TY 20W(MINDULLE) CAT 2 slowly re-intensifying// Bay of Bengfal: Invest 98B Tropical Cyclone Formation alert//Atlantic:18L(SAM) peaking again at CAT 4,28/09utc

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. HOWEVER THE FORECAST HAS BEEN TRUNCATED TO 96 HOURS DUE TO EXTRA-TROPICAL TRANSITION. FORECAST DISCUSSION: THE MAJORITY OF GLOBAL MODEL FIELDS AND JMA UPPER-LEVEL ANALYSIS CHARTS INDICATE THAT THE BLOCKING RIDGE TO THE NORTH HAS ERODED AND RETREATED WESTWARD, AND THUS THE SUBTROPICAL RIDGE(STR) TO THE SOUTHEAST HAS BECOME THE DOMINANT STEERING MECHANISM. THUS, TY 20W HAS STARTED MOVING NORTHWEST AT A FAIR CLIP OVER THE PAST SIX HOURS. IT IS FORECAST TO CONTINUE TO ACCELERATE, SLOWLY AT FIRST, THEN AT A GRADUALLY INCREASING PACE, THROUGH THE NEXT 24 TO 36 HOURS. AS THE RIDGE TO THE EAST REORIENTS TO A NORTH-SOUTH AXIS, TY 20W WILL IN RESPONSE TURN NORTHWARD. THE SYSTEM THEN TURNS NORTHEAST AND ACCELERATES SHARPLY AFTER 36H AHEAD OF A MID-LATITUDE TROUGH RAPIDLY APPROACHING FROM THE WEST. A SURFACE LOW AND COLD FRONT ASSOCIATED WITH THIS MID-LATITUDE SYSTEM WILL DRAG ACROSS THE SEA OF JAPAN AND LIE ROUGHLY ALONG CENTRAL HONSHU BY 48H. BY 72H, TY 20W WILL APPROACH AND BEGIN INTERACTING WITH THIS BAROCLINIC ZONE AT THE SURFACE, AND START TO BECOME ABSORBED UNDER THE ASSOCIATED UPPER-LEVEL TROUGH, MARKING THE START OF EXTRA-TROPICAL TRANSITION (ETT). BY 84H THE SYSTEM SHOWS MARKED THERMAL ADVECTION WITH STRONG, COLD, DRY, NORTHWESTERLY WINDS PUSHING SOUTH FROM HONSHU AND WRAPPING INTO THE CORE OF THE SYSTEM. THE ETT PROCESS IS FORECAST TO BE COMPLETE BY 96H WITH THE SYSTEM DEVELOPING WELL-DEFINED COLD AND WARM FRONTS AND EMBEDDED UNDER A 500 MB LOW HEIGHT CENTER. WHILE THE TRACK IS FORECAST TO REMAIN OFFSHORE AND BE UNDERGOING ETT AS IT PASSES YOKOSUKA, STRONG GALE FORCE WINDS CAN BE EXPECTED OVER EASTERN HONSHU, PARTICULARLY AS THE SYSTEM PASSES AND THE STRONG GRADIENT-INDUCED WINDS BETWEEN TY 20W AND THE TRANSIENT HIGH PRESSURE SYSTEM MOVING IN BEHIND THE SYSTEM DEVELOP OVER EAST-CENTRAL HONSHU.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TY 20W SEEMS TO STILL BE STRUGGLING TO REINTENISFY AFTER BEING KNOCKED LOW BY THE RECENT EYEWALL REPLACEMENT CYCLE (ERC) AND THE EFFECTS OF UPWELLING. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAGGED, ROUGHLY 55 KM WIDE EYE, THOUGH BOTH THE SUBJECTIVE AND OBJECTIVE FIXES ARE BEGINNING TO SCATTER AS THEY STRUGGLE TO LOCATE A PRECISE CENTER. A PICTURESQUE 280409Z AMSR2 89GHZ MICROWAVE IMAGE SHOWED AN INNER BAND OF WEAK CONVECTION IN THE MIDDLE OF A QUITE LARGE OUTER BAND OF MORE SIGNIFICANT CONVECTION. LATER ENHANCED INFRARED IMAGERY SHOWS DEEP CONVECTION AND VERTICAL HOT TOWERS FLARING UP ON THE UPSHEAR (SOUTHWEST) SIDE OF THIS OUTER BAND AND WRAPPING CLOSER TO THE CORE, POSSIBLY INDICATING THAT FINALLY, THE CORE MAY START CONSTRICTING ONCE MORE AND START THE LONG-AWAITED REINTENSIFICATION. THE INITIAL POSITION, DUE TO THE RAGGED NATURE OF THE EYE, IS ASSESSED WITH ONLY MEDIUM CONFIDENCE. THE INITIAL INTENSITY REMAINS ASSESSED AT 95 KNOTS/CAT 2 WITH MEDIUM CONFIDENCE JUST SLIGHTLY BELOW THE ADT AND SATCON AND AT THE MEDIAN OF THE AGENCY CURRENT INTENSITY ESTIMATES, THOUGH THE AGENCY DATA-T NUMBERS WERE FAR LOWER, WITH PGTW AND KNES AT T4.5. THE SYSTEM IS NOW MOVING NORTHWEST AT ABOUT 15 KM/H, TAKING IT OVER A BETTER OCEANOGRAPHIC ENVIRONMENT AND AWAY FROM THE COLD POOL. OTHERWISE THE ENVIRONMENT IS VERY FAVORABLE, WITH LOW SHEAR, AND ROBUST RADIAL OUTFLOW. THE INITIAL WIND RADII HAVE BEEN ADJUSTED ABOUT 20 PERCENT LARGER BASED ON A THE AMSR2 WINDSPEED PRODUCT FROM 280409Z.

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD CROSS-TRACK AGREEMENT THROUGH THE FORECAST PERIOD, WITH MINIMAL SPREAD OF 120 KM AT 48H, INCREASING TO 240 KM AT 96H. ALONG-TRACK SPREAD UNSURPRISINGLY INCREASES STEADILY AFTER 48H, TO 410 KM BY 120H. THE JTWC TRACK REMAINS CONSISTENT WITH THE PRIOR FORECAST WITH HIGH CONFIDENCE THROUGH THE DURATION. THE BULK OF THE INTENSITY GUIDANCE IS IN FAIRLY GOOD AGREEMENT, THOUGH THE COAMPS-TC FAMILY ARE DISSENTING, AND SHOWING STEADY WEAKENING FROM 00H. THE REMAINDER OF THE GUIDANCE SUPPORTS THE SHAPE OF THE INTENSITY CURVE IT SHOULD BE NOTED THAT THE RAPID INTENSIFICATION PREDICTION AID (RIPA) HAS BEEN TRIGGERED FOR THE SECOND CONSECUTIVE RUN, INDICATING A NEAR-TERM RI TO 135 KNOTS/CAT 4 BY 24H. AT THIS POINT, WHILE THE AID IS TRIGGERING, THE CONSTITUENTS OF IT, INCLUDING THE MID-LEVEL HUMIDITY, SST POTENTIAL AND 200 MB DIVERGENCE ARE ALL NEUTRAL OR UNFAVORABLE FOR RI. THUS WHILE THE SYSTEM IS EXPECTED TO INTENSIFY, IT IS NOT EXPECTED TO RI AT THIS TIME. THE JTWC FORECAST TRACES THE INTENSITY CURVE, BUT SITS ABOUT 10 KNOTS HIGHER THAN THE CONSENSUS MEAN AND ABOVE ALL THE GUIDANCE THROUGH 48H, THEN CLOSELY TRACKS THE MEAN THEREAFTER, WITH MEDIUM CONFIDENCE.

28/0815UTC.

THE AREA OF CONVECTION (INVEST 91W) HAS PERSISTED NEAR 21.3N 153.2E, APPROXIMATELY 1470 KM EAST-SOUTHEAST OF IWO TO. MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 280650Z SSMIS 89GHZ MICROWAVE IMAGE DEPICT PERSISTENT CONVECTION OFFSET TO THE SOUTHEASTERN PERIPHERY OF AN EXPOSED LOW LEVEL CIRCULATION (LLC). A 272143Z METOP-A ASCAT PASS SHOWS HIGHER WINDS IN THE EASTERN HEMISPHERE OF THE ELONGATED LLC. ENVIRONMENTAL ANALYSIS INDICATES GENERALLY FAVORABLE CONDITIONS FOR DEVELOPMENT, WITH GOOD EQUATORWARD OUTFLOW AND WARM (30C) SEA SURFACE TEMPERATURES (SST) AND LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS). NUMERICAL MODELS AGREE THAT 91W WILL TRACK NORTH-NORTHEAST OVER THE NEXT SEVERAL DAYS, BUT DISAGREE REGARDING INTENSIFICATION, WITH NAVGEM SHOWING INTENSIFICATION BUT ECMWF AND JMA REMAINING BELOW WARNING CRITERIA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1010 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.

THE AREA OF CONVECTION (INVEST 98B) PREVIOUSLY LOCATED NEAR 21.3N 89.0E IS NOW LOCATED NEAR 21.3N 88.9E, APPROXIMATELY 147 KM SOUTH-SOUTHEAST OF KOLKATA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT INVEST 98B CONTINUES TO RAPIDLY CONSOLIDATE, WITH BANDS OF DEEP CONVECTION NOW WRAPPING INTO A WELL- DEFINED CENTER JUST OFFSHORE SOUTH OF KOLKATA, INDIA. ANIMATED RADAR DATA FROM INDIA INDICATES THE PRESENCE OF A WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH MODERATE TO STRONG CONVECTIVE BANDS, PARTICULARLY ON THE SOUTHEAST SIDE, WRAPPING INTO AND AROUND THE LLCC. SIMILARLY AT 280726Z AMSR2 89 GHZ MICROWAVE IMAGE SHOWS DEVELOPMENTAL BANDING WRAPPING INTO THE CENTER DEFINED BY A LOW EMISSIVITY REGION. A PREVIOUS 280246Z ASCAT-B AND 280314Z ASCAT-C PASS INDICATED 30-35 KNOT WINDS WITH SOME HIGHER WINDS UNDER DEEP CONVECTION IN THE EASTERN SEMICIRCLE, THOUGH WINDS IN THE REMAINDER OF THE CIRCULATION WERE 25 KNOTS OR LESS. THE ENVIRONMENT IS FAVORABLE FOR DEVELOPMENT, WITH AN ANTICYCLONE ALOFT JUST TO THE NORTHEAST PROVIDING GOOD RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR. SSTS REMAIN VERY WARM. WHILE THE SYSTEM IS CURRENTLY MOVING ONSHORE, IT WILL DO SO OVER A REGION OF SWAMPY GROUND IN A RIVER DELTA. THUS INTENSIFICATION OVER LAND IS A DISTINCT POSSIBILITY. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 34 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO HIGH.

HOURLY LOOP(5H). INVEST 98B.

INVEST 98B. NUMERICAL MODEL GUIDANCE IS CURRENTLY LIMITED, BUT GENERALLY AGREES ON SLOW BUT STEADY NORTHWEST MOVEMENT OVER THE NEXT 24 HOURS.

28/00UTC.

CURRENT INTENSITY IS 115KNOTS/CAT 4 AND IS FORECAST TO PEAK AT 120KNOTS BY 28/18UTC.

HU 18L(SAM). TRACK AND INTENSITY GUIDANCE.

HU 18L(SAM). 28/10UTC. EARLY DAILIGHT IMAGERY.

28/0915UTC.