ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM BLANCA DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT FRI JUN 20 2003 BLANCA HAS HAD ANOTHER MAJOR CONVECTIVE BURST THIS MORNING. HOWEVER...FIRST LIGHT VISIBLE IMAGERY INDICATES THE LOW-LEVEL CENTER IS PARTIALLY EXPOSED ON THE EASTERN SIDE OF THE CONVECTION. SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM AFWA...AND 35 KT FROM TAFB AND SAB. THE MAXIMUM INTENSITY REMAINS 35 KT IN THIS ADVISORY. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 265/3. BLANCA IS ON THE SOUTH SIDE OF A WEAK SUBTROPICAL RIDGE...WITH LARGE-SCALE MODELS INDICATING THAT THIS FEATURE WILL PERSIST THROUGH THE FORECAST PERIOD. THIS SHOULD KEEP BLANCA ON A SLOW WESTWARD TO WEST-NORTHWESTWARD TRACK. MOST NHC GUIDANCE AGREES WITH THIS SCENARIO...ALTHOUGH ONCE AGAIN THE GUIDANCE IS SPLIT SPEEDWISE BETWEEN THE SLOWER DYNAMICAL MODELS AND THE FASTER NHC91/BAMD MODELS. THE FORECAST TRACK WILL STAY SLOW AND SIMILAR TO THE PREVIOUS PACKAGE. ONE ALTERNATE POSSIBILITY IS THAT THE LARGE BUT DISORGANIZED AREA OF DISTURBED WEATHER SOUTH OF THE GULF OF TEHUANTEPEC MAY CHANGE THE LOW/MID-LEVEL FLOW ENOUGH FOR BLANCA TO MOVE EASTWARD...AS INDICATED BY THE GFDN. SHOULD THAT OCCUR...THE LARGER DISTURBANCE WOULD LIKELY ABSORB THE SMALLER BLANCA. BLANCA WILL CONTINUE IN AN ENVIRONMENT OF EASTERLY SHEAR THROUGH THE FORECAST PERIOD...WITH LARGE-SCALE MODELS INDICATING SOME INCREASE IN SHEAR AFTER 24 HR. THIS SHEAR...AIDED BY EXTENSIVE MID/UPPER-LEVEL DRY AIR AND STABLE LOW-LEVEL STRATOCUMULUS NEAR THE STORM...SHOULD CAUSE A STEADY WEAKENING EVEN THOUGH BLANCA SHOULD REMAIN OVER RELATIVELY WARM WATER. THE INTENSITY FORECAST CALLS FOR A STEADY-STATE STORM FOR 24 HR FOLLOWED BY SLOW WEAKENING UNTIL DISSIPATION. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 20/1500Z 15.5N 106.0W 35 KT 12HR VT 21/0000Z 15.5N 106.6W 35 KT 24HR VT 21/1200Z 15.6N 107.3W 30 KT 36HR VT 22/0000Z 15.8N 108.1W 25 KT 48HR VT 22/1200Z 15.9N 108.8W 25 KT...DISSIPATING 72HR VT 23/1200Z 16.0N 110.0W 20 KT...REMNANT LOW 96HR VT 24/1200Z 16.0N 112.0W 20 KT...REMNANT LOW 120HR VT 25/1200Z...DISSIPATED NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC