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| #49337 (Received by flhurricane at: 11:11 PM 30.Sep.2005) TCDAT4 TROPICAL DEPRESSION NINETEEN DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI SEP 30 2005 AN SSM/IS OVERPASS AT 2227Z INDICATED THAT THE LOW-LEVEL CENTER OF TROPICAL DEPRESSION NINETEEN WAS EXPOSED TO THE NORTH OF STRONG AND PERSISTENT CONVECTION. SHORTWAVE IMAGERY FROM METEOSAT-8 SINCE THAT TIME SUGGESTS THIS IS STILL THE CASE...BUT IT CANNOT BE DETERMINED JUST HOW FAR THE CENTER IS FROM THE CONVECTION AT THE MOMENT. SATELLITE INTENSITY ESTIMATES ARE 30 KT FROM TAFB AND SAB...AND 25 KT FROM AFWA. THE INITIAL INTENSITY IS INCREASED TO 30 KT. THE INITIAL MOTION IS A RATHER UNCERTAIN 310/2. OTHER THAN THAT... THERE IS LITTLE CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS ADVISORY. A DEEP LAYER LOW PRESSURE SYSTEM CENTERED ABOUT 700 N MI NORTH OF THE DEPRESSION IS FORECAST TO MOVED WESTWARD FOR THE NEXT FEW DAYS...WHICH SHOULD CAUSE THE DEPRESSION TO MOVE IN A GENERAL NORTHWESTWARD OR NORTHWARD DIRECTION FOR 72-96 HR. THE TRACK GUIDANCE GENERALLY AGREES WITH THIS ALTHOUGH THERE IS SOME SPREAD BETWEEN THE MORE WESTWARD GFS AND THE MORE EASTWARD NOGAPS. THE TRACK FORECAST THROUGH 96 HR IS DOWN THE MIDDLE OF THE ENVELOPE OF DYNAMICAL GUIDANCE. AFTER 96 HR...THE LARGE-SCALE MODELS SUGGEST A LOW/MID-LEVEL RIDGE MAY FORM NORTH OF THE CYCLONE...WHICH COULD STEER IT MORE WESTWARD. THE FORECAST TRACK WILL NOT SHOW THIS YET...BUT WILL SLOW THE SYSTEM DOWN IN RESPONSE TO THIS POSSIBILITY. THE DEPRESSION IS CURRENTLY EXPERIENCING 15-20 KT OF NORTHERLY OR NORTHWESTERLY VERTICAL SHEAR...ALTHOUGH THIS NOT STOPPING THE CONVECTION THUS FAR. THE SHIPS MODEL FORECASTS DECREASING SHEAR IN ABOUT 12 HR AND MAINTAINS THIS THROUGH ABOUT 60 HR. THIS SHOULD ALLOW THE CYCLONE TO STRENGTHEN...AND THE INTENSITY FORECAST CALLS FOR A PEAK INTENSITY OF 50 KT IN 48-72 HR. THIS IS A BIT LESS THAN EITHER THE SHIPS OR GFDL ARE FORECASTING. THE LARGE-SCALE MODELS ARE FORECASTING SIGNIFICANT SOUTHWESTERLY SHEAR ON THE SOUTH AND SOUTHEAST SIDE OF THE DEEP-LAYER LOW...AND IF THE DEPRESSION GETS TOO CLOSE TO THAT THE SHEAR WILL BE MUCH STRONGER THAN SHIPS IS FORECASTING. THUS...THE INTENSITY FORECAST WILL REMAIN ON THE CONSERVATIVE SIDE UNTIL IT IS MORE APPARENT THAT THE CYCLONE WILL STAY SOUTH OF THE STRONGER SHEAR. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 01/0300Z 12.3N 33.1W 30 KT 12HR VT 01/1200Z 12.5N 33.3W 35 KT 24HR VT 02/0000Z 13.0N 33.9W 40 KT 36HR VT 02/1200Z 14.2N 34.6W 45 KT 48HR VT 03/0000Z 15.8N 35.2W 50 KT 72HR VT 04/0000Z 19.5N 36.5W 50 KT 96HR VT 05/0000Z 23.5N 36.5W 45 KT 120HR VT 06/0000Z 26.5N 36.5W 45 KT |
