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c789654|2011-12-30 19:13
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JTWC 第4報 依舊測預上90KTS
REMARKS:292100Z POSITION NEAR 13.3S 82.0E.TROPICAL CYCLONE (TC) 04S, LOCATED APPROXIMATELY 680 NM EAST-SOUTHEAST OF DIEGO GARCIA, HAD TRACKED WEST-SOUTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY DEPICTS CONSOLIDATING CONVECTION OVER THE LOW-LEVEL CIRCULATION CENTER (LLCC) WITH AN INCREASE IN SYMMETRY. THE CURRENT POSITION IS BASED ON THE PGTW CENTER FIX WITH LOW CONFIDENCE DUE TO THE CLOUD COVER OVER THE LLCC IN THE IR IMAGERY. THE CURRENT INTENSITY IS AN AVERAGE VALUE OF THE DVORAK ESTIMATES RANGING FROM 35-55 KNOTS. UPPER-LEVEL ANALYSIS INDICATES THAT TC 04S IS A FEW DEGREES EQUATORWARD OF THE SUBTROPICAL RIDGE AXIS IN AN AREA OF MODERATE (20-KNOT) EASTERLY VERTICAL WIND SHEAR (VWS) WITH EXCELLENT DIVERGENCE ALOFT. RECENT ANIMATED WATER VAPOR IMAGERY SHOWS GOOD RADIAL OUTFLOW WHICH SEEMS TO BE OVERCOMING THE VWS. TC 04S IS FORECAST TO TRACK WEST-SOUTHWESTWARD THROUGH TAU 36 UNDER THE MID TO UPPER-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTH. AFTER TAU 36, TC 04S IS EXPECTED TO TURN SOUTHWESTWARD TOWARD A WEAKNESS IN THE SUBTROPICAL RIDGE CREATED BY AN APPROACHING, DEEP MID-LATITUDE SHORTWAVE TROUGH, WHICH WILL LEAD TO A DECREASE IN VWS AND IMPROVED POLEWARD OUTFLOW. THEREFORE, THE SYSTEM IS FORECAST TO INTENSIFY AT A FASTER RATE TO A PEAK INTENSITY OF 90 KNOTS BY TAU 48. MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72. IN THE EXTENDED PERIOD, TC 04S WILL SLOW AS IT ENCOUNTERS INCREASING VWS AND CONVERGENCE ALOFT ASSOCIATED WITH THE AFOREMENTIONED TROUGH AND WILL BEGIN TO WEAKEN. MODEL GUIDANCE DIVERGES AFTER TAU 72 WITH INCREASED UNCERTAINTY IN THE TRACK. THIS FORECAST FAVORS THE MORE WESTWARD TRACK UNDER THE STEERING INFLUENCE OF A RE-BUILDING SUBTROPICAL RIDGE AS THE MID-LATITUDE TROUGH PROPAGATES OUT OF THE AREA. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 291800Z IS 18 FEET. NEXT WARNINGS AT 300900Z AND 302100Z.//NNNN
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