ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DANNY DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU JUL 17 2003 DANNY CONTINUES TO BECOME BETTER ORGANIZED AS INDICATED BY IMPROVED BANDING FEATURES AND A 17/0339Z TRMM OVERPASS INDICATING A 10 NMI DIAMETER EYE-LIKE FEATURE. THE INITIAL INTENSITY IS INCREASED TO 45 KT BASED ON A 45-KT SATELLITE INTENSITY ESTIMATE FROM BOTH TAFB AND SAB...AND THE AFOREMENTIONED EYE FEATURE. UPPER-LEVEL OUTFLOW IS VERY CIRCULAR AND CONTINUES TO IMPROVE. THE INITIAL MOTION IS 340/9. RECENT TRMM OVERPASSES AT 0339Z AND 0517Z CONFIRM THE SLOWER FORWARD SPEED ON THE PREVIOUS ADVISORY... AND ALSO A POSITION TO THE SOUTHEAST OF THE CONVENTIONAL SATELLITE FIX POSITIONS. THE FORECAST TRACK HINGES STRONGLY ON THE FUTURE INTENSITY OF DANNY AND THE VERTICAL DEPTH OF THE CYCLONE. THE GLOBAL AND REGIONAL MODELS ARE OF LITTLE USE EXCEPT FOR NOGAPS AND ESPECIALLY THE CANADIAN MODEL. THE GFS...UKMET...GFDN...AND GFDL MODELS WEAKEN DANNY FROM THE OUTSET AND LOSE AN IDENTIFIABLE LOW-LEVEL CIRCULATION IN 36 TO 48 HOURS. MEANWHILE ...INFRARED AND TRMM MCIROWAVE DATA SUGGEST THAT DANNY IS CLOSER TO BECOMING A HURRICANE THAN IT IS TO DISSIPATING INTO A NON-ENTITY. SINCE THE INTENSITY FORECAST CALLS FOR DANNY TO BECOME A HURRICANE IN 24 TO 36 HOURS...THE SYSTEM SHOULD REMAIN INTACT ALL THE WAY AROUND THE DEEP-LAYERED SUBTROPICAL RIDGE THAT IS FORECAST TO REMAIN ALONG ABOUT 35N LATITUDE THROUGHOUT THE 5 DAY PERIOD. THE CANADIAN MODEL HANGS ONTO A LOW-LEVEL CIRCULATION THROUGH 120 HOURS...WHICH IS SIMILAR TO THE NOGAPS...LBAR..AND ALL THREE BAM MODELS. THE OFFICIAL FORECAST TRACK CALLS FOR DANNY TO MAKE A LARGE ANTICYCLONIC LOOP AROUND THE SUBTROPICAL HIGH AND IS CLOSE TO THE PREVIOUS FORECAST TRACK...EXCEPT FOR THE ADDITION OF A 120-HOUR POSITION. THE MOST RECENT ANALOG FOR A HIGH-LATITUDE CLOCKWISE- LOOPING TROPICAL CYCLONE WOULD BE HURRICANE ALBERTO IN 2000. DANNY CURRENTLY HAS A CONVECTIVE CLOUD AND OUTFLOW PATTERN MORE REMINISCENT OF A HURRICANE. THE CENTRAL CORE CONVECTION REMAINS SMALL...BUT TIGHTLY WOUND AROUND THE WELL-DEFINED LOW-LEVEL CENTER AS NOTED IN MICROWAVE SATELLITE DATA. SUBJECTIVE SST ANALYSES THIS MORNING INDICATE THAT THE SHIPS INTENSITY MODEL HAS SSTS TOO COLD ALONG THE PATH OF DANNY. IN FACT...SSTS WILL ACTUALLY INCREASE FROM THE CURRENT 80F TO NEAR 82 F IN 24 HOURS AS DANNY PASSES OVER OR NEAR A WARM EDDY ON THE SOUTH SIDE OF THE GULFSTREAM NEAR 40N AND 52W. THE WARM SSTS...COUPLED WITH THE IMPRESSIVE OUTFLOW PATTERN AND FORECAST VERTICAL SHEAR OF 5 KT OR LESS...SHOULD ALLOW DANNY TO REACH AND MAINTAIN AT LEAST MINIMAL HURRICANE STRENGTH UNTIL 36 HOURS...PERHAPS EVEN LONGER IF THE CYCLONE MAKES A TIGHTER LOOP THAN CURRENTLY FORECAST KEEPING IT OVER WARM WATER LONGER. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 17/0900Z 33.8N 55.8W 45 KT 12HR VT 17/1800Z 35.0N 56.1W 55 KT 24HR VT 18/0600Z 36.6N 55.9W 65 KT 36HR VT 18/1800Z 38.4N 54.5W 65 KT 48HR VT 19/0600Z 39.7N 52.5W 60 KT 72HR VT 20/0600Z 41.3N 47.5W 55 KT 96HR VT 21/0600Z 41.0N 43.0W 45 KT 120HR VT 22/0600Z 39.0N 39.0W 35 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC