ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ERIKA DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT THU AUG 14 2003 A RECONNAISSANCE PLANE THIS EVENING FOUND A MUCH BETTER DEFINED LOW-LEVEL CIRCULATION. MAXIMUM FLIGHT-LEVEL WINDS WERE 47 KT IN THE NORTHEAST AND NORTHWEST QUADRANTS AT 1500 FT...WHICH EQUATES TO ABUT 38 KT AT THE SURFACE. HOWEVER...THE CENTRAL CONVECTION HAS INCREASED MARKEDLY SINCE THE LAST RECON WIND REPORTS...SO THE INITIAL INTENSITY IS BUMPED UP TO 40 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 270/20. THE LOW-LEVEL CENTER HAS ACTUALLY BEEN PROPAGATING WEST-NORTHWESTWARD DURING THE PAST 6 HOURS...BUT THAT MOTION IS BELIEVED TO BE DUE TO RE-ORGANIZATION OF THE LOW-LEVEL CENTER WITHIN THE DEVELOPING CENTRAL DENSE OVERCAST REGION. THERE MAY EVEN BE A SLIGHT SOUTHWARD JOG DURING THE NIGHT AS THE CONVECTION WRAPS AROUND THE SOUTH SIDE OF THE CENTER...BUT THE GENERAL MOTION SHOULD BE WESTWARD. AT 500 MB...ALL OF THE GLOBALS MODELS MAINTAIN THE SAME DISTANCE BETWEEN ERIKA AND A STRONG HIGH PRESSURE CENTER CURRENTLY OVER NORTHERN MISSISSIPPI AS BOTH SYSTEMS MOVE WESTWARD IN TANDEM. THE FORECAST TRACK BECOMES A LITTLE MURKY AFTER 24 HOURS AS ALL THE GLOBAL MODELS AND THE GFDL WEAKEN ERIKA SIGNIFICANTLY...AND TAKE THE CYCLONE SLOWLY SOUTHWARD JUST BEFORE IT REACHES THE WESTERN GULF COAST SATURDAY MORNING. SINCE THE OFFICIAL FORECAST CALLS FOR STRENGTHENING INSTEAD OF WEAKENING TO OCCUR...ERIKA IS EXPECTED TO REMAIN A VERTICALLY DEEP SYSTEM AND BE STEERED WESTWARD BY THE DEEP-LAYERED EASTERLY FLOW ACROSS THE NORTHERN GULF THAT ALL OF THE MODELS ARE MAINTAINING THROUGHOUT THE PERIOD. THE OFFICIAL FORECAST TRACK IS A LITTLE FASTER AND SLIGHTLY NORTH OF THE PREVIOUS TRACK DUE TO THE FARTHER NORTH INITIAL POSITION AND FASTER MOTION. A GRADUAL DECREASE IN FORWARD SPEED IS EXPECTED AFTER 24 HOURS AS THE LOW-LEVEL STEERING FLOW WEAKENS ACROSS TEXAS AND LOUISIANA. THIS TRACK SCENARIO IS CONSISTENT WITH THE MEDIUM AND DEEP BAM MODELS...AND THE GLOBAL MODEL'S MID-LEVEL CENTER TRACK POSITIONS. SINCE THE 36 HOUR FORECAST POSITION IS NEAR BROWNSVILLE TEXAS...A HURRICANE WATCH HAS BEEN ISSUED FROM PORT O'CONNOR TEXAS SOUTHWARD TO BOCA SANTA MARIA MEXICO. ERIKA CONTINUES TO GET BETTER ORGANIZED BASED ON SATELLITE IMAGERY AND THE LAST RECON REPORTS. HOWEVER...THE CYCLONE IS MOVING QUITE FAST AND THAT WILL LIMIT THE TIME THAT ERIKA WILL HAVE TO STRENGTHEN. THE OUTFLOW PATTERN IS VERY IMPRESSIVE FOR SUCH A FAST MOVING TROPICAL STORM. HOWEVER... THE FAST MOTION IS KEEPING THE CONVECTION FROM WRAPPING COMPLETELY AROUND THE CENTER FOR MORE THAN JUST A COUPLE OF HOURS AT A TIME. THIS SHOULD LIMIT INTENSIFICATION FOR THE NEXT 24 HOURS OR SO UNTIL THE CYCLONE BEGINS TO SLOW DOWN. AFTER THAT TIME...SOME SIGNIFICANT STRENGTHENING COULD OCCUR RIGHT UP UNTIL LANDFALL. THE OFFICIAL INTENSITY FORECAST IS LOWER THAN THE SHIPS INTENSITY MODEL WHICH BRINGS THE CYCLONE UP TO NEAR 70-75 KT AT LANDFALL. THE GFDL MODEL WEAKENS ERIKA TO BELOW TROPICAL DEPRESSION STRENGTH IN ABOUT 24 HOURS...WHICH SEEMS UNLIKELY AT THIS TIME. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 15/0300Z 26.6N 86.5W 40 KT 12HR VT 15/1200Z 26.5N 89.9W 45 KT 24HR VT 16/0000Z 26.5N 93.7W 55 KT 36HR VT 16/1200Z 26.4N 97.0W 65 KT 48HR VT 17/0000Z 26.3N 99.9W 30 KT...DISSIPATING INLAND 72HR VT 18/0000Z 26.5N 104.5W 20 KT...DISSIPATING INLAND 96HR VT 19/0000Z...DISSIPATED INLAND NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:57 UTC