14W(MUIFA):over the Yellow Sea by 24h//15W(MERBOK): ETT with Hurricane force winds//16W(NANMADOL):up to CAT4 within 48h//1509utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 14W(MUIFA)AND 16W(NANMADOL). 3HOURLY SATELLITE BULLETINS ARE STILL ISSUED ON 15W(MERBOK).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM IS STRIPPED OF DEEP CENTRAL CONVECTION AS IT TRACKED OVER THE COASTAL AREAS OF NORTHEAST CHINA EXPOSING A RAGGED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC THAT MATCHED WITH A LLCC IN A COMPOSITE RADAR LOOP. THE INITIAL INTENSITY OF 45KTS IS EXTRAPOLATED FROM NUMEROUS NEARBY SURFACE WIND AND SEA LEVEL PRESSURE OBSERVATIONS AND CONSISTENT WITH AGENCY AND AUTOMATED DVORAK ESTIMATES THAT SHOW A RAPID WEAKENING TREND. ANALYSIS INDICATES AN UNFAVORABLE ENVIRONMENT WITH MODERATE TO HIGH VWS, FRICTIONAL EFFECTS OF LAND INTERACTION, AND COOLING SSTS IN THE YELLOW SEA.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS MUIFA WILL CONTINUE NORTHWARD IN THE EAST CHINA SEA AND MAKE ANOTHER LANDFALL ON SHANDONG BANDAO PENINSULA, CREST THE STR AXIS, AND AFTER TAU 12, ACCELERATE NORTHEASTWARD VIA THE YELLOW SEA AND MAKE A FINAL LANDFALL ON POHAI PENINSULA JUST BEFORE TAU 24. THE UNFAVORABLE CONDITIONS WILL CONTINUE TO RAPIDLY ERODE THE SYSTEM LEADING TO DISSIPATION BY TAU 36, LIKELY SOONER, AS IT DRAGS FURTHER INLAND INTO NORTHEASTERN CHINA.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST. THERE IS ONLY MEDIUM CONFIDENCE IN THE INTENSITY FORECAST DUE TO THE UNCERTAINTIES OF LAND INTERACTION LEADING TO A POSSIBLE EARLY DISSIPATION.

REMARKS: 150300Z POSITION NEAR 38.3N 165.5E. 15SEP22. TYPHOON 15W (MERBOK), LOCATED APPROXIMATELY 1050 NM NORTH OF WAKE ISLAND, HAS TRACKED NORTH-NORTHEASTWARD AT 33 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND WATER VAPOR IMAGERY SHOW THAT WHILE TY 15W RETAINS A WELL DEFINED LOW LEVEL CIRCULATION CENTER (LLCC), THE CONVECTIVE SIGNATURE IS BEGINNING TO ELONGATE AND ERODE AS THE SYSTEM INTERACTS WITH A FRONT BEARING DOWN FROM THE NORTHWEST AND STRONG UPPER-LEVEL FLOW FROM THE SOUTHWEST. THE IMAGERY ALSO SHOWS A STRONG UPPER-LEVEL LOW AND ACCOMPANYING SURFACE FEATURE, LOCATED APPROXIMATELY 450NM TO THE NORTHWEST, MOVING RAPIDLY SOUTHEASTWARD TOWARDS A RENDEZVOUS WITH TY 15W. THE SYSTEM HAS STARTED EXTRATROPICAL TRANSITION (ETT) AS IT HAS NOW MOVED UNDER THE RIGHT REAR REGION OF A STRONG 100-PLUS KNOT JET MAX AND IS QUICKLY DEVELOPING FRONTAL CHARACTERISTICS DUE TO STRONG LOW-LEVEL TEMPERATURE ADVECTION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE, WHILE THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, IN LINE WITH THE SUBJECTIVE AND OBJECTIVE FIX DATA. EVEN WHILE THE SYSTEM HAS BEGUN ETT, THE VERY STRONG BAROCLINIC FORCING AND PRESENCE OF A STING JET IN THE LOWER LEVELS, MEANS THAT IT WILL MAINTAIN INTENSITY AS A MINIMAL TYPHOON, WITH GUSTS UP TO OR EXCEEDING 80 KNOTS, PARTICULARLY IN THE REGION OF THE STING JET, THROUGH AT LEAST THE NEXT 12 TO 18 HOURS BEFORE FINALLY BEGINNING TO WEAKEN SLIGHTLY AS IT APPROACHES THE WESTERN ALEUTIANS. ETT WILL BE VERY RAPID IN THIS SCENARIO, AS THE SYSTEM IS SCREAMING TO THE NORTH AT OVER 35 KNOTS AND THE SYSTEM WILL TRANSITION TO A HURRICANE FORCE EXTRATROPICAL LOW, WITH A DRAMATICALLY EXPANDING WIND FIELD, WITHIN THE NEXT 12 HOURS. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 150000Z IS 35 FEET.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A LARGE SYSTEM WITH EXTENSIVE FEEDER BANDS TRAILING TO THE SOUTH ALL THE WAY TO THE PHILIPPINES. THE CENTRAL CONVECTION HAS BECOME MORE CONSOLIDATED AND HAS DEVELOPED A RAGGED, FORMATIVE EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE FORMATIVE EYE FEATURE IN THE MSI LOOP. THE INITIAL INTENSITY OF 65KTS IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE UPGRADE TO TYPHOON INTENSITY. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW VWS AND STRONG OUTFLOW OVER WARM SST.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY NANMADOL WILL CONTINUE WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE NORTH. AFTER TAU 48, IT WILL TURN MORE NORTHWESTWARD THEN AFTER TAU 72, WILL CREST THE STR AXIS AND RECURVE NORTHEASTWARD, MAKE LANDFALL OVER KYUSHU, JAPAN, NEAR SASEBO BY TAU 96. AFTERWARD, TY 16W WILL ACCELERATE NORTHEASTWARD AND BY TAU 12O WILL BE IN THE SEA OF JAPAN (SOJ) JUST OFF THE COAST OF HONSHU. THE FAVORABLE CONDITIONS WILL FUEL A GRADUAL THEN RAPID INTENSIFICATION TO A PEAK OF 120KTS BY TAU 48 WITH THE ADDITION OF A POLEWARD OUTFLOW CHANNEL. AFTERWARD, INCREASING VWS, LAND INTERACTION, THEN COOLING SST IN THE SOJ WILL GRADUALLY ERODE THE SYSTEM. BY TAU 120, THE SYSTEM WILL BE REDUCED TO 55KTS AS IT ENTERS THE BAROCLINIC ZONE AND BEGINS EXTRA-TROPICAL TRANSITION.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT UP TO TAU 72 WITH A GRADUAL AND EVEN SPREAD TO 130NM. AFTERWARD, THE SPREAD INCREASES TO 400NM+ AT TAU 120 WITH NVGM THE ERRATIC OUTLIER TO THE LEFT OF THE MAIN PACK IN THE MID-POTION AND THEN TO THE RIGHT IN THE EXTENDED PORTION OF THE FORECAST. THERE IS ALSO SIGNIFICANT ALONG TRACK VARIATIONS IN THE MODELS BEYOND TAU 72. IN VIEW OF THIS, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72 THEN LOW CONFIDENCE AFTERWARD. THERE IS MEDIUM CONFIDENCE IN THE INTENSITY FORECAST UP TO TAU 72 WHERE THERE IS SOME VARIABILITY IN THE PEAK INTENSITY, THEN LOW CONFIDENCE AFTER TAU 72 DUE TO THE LARGE SPREAD AND VARIATIONS IN THE SPEEDS THAT DIRECTLY AFFECT THE FORECAST INTENSITIES.