12W(YAGI) reached Super Typhoon Intensity now approaching HAINAN island// TD 13W// INVEST 94W// 0509utc

JTWC IS ISSUING 6HOURLY WARNINGS ON 12W AND 13W. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON BOTH SYSTEMS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: AFTER AN IMPRESSIVE PERIOD OF EXTREMELY RAPID INTENSIFICATION, TYPHOON 12W HAS WEAKENED WHILE UNDERGOING AN EYEWALL REPLACEMENT CYCLE (ERC) AS PREDICTED BY THE CIMSS M-PERC PRODUCT. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 15NM ROUND EYE, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. EIR IMAGERY, HOWEVER, DOES SHOW A CLEAR WEAKENING TREND WITH EROSION OF THE EYEWALL OVER THE NORTHWESTERN QUADRANT AND WARMING CLOUD TOP TEMPERATURES. A 050546Z ATMS 88.2GHZ MICROWAVE IMAGE REVEALS A COMPACT EYEWALL WITH A BREAK IN THE EYEWALL OVER THE NORTHWESTERN QUADRANT, WITH FRAGMENTED SPIRAL BANDING. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR THUS, THE CURRENT WEAKENING TREND IS SOLELY ATTRIBUTED TO THE ERC. THE INITIAL INTENSITY OF 125 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY CURRENT INTENSITY ESTIMATES, WITH OBJECTIVE ESTIMATES RANGING FROM 117 TO 124 KNOTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TYPHOON 12W PEAKED AT ABOUT 135-140 KNOTS NEAR 042100Z AS REFLECTED IN EARLIER SAR DATA BUT HAS SUBSEQUENTLY WEAKENED DUE TO THE ONGOING ERC. WHILE ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE OVER THE NEXT 12 HOURS, SOME RE-INTENSIFICATION IS POSSIBLE AFTER THE ERC COMPLETES. AFTER TAU 12, THE SYSTEM WILL TRACK WESTWARD APPROACHING HAINAN ISLAND, WITH A MORE PRONOUNCED WEAKENING TREND DUE TO INTERACTION WITH LAND. AFTER TAU 24, RAPID WEAKENING WILL OCCUR AS THE SYSTEM TRACKS OVER SOUTHERN CHINA AND NORTHERN VIETNAM, WITH LANDFALL EXPECTED NEAR TAU 48. AS THE SYSTEM TRACKS INTO THE RUGGED TERRAIN OF NORTHERN VIETNAM, IT WILL DISSIPATE BY TAU 72.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE USED IN THE JTWC CONSENSUS (CONW) REMAINS IN TIGHT AGREEMENT WITH A 45-50NM CROSS-TRACK SPREAD FROM TAU 36 TO TAU 48. PROBABILISTIC GUIDANCE FROM THE ECMWF (EPS) AND GFS (GEFS) ENSEMBLES ALSO REMAINS IN TIGHT AGREEMENT SUPPORTING THE JTWC TRACK FORECAST WITH HIGH CONFIDENCE. RELIABLE INTENSITY GUIDANCE IS ALSO IN VERY GOOD AGREEMENT SUPPORTING THE RAPID WEAKENING PHASE EXPECTED AFTER TAU 24.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL CLUSTER OF FLARING CONVECTION SHEARED TO THE SOUTH OF THE LLCC, WHICH ACCOUNTS FOR THE RECENT FULL-EXPOSURE OF THE LLCC. VIGOROUS EQUATORWARD OUTFLOW WITH TRANSVERSE BANDING AROUND THE EASTERN AND SOUTHERN PERIPHERIES AIDED IN THE SYSTEM REACHING A PEAK INTENSITY OF 35 KTS AT 050000Z; HOWEVER, THE INTENSITY WEAKENED TO 30 KTS AT 050600Z ONCE THE SYSTEM DECOUPLED. TD 13W IS LOCATED UNDERNEATH A TUTT CELL AND IMMEDIATELY ADJACENT TO AN EXTENSIVE AREA OF DRY AIR AND SUBSIDENCE TO THE WEST OF ITS CURRENT POSITION AND FORECAST TRACK. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANIMATED VISIBLE SATELLITE IMAGERY SHOWING A FULLY EXPOSED LLCC. THE INITIAL INTENSITY OF 30 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON SUBJECTIVE AGENCY DVORAK ESTIMATES IN GOOD AGREEMENT AND RECENT SCATTEROMETRY WINDSPEEDS RANGING FROM 25-35 KTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 13W HAS A FEW ADVANTAGES IN THE SHORT TERM, INCLUDING THE VIGOROUS EQUATORWARD OUTFLOW MENTIONED ABOVE, A WELL-WRAPPED LOW LEVEL CLOUD SYSTEM, AND WARM SSTS OF 27-28C THROUGHOUT THE FORECAST PERIOD. ALTHOUGH THE INTENSITY WEAKENED SLIGHTLY (BY 5 KTS) AFTER THE SYSTEM BECAME DECOUPLED, THE MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS WILL ALLOW THE INTENSITY TO FLUCTUATE UPWARDS TO 35 KTS AGAIN NEAR TAU 12. HOWEVER, THE POSITION IN RELATION TO THE TUTT CELL OVERHEAD IS PROBLEMATIC DUE TO A WEAK CONVERGENT INFLUENCE ALOFT, WHICH WILL INHIBIT FURTHER DEVELOPMENT. TD 13W HAS A STRONG STEERING INFLUENCE WHICH WILL RECURVE IT AROUND THE STR AXIS AND CAUSE IT TO ACCELERATE NORTHEASTWARD AS IT NEARS THE MID-LATITUDE WESTERLIES. THE ENVIRONMENT WILL BECOME INCREASINGLY HOSTILE WITH UNFAVORABLE VWS (30-34 KTS) BY TAU 24 AND BEYOND. BY TAU 36, THE SYSTEM WILL VENTURE INTO MID-LATITUDE TERRITORIES WHERE A STRONG SHARED ENERGY JET MAX EXISTS POLEWARD. A BAROCLINIC INFLUENCE IN THE HIGHER LATITUDES WILL LEAD TO THE EXTRATROPICAL TRANSITION OF TD 13W BY TAU 48.

MODEL DISCUSSION: THE DYNAMICAL MODEL GUIDANCE REMAINS CONSISTENTLY IN VERY TIGHT AGREEMENT FOR THE TRACK OF TD 13W, THEREFORE THE JTWC TRACK FORECAST ALIGNS CLOSELY WITH THE CONSENSUS MEAN. NUMERICAL MODEL GUIDANCE IS ALSO IN GOOD AGREEMENT CONCERNING A GRADUAL DECREASE IN THE INTENSITY, BUT WHEN ACCOUNTING FOR THE OVERALL PACE OF THE SYSTEM, THE JTWC FORECAST IS HEDGED AT OR ABOVE THE INTENSITY CONSENSUS. CONFIDENCE IS HIGH FOR BOTH THE JTWC TRACK AND INTENSITY FORECASTS.