Tropical Storm BILL

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TROPICAL STORM BILL DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SUN JUN 29 2003
 
AIR FORCE RESERVE RECON FIXES EARLIER THIS AFTERNOON INDICATED THAT
THE CENTER OF BILL HAD MOVED NORTHWARD AND CLOSER TO THE DEEP
CONVECTION. HOWEVER...THE CENTER OF BILL IS NOT EMBEDDED WITHIN THE
CDO-LOOKING FEATURE. INSTEAD...SATELLITE ESTIMATES SUGGEST THE
LOW-LEVEL CENTER IS LOCATED ALONG THE SOUTHWEST EDGE OF THE COLD
CLOUD CANOPY. THIS ALSO YIELDS A SHEAR PATTERN INTENSITY ESTIMATE
OF ABOUT 45 KT...WHICH IS CLOSE TO THE LAST RECON REPORTED SURFACE
WIND ADJUSTMENT OF 43 KT. THERE IS STILL SOME SOUTHEASTERLY
UPPER-LEVEL SHEAR IMPINGING ON THE CYCLONE...BUT THE OVERALL
OUTFLOW PATTERN HAS IMPROVED DURING THE PAST 6 HOURS.

THE INITIAL MOTION ESTIMATE IS 350/12. WHILE RECON FIXES SUGGEST A
NORTH TO SLIGHTLY EAST OF DUE NORTH TRACK...MY FEELING IS THAT THIS
MOTION HAS BEEN DUE PRIMARILY AS A RESAULT OF DEVELOPMENT OF THE
CENTER CLOSER TO THE DEEP CONVECTION...RATHER THAN AN ACTUAL
TRANSLATIONAL MOTION. LATEST UPPER-AIR DATA INDICATE THE MID- TO
UPPER-LEVEL RIDGE AXIS PREVIOUSLY ALONG THE GULF COAST HAS MIGRATED
NORTHWARD TO ABOUT 30N LATITUDE WITH MODERATE WESTERLY FLOW ACROSS
THE MISSOURI AND TENNESSEE VALLEYS AHEAD OF A WEAK SHORTWAVE TROUGH
CURRENTLY LOCATED OVER THE CENTRAL PLAINS. MOST OF THE GLOBAL
MODELS MAINTAIN THE CURRENT RIDGE-TROUGH PATTERN AND THERE IS A
FAIRLY TIGHT CLUSTERING OF THE NHC MODEL GUIDANCE SUITE UNTIL
LANDFALL. AFTER THAT...THE MODELS DIVERGE SIGNIFICANTLY WITH THE
GFDL TAKING BILL INTO WESTERN KENTUCKY IN 72 HOURS WHILE THE UKMET
HAS BILL IN CENTRAL SOUTH CAROLINA AT THE SAME TIME. THE OFFICIAL
FORECAST TRACK WAS ADJUSTED SLIGHTLY EAST OF THE PREVIOUS FORECAST
DUE TO THE MORE EASTWARD LOCATION OF THE INITIAL POSITION.
HOWEVER...THERE IS GOOD AGREEMENT BY THE MODELS ON LANDFALL
OCCURRING SOMEWHERE ALONG THE SOUTH CENTRAL LOUISIANA COAST BY LATE
MONDAY.

THE INTENSITY FORECAST IS A LITTLE MORE PROBLEMATIC. THE UPPER-LEVEL
FLOW PATTERN IS FORECAST TO REMAIN STRONGLY DIFLUENT UNTIL JUST
PRIOR TO LANDFALL. WATER TEMPERATURES CURRENTLY BENEATH BILL ARE
AROUND 83F/28C AND ARE AROUND 86F/30C ALONG AND JUST OFFSHORE THE
LOUISIANA COAST. WITH WARMER WATER AHEAD AND SLIGHTLY DECREASING
VERTICAL SHEAR EXPECTED...IT IS POSSIBLE THAT BILL COULD STRENGTHEN
INTO A CATEGORY 1 HURRICANE JUST BEFORE MAKING LANDFALL. THE SHIPS
INTENSITY MODEL BRINGS BILL UP TO 62 KT...JUST BELOW HURRICANE
STRENGTH...IN 24 HOURS. FOR THIS REASON...A HURRICANE WATCH HAS
BEEN ISSUED FOR A SMALL PORTION OF THE SOUTH CENTRAL LOUISIANA
COAST. IF THE LOW-LEVEL CENTER TUCKS IN UNDER THE COLD CLOUD TOPS
LATER TONIGHT...THEN A STRONGER CYCLONE THAN FORECAST WOULD RESULT.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      30/0300Z 26.3N  91.3W    45 KT
 12HR VT     30/1200Z 27.6N  91.6W    50 KT
 24HR VT     01/0000Z 29.6N  91.9W    60 KT
 36HR VT     01/1200Z 31.9N  91.0W    30 KT...INLAND
 48HR VT     02/0000Z 33.3N  88.5W    20 KT...INLAND REMNANT LOW
 72HR VT     03/0000Z 35.0N  83.0W    20 KT...INLAND REMNANT LOW
 96HR VT     04/0000Z 36.0N  75.5W    25 KT...REMNANT LOW

 
 
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