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ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ARLENE DISCUSSION NUMBER 23 NATIONAL WEATHER SERVICE MIAMI FL 11 PM EDT WED JUN 16 1999 AN AIR FORCE HURRICANE PLANE FOUND HIGHEST WINDS AROUND 40 KNOTS IN THE NORTHEAST QUADRANT AT A FLIGHT LEVEL OF 1100 FEET...AND THE CENTRAL PRESSURE IS NOW UP TO 1015 MB. SATELLITE IMAGERY SHOWS VERY LITTLE...IF ANY...DEEP CONVECTION. THESE OBSERVATIONS IMPLY THAT ARLENE IS BARELY OF TROPICAL STORM STRENGTH. THE SYSTEM IS IN AN AREA OF CONFLUENT UPPER-LEVEL FLOW TO THE NORTH OF A LARGE UPPER- LEVEL CYCLONE TO ITS SOUTH...AND THE ASSOCIATED SUBSIDENCE MAY BE INHIBITING THE REDEVELOPMENT OF CONVECTION. VERTICAL SHEAR APPEARS TO BE INCREASING OVER THE AREA AND SEA SURFACE TEMPERATURES ARE MARGINAL. THEREFORE... FURTHER WEAKENING IS LIKELY. THE OFFICIAL FORECAST CALLS FOR A DISSIPATING CYCLONE IN 48 HOURS. FORWARD MOTION HAS SLOWED TO A DRIFT BUT TRACK GUIDANCE INDICATES A MOSTLY NORTHWARD MOTION DURING THE NEXT 12 TO 24 HOURS WITH A GRADUAL TURN TOWARD THE NORTH-NORTHEAST THEREAFTER. THIS IS CONSISTENT WITH A MOVEMENT AROUND THE PERIPHERY OF THE SUBTROPICAL ANTICYCLONE...AND IS ALSO VERY SIMILAR TO THE SHALLOW-LAYER BAM TRACK. PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 17/0300Z 31.8N 62.7W 35 KTS 12HR VT 17/1200Z 33.0N 63.0W 30 KTS 24HR VT 18/0000Z 34.7N 63.0W 30 KTS 36HR VT 18/1200Z 37.0N 62.5W 25 KTS 48HR VT 19/0000Z 39.5N 61.0W 25 KTS...DISSIPATING 72HR VT 20/0000Z...DISSIPATED NNNN