ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC