WDPN32 PGTW 210300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (GAEMI) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.9N 125.6E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 589 NM SOUTH-SOUTHWEST OF KADENA AB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 8 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL CENTRAL DENSE OVERCAST (CDO) FEATURE WITH CYCLING DEEP CONVECTION EXHIBITING EXTREMELY COLD CLOUD TOPS APPROACHED -90C. HOWEVER, THE CDO IS DISPLACED TO THE EAST-SOUTHEAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC), THE FAR EASTERN OUTER BANDS OF WHICH ARE EVIDENT IN THE ANIMATED MSI, FULLY EXPOSED IN RELATIVELY DRY, SUBSIDENT AIR EAST OF THE CENTER. A 202204Z SSMIS 91GHZ MICROWAVE IMAGE SHOWED A NASCENT EYE FEATURE, BUT COMPARISON TO THE 36GHZ IMAGE CONFIRMS THE VORTEX REMAINS TILTED TO THE SOUTHWEST IN LIGHT OF MODERATE NORTHEASTERLY SHEAR ESTIMATED AT ABOUT 17 KNOTS IN THE LATEST CIMSS ESTIMATE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN EXTRAPOLATION OF THE LOW LEVEL CIRCULATION SEEN IN THE MICROWAVE IMAGE AND ANALYSIS OF THE OUTER BANDS OF EVIDENT IN THE MSI. THE INITIAL INTENSITY IS INCREASED TO 45 KNOTS BASED ON A 202142Z SMAP PASS WHICH SHOWED WINDS UP TO 45 KNOTS (10-MIN) WHICH WHEN CONVERTED SUPPORTS A POSSIBLE INTENSITY UP TO 50 KNOTS. CONDITIONS ARE OVERALL FAVORABLE (VERY WARM SSTS, HIGH OHC AND GOOD POLEWARD AND EQUATORWARD OUTFLOW) THOUGH THE EASTERLY SHEAR IS KEEPING THE VORTEX TILTED AND THUS CAPPING INTENSIFICATION. THE SYSTEM HAS SLOWED CONSIDERABLY OVER THE PAST 12 TO 24 HOURS AS IT HAS MOVED INTO A COMPETING STEERING ENVIRONMENT, WITH A STRONG STR CENTERED SOUTH OF HONSHU AND A BUILDING NEAR EQUATORIAL RIDGE (NER) NOSING IN ACROSS THE PHILIPPINES TO THE SOUTH. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT, WITH STR TO THE NORTH AND NER TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 41 KTS AT 201705Z CIMSS ADT: 44 KTS AT 210000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 05W (GAEMI) HAS CONTINUED TO TRACK GENERALLY WEST-NORTHWESTWARD BUT HAS SLOWED DOWN CONSIDERABLY OVER THE PAST 24 HOURS AS IT MOVES INTO A COMPETING STEERING PATTERN. THE SLOW TRACK SPEED IS FORECAST TO CONTINUE THROUGH ABOUT TAU 48, BUT THE MOTION VECTOR WILL GRADUALLY SHIFT OVER TO NORTH-NORTHWESTWARD AFTER TAU 24 AS THE RIDGE TO THE NORTH REORIENTS TO A MORE NORTH-SOUTH AXIS. AFTER THE RIDGE PATTERN STABILIZES ON THE NEW AXIS, THE SYSTEM PICKS UP SPEED AS IT APPROACHES THE SOUTHWESTERN RYUKYU ISLANDS AFTER TAU 72. AFTER PASSING THROUGH THE RYUKYUS, TS 05W WILL TURN ONTO A NORTHWESTWARD TRACK, HEADING TOWARDS A BREAK IN THE STEERING RIDGE WHICH DEVELOPS OVER EASTERN CHINA. THE SYSTEM IS EXPECTED TO SKIRT THE NORTHEASTERN TIP OF TAIWAN, THEN MAKE LANDFALL ALONG THE SOUTHEASTERN CHINA COASTLINE BEFORE TAU 120. INTENSIFICATION WILL BE SLOW AND HALTING FOR THE NEXT 36-48 HOURS, AS THE MODEL GUIDANCE INDICATES AN UPTICK IN NORTHEASTERLY SHEAR, THE START OF WHICH IS ALREADY HAPPENING. THIS WILL KEEP THE VORTEX MISALIGNED AND KEEP A LID ON ANY SIGNIFICANT INTENSIFICATION. BUT LIKE A SHAKEN UP CAN OF SODA, THE SYSTEM WILL BE PRIMED FOR AN EXPLOSIVE RELEASE ONCE THE CAP IS TAKEN OFF. SHEAR IS EXPECTED TO DECREASE A NOTCH BY AROUND TAU 48, AND THE MESOSCALE MODELS ARE IN GOOD AGREEMENT THAT ONCE THIS OCCURS, THE SYSTEM WILL QUICKLY SYMMETRIZE, AND RAPIDLY INTENSIFY BETWEEN TAUS 48 AND 72, SUPPORTED BY PASSAGE OVER A POOL OF VERY WARM, HIGH OHC WATERS. THE PEAK INTENSITY REACHED WILL DEPEND UPON THE STARTING INTENSITY BUT WILL BE AT LEAST 100 KNOTS, OCCURRING AS THE SYSTEM APPROACHES AND PASSES WEST OF ISHIGAKIJIMA. THE SYSTEM WILL WEAKEN SLIGHTLY AS IT MOVES NORTHEAST OF TAIWAN BUT MORE SIGNIFICANT WEAKENING IS EXPECTED PRIOR TO LANDFALL DUE TO RAPIDLY INCREASING SHEAR AND DECREASING SSTS, THOUGH IT IS STILL EXPECTED TO BE A TYPHOON AT LANDFALL. MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT, AT LEAST THROUGH TAU 48, THAT THE SYSTEM WILL VERY SLOWLY DRIFT NORTHWESTWARD IN A GENERALLY WEAK STEERING PATTERN. THE NAVGEM MODEL IS THE ONLY OUTLIER SHOWING A SIGNIFICANTLY FURTHER WEST TRACK, BUT STILL SHOWS THE SYSTEM TURNING NORTHWARD, WHERE IT REJOINS THE PACK BY TAU 48. THE REMAINDER OF THE CONSENSUS ARE TIGHTLY PACKED ABOUT THE MEAN. AFTER TAU 48, THE GUIDANCE SPREADS OUT BOTH ALONG- AND CROSS-TRACK, WITH THE UKMET ENSEMBLE MEAN, NAVGEM, EGRR AND GALWEM TAKING THE SYSTEM OVER TAIWAN, WHILE THE ECMWF TRACKS IT EAST OF ISHIGAKIJIMA AND NEAR SHANGHAI BY TAU 120. THE GFS AND GFS ENSEMBLE ARE SLIGHTLY CLOSER TO TAIWAN BUT OTHERWISE CONSISTENT WITH THE CONSENSUS MEAN. THE JTWC FORECAST LIES JUST EAST OF THE CONSENSUS MEAN, SPLITTING THE DIFFERENCE BETWEEN THE ECMWF AND THE GFS TRACKERS. CONFIDENCE IN THE 72 HOUR FORECAST IS MEDIUM. SIGNIFICANT DIFFERENCES IN THE GFS AND ECMWF MODEL FIELDS AFTER TAU 72 SUGGEST THE MODELS ARE NOT HANDLING THE SCENARIO WELL, LENDING LOW CONFIDENCE IN THE EXTENDED FORECAST. INTENSITY GUIDANCE IS IN GENERAL GOOD AGREEMENT ON STEADY INTENSIFICATION, THOUGH THE HAFS-A AND CTCX MODELS SUPPORT A PERIOD OF RI BETWEEN TAU 48 AND 72. THE JTWC FORECAST TRACKS BELOW THE CONSENSUS MEAN TO TAU 48, THEN JUMPS UP ABOVE IT TOWARDS THE HAFS-A SOLUTION, THOUGH THE PEAK INTENSITY IS ABOUT 25 KNOTS LOWER THAN THAN THE HAFS-A PEAK AT 125 KTS. CONFIDENCE IS HIGH THOUGH TAU 72, BUT MEDIUM THEREAFTER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN