TY 20W(MINDULLE) a powerful CAT 4 once again//Atlantic: Hu 18L(SAM) CAT 4: confirmed by aircraft recon,29/06utc

JTWC IS ISSUING 6HOURLY WARNINGS ON TY 20W. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON 20W,91W AND THE REMNANTS OF TC 03B.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY 20W REMAINS IN A FAVORABLE ENVIRONMENT AS IT ROUNDS THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) CENTERED OVER THE MARIANAS. THE SYSTEM CONTINUES TO EXHIBIT HEALTHY RADIAL OUTFLOW, WITH AN ENHANCED POLEWARD OUTFLOW CHANNEL WRAPPING AROUND THE STR TO THE EAST. TY 20W REMAINS OVER A REGION OF WARM SSTS (29 TO 30C), BUT THE SLOW FORWARD MOTION IS INDUCING SOME UPWELLING, WHICH IS CONSTRAINING THE OTHERWISE FAVORABLE CONDITIONS FOR FURTHER INTENSIFICATION. THE INNER CORE STRUCTURE HAS ALSO IMPROVED SINCE SIX HOURS AGO, WHICH IS INDICATIVE OF A GRADUALLY INTENSIFYING SYSTEM. HOWEVER, SHIPS GUIDANCE AND OTHER MEMBERS OF ICNW HAVE FALLEN OFF DRAMATICALLY SINCE THE LAST CYCLE, SUGGESTING THAT TY 20W IS LIKELY AT OR NEAR ITS PEAK INTENSITY. BY AROUND 24H, THE SYSTEM IS FORECAST TO TURN TOWARD THE NORTHEAST, GRADUALLY WEAKEN, AND ACCELERATE AROUND THE STR AHEAD OF AN APPROACHING MID-LATITUDE TROUGH. UPON INTERACTING WITH THE BAROCLINIC ZONE, EXTRATROPICAL TRANSITION SHOULD BE WELL UNDERWAY BY 72H, WITH EXTRATROPICAL TRANSITION EXPECTED TO BE COMPLETE BY 96H.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION WRAPPING AROUND A LARGE 75 KM DIAMETER EYE. THE INNER CORE OF TY 20W HAS GRADUALLY BECOME BETTER ORGANIZED AND LESS RAGGED OVER THE LAST 6 HOURS, WHICH IS REFLECTED IN THE HIGHER INTENSITY ASSESSMENT OF 115 KNOTS/CAT 4. THE INITIAL INTENSITY IS BASED ON DVORAK ESTIMATES OF T6.0 (PGTW AND RJTD) AND A SATCON OF 118 KNOTS. THE ENVIRONMENT HAS BEEN FAVORABLE FOR INTENSIFICATION, BUT THE EARLIER STRUGGLE OF TY 20W TO CONSOLIDATE ITS INNER CORE STRUCTURE RESULTED IN ONLY GRADUAL INTENSIFICATION. THE EYE REMAINS LARGE, SO CONSERVATION OF ANGULAR MOMENTUM IS RESTRAINING ITS CURRENT INTENSIFICATION RATE ALONGSIDE THE PRESENCE OF UPWELLING DUE TO THE SLOW FORWARD MOTION. GIVEN THE LARGE EYE, THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE.

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN EXCELLENT AGREEMENT, AND BOTH CROSS- AND ALONG-TRACK ERRORS ARE LOW IN THE NEAR TERM. ALONG-TRACK ERRORS INCREASE AT EXTENDED FORECAST DUE TO ACCELERATION INTO THE MID-LATITUDE WESTERLIES, BUT OVERALL CONFIDENCE IN THE TRACK FORECAST IS HIGH THROUGHOUT THE FORECAST PERIOD. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT ON THE OVERALL SCENARIO OF MAINTAINING CURRENT INTENSITY FOR ABOUT 24 HOURS FOLLOWED BY STEADY WEAKENING. THE OVERALL INTENSITY FORECAST CONFIDENCE IS MEDIUM, GIVEN SOME NEAR-TERM UNCERTAINTY WITH RESPECT TO PEAK INTENSITY.

THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR 21.3N 153.2E IS NOW LOCATED NEAR 21.8N 154.8E, APPROXIMATELY 1945 KM SOUTHEAST OF YOKOSUKA, JAPAN. MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 290314Z AMSR2 89GHZ MICROWAVE IMAGE DEPICT FLARING CONVECTION SHEARED TO THE SOUTHEAST OF AN EXPOSED LOW LEVEL CIRCULATION (LLC). ENVIRONMENTAL ANALYSIS INDICATES MARGINAL CONDITIONS FOR DEVELOPMENT, WITH GOOD EQUATORWARD OUTFLOW AND WARM (30C) SEA SURFACE TEMPERATURES (SST) BEING OFFSET BY MODERATE TO STRONG (20-25 KTS) NORTHWESTERLY VERTICAL WIND SHEAR (VWS) FLOWING OUTWARD FROM TY 20W. NUMERICAL MODELS SHOW LITTLE IN THE WAY OF DEVELOPMENT, REMAINING BELOW WARNING CRITERIA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 22 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 REMAINS MEDIUM.

THE AREA OF CONVECTION (INVEST 98B) PREVIOUSLY LOCATED NEAR 21.8N 88.3E, IS NOW LOCATED NEAR 22.8N 87.5E, APPROXIMATELY 540 KM WEST-NORTHWEST OF KOLKATA. INVEST 98B HAS TRACKED OVER LAND AND IS FORECAST TO REMAIN OVER LAND AS IT CONTINUES ON ITS NORTHWESTWARD TRAJECTORY. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. IN VIEW OF THE UNFAVORABLE FORECAST FOR THIS SYSTEM, IT IS NO LONGER CONSIDERED SUSPECT FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS.

AN AREA OF CONVECTION (RMNTS 03B) HAS PERSISTED NEAR 20.3N 76.7E, APPROXIMATELY 130 KM EAST-NORTHEAST OF MUMBAI. THE REMNANTS OF 03B CONTINUE TO TRAVEL WEST ACROSS THE INDIAN SUBCONTINENT THROUGH AN AREA OF LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) AND ROBUST EQUATORWARD OUTFLOW. SURFACE OBSERVATIONS INDICATE WEAK LOW LEVEL TURNING ON THE NORTHEAST SIDE OF AN AREA DEEP CONVECTION. NUMERICAL MODELS ARE IN GOOD AGREEMENT THAT THE REMNANTS OF 03B WILL CONSOLIDATE AND INTENSIFY AS IT MOVES INTO THE NORTH ARABIAN SEA IN THE NEXT FEW DAYS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS LOW.

CURRENT INTENSITY IS 120KNOTS/CAT 4 AND IS FORECAST TO PEAK AT 125KNOTS BY 30/00UTC. NHC points out :"Sam has looked a little less impressive on satellite imagery this afternoon, particularly on the infrared channels where the eye is not very well-defined. However, observations from the Air Force Hurricane Hunters indicate that the hurricane is maintaining category 4 intensity since a blend of the latest flight-level and SFMR-observed surface winds support maintaining 115-kt winds. The aircraft also measured a quite low central pressure of 947 mb on two passes through the eye. Upper-level outflow remains well defined except over the southwest quadrant of the circulation, and several arc clouds are seen emanating from the system over the western semicircle, indicative of some dry mid-level air in the environment. However, this dry air is apparently not significantly affecting the inner core of Sam, given that it has remained a powerful hurricane."

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

FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 100 NM EITHER SIDE OF A LINE FROM 6.8N 21.2W TO 8.3N 26.2W WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 25 TO 30 KNOTS. METSAT IMAGERY AT 281800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 6.8N 21.2W. THE SYSTEM IS MOVING WEST-NORTHWEST AT 8-12 KNOTS. 2. REMARKS: A BROAD AREA OF LOW PRESSURE LOCATED OVER THE FAR EASTERN ATLANTIC, SEVERAL HUNDRED MILES SOUTH-SOUTHEAST OF THE CABO VERDE ISLANDS, IS PRODUCING A LARGE AREA OF SHOWERS AND THUNDERSTORMS. THIS SHOWER ACTIVITY IS GRADUALLY BECOMING BETTER ORGANIZED AND A TROPICAL DEPRESSION IS EXPECTED TO FORM IN THE NEXT 24 HOURS.

29/0645UTC.