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| #56981 (Received by flhurricane at: 4:03 PM 15.Nov.2005) TCDAT2 TROPICAL DEPRESSION TWENTY-SEVEN DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 4 PM EST TUE NOV 15 2005 THE AIR FORCE RECONNAISSANCE AIRCRAFT CONFIRMS WHAT THE SATELLITE IMAGERY HAS BEEN INDICATING TODAY... THAT THE DEPRESSION REMAINS QUITE POORLY ORGANIZED. THE CIRCULATION IS ELONGATED WEST-SOUTHWEST TO EAST-NORTHEAST... WITH ONLY VERY WEAK WESTERLY WINDS ON THE SOUTHWESTERN SIDE AND A BROAD AREA OF WEAK WINDS AROUND THE ESTIMATED CENTER LOCATION. THE LOWEST PRESSURE REPORTED BY THE AIRCRAFT HAS BEEN 1006 MB. EVEN THOUGH THE CIRCULATION IS A BIT SLOPPY... SOME DEEP CONVECTION REMAINS CLOSE BY... BUT ONLY ON THE EASTERN SIDE DUE TO CONTINUING WESTERLY SHEAR. PERHAPS GENEROUSLY... THE SYSTEM REMAINS A DEPRESSION WITH 30 KT WINDS... BASED ON FLIGHT LEVEL WINDS OF 41 KT... A FEW SHIP REPORTS OF ABOUT 30 KT IN THE SOUTHEASTERN QUADRANT... AND DVORAK SATELLITE ESTIMATES. THE CIRCULATION CENTER IS MOVING JUST NORTH OF DUE WEST AT ABOUT 11 KT. THE TRACK FORECAST REMAINS RELATIVELY STRAIGHTFORWARD THROUGH ABOUT 48 HOURS... AS A LOW- TO MID-LEVEL RIDGE IS FORECAST TO PERSIST OVER THE EXTREME WESTERN ATLANTIC AND CONTINUE TO DRIVE THE CYCLONE WESTWARD. AFTER THAT... THERE ARE SEVERAL FACTORS COMPLICATING THE TRACK FORECAST. DYNAMICAL MODELS AGREE THE WESTERN ATLANTIC RIDGE WILL BREAK DOWN AND CAUSE THE TROPICAL CYCLONE TO MOVE MORE SLOWLY ON DAYS 3-5. HOWEVER... EACH MODEL FORECASTS A DIFFERENT EVOLUTION OF THE BROAD LOW CURRENTLY OVER THE SOUTHWESTERN CARIBBEAN... AND EACH SHOWS AN UPPER-LEVEL TROUGH OVER THE EASTERN UNITED STATES BY THAT TIME... BUT WITH VARYING STRENGTH OVER THE GULF OF MEXICO. THE TROPICAL CYCLONE WILL MOST LIKELY BECOME EMBEDDED WITHIN WEAK STEERING CURRENTS BETWEEN THESE TWO FEATURES... ALTHOUGH ONE COULD END UP HAVING MORE INFLUENCE THAN THE OTHER. MOST OF THE MODELS FAVOR A SLOW NORTHWARD COMPONENT TO THE MOTION ON DAYS 4 AND 5. THE NEW OFFICIAL FORECAST FOLLOWS THIS SCENARIO AND IS FASTER THAN THE PREVIOUS ADVISORY THROUGH 72 HOURS... THEN SIMILARLY SLOW THEREAFTER. ALTHOUGH THE SYSTEM IS BARELY HANGING ON TO TROPICAL CYCLONE STATUS... ITS ENVIRONMENT SHOULD GRADUALLY BECOME MORE CONDUCIVE FOR STRENGTHENING. IF THE CYCLONE SURVIVES THE NEXT 24 HOURS OR SO OF CONTINUED WESTERLY SHEAR... THE DEVELOPING UPPER-LEVEL ANTICYCLONE OVER THE WEST-CENTRAL CARIBBEAN WILL CREATE A WEAKER SHEAR ENVIRONMENT. THIS COULD ALLOW FOR A TROPICAL STORM TO DEVELOP IN 24-36 HOURS AS SUGGESTED BY THE SHIPS GUIDANCE. SHIPS PEAKS AT 55 KT IN ABOUT 72 HOURS... WHILE THE GFDL PEAKS AT 77 KT A LITTLE LATER. THE OFFICIAL FORECAST IS IN BETWEEN AND STILL ANTICIPATES DEVELOPMENT INTO A HURRICANE... ALTHOUGH A WEAKENING TREND IS NOW INTRODUCED AT THE END OF THE FORECAST IN ANTICIPATION OF INCREASING SOUTHWESTERLY SHEAR IN ADVANCE OF THE TROUGH EXPECTED TO DEVELOP OVER THE GULF OF MEXICO. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 15/2100Z 14.8N 69.0W 30 KT 12HR VT 16/0600Z 14.9N 70.7W 30 KT 24HR VT 16/1800Z 15.0N 73.0W 35 KT 36HR VT 17/0600Z 15.2N 75.2W 40 KT 48HR VT 17/1800Z 15.4N 77.5W 45 KT 72HR VT 18/1800Z 15.5N 81.0W 55 KT 96HR VT 19/1800Z 16.0N 82.0W 65 KT 120HR VT 20/1800Z 16.5N 82.5W 60 KT |
