ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM HURRICANE JUAN DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI SEP 26 2003 JUAN HAS SHOWED AN EYE OR WARM SPOT FOR THE PAST SEVERAL HOURS AND IS GENERATING CONVECTION AS COLD AS -70C IN THE WESTERN SEMICIRCLE. THE CIRRUS OUTFLOW IS FAIR TO GOOD OVER THE NORTHEASTERN SEMICIRCLE...AND POOR OR RESTRICTED TO THE SOUTHWEST AS UPPER-LEVEL WESTERLIES IMPINGE ON THE HURRICANE. SATELLITE INTENSITY ESTIMATES ARE 77 KT FROM AFWA AND TAFB...AND 65 KT FROM SAB. THE INITIAL INTENSITY IS RAISED TO 70 KT. THE INITIAL MOTION IS A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK...360/7. OTHER THAN THAT...THERE IS LITTLE CHANGE IN THE SYNOPTIC PATTERN OR FORECAST PHILOSOPHY. A DEEP-LAYER RIDGE OVER THE NORTH CENTRAL ATLANTIC AND A DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES SHOULD STEER JUAN ON A NORTHWARD TO NORTH- NORTHWESTWARD TRACK WITH GRADUAL ACCELERATION THROUGH 48 HR. THIS SHOULD BE FOLLOWED BY A NORTH-NORTHEASTWARD MOTION AS JUAN GETS ABSORBED INTO THE TROUGH. ALL GUIDANCE AGREES WITH THIS SCENARIO...AND THE OFFICIAL FORECAST BRINGS THE CENTER TO THE SOUTH COAST OF NOVA SCOTIA IN ABOUT 48 HR. ALL LARGE-SCALE MODELS FORECAST THE UPPER-LEVEL TROUGH CURRENTLY AFFECTING JUAN TO WEAKEN...LEAVING THE HURRICANE TO MOVE THROUGH AN AREA OF LIGHT TO MODERATE SHEAR THROUGH 36 HR. SHOULD THIS VERIFY...JUAN COULD STRENGTHEN MORE THAN CURRENTLY FORECAST BEFORE IT REACHES THE COLD WATER NORTH OF THE GULF STREAM. HOWEVER... WATER VAPOR IMAGERY SUGGESTS THE MODELS MIGHT BE A LITTLE TOO FAST IN WEAKENING THE SHEAR...AS A STRONG BAND OF UPPER-LEVEL WESTERLY TO NORTHWESTERLY FLOW IS JUST SOUTHWEST OF JUAN. THE INTENSITY FORECAST WILL GO WITH THE SCENARIO THAT THE CONDITIONS WILL BE LESS FAVORABLE THAN SHOWN IN THE MODELS BUT MORE FAVORABLE THAN CURRENTLY SEEN IN THE IMAGERY...AND THUS CALL FOR A LITTLE MORE STRENGTHENING. JUAN SHOULD START TO WEAKEN ONCE IT MOVES NORTH OF THE GULF STREAM...AND IT SHOULD BECOME EXTRATROPICAL BY 72 HR. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 27/0300Z 33.7N 61.9W 70 KT 12HR VT 27/1200Z 35.1N 62.1W 75 KT 24HR VT 28/0000Z 37.2N 62.8W 75 KT 36HR VT 28/1200Z 40.1N 63.2W 75 KT 48HR VT 29/0000Z 44.8N 62.8W 65 KT 72HR VT 30/0000Z 57.1N 58.9W 40 KT...EXTRATROPICAL 96HR VT 01/0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:59 UTC