ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE BILL DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009 1100 AM AST MON AUG 17 2009 SATELLITE IMAGERY INDICATES THAT BILL CONTINUES TO INTENSIFY THIS MORNING...WITH A UNIFORM CENTRAL DENSE OVERCAST AROUND THE CENTER. THE INTENSITY IS RAISED TO 80 KT BASED ON A DVORAK T-NUMBER OF 4.5 FROM TAFB AT 1200 UTC. MICROWAVE IMAGERY FROM A 1132 UTC TRMM PASS SHOWS SEVERAL CONVECTIVE BANDS SPIRALING AROUND THE CENTER...BUT NO EVIDENCE OF AN EYE. BILL SHOULD PASS VERY CLOSE TO NOAA BUOY 41041 IN THE NEXT FEW HOURS...WHICH SHOULD HELP PROVIDE INFORMATION ON THE WINDS AND CENTRAL PRESSURE OF THE CYCLONE. THE OCEANIC AND ATMOSPHERIC ENVIRONMENT CONTINUES TO BE FAVORABLE FOR INTENSIFICATION. WHILE THE SHIPS RI INDEX SHOWS A 35 PERCENT CHANCE OF AN INCREASE OF 30 KT OR MORE IN THE NEXT 24 HOURS... MICROWAVE IMAGERY SUGGESTS THAT BILL DOES NOT YET HAVE A WELL DEFINED INNER CORE STRUCTURE. THE OFFICIAL INTENSITY FORECAST IS ABOVE THE PREVIOUS PACKAGE FOR THE FIRST 36 HOURS DUE TO THE OBSERVED INTENSIFICATION AND IS IN BEST AGREEMENT WITH SHIPS AND LGEM. BEYOND THAT TIME...THE STATISTICAL MODELS SHOW THE INTENSITY LEVELING OFF...WHILE THE HWRF AND GFDL SHOW STRENGTHENING THROUGH THE END OF THE PERIOD. GIVEN THIS UNCERTAINTY...THE OFFICIAL FORECAST SHOWS A PEAK IN INTENSITY AT DAYS 3 AND 4...AND A SLIGHT DECREASE AT DAY 5. BILL CONTINUES ON A HEADING OF 285/14...WITHIN THE DEEP-LAYER FLOW OF A RIDGE EXTENDING WESTWARD OVER THE CENTRAL ATLANTIC FROM AFRICA. GLOBAL MODELS AND WATER VAPOR IMAGERY INDICATE A PERSISTENT MID-ATLANTIC TROUGH SITUATED ALONG 53W WHICH SHOULD CAUSE THE CYCLONE TO TURN MORE TOWARD THE NORTHWEST BY DAY 3. BEYOND THIS TIME...THE FLOW AROUND A LARGE MID- TO UPPER-LEVEL LOW THAT DEVELOPS OVER THE EASTERN UNITED STATES SHOULD INDUCE A MORE NORTH-NORTHWESTWARD TURN. ALL OF THE TRACK MODEL GUIDANCE...WITH THE EXCEPTION OF THE UKMET...IS IN GOOD AGREEMENT ON THIS SCENARIO. THE UKMET HAS A MUCH STRONGER SUBTROPICAL RIDGE THAN THE REST OF THE GLOBAL MODELS AND THE GFS AND ECMWF ENSEMBLE MEANS. AS A RESULT...THIS MODEL KEEPS BILL TOO FAR SOUTH TO FEEL THE EFFECTS OF THE CLOSED LOW LATE IN THE PERIOD. THE OFFICIAL FORECAST IS ESSENTIALLY AN UPDATE OF THE PREVIOUS PACKAGE THROUGH DAY 3...AND IS SHIFTED SLIGHTLY TO THE RIGHT TOWARD THE MODEL CONSENSUS AT DAYS 4 AND 5. THE INITIAL 34-KT WIND RADII WERE MODIFIED BASED ON A 0920 UTC QUIKSCAT PASS. FORECAST POSITIONS AND MAX WINDS INITIAL 17/1500Z 14.1N 45.2W 80 KT 12HR VT 18/0000Z 14.7N 47.5W 90 KT 24HR VT 18/1200Z 15.5N 50.1W 95 KT 36HR VT 19/0000Z 16.6N 52.6W 100 KT 48HR VT 19/1200Z 18.0N 55.1W 105 KT 72HR VT 20/1200Z 21.5N 60.0W 110 KT 96HR VT 21/1200Z 26.0N 64.0W 110 KT 120HR VT 22/1200Z 31.5N 66.5W 105 KT $$ FORECASTER BRENNAN/ROBERTS NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:05 UTC