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#110531 (Received by flhurricane at: 10:46 PM 12.Sep.2006) TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 1100 PM EDT TUE SEP 12 2006 THE DEPRESSION IS RATHER DISORGANIZED TONIGHT AND CONSISTS OF A BROAD AREA OF LOW PRESSURE WITH MULTIPLE LOW-LEVEL SWIRLS. AN AVERAGE POSITION OF THE LARGER CIRCULATION GYRE IS USED FOR THE HIGHLY UNCERTAIN INITIAL POSITION. THIS POSITION IS NUDGED SOUTHWARD A LITTLE BIT FROM THE PREVIOUS ADVISORY... IN AGREEMENT WITH AN EARLIER QUIKSCAT PASS SUGGESTING THAT THE CENTER WAS SOUTH OF 12N. CONVECTION NEAR THE MIDDLE OF THE DEPRESSION IS SCANT... THOUGH THERE IS A SOMEWHAT CURVED BAND TO THE SOUTHEAST OF THE CENTER AND HEAVY CLUSTERS OF THUNDERSTORMS RACING WESTWARD AWAY FROM THE CIRCULATION. THE INITIAL INTENSITY IS BEING HELD AT 30 KT AND IS SUPPORTED BY BELIEVABLE 25-30 KT WIND VECTORS FROM QUIKSCAT. ALTHOUGH THE DEPRESSION IS OVER WARM WATER AND EXPERIENCING RELATIVELY LOW VERTICAL WIND SHEAR... IT WILL PROBABLY TAKE SOME TIME FOR THE LARGE SYSTEM TO CONSOLIDATE. THE INTENSITY FORECAST IS LOWERED FROM THE PREVIOUS PACKAGE AND IS MUCH LOWER THAN SHIPS... WHICH SEEMS TO BE MUCH TOO FAST IN MAKING THE DEPRESSION ALMOST A HURRICANE IN 36 HOURS. THE GFDL HAS A SEEMINGLY MORE REALISTIC DEPICTION OF THE FUTURE INTENSITY CHANGE... SLOW AT FIRST THEN MORE RAPID IN THE EXTENDED PERIOD... AND IS USED AS THE PRIMARY GUIDANCE FOR THE INTENSITY FORECAST. THE BEST ESTIMATE OF INITIAL MOTION IS 270/14. A STRENGTHENING MIDDLE-LEVEL RIDGE NORTH OF THE CYCLONE SHOULD KEEP THE CYCLONE ON THIS GENERAL TRACK WITH AN INCREASE IN FORWARD SPEED OVER THE NEXT COUPLE OF DAYS. BEYOND 48 HOURS... THE RIDGE WEAKENS OVER THE CENTRAL ATLANTIC... ALLOWING THE DEPRESSION TO START MOVING MORE TO THE NORTHWEST. MODELS ARE GENERALLY SHOWING MORE OF A WEAKNESS IN THE SUBTROPICAL RIDGE THAN EARLIER TODAY AND... CONSEQUENTLY... THE OFFICIAL FORECAST IS SHIFTED NORTHWARD AT DAYS 3-5. THE FORECAST IS STILL ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE... AND CLOSE TO THE GFDL. FORECAST POSITIONS AND MAX WINDS INITIAL 13/0300Z 11.8N 25.3W 30 KT 12HR VT 13/1200Z 12.1N 27.8W 35 KT 24HR VT 14/0000Z 12.4N 31.3W 40 KT 36HR VT 14/1200Z 12.9N 34.8W 45 KT 48HR VT 15/0000Z 13.8N 38.0W 50 KT 72HR VT 16/0000Z 16.3N 43.0W 60 KT 96HR VT 17/0000Z 19.0N 47.0W 75 KT 120HR VT 18/0000Z 21.5N 50.0W 90 KT $$ FORECASTER BLAKE/AVILA |