MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 20W (HAGIBIS) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 20W (HAGIBIS), LOCATED APPROXIMATELY 204 NM NORTH-NORTHWEST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST- NORTHWESTWARD AT 13 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL CONVECTIVE BANDS WRAPPING INTO A SYMMETRIC, 8 NM DIAMETER EYE SURROUNDED BY A DEFINED EYEWALL, LEADING TO HIGH CONFIDENCE IN THE INITIAL POSITION. BASED ON THE DVORAK CURRENT INTENSITY (CI) ESTIMATES OF T6.5/127 KTS FROM PGTW/RJTD AND T7.0/140 KTS FROM RCTP, THE INITIAL INTENSITY IS SET AT 135 KTS WITH GOOD CONFIDENCE. THE SYSTEM HAS BEEN UNDERGOING AN EYEWALL REPLACEMENT CYCLE (ERC), WITH A SECONDARY EYEWALL CLEARLY EVIDENT IN 071945Z SSMIS 91 GHZ MICROWAVE IMAGE. UPPER-LEVEL ANALYSIS INDICATES THE CONTINUED PRESENCE OF STRONG RADIAL OUTFLOW, ENHANCED TOWARDS THE EAST AND SOUTH. TO THE NORTH OF THE SYSTEM, THERE IS AN AREA OF DRY AIR WITH HIGH VERTICAL WIND SHEAR (VWS), INHIBITING STRONG DEVELOPMENT OF A POLEWARD OUTFLOW CHANNEL. STY 20W REMAINS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (05-10 KTS) VWS AND WARM (29-31 CELSIUS) SEA SURFACE TEMPERATURES (SST). UPON COMPLETION OF THE CURRENT ERC, THERE WILL BE A POSSIBILITY FOR A BRIEF PERIOD OF RE-INTENSIFICATION. HOWEVER, CLOUD TOP TEMPERATURES HAVE WARMED SLIGHTLY, AND THE DEEPEST CONVECTION HAS BECOME MORE RAGGED WITH SOME COOLING OF THE EYE. ANY RE-INTENSIFICATION IN THE NEAR TERM WILL BE GRADUAL. THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST REMAINS THE PRIMARY STEERING INFLUENCE AS STY 20W TRACKS WEST-NORTHWESTWARD ALONG ITS SOUTHWESTERN PERIPHERY. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE LAST PROGNOSTIC REASONING MESSAGE. B. THROUGH TAU 24, STY 20W WILL TRACK NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE AFOREMENTIONED STR. AT TAU 24, THE SYSTEM WILL SHIFT TO A MORE NORTH-NORTHWESTWARD TRACK, SLOWING SLIGHTLY AS IT GAINS LATITUDE. THE ENVIRONMENT IS EXPECTED TO REMAIN FAVORABLE THROUGH TAU 72 WITH LOW VWS, HIGH SST, AND GOOD UPPER- LEVEL OUTFLOW. DURING THIS PERIOD, THE OFFICIAL INTENSITY FORECAST IS SLIGHTLY MORE AGGRESSIVE THAN THE INTENSITY CONSENSUS GIVEN THE LIKELIHOOD OF RE-INTENSIFICATION AS STY 20W TRAVERSES AN AREA OF GREATER MAXIMUM POTENTIAL INTENSITY (MPI). AFTERWARDS, GRADUAL WEAKENING IS EXPECTED AS THE OUTFLOW BEGINS TO BE DISRUPTED TO THE NORTHWEST DUE TO INTERACTION WITH AN APPROACHING TROUGH. WITH THE GFS AND GFS ENSEMBLE AS THE EASTERNMOST OUTLIER AND THE UKMET AS THE WESTERNMOST OUTLIER, THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH TAU 72, LENDING GOOD CONFIDENCE TO THIS PORTION OF THE JTWC TRACK FORECAST. C. IN THE EXTENDED PERIOD, A SHORTWAVE TROUGH OVER JAPAN IS EXPECTED TO DEEPEN, ERODING THE STR AND ALLOWING STY 20W TO TURN NORTHWARD AS IT ROUNDS THE STR AXIS. AROUND TAU 96, THE SYSTEM WILL BEGIN TO RECURVE, TRACKING NORTHEASTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM WILL SLOWLY WEAKEN IN RESPONSE TO INCREASED VWS ASSOCIATED WITH THE APPROACHING TROUGH, OFFSETTING THE OTHERWISE FAVORABLE ENVIRONMENT. THE NUMERICAL MODELS HAVE A CROSS- TRACK SPREAD OF 130 NM AT TAU 120. HOWEVER, THERE IS VARIATION IN THE TIMING OF THE RECURVATURE, RESULTING IN UNCERTAINTIES WITH THE FORWARD MOTION OF THE SYSTEM AND LOW CONFIDENCE IN THE EXTENDED JTWC FORECAST.// NNNN NNNN