ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM LESTER DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT WED OCT 13 2004 RADAR IMAGERY FROM ACAPULCO MEXICO INDICATES THAT LESTER RETAINS A SMALL BUT WELL-ORGANIZED CIRCULATION...WHILE SATELLITE IMAGERY SHOWS CONVECTION WITH TOPS COLDER THAN -80C JUST EAST OF THE CENTER. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB...AND 45 KT FROM SAB AND AFWA. THE INITIAL INTENSITY IS INCREASED TO 45 KT FOR THIS ADVISORY. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 300/7. LESTER IS MOVING ALONG THE SOUTH SIDE OF A NARROW MID/UPPER-LEVEL RIDGE ALONG 20N- 21N...AND IS NORTHEAST OF A LARGE BUT POORLY ORGANIZED AREA OF DISTURBED WEATHER. LARGE-SCALE MODELS FORECAST THE RIDGE TO HOLD FOR 24-48 HR...THEN STRENGTHEN WITH AN ANTICYCLONE DEVELOPING NEAR THE SOUTHERN GULF OF CALIFORNIA. THIS PATTERN SHOULD KEEP LESTER ON A WEST-NORTHWESTWARD TO WESTWARD TRACK FOR 24-48 HR...FOLLOWED BY A WESTWARD MOTION FROM 48-96 HR. AFTER 96 HR...LESTER MAY APPROACH THE WESTERN END OF THE RIDGE...WHICH WOULD AGAIN ALLOW A MORE NORTHWARD MOTION. WHILE DYNAMICAL MODELS AGREE ON THE GENERAL MOTION...THERE ARE DIFFERENCES IN JUST HOW FAR NORTH LESTER WILL TRACK BEFORE TURNING WESTWARD DUE TO HOW THEY HANDLE INTERACTION BETWEEN LESTER AND THE DISTURBANCE. THE NEW FORECAST TRACK IS NUDGED A LITTLE NORTH OF THE PREVIOUS TRACK IN AGREEMENT WITH THE NOGAPS AND THE CONU CONSENSUS MODEL. THE TRACK KEEPS THE CENTER MOVING PARALLEL TO THE MEXICAN COAST FOR ABOUT 24 HR BEFORE IT GRADUALLY GETS FARTHER AWAY. HOWEVER...ANY MOTION NORTH OF THE FORECAST TRACK COULD BRING THE CENTER ONSHORE. LESTER IS EXPERIENCING LIGHT-MODERATE SOUTHERLY SHEAR. LARGE-SCALE MODELS NOW SUGGEST THAT SOUTHERLY/SOUTHWESTERLY SHEAR MAY PERSIST FOR 48 HR BEFORE DECREASING. SINCE LESTER HAS STRENGTHENED DESPITE THE SHEAR...THE INTENSITY FORECAST CALLS FOR SLOW STRENGTHENING FOR 48 HR...WITH THE CYCLONE REACHING HURRICANE STRENGTH AS THE SHEAR DIMINISHES. THIS BASICALLY FOLLOWS THE SHIPS MODEL. LESTER WILL LIKELY REMAIN A SMALLER THAN AVERAGE TROPICAL CYCLONE AND THUS IT WILL BE SUSCEPTIBLE TO RAPID FLUCTUATIONS IN STRENGTH...INCLUDING THE POSSIBILITY IT COULD GET STRONGER THAN FORECAST IN THE 72-120 HR TIMEFRAME WHEN THE SHEAR IS FORECAST TO BE LIGHT. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 13/0900Z 16.8N 100.6W 45 KT 12HR VT 13/1800Z 17.1N 101.4W 50 KT 24HR VT 14/0600Z 17.2N 102.2W 55 KT 36HR VT 14/1800Z 17.2N 103.0W 60 KT 48HR VT 15/0600Z 17.2N 104.1W 65 KT 72HR VT 16/0600Z 17.5N 106.5W 70 KT 96HR VT 17/0600Z 18.0N 108.5W 70 KT 120HR VT 18/0600Z 19.0N 110.5W 65 KT $$ NNNN
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Page last modified: Wednesday, 13-Oct-2004 08:36:37 UTC