WDPN31 PGTW 162100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 10.2N 122.5E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 278 NM SOUTH-SOUTHEAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WESTWARD AT 18 KTS SIGNIFICANT WAVE HEIGHT: 28 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS BROAD AREA OF CONVECTION MOVING THROUGH THE PHILIPPINE ARCHIPELAGO. THERE IS NO CLEAR-CUT CENTER EVIDENT IN THE EIR, AND BY THE 2000Z HOUR, THE CONVECTIVE MASS HAS BECOME INCREASINGLY DISORGANIZED AND FRAGMENTED. A 161719Z AMSR2 89GHZ COLOR COMPOSITE IMAGE REVEALED A WEAK MICROWAVE EYE FEATURE OVER THE SOUTHERN PORTION OF NEGROS ISLAND, WITH STRONG CONVECTIVE BANDS PRIMARILY LIMITED TO THE SOUTHERN HEMISPHERE OF THE ROTATION AND MUCH WEAKER LOW LEVEL BANDS TO THE NORTH AND EAST. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN EXTRAPOLATION OF THE MICROWAVE EYE FEATURE AND THE LACK OF A WELL-DEFINED CENTER IN THE EIR. THE INITIAL INTENSITY IS SET AT WHAT IS LIKELY A BIT GENEROUS 110 KNOTS, WITH LOW CONFIDENCE. AS EXPECTED FOR A WEAKENING SYSTEM CROSSING LAND, DVORAK CURRENT INTENSITY ESTIMATES ARE SPREAD ACROSS A WIDE RANGE FROM T5.0 (RJTD) TO T7.0 (PGTW) WITH THE OBJECTIVE ESTIMATES FALLING ROUGHLY IN THE MIDDLE. OF NOTE THE SATCON HAS RECENTLY DROPPED FROM 140 KNOTS TO 89 KNOTS BY 1740Z, DUE TO A VERY LOW SSMIS ESTIMATE OF 69 KNOTS. THUS THE SATCON IS NOT USED IN THE INITIAL INTENSITY ESTIMATION. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE, WITH WARM SSTS, MODERATE EASTERLY SHEAR AND GOOD WESTWARD AND POLEWARD OUTFLOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T7.0 - 140 KTS RJTD: T5.0 - 90 KTS KNES: T6.0 - 115 KTS CIMSS SATCON: 89 KTS AT 161741Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 20-25 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG WESTWARD OTHER FACTORS: MODERATE POLEWARD OUTFLOW ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: WHILE THE CONVECTIVE SIGNATURE OF TY 28W HAS DEGRADED SIGNIFICANTLY OVER THE PAST FEW HOURS, NOW THAT IT IS MOVING BACK OVER THE RELATIVELY OPEN WATERS OF THE SULU SEA, IT IS EXPECTED TO SLOWLY REORGANIZE. THE SYSTEM IS FORECAST TO TRACK WESTWARD THROUGH TAU 12, CROSSING THE NORTHERN PORTION OF PALAWAN WITHIN THE NEXT 12 HOURS, THEN GRADUALLY TURNING MORE NORTHWESTWARD WITH EACH PASSING HOUR. BY TAU 48, IT WILL TURN SHARPLY POLEWARD AS IT ROUNDS THE STR AS THE RIDGE RETREATS EASTWARD. AS THE SYSTEM DISSIPATES BY TAU 120, IT WILL TURN EAST-SOUTHEASTWARD FOLLOWING THE LOW-LEVEL FLOW PATTERN. AS THE SYSTEM CONTINUES MOVING WESTWARD, AN UPPER-LEVEL ANTICYCLONE IS EXPECTED TO FORM OVER THE SYSTEM, BOTH REDUCING THE VWS AND INCREASING THE AVAILABLE OUTFLOW, WHICH WILL ALSO REACH INTO THE SOUTHERN REACHES OF THE MID-LATITUDE WESTERLIES. PASSAGE OVER PALAWAN IS EXPECTED TO HAVE LITTLE IN THE WAY OF IMPACT ON THE INTENSITY. ONCE IN THE SOUTH CHINA SEA, THE SYSTEM WILL HAVE ABOUT 24 HOURS, WHERE THE IMPROVED OUTFLOW, WARM SSTS AND REDUCED VWS CAN WORK THEIR MAGIC, LEADING TO A PERIOD OF INTENSIFICATION TO A PEAK OF 110 KNOTS BY TAU 36. BY AROUND TAU 48 OR SHORTLY THEREAFTER, THE SYSTEM WILL CROSS THE 26C ISOTHERM AND UPPER-LEVEL WINDS SHIFT TO SOUTHERLY, LEADING TO DRAMATICALLY INCREASED SOUTHERLY SHEAR. BY TAU 72 THE SHEAR WILL DOMINATE THE STRONG OUTFLOW, AND THE SYSTEM WILL BECOME DECAPITATED, EXPOSING THE LOW-LEVEL CIRCULATION AND MARKING THE ONSET OF RAPID WEAKENING. THE SYSTEM WILL FULLY DISSIPATE NO LATER THAN TAU 120 TO THE SOUTHEAST OF HONG KONG. MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH TAU 48, WITH A MINIMAL SPREAD OF ONLY 50NM AT THIS POINT. AS THE SYSTEM RECURVES THE GUIDANCE SPREADS BUT STILL REMAINS IN RELATIVELY GOOD AGREEMENT, WITH SPREAD OF 90NM AT TAU 72 INCREASING TO 120NM AT TAU 120. THE BULK OF THE GUIDANCE IS CONSTRAINED WITHIN A TIGHT ENVELOPE THROUGH THE FORECAST PERIOD, WITH THE NOTABLE EXCEPTION OF GALWEM, WHICH CARRIES THE SYSTEM INTO SOUTHERN CHINA TO THE WEST OF HONG KONG. THE JTWC FORECAST LIES ALONG THE NORTHERN SIDE OF THE ENVELOPE THROUGH TAU 48, THEN ON THE INSIDE OF THE RECURVE TRACK THROUGH TAU 120. CONFIDENCE IS HIGH THROUGH TAU 72, THEN LOW THEREAFTER AS THE RATE OF WEAKENING WILL HAVE A LARGE IMPACT ON THE ULTIMATE TRACK. INTENSITY GUIDANCE IS IN AGREEMENT ON THE OVERALL WEAKENING, INTENSIFYING, WEAKENING TREND BUT DEPICTS FAIRLY LARGE DIFFERENCES IN THE ACTUAL INTENSITIES. THE SHIPS-GFS MARKS THE LOW SIDE OF THE ENVELOPE, BOTTOMING OUT AT 80 KNOTS BY TAU 24, THEN ONLY REINTENSIFYING TO 90KTS BEFORE RAPIDLY WEAKENING. THE COAMPS-TC ON THE OTHER HAND INDICATES WEAKENING TO 100 KNOTS, FOLLOWED BY A PEAK OF 110 KNOTS AND RAPID WEAKENING. THE JTWC FORECAST CLOSELY TRACKS THE COAMPS-TC, ROUGHLY 15 KNOTS HIGHER THAN THE CONSENSUS MEAN, THROUGH MOST OF THE FORECAST. UNCERTAINTY REMAINS HIGH THROUGH THE FORECAST, AS THE ULTIMATE INTENSITY REACHED IN THE SCS AND THEREAFTER IS HIGHLY DEPENDENT UPON HOW WELL THE SYSTEM HOLDS TOGETHER IN THE NEAR-TERM AND HOW QUICKLY IT REORGANIZES IN THE SULU SEA. THUS THERE IS LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN