WDPS31 PGTW 092100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05P (FIVE) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.0S 177.0E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 139 NM SOUTHWEST OF SUVA, FIJI MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED JUST UNDER THE WESTERN EDGE OF A CURVED BAND OF DEEP CONVECTION. ADDITIONALLY, EIR SHOWS EXTENSIVE, FRAGMENTED CONVECTIVE BANDING DISPLACED OVER THE NORTHERN AND EASTERN SEMICIRCLES ASSOCIATED WITH LOW-LEVEL CONVERGENT FLOW AND STRONG UPPER-LEVEL DIFFLUENCE. ANIMATED WATER VAPOR IMAGERY AND UW-CIMSS FEATURE TRACK WINDS CONTINUE TO SHOW AN UPPER-LEVEL TROUGH AND POSSIBLE CLOSED LOW OVER THE SYSTEM, WHICH IS HINDERING DEVELOPMENT OF THE CONVECTION. A 091558Z SSMIS 91GHZ COMPOSITE MICROWAVE IMAGE REVEALS SOME TILT WITH THE LLCC POSITIONED SLIGHTLY NORTHWEST OF THE UPPER-LEVEL CIRCULATION CENTER. HOWEVER, THE OVERALL CONVECTIVE STRUCTURE HAS IMPROVED AS EVIDENCED IN THE SSMIS 37GHZ IMAGE, WHICH SHOWS CONVECTIVE BANDING WRAPPING INTO A DEFINED, ELONGATED LLCC. BASED ON THIS IMAGE, THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE AND IS HEDGED SLIGHTLY HIGHER THAN THE PGTW AND KNES DVORAK ESTIMATES BASED ON THE IMPROVED ORGANIZATION AND CIMSS ADT ESTIMATE. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN NEAR EQUATORIAL RIDGE (NER) TO THE NORTHEAST AND SUBTROPICAL RIDGE (STR) TO THE SOUTH-SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS KNES: T2.5 - 35 KTS PHFO: T3.5 - 55 KTS CIMSS ADT: 43 KTS AT 091740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 20-25 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: DRY AIR ENTRAINMENT ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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: TC 05P IS SLOWING AND IS EXPECTED TO TURN SHARPLY WESTWARD TO WEST-SOUTHWESTWARD IN THE NEXT 12 HOURS AS THE STR TO THE SOUTH BECOMES THE DOMINANT STEERING INFLUENCE THROUGH TAU 36. AFTER TAU 36, AN APPROACHING MAJOR SHORTWAVE TROUGH IS EXPECTED TO WEAKEN THE STR, WHICH WILL LEAD TO A FASTER SOUTHEASTWARD TRACK TOWARD THE BREAK IN THE STR ALONG THE WESTERN AND SOUTHWESTERN PERIPHERY OF THE WEAK STEERING RIDGE POSITIONED TO THE EAST. THE SYSTEM IS EXPECTED TO REMAIN WITHIN A COMPLEX UPPER-LEVEL ENVIRONMENT UNDER A BROAD UPPER-LEVEL TROUGH, HOWEVER, SLIGHT INTENSIFICATION IS ANTICIPATED DUE TO ROBUST POLEWARD OUTFLOW WITH A PEAK INTENSITY OF 45-50 KNOTS. AFTER TAU 72, TC 05P WILL GRADUALLY WEAKEN AS IT BECOMES FURTHER EMBEDDED WITHIN THE UPPER-LEVEL TROUGH. NEAR TAU 96, TC 05P IS FORECASTED TO GRADUALLY TRANSITION INTO A SUBTROPICAL CYCLONE. MODEL DISCUSSION: THE NUMERICAL MODELS AND ENSEMBLE GUIDANCE (EPS AND GEFS) SUPPORT THE JTWC FORECAST TRACK WITH FAIR CONFIDENCE WITH SOME UNCERTAINTY IN THE EXACT TRACK DUE TO THE COMPLEX, RAPIDLY-EVOLVING SYNOPTIC PATTERN. THUS, OVERALL CONFIDENCE IN THE JTWC TRACK IS MEDIUM. THERE IS ALSO UNCERTAINTY IN THE JTWC INTENSITY FORECAST DUE TO THE PRESENCE OF THE UPPER-LEVEL TROUGH OVER THE SYSTEM AND THE POTENTIAL FOR DRY AIR ENTRAINMENT, WHICH IS EXPECTED TO LIMIT DEVELOPMENT. THE BULK OF THE RELIABLE INTENSITY GUIDANCE SUPPORTS THE JTWC FORECAST WITH HWRF PEAKING SLIGHTLY HIGHER TO 55 KNOTS AT TAU 84. AFTER TAU 72, THE JTWC INTENSITY FORECAST IS LOWER THAN THE INTENSITY GUIDANCE DUE TO INCREASING VERTICAL WIND SHEAR AND COOLER SST VALUES (24-26C). FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN