TY 19W(CHANTHU). WARNING 29 ISSUED AT 13/09UTC.SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY 19W HAS CONTINUED TO TRACK RATHER QUICKLY POLEWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE OVER THE PAST SIX HOURS, THOUGH IS SHOWING SOME SIGNS OF SLOWING DOWN AFTER THE 0600Z HOUR. A BUILDING RIDGE TO THE WEST OVER EAST-CENTRAL CHINA IS EXPECTED TO EXTEND EAST ACROSS THE SHANDONG PENINSULA INTO THE YELLOW SEA AND EFFECTIVELY BLOCK FURTHER POLEWARD MOVEMENT AFTER 12H. ONCE THIS RIDGE IS IN PLACE, TY 19W IS FORECAST TO REMAIN QUASI-STATIONARY OR DRIFT SLOWLY EASTWARD IN A COMPETING STEERING FLOW BETWEEN THE RIDGE TO THE WEST AND THE LARGE STR EAST-SOUTHEAST OF JAPAN. WHILE VERTICAL WIND SHEAR(VWS) IS FORECAST TO DECREASE AFTER 12H, THE QUASI-STATIONARY MOTION OVER RELATIVELY COOL AND LOW OCEAN HEAT CONTENT WATERS, COMBINED WITH A REDUCTION IN OUTFLOW ALOFT, WILL RESULT IN STEADY WEAKENING TO 40 KNOTS BY 72H. AFTER 48H, AN APPROACHING MID-LATITUDE TROUGH WILL ERODE THE WESTERN RIDGE AND BY 72H WILL EJECT TY 19W OUT OF THE WEAK STEERING FLOW AND ACCELERATE NORTHEASTWARD. THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY 96H AS IT BEGINS TO INTERACT WITH THE BAROCLINIC ZONE. AS THE SYSTEM ACCELERATES NORTHEAST ALONG THE SOUTHERN COAST OF KOREA, IT WILL INCREASE SLIGHTLY IN INTENSITY AS ROBUST POLEWARD OUTFLOW OFFSETS INCREASING VWS. BY 120H THE SYSTEM WILL COMPLETE ETT AS IT MOVES UNDER THE 200MB JET AND DEVELOPS FRONTAL CHARACTERISTICS.
TY 19W(CHANTHU). SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TY 19W CONTINUES TO RAPIDLY WEAKEN AS IT TRACKS NORTHWARD TO THE EAST OF SHANGHAI. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT CORE OF MODERATE CONVECTIVE ACTIVITY SURROUNDED BY A MOAT OF WEAK CONVECTION AND SPIRAL BANDS OF WEAK CONVECTION AROUND THE PERIPHERY OF THE SYSTEM. A 130455Z AMSR2 89GHZ MICROWAVE IMAGE SHOWED MODERATE CONVECTION ON THE NORTHERN HEMISPHERE OF THE LOW LEVEL CIRCULATION CENTER, WITH MINIMAL CONVECTION TO THE SOUTH. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN EXTRAPOLATION OF THE WEAK LLCC EVIDENT IN THE AMSR2 IMAGERY SUPPORTED BY ANALYSIS OF ANIMATED RADAR DATA. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE AT 75 KNOTS/CAT 1, HEDGED BELOW THE AGENCY CURRENT INTENSITY ESTIMATES OF 90 KNOTS IN LIGHT OF THE MUCH LOWER DATA-T NUMBERS RANGING BETWEEN T4.0-4.5 (65-75 KTS). ADDITIONALLY, THE AMSR2 WINDSPEED PRODUCT INDICATED MAXIMUM WINDS OF 75 KNOTS. TY 19W IS MOVING THROUGH A MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE TO STRONG (20-25 KTS) VERTICAL WIND SHEAR OFFSET BY ROBUST POLEWARD OUTFLOW. SSTS HAVE COOLED TO 27C BUT STILL REMAIN WARM ENOUGH TO SUSTAIN THE TROPICAL CYCLONE.
TY 19W(CHANTHU).MICROWAVE IMAGE SHOWED MODERATE CONVECTION ON THE NORTHERN HEMISPHERE OF THE LOW LEVEL CIRCULATION CENTER, WITH MINIMAL CONVECTION TO THE SOUTH.
TY 19W(CHANTHU). MODEL DISCUSSION: THOUGH ALL MODEL TRACKERS AGREE THAT THE SYSTEM WILL ENTER THE WEAK STEERING PATTERN AND BECOME QUASI-STATIONARY, THEY SHOW CONSIDERABLE UNCERTAINTY IN REGARDS TO THE DIRECTION OF THE DRIFT, WITH THE ECMWF AND JGSM DRIFTING TOWARDS SHANGHAI AND THE REMAINDER SHOWING A DRIFT EAST FOLLOWED BY A CLOCKWISE LOOP THROUGH 72H. THE JTWC FORECAST LIES ON THE NORTHERN SIDE OF THE BULK OF THE EASTERN GROUPING OF TRACKERS WITH LOW CONFIDENCE THROUGH 72H. ALL GUIDANCE MEMBERS AGREE ON THE EJECTION OF THE SYSTEM TO THE NORTHEAST BY 72H, AND ARE IN REMARKABLY GOOD CROSS-TRACK AGREEMENT THROUGH 120H. THE JTWC FORECAST TRACK LIES JUST NORTH AND SLIGHTLY SLOWER THAN THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE. THE MAJORITY OF THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT, THOUGH THERE REMAINS A FAIR AMOUNT OF UNCERTAINTY IN REGARDS TO THE PACE OF THE WEAKENING AND THUS THE STARTING INTENSITY IN THE EXTENDED RANGE FORECAST, LENDING MEDIUM TO LOW CONFIDENCE IN THE INTENSITY FORECAST.
19W(CHANTHU). HWRF AT 13/00UTC. INTENSITY GUIDANCE: 83KNOTS AT +0H.
NORTH INDIAN. INVEST 95B. TROPICAL CYCLONE FORMATION ALERT CANCELLED AT 13/06UTC. REMARKS: THIS CANCELS REF A (WTIO21 PGTW 120700). AN AREA OF CONVECTION HAS PERSISTED NEAR 20.4N 86.3E, APPROXIMATELY 315 KM SOUTHWEST OF KOLKATA. ANIMATED MULTISPECTRAL IMAGERY AND A 0257Z METOP-A PASS DEPICTS OFFSHORE LOW LEVEL WINDS PARALLELING THE INDIAN COAST. SURFACE OBSERVATIONS FROM THE REGION PROVIDE ADDITIONAL SUPPORT TO THE FACT THAT THE LOW LEVEL CIRCULATION CENTER (LLCC) IS OVER LAND AT THIS TIME. WINDS OFFSHORE REMAIN IN THE 28-33 KNOT RANGE, AND SURFACE PRESSURES SUPPORT A 30 KNOT INTENSITY. ALTHOUGH THE SURFACE WINDS ARE RELATIVELY STRONG OFFSHORE, AND ENVIRONMENTAL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT, WITH LOW (10KT) VERTICAL WIND SHEAR (VWS) AND GOOD EQUATORWARD OUTFLOW, 95B HAS MADE LANDFALL AND THEREFORE IS NOT EXPECTED TO INTENSIFY FURTHER.MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28-33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 993 MB. INVEST 95B HAS MADE LANDFALL AND IS NO LONGER CONSIDERED SUSPECT FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS.
INVEST 95B. GLOBAL MODELS ARE GOOD IN AGREEMENT, THAT INVEST 95B HAS MADE LANDFALL ON THE NORTHEASTERN COAST OF INDIA AND WILL CONTINUE TO TRACK NORTHWESTWARD FURTHER INLAND WHILE SLOWLY DISSIPATING.
13/00UTC.
ATLANTIC. TS 14L(NICHOLAS). WARNING 5 ISSUED AT 13/09UTC. CURRENT INTENSITY IS 50KNOTS ANS IS FORECAST TO PEAK AT 60KNOTS BY 13/18UTC.
TS 14L(NICHOLAS). GUIDANCE.
