WDPN32 PGTW 100300 AMD MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (BOLAVEN) WARNING NR 013 AMENDED// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.7N 146.5E INITIAL INTENSITY: 70 KTS GEOGRAPHIC REFERENCE: 93 NM EAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 33 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TYPHOON (TY) 15W (BOLAVEN) CONTINUES TO SLOWLY BUT STEADILY INTENSIFY AS IT APPROACHES THE SOUTHERN MARIANAS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS DEEP CONVECTION CONTINUING TO CYCLE AND MAKE MULTIPLE ATTEMPTS TO WRAP UPSHEAR, BUT HAS AS OF YET, BEEN UNABLE TO PERSIST ON THE NORTHERN SIDE OF THE CIRCULATION. THE CENTRAL DENSE OVERCAST (CDO) FEATURE CONTINUES TO OBSCURE THE LOW LEVEL CIRCULATION CENTER (LLCC). THANKFULLY THE SYSTEM IS WITHIN RANGE OF THE GUAM RADAR WHICH SHOWS SPIRAL RAINBANDS WRAPPING INTO AN INCREASINGLY WELL-DEFINED RADAR EYE, WHICH PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. RADAR VELOCITY DATA INDICATES A SPEED MAXIMUM ON THE NORTHWEST SIDE OF THE EYEWALL, WITH WINDS OF 75 KNOTS AT ABOUT 10000 FEET. THIS PROVIDED HIGH CONFIDENCE TO THE INITIAL INTENSITY ASSESSMENT, SLIGHTLY LOWER THAN THE BULK OF THE OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES. THE SYSTEM HAS BEEN TRACKING IN A STAIR STEP MOTION, WITH PERIODS OF WESTWARD MOTION, FOLLOWED BY SUDDEN SHIFTS TO A MORE NORTHWARD TRACK. OVER THE PAST COUPLE OF HOURS, THE TRACK HAS BEEN TRENDING MORE WESTWARD ONCE MORE. AVERAGED OVER THE PAST SIX HOURS HOWEVER, THE TRACK MADE GOOD IS TOWARDS THE NORTHWEST AT 12 KNOTS. THE 0000Z SOUNDING FROM GUAM INDICATES WEAKENING WINDS ABOVE 400MB BUT PERSISTENT 30-35 KNOT NORTH-NORTHEASTERLY FLOW BETWEEN ABOUT 500-700MB. THESE ENHANCED MID-LEVEL WINDS CONTINUE TO PUT PRESSURE ON THE VORTEX, WHICH REMAINS TILTED SOUTHWEST WITH HEIGHT, INHIBITING THE ONSET OF MORE RAPID INTENSIFICATION (RI). OTHERWISE, THE ENVIRONMENT IS RIPE FOR EXPLOSIVE DEVELOPMENT, WITH VERY LOW (0-5 KNOTS) DEEP-LAYER AVERAGED SHEAR, WARM (29-30C) SSTS AND GOOD RADIAL OUTFLOW. INITIAL WIND RADII BASIS: SMAP DATA CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.5 - 77 KTS RJTD: T4.0 - 65 KTS KNES: T4.5 - 77 KTS CIMSS SATCON: 72 KTS AT 092210Z CIMSS ADT: 74 KTS AT 090000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: MID-LEVEL, SUB-OUTFLOW SHEAR ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: IN THE NEAR-TERM FORECAST, THE NEXT 6 TO 12 HOURS, TY 15W IS LIKELY TO CONTINUE TRACKING SOMEWHAT ERRATICALLY AS THE VORTEX CONTINUES TO SYMMETRIZE, THOUGH IN GENERAL IT WILL CONTINUE TO TRACK TOWARDS THE WEST-NORTHWEST. THE CENTER IS EXPECTED TO PASS VERY CLOSE TO THE NORTHEAST TIP OF ROTA, WITHIN THE NEXT SIX HOURS OR SO. AFTER PASSING THE MARIANAS, THE TRACK WILL SHIFT MORE NORTH-NORTHWESTWARD AS THE STR TO THE NORTH RAPIDLY RE-CENTERS TO THE NORTHEAST AND THE WESTERN EXTENSION OF THE RIDGE RAPIDLY ERODES AHEAD OF AN APPROACHING DEEP-LAYER TROUGH. TY 15W WILL SLOW DOWN AFTER TAU 24 AS IT APPROACHES THE RIDGE AXIS, WITH IT ROUNDING THE AXIS BETWEEN TAU 36 AND TAU 48. AFTER ROUNDING THE RIDGE TY 15W WILL RAPIDLY PICK UP THE PACE AND SHOOT OFF TO THE NORTHEAST ALONG THE TIGHT GRADIENT BETWEEN THE STR TO THE EAST AND DEEP TROUGH TO THE NORTHWEST. AS THE SYSTEM HAS YET TO AXISYMMETRIZE DUE TO THE PRESENCE OF MODERATE MID-LEVEL SHEAR, INTENSIFICATION HAS BEEN SLOW BUT STEADY. HOWEVER, ALL AVAILABLE GUIDANCE AS WELL AS THE TRENDS IN THE GUAM SOUNDINGS, SUGGEST THE MID-LEVEL SHEAR WILL WEAKEN SIGNIFICANTLY OR EVEN DISAPPEAR IN SHORT ORDER. THIS WILL ALLOW THE VORTEX TO SYMMETRIZE AND THEN THE FUN BEGINS, WITH THE ONSET OF RI ANTICIPATED AROUND TAU 12. AFTER TAU 12, THE SYSTEM WILL BEGIN TAPPING INTO A ROBUST POLEWARD OUTFLOW CHANNEL, INTO THE BASE OF THE TROUGH PASSING BY TO THE NORTH, WHICH ALONG WITH OTHER FAVORABLE CONDITIONS, WILL SUPPORT EXPLOSIVE INTENSIFICATION BETWEEN TAU 24 AND TAU 48. THE SYSTEM IS CURRENTLY FORECAST TO PEAK AT TAU 48 AT 135 KNOTS, BUT ADDITIONAL INTENSIFICATION IS POSSIBLE UP THROUGH TAU 60. BY TAU 72, DEEP-LAYER SHEAR WILL START TO MAKE ITS PRESENCE KNOWN, AND BEGIN TO OFFSET THE CONTINUING STRONG POLEWARD OUTFLOW, AND THE SYSTEM WILL BEGIN TO SLOWLY WEAKEN. MORE RAPID WEAKENING AS THE SYSTEM GETS SHEARED APART. TY 15W WILL BEGIN EXTRATROPICAL TRANSITION (ETT) BY TAU 120 AS IT MOVES NORTH OF THE 26C ISOTHERM AND COMES IN PHASE WITH A 500MB TROUGH AND EMBEDS UNDER A 200MB JET MAX. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE REMAINS IN VERY GOOD AGREEMENT THROUGH THE MAJORITY OF THE FORECAST PERIOD. IN THE NEAR-TERM HOWEVER, THE JTWC FORECAST DEVIATES ABOUT 20NM SOUTH OF THE GUIDANCE ENVELOPE, TO ACCOUNT FOR THE RECENTLY OBSERVED TRACK MOTION, WHICH IS MORE WESTWARD THAN THE MODEL GUIDANCE WOULD SUGGEST. THE JTWC TRACK REMAINS SOUTH OF THE ENVELOPE TO TAU 24, BUT THEN REJOINS AND CLOSELY TRACKS THE CONSENSUS MEAN THOUGH TAU 72. CROSS-TRACK SPREAD IS VERY TIGHT, REACHING A MAXIMUM OF 100NM AT TAU 72. AFTER TAU 72, CROSS-TRACK SPREAD INCREASES TO A MODEST 270NM, BUT ALONG-TRACK SPREAD INCREASES SHARPLY, TO OVER 800NM BY TAU 120 BETWEEN THE GFS (SLOW) AND ECMWF (FAST). IN LIGHT OF THE LARGE ALONG-TRACK UNCERTAINTY AFTER TAU 72, THE JTWC FORECAST IS SET WITH HIGH CONFIDENCE IN THE FIRST 72 HOURS, THEN LOW CONFIDENCE THROUGH TAU 120. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH ALL BUT THE SHIPS GUIDANCE INDICATING RI AFTER TAU 12, WITH A PEAK ABOVE 120 KNOTS. THE RIPA, RICN, FRIA AND INDIVIDUAL RI AIDS ARE ALL CONTINUING TO FIRE, AND THE COAMPS-TC ENSEMBLE RI PROBABILITIES NOW EXCEED 80 PERCENT UP THROUGH TAU 48, PROVIDING HIGH CONFIDENCE IN THE ONSET OF RI AND THE FORECAST TO TAU 72. IN THE LATER TAUS, ALL OF THE GUIDANCE SUGGESTS A STEADY WEAKENING TREND AND THE JTWC FORECAST TRACKS CLOSE TO THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM 4. JUSTIFICATION FOR AMENDMENT: ADJUSTED THE FORECAST TRACK MORE WESTWARD THROUGH TAU 24 TO ACCOUNT FOR NEAR-TERM MOTION TRENDS.// NNNN