TS 12W(YAGI) Rapid Intensification possible once over the South China Sea//INVEST 93W// 0209utc

JTWC IS ISSUING 6HOURLY WARNINGS ON 12W. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON 12W, ON THE REMNANTS OF 02A AND ON THE REMNANTS OF 01C

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MSI DEPICTS BROAD, RAGGED OUTFLOW IN THE EQUATORWARD DIRECTION AND TO THE SW, INDICATING THE UPSHEAR SIDE IS TO THE NE. THE LLCC HAD PREVIOUSLY BEEN PARTIALLY EXPOSED BY THE VIGOROUS UPPER LEVEL FLOW, BUT THE LLCC HAS BECOME OBSCURED ONCE AGAIN BY A CDO FEATURE. A SLIGHT EXPANSION OF THE COLDER CLOUD TOPS IN THE CDO IMPLY CONTINUED DEVELOPMENT AS THE SYSTEM BRUSHES UP AGAINST THE COAST OF LUZON. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A RADAR FIX IDENTIFYING THE LLCC JUST OFF THE SE COAST OF LUZON. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A 020139Z ASCAT IMAGE SHOWING A SWATH OF VELOCITY MAXIMA OF 45-47 KTS IN THE SOUTHEAST QUADRANT UNDER CONVECTION. INTENSITY ESTIMATES DMINT, DPRINT, AND SATCON SUPPORT THE ASSESSMENT WITH ESTIMATES RANGING FROM 40-43 KTS, AND AGENCY SUBJECTIVE DVORAK ESTIMATES TARGET AN INITIAL INTENSITY OF BETWEEN 25 AND 35 KTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: THE STR TO THE EAST WILL DRIVE TS 12W (YAGI) INTO LUZON DURING THE NEXT 12-15 HOURS, WHERE THE DOMINANT STEERING INFLUENCE WILL CHANGE HANDS TO THE STR SITUATED OVER EASTERN CHINA. DEVELOPMENT IN THE SHORT-TERM WILL BE IMPEDED BY THE BRIEF TRACK ACROSS LUZON. AFTER THE SYSTEM EMERGES FROM LUZON ON THE NW SIDE NEAR TAU 24, IT WILL FIND A MUCH MORE FAVORABLE ENVIRONMENT FOR DEVELOPMENT. SIGNALS FOR RI ARE PRESENT, GIVEN THE WARM SSTS OF 30-31C, LOW VWS OF LESS THAN 10 KTS, AND MODERATE EXHAUST MECHANISMS IN PLACE. THE TRACK GUIDANCE UNDERSTANDABLY SPREADS AFTER TAU 24, BUT OVERALL THERE IS INCREASING AGREEMENT THAT TS 12W WILL ACCELERATE AND FORGE GENERALLY WESTWARD, EVENTUALLY MAKING LANDFALL ALONG THE SOUTHERN COAST OF CHINA. AFTER AN INITIAL PERIOD OF INTENSIFICATION WITH RI POSSIBLE AFTER TAU 48, TS 12W IS EXPECTED TO REACH PEAK INTENSITY BY TAU 72 IN THE SOUTH CHINA SEA. DEVELOPMENT WILL PLATEAU AFTER TAU 72 AS THE SYSTEM TRACKS OVER LOWER OHC VALUES AND BEGINS TO ENCOUNTER LAND INFLUENCES BY TAU 96, AT WHICH POINT THE SYSTEM WILL WEAKEN.

MODEL DISCUSSION: MESOSCALE MODEL GUIDANCE (HAFS-A AND HWRF) CARRIES A TRACK SIMILAR TO THE JTWC FORECAST, WHICH SLOWS TS 12W AFTER ITS EMERGENCE INTO THE SOUTH CHINA SEA, WHERE POSSIBLE RI COULD OCCUR. THE PEAK INTENSITY FROM HAFS-A AND HWRF OCCURS NEAR TAU 72, WHEREAS GLOBAL MODELS MAINTAIN A SLIGHTLY FASTER TRACK AND ARE SPLIT BETWEEN A TAU 72 AND A TAU 96 PEAK INTENSITY. THE BULK OF THE TRACK GUIDANCE HAS COME INTO BETTER AGREEMENT CONCERNING THE WESTWARD TRACK ACROSS THE SOUTH CHINA SEA AFTER TS 12W EITHER BENDS AROUND THE NE SIDE OR SHALLOWS ITS WESTWARD TURN AND TRACKS ACROSS LUZON. AT TAU 48, THERE IS A 48 NM CROSS-TRACK SPREAD OF THE RELIABLE MODEL GUIDANCE. THE GFS ENSEMBLE (GEFS) SUPPORTS THE WESTWARD TRACK BEYOND TAU 24 WITH ABOUT 70 PERCENT AGREEMENT, AND THE ECMWF ENSEMBLE (EPS) PRESENTS A MUCH TIGHTER AGREEMENT SUPPORTING THE JTWC TRACK WITH MEDIUM CONFIDENCE.