South China Sea: TS 04W forecast to reach Typhoon intensity by 24h//HU 03E(CALVIN) peaked at CAT 3 US// SS 05L(DON)//1506utc

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

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A LARGE SYSTEM (440NM+ ACROSS) IN THE SOUTH CHINA SEA (SCS) THAT CONTINUED TO CONSOLIDATE AND HAS INTENSIFIED INTO A TROPICAL STORM WITH ITS BROAD RAIN BANDS TRAILING SOUTHWESTWARD ALL THE WAY TO BORNEO. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A RAGGED BUT DEFINED LLC FEATURE IN THE 142155Z SSMIS, THE INTENSITY IS ASSESSED WITH HIGH CONFIDENCE FROM THE PGTW AND D-PRINT DVORAK ESTIMATES AND REFLECTS THE 6-HR CONVECTIVE AND WRAP IMPROVEMENTS. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH STRONG POLEWARD OUTFLOW, LOW VWS ALOFT, AND WARM SST IN THE SOUTH CHINA SEA (SCS). THE SYSTEM IS ALSO TAPPING INTO A POLEWARD OUTFLOW CHANNEL EMANATING FROM A TUTT TO THE NORTHWEST, ALSO EVIDENT IN THE EIR LOOP.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 04W WILL CONTINUE TO TRACK GENERALLY WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR, OVER THE WARM SCS, MAKE LANDFALL ON THE LEIZHOU PENINSULA NEAR ZHANJIANG BEFORE TAU 60, AND CROSS THE GULF OF TONKIN BEFORE MAKING A FINAL LANDFALL ALONG THE VIETNAM-CHINA BORDER AFTER TAU 72. THE FAVORABLE ENVIRONMENT WILL FUEL SIGNIFICANT INTENSIFICATION TO A PEAK OF 90KTS AT TAU 48. LAND INTERACTION WITH RUGGED TERRAIN WILL MOSTLY BE RESPONSIBLE FOR THE GRADUAL THEN RAPID EROSION AFTER TAU 48, LEADING TO DISSIPATION BY TAU 120 AS IT TRACKS DEEP INTO THE CHINESE INTERIOR.

MODEL DISCUSSION: THERE IS OVERALL GOOD AGREEMENT AMONG THE NUMERICAL TRACK MODELS WITH AN EVEN AND GRADUAL SPREAD TO A MERE 158NM BY TAU 72. AFTERWARD, THE TRACKERS SIGNIFICANTLY SPREAD OUT TO 670NM+ BY TAU 120, AN INDICATION OF A WEAK VORTEX, LENDING MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS UP TO TAU 72, THEN LOW CONFIDENCE AFTERWARD.