WDPS31 PGTW 190900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 26P (GINA) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.3S 168.7E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 87 NM NORTH-NORTHEAST OF PORT VILA, VANUATU MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS FLARING CONVECTION WITH ASSOCIATED CIRRUS SHIELD OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). CONVECTION CONTINUES TO BE SHEARED TOWARD THE SOUTHEAST AS THE SYSTEM INTERACTS WITH A HIGH-AMPLITUDE TROUGH TO THE WEST. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE GIVEN THE RECENT OBSCURATION OF THE LLCC. GIVEN THE LACK OF SCATTEROMETRY AND SURFACE OBSERVATIONS, THE INITIAL INTENSITY IS HELD AT 35 KNOTS BASED ON AGENCY DVORAK ESTIMATES. TROPICAL STORM FORCE WINDS ARE LIKELY ISOLATED WITHIN THE BRIEF BURSTS OF DEEP CONVECTION. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS KNES: T2.5 - 35 KTS PHFO: T2.5 - 35 KTS NFFN: T3.0 - 45 KTS CIMSS ADT: 31 KTS AT 190540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 26P CONTINUES TO STRUGGLE TO MAINTAIN PERSISTENT DEEP CONVECTION, GIVEN THE MODERATE VERTICAL WIND SHEAR AND LAND INTERACTION WITH THE ISLANDS OF VANUATU. THE LLCC CONTINUES TO ALTERNATE BETWEEN PARTIALLY EXPOSED TO BECOMING BRIEFLY TUCKED UNDERNEATH BURSTS OF FLARING CONVECTION. IN THE NEAR TERM, ENVIRONMENTAL CONDITIONS SHOULD CONTINUE TO REMAIN MARGINAL TO SUPPORT A MAINTENANCE OF INTENSITY AT AROUND 35 KNOTS. AFTER TAU 24, VERTICAL WIND SHEAR IS FORECAST TO INCREASE, AND TC 26P IS FORECAST TO DISSIPATE BY TAU 36 TO 48. THE REMNANT OF TC 26P IS THEN FORECAST TO TURN TOWARD THE SOUTHEAST BY TAU 72, WHICH IS INDICATED BY THE EXTRA FORECAST POSITION. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE GENERALLY AGREES ON A SOUTHWESTWARD TRACK, WITH AN EVENTUAL TURN TOWARD THE SOUTH AND SOUTHEAST. THE GFS CONTINUES TO INITIALIZE A DEEPER VORTEX COMPARED TO ECMWF, WITH THE FORMER BEING A WESTERN OUTLIER. THUS, THE OFFICIAL JTWC TRACK FOLLOWS CLOSE TO CONSENSUS AND THE ECMWF. THE INTENSITY FORECAST IS HELD AT 35 KNOTS DESPITE THE MORE AGGRESSIVE HWRF AND GFS GUIDANCE SUGGESTING INTENSIFICATION TO 45 KNOTS, GIVEN THE AFOREMENTIONED BIAS REGARDING THE INITIALIZATION OF A DEEPER SYSTEM. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN