Typhoon 28W(RAI) down 55knots in 24H, intensity to fall below 35knots in 36h// Invest 94B and Invest 98W, 20/03utc

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. HOWEVER THE WARNING HAS BEEN TRUNCATED TO 48 HOURS. FORECAST DISCUSSION: TY 28W CONTINUES ITS PRECIPITOUS WEAKENING TREND. THE SYSTEM IS FORECAST TO CONTINUE TRACKING NORTHEAST THROUGH THE NEXT 12 HOURS THEN TURN EASTWARD IN A GRACEFUL ARC THROUGH 48H. AS THE SYSTEM WEAKENS AND THE LOW LEVEL CENTER BECOMES EXPOSED, THE SYSTEM WILL SLOW DOWN AND TURN EASTWARD UNDER THE INFLUENCE OF THE LOWER LEVEL FLOW. SHEAR IS ALREADY AT 20 KNOTS OR SLIGHTLY HIGHER BASED ON THE CIMSS ANALYSIS, AND WILL ONLY GET WORSE FROM HERE ON OUT. BY 12H SHEAR IS EXPECTED TO BE ABOVE 35 KNOTS AS THE SYSTEM STARTS TO FEEL THE SOUTHERN SIDE OF THE STRONG WESTERLIES PRESENT IN A BAND OVER CENTRAL CHINA. BY 24H, IF NOT BEFORE, THE SHEAR WILL DECAPITATE TY 28W, EXPOSE THE LLCC AND INITIATE THE SYSTEMS DEMISE. THE RESIDUAL CIRCULATION WILL TAKE SOME TIME TO SPIN DOWN TO LESS THAN 25 KNOTS, BUT NEVERTHELESS, IT IS EXPECTED TO FULLY DISSIPATE BELOW WARNING THRESHOLD NO LATER THAN 48H, TO THE SOUTHWEST OF TAIWAN.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: AS THE SUN HAS RISEN OVER TY 28W, IT HAS REVEALED A RAPIDLY WEAKENING CYCLONE, THOUGH THE CENTRAL CIRCULATION APPEARS TO BE RELATIVELY INTACT. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A WELL DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH A SMALL POCKET OF FLARING CONVECTION BLOOMING NEAR THE ASSESSED CENTER AND BEING SHEARED TO THE NORTH, WHILE THE REMAINDER OF THE CIRCULATION IS DEVOID OF SIGNIFICANT CONVECTION. A 192247Z SSMIS 37GHZ MICROWAVE IMAGE SHOWED A WELL DEFINED LOW EMISSIVITY REGION IDENTIFYING THE LLCC, WITH SHALLOW BANDING TO THE EAST AND SOUTH, WRAPPING INTO THE TIGHT CIRCULATION CENTER. EXTRAPOLATION OF THE MICROWAVE IMAGERY PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS A BIT MORE TRICKY DUE TO THE VERY RAPID UNRAVELING OF THE SYSTEM. AGENCY FIXES RANGE FROM A POSITION ONLY FIX FROM KNES, TO RJTD T5.5. MEANWHILE, ADT WAS T4.7 USING THE SHEAR METHOD, THROUGH THE RAW ADT WAS ONLY T1.5. SATCON WAS TOOL OLD FOR USE IN THIS ANALYSIS, AND THE AI ADJUSTED ADT WAS 63 KNOTS. THE INITIAL INTENSITY IS THUS SET AT A GENEROUS 70 KNOTS, BASED ON A BLEND OF THE AVAILABLE DATA WITH LOW CONFIDENCE. THE SYSTEM IS MOVING INTO AN EVEN MORE UNFAVORABLE ENVIRONMENT, WITH SSTS BELOW 25C, MODERATE VWS AND DRY AIR ENTRAINMENT.

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH THE FORECAST PERIOD, THOUGH SOME ALONG-TRACK SPREAD IS INTRODUCED BY 48H AS THE MODELS STRUGGLE WITH THE DISSIPATING VORTEX. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND TRACKS THE LEFT SIDE OF THE GUIDANCE ENVELOPE THROUGH 36H THEN MOVES TO THE RIGHT SIDE BY 48H AS THE BULK OF THE GUIDANCE IS MISSING THE TURN SOUTHEASTWARD. OVERALL CONFIDENCE IS MEDIUM DUE TO THE UNCERTAINTY IN THE ULTIMATE DISSIPATION TIMELINE AND THE IMPACT OF THE LOW-LEVEL FLOW ON THE REMNANT VORTEX AFTER 36H. INTENSITY GUIDANCE IS IN GOOD AGREEMENT, AND THE JTWC FORECAST IS RIGHT DOWN THE MIDDLE OF THE ENVELOPE, WITH MEDIUM CONFIDENCE.

AN AREA OF CONVECTION (INVEST 94B) HAS PERSISTED NEAR 4.8N 93.7E, APPROXIMATELY 435 NM SOUTHWEST OF PHUKET, THAILAND. ANIMATED ENHANCED INFRARED SATELITE IMAGERY DEPICTS BROAD DEEP CONVECTION OVER A LOW LEVEL CIRCULATION (LLC). RECENT SCATTEROMETRY DATA SHOWS 25 TO 30 KT WINDS SURROUNDING A LLC. ENVIRONMENTAL ANALYSIS DEPICTS MARGINALLY FAVORABLE CONDITIONS FOR DEVELOPMENT WITH ROBUST POLEWARD OUTFLOW ALOFT AND WARM (28-29C) SEA SURFACE TEMPERATURES, OFFSET BY HIGH (15-25KT) VERTICAL WIND SHEAR. GLOBAL MODELS ARE IN AGREEMENT THAT 94B WILL HAVE A GENERAL EASTWARD TRACK INTO THE NORTH-WESTERN TIP OF SUMATRA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS LOW.

GLOBAL MODELS ARE IN AGREEMENT THAT 94B WILL HAVE A GENERAL EASTWARD TRACK INTO THE NORTH-WESTERN TIP OF SUMATRA.