MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (HAGIBIS) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 20W (HAGIBIS), LOCATED APPROXIMATELY 638 NM EAST OF ANDERSEN AFB, GUAM, HAS TRACKED WESTWARD AT 18 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A RAPIDLY CONSOLIDATING SYSTEM WITH TIGHTLY-CURVED DEEP CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). A 052242Z MHS 89GHZ COLOR COMPOSITE IMAGE SHOWS A PARTIALLY-EXPOSED LLCC WITH CONVECTIVE BANDING WRAPPING INTO THE SOUTHEAST QUADRANT. OVERALL, THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION. UPPER-LEVEL ANALYSIS INDICATES NEAR-RADIAL OUTFLOW WITH LOW VERTICAL WIND SHEAR. SST VALUES OF 30-31C AND HIGH OCEAN HEAT CONTENT VALUES ALSO SUPPORT SIGNIFICANT INTENSIFICATION. THE CURRENT INTENSITY IS ASSESSED AT 45 KNOTS, HEDGED ABOVE DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS), BASED ON A 05/2340Z ADT ESTIMATE OF T2.9 (APPROXIMATELY 45 KNOTS). THE SYSTEM IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. ADDITIONALLY, THIS FORECAST REMAINS HIGHLY CONSISTENT WITH THE PREVIOUS JTWC FORECAST. B. TS 20W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE STR. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN VERY FAVORABLE THROUGH THE FORECAST PERIOD WITH ROBUST OUTFLOW, WARM SST AND HIGH OCEAN HEAT CONTENT VALUES SUPPORTING PERIODS OF RAPID INTENSIFICATION (RI). JTWC INTENSITY GUIDANCE CONTINUES TO INDICATE SOME POTENTIAL FOR RI WITHIN THE NEXT 36 HOURS, BEFORE THE SYSTEM HITS THE NORTHERN MARIANAS. THIS FORECAST INDICATES A TYPHOON- STRENGTH SYSTEM (75-80 KNOTS) IMPACTING THE NORTHERN MARIANAS, HOWEVER, THERE IS UNCERTAINTY IN THE EXACT INTENSITY WITH POTENTIAL FOR A STRONGER SYSTEM. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU 36 WITH A 32 NM SPREAD IN SOLUTIONS AT TAU 36. AFTER TAU 36, TS 20W WILL CONTINUE TO INTENSIFY UNDER FAVORABLE CONDITIONS. C. IN THE EXTENDED PERIOD, TS 20W WILL GENERALLY TRACK NORTHWESTWARD TOWARD A BREAK IN THE STR ASSOCIATED WITH A DEEP, DYNAMIC SHORTWAVE TROUGH FORECAST TO DEEPEN OVER WESTERN JAPAN. IMPROVED POLEWARD OUTFLOW ASSOCIATED WITH THIS SHORTWAVE TROUGH WILL AID IN BOOSTING THE INTENSITY TO SUPER TYPHOON STRENGTH. THERE IS INCREASING UNCERTAINTY AFTER TAU 96 AS THE NUMERICAL MODEL GUIDANCE DIVERGES WITH A 200 NM SPREAD IN SOLUTIONS AT TAU 120, THEREFORE, THERE IS NOW MODERATE CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN