ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM MIRIAM DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP142006 200 PM PDT SUN SEP 17 2006 MIRIAM HAS BECOME LESS ORGANIZED THIS AFTERNOON WITH DIMINISHING CONVECTION SOUTHWEST OF AN EXPOSED LOW-LEVEL CENTER OF CIRCULATION. OBVIOUSLY THIS SYSTEM IS FEELING THE EFFECTS OF VERTICAL WIND SHEAR AND PERHAPS DRY AIR ENTRAINMENT. OBSERVATIONS FROM THE MEXICAN NAVY AT ISLA CLARION REPORTED MAXIMUM WINDS NEAR 26 KT AND GUSTS TO 39 KT OVER THE PAST FEW HOURS. SHIP A8HR7 ABOUT 170 NM TO THE SOUTHWEST OF THE CENTER REPORTED 39 KT...HOWEVER THESE WINDS WERE ON THE PERIPHERY OF THE CIRCULATION AND LIKELY NOT REPRESENTATIVE OF MIRIAM'S ACTUAL INTENSITY. MOREOVER A QUALITY CONTROL CHECK FROM THE OCEAN PREDICTION CENTER INDICATED THAT THE SHIP'S WINDS WERE RUNNING A LITTLE HIGH. BASED ON THESE OBSERVATIONS AND CURRENT INTENSITY NUMBERS OF 2.5 FROM TAFB AND SAB...THE INITIAL INTENSITY IS REDUCED TO 35 KT. MIRIAM WILL BE MOVING INTO AN AREA OF INCREASED WIND SHEAR AND COOLER WATERS OVER THE NEXT COUPLE OF DAYS AS INDICATED BY MOST OF THE GLOBAL MODELS. THEREFORE...THE OFFICIAL FORECAST CALLS FOR STEADY WEAKENING TO A REMNANT LOW IN 72 HOURS... BUT THIS COULD OCCUR SOONER. THE FORWARD MOTION IS A SLOW 010/4...SINCE MIRIAM IS EMBEDDED WITHIN RATHER WEAK STEERING CURRENTS. MODELS ARE IN FAIR AGREEMENT IN INDICATING A NORTHWARD MOTION FOLLOWED BY A MORE NORTHWESTWARD TURN AS THE SYSTEM BECOMES SHALLOW AND STEERED BY THE LOW-LEVEL FLOW. THIS FORECAST IS SIMILAR TO BUT NUDGED TO THE LEFT OF THE PREVIOUS ONE TO BE BETTER ALIGNED WITH THE MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 17/2100Z 19.3N 114.0W 35 KT 12HR VT 18/0600Z 20.1N 114.0W 30 KT 24HR VT 18/1800Z 20.9N 114.6W 30 KT 36HR VT 19/0600Z 21.9N 115.6W 25 KT 48HR VT 19/1800Z 23.0N 116.5W 25 KT...DISSIPATING 72HR VT 20/1800Z 25.0N 117.5W 20 KT...REMNANT LOW 96HR VT 21/1800Z...DISSIPATED $$ FORECASTER MAINELLI/CANGIALOSI NNNN
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Page last modified: Sunday, 17-Sep-2006 20:40:03 UTC