREADY SPREAD ONSHORE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 29.9N  88.5W    45 KT
 12HR VT     10/1800Z 30.8N  88.0W    35 KT...EXTRATROPICAL
 24HR VT     11/0600Z 31.0N  86.4W    30 KT...EXTRATROPICAL
 36HR VT     11/1800Z 30.4N  84.4W    25 KT...EXTRATROPICAL
 48HR VT     12/0600Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 
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