04W(PRAPIROON) landfall within 24h//05W(GAEMI) intensifying and peaking by 48h//INVEST 94W// 2209utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 04W AND 05W

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM 04W (PRAPIROON) AS HAVING A WELL-DEFINED AND SYMMETRIC CDO OVER THE CENTER OF THE OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). ENVIRONMENTAL ANALYSIS INDICATES THAT 04W IS CURRENTLY IN A FAVORABLE ENVIRONMENT FOR INTENSIFICATION CHARACTERIZED BY MODERATE RADIAL OUTFLOW ALOFT, LOW VERTICAL WIND SHEAR, AND VERY WARM (30-31 C) SEA SURFACE TEMPERATURES. HOWEVER, AS 04W APPROACHES LAND, THE ENVIRONMENT WILL VERY RAPIDLY WORSEN. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 220518Z GMI 37 GHZ MICROWAVE IMAGE SHOWING A DEFINED MICROWAVE EYE FEATURE. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 04W IS FORECAST TO CONTINUE TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE STR FOR THE REMAINDER OF THE FORECAST PERIOD. LANDFALL IS FORECAST TO OCCUR BETWEEN TAU 12 AND 24 ABOUT 100 NM EAST OF HANOI, VIETNAM. AFTER MAKING LANDFALL 04W IS EXPECTED TO QUICKLY WEAKEN, AND AROUND TAU 36, MAKE A SOUTHWESTWARD TURN AS THE LOWER-LEVEL STEERING PATTERN COMES INTO EFFECT, WITH DISSIPATION FORECAST TO OCCUR NEAR TAU 48. THE CURRENT 55 KNOT INTENSITY IS FORECAST TO CONTINUE FOR THE NEXT 12 HOURS AS THE VERY WARM AND HIGH OHC PROVIDE AMPLE ENERGY TO THE SYSTEM. IF THE TRACK SPEED SLOWS TOO MUCH, THERE MAY BE ENOUGH TIME FOR FURTHER INTENSIFICATION, BUT IF TRACK SPEEDS ARE MAINTAINED THEN THERE WILL NOT BE ENOUGH TIME FOR THE SYSTEM TO TAP INTO THE AVAILABLE ENERGY OF THE ENVIRONMENT BEFORE MAKING LANDFALL.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD AGREEMENT IN THE NEAR TERM WITH A 60 NM CROSS-TRACK SPREAD AT TAU 24. MANY MODELS BECOME ERRATIC AFTERWARDS THOUGH AS THE VORTEX WEAKENS, BUT MOST CALL FOR A WESTWARD TURN WITH VARYING DEGREES. OVERALL, THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE. THE INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH THE EXCEPTION OF HWRF, WHICH HAS A PEAK INTENSITY OF 70 KTS AT TAU 12. THE REST OF CONSENSUS EITHER STARTS A WEAKENING TREND OR MAINTAINS THE 55 KNOT INTENSITY AS 04W CROSSES THE GULF OF TONKIN. THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE DUE IN PART TO THE POSSIBILITY OF INTENSIFICATION IF TRACK SPEEDS SLOW TOO MUCH.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 05W (GAEMI) AS HAVING A SMOOTH CDO OBSCURING THE SOUTHERN SEMICIRCLE OF THE SYSTEM. BANDING FEATURES CAN BE SEEN ALONG THE SOUTHWEST QUADRANT, WRAPPING INTO THE CENTER. VERTICAL WIND SHEAR HAS SHIFTED TO A MORE NORTHERLY DIRECTION AND IS STILL EVIDENT BUT SEEMS TO BE SLIGHTLY WEAKENING AS THE CONVECTION IS NOT BLOWING OFF AS VIGOROUSLY. THE NORTHERN PERIPHERY OF THE LOW-LEVEL CIRCULATION CENTER (LLCC) REMAINS EXPOSED, DUE IN PART TO A TONGUE OF DRY AIR THAT IS PLACED JUST NORTH OF THE LLCC, HINDERING CONVECTIVE DEVELOPMENT AS WELL AS THE SHEAR. ENVIRONMENTAL ANALYSIS INDICATES THAT 05W IS IN A MARGINALLY FAVORABLE ENVIRONMENT FOR INTENSIFICATION CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT, LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND WARM (30-31 C) SEA SURFACE TEMPERATURES. THESE FACTORS ARE OFFSET BY THE PRESENCE OF DRY AIR TO THE NORTH. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A 220523Z AMSR2 36 GHZ MICROWAVE IMAGE REVEALING LOW-LEVEL CLOUDS OUTLINING THE CENTER OF 05W. THE INITIAL INTENSITY OF 55 KTS IS ALSO ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS O5W IS FORECAST TO CONTINUE TRACKING NORTH-NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF A NORTH-SOUTH ORIENTED STR PLACED TO ITS EAST THROUGH TAU 48. AFTER TAU 48, RIDGING EXTENDING ACROSS EASTERN CHINA WILL TAKE OVER AS THE STEERING MECHANISM AND DRIVE 05W WESTWARD THROUGH TAU 96. THE SYSTEM IS FORECAST TO MAKE LANDFALL ALONG THE EASTERN COAST OF CHINA, NORTHWEST OF TAIWAN, JUST AFTER TAU 72. AFTER MAKING LANDFALL, 05W IS EXPECTED TO RAPIDLY WEAKEN AND THE LOW-LEVEL STEERING PATTERN WILL PUSH THE SYSTEM POLEWARD AS IT DISSIPATES. REGARDING THE INTENSITY FORECAST, 05W IS FORECAST TO CONTINUE TO INTENSIFY THROUGH TAU 48 AS VERTICAL WIND SHEAR IS ANTICIPATED TO DROP AND THE DRY AIR TO BE GONE. HIGH SEA SURFACE TEMPERATURES AND OHC ARE GOING TO BE LARGE FACTORS IN THE INTENSIFICATION OF 05W. THE PEAK INTENSITY OF 90 KTS IS FORECAST TO OCCUR AROUND TAU 48, NEAR ISHIGAKIJIMA BEFORE THE WESTWARD TURN IS INITIATED. AFTER TAU 48, VERTICAL WIND SHEAR WILL RISE TO ABOVE 20 KTS AND SEA SURFACE TEMPERATURES WILL DROP, WHICH WILL START THE WEAKENING TREND OF 05W. HOWEVER, AT LANDFALL, 05W IS FORECAST TO STILL BE OF TYPHOON STRENGTH. AFTER LANDFALL, THE SYSTEM WILL DETERIORATE IN RESPONSE TO TERRAIN INTERACTION AND WILL DISSIPATE NEAR THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH A 200 NM CROSS-TRACK SPREAD AT TAU 72, AROUND THE TIME OF LANDFALL. NAVGEM MAKES UP THE SOUTHERNMOST MEMBER, TRACKING THE SYSTEM THROUGH CENTRAL TAIWAN. THE GFS ENSEMBLE MEAN MAKES UP THE NORTHERNMOST MEMBER, TRACKING THE SYSTEM AROUND 60 NM NORTH OF THE COAST OF TAIWAN. THE JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE JUST NORTH OF CONSENSUS, HUGGING THE NORTHERN COAST OF TAIWAN. THE INTENSITY GUIDANCE IS IN RELATIVELY GOOD AGREEMENT WITH THE EXCEPTION OF RAPID INTENSIFICATION AIDS APPEARING. GUIDANCE OTHERWISE AGREES ON A PEAK INTENSITY OF AROUND 70 TO 90 KTS AT TAU 48 BEFORE WEAKENING RATHER QUICKLY. THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE, ALONG THE HIGHER END OF GUIDANCE WITH A PEAK INTENSITY OF 90 KTS.