WDPS31 PGTW 011500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15P (JUDY) WARNING NR 011// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.2S 170.2E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 185 NM SOUTHEAST OF PORT VILA, VANUATU MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 39 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) IMAGERY DEPICTS A SYMMETRICAL SYSTEM WITH DEEP CONVECTIVE BANDS IN THE EASTERN AND SOUTHERN PERIPHERIES WRAPPING INTO AN ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). UNFORTUNATELY, THERE WERE NO USEFUL MICROWAVE IMAGERY PASSES DURING THIS FORECAST CYCLE. THE SSMIS AND ASCAT PASSES WERE PARTIAL AND REVEALED ACTIVITY RATHER FAR FROM THE CENTER. TC JUDY IS IN A MARGINALLY FAVORABLE ENVIRONMENT FOR FURTHER TROPICAL ACTIVITY. THESE CONDITIONS ARE CHARACTERIZED BY CONSTANT POLEWARD OUTFLOW ALOFT, MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS), A STRONG 850 MB VORTICITY SIGNATURE, AND WARM (28-29 C) SEA SURFACE TEMPERATURES (SST). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED EIR AND MULTI-AGENCY FIX LOCATIONS. THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH MEDIUM CONFIDENCE AND SET SLIGHTLY HIGHER THAN MULTI-AGENCY AND AUTOMATED DVORAK ESTIMATES. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS KNES: T6.0 - 115 KTS PHFO: T5.5 - 102 KTS NFFN: T5.5 - 102 KTS CIMSS SATCON: 92 KTS AT 011010Z CIMSS ADT: 95 KTS AT 011230Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE 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 JUDY CONTINUES ITS SOUTHEASTWARD TRACK AS IT HUGS THE OUTER PERIPHERY OF STR TO THE EAST-NORTHEAST. BY TAU 12, THE SYSTEM WILL ENTER A MORE HOSTILE ENVIRONMENT CHARACTERIZED BY STRONGER VWS AND WILL DECREASE IN INTENSITY TO 100 KNOTS AS A RESULT. BY TAU 24, THE SYSTEM WILL BEGIN ITS SUBTROPICAL TRANSITION AND A FURTHER DECREASE IN INTENSITY TO 90 KNOTS IS ANTICIPATED AS THE SYSTEM CROSSES THE 26 C ISOTHERM. BY TAU 36, TC JUDY WILL CONTINUE ITS SUBTROPICAL TRANSITION AND WILL START TO FEEL THE EFFECTS OF DRY AIR ENTRAINMENT FROM THE NORTHWEST BEING WRAPPED INTO THE CENTER. BY TAU 48, TC JUDY WILL BECOME FULLY SUBTROPICAL. MODEL DISCUSSION: THE JTWC TRACK CONSENSUS MEMBERS ARE IN GOOD AGREEMENT SHOWING A CONTINUOUS SOUTHEASTWARD TRAJECTORY. THE NAVGEM TRACKER IS THE OUTLIER WITH A MORE SOUTHWARD TRACK THAN THE OTHER MEMBERS. BECAUSE OF THIS, THE JTWC FORECAST TRACK TO PLACED SLIGHTLY TO THE LEFT OF CONSENSUS THROUGHOUT THE FORECAST PERIOD. THE FORECAST MODEL ENVELOPE HAS A 48 NM SPREAD BY TAU 24 WHICH PROGRESSIVELY INCREASES TO 90 NM BY TAU 48. AS A RESULT, THE JTWC FORECAST TRACK IS SET WITH HIGH CONFIDENCE. THE JTWC INTENSITY CONSENSUS MEMBERS ARE ALSO IN GOOD AGREEMENT SHOWING A GRADUAL DECREASE THROUGHOUT THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM// NNNN