WDPN31 PGTW 240300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (LUPIT) WARNING NR 041// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 22W (LUPIT), LOCATED APPROXIMATELY 330 NM SOUTH-SOUTHWEST OF OKINAWA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. TS LUPIT HAS INCREASED IN FORWARD TRACK SPEED OVER THE PAST 12 HOURS AS THE SUBTROPICAL STEERING RIDGE HAS BECOME MORE DEFINED. THE CURRENT POSITION IS BASED ON ANIMATED MULTISPECTRAL IMAGERY WHICH SHOWS TWO CONVECTIVE BANDS WRAPPING INTO A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). METSAT IMAGERY ALSO INDICATES WANING DEEP CONVECTION AND A DRY SLOT INDICATIVE OF DRY AIR ENTRAINMENT IN THE SOUTHWEST QUADRANT, THOUGH THE 232136Z 37 GHZ SSMIS MICROWAVE IMAGE DEPICTS A MICROWAVE EYE. THEREFORE, THE CURRENT INTENSITY IS AN AVERAGE OF DECLINING DVORAK ESTIMATES FROM PGTW (55 KNOTS) AND RJTD (45 KNOTS). 3. FORECAST REASONING A. THE FORECAST REASONING HAS CHANGED SIGNIFICANTLY SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. BASED ON CURRENT MOTION AND A MORE DEFINED STEERING INFLUENCE, TS LUPIT IS EXPECTED TO CONTINUE ON A FASTER (THAN THE PREVIOUS FORECAST) EAST-NORTHEASTWARD TRACK THROUGH TAU 72. THE INTENSITY WILL SLOWLY DECREASE OVER THE NEXT 72 HOURS AS DRY AIR ALONG THE WESTERN PORTION OF LUPIT CONTINUES TO INTRUDE UPON THE CENTRAL PORTIONS OF THE SYSTEM AT THE MID- AND UPPER-LEVELS. ADDITIONALLY, THE SYSTEM WILL START TO ENCOUNTER INCREASINGLY UNFAVORABLE VERTICAL WIND SHEAR AS IT GAINS LATITUDE. NUMERICAL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A TRACK SOUTHEAST OF OKINAWA, JAPAN. HOWEVER, THE GFS AND TCLAPS SOLUTIONS ARE WESTERN OUTLIERS THAT DEPICT A FASTER, MORE INTENSE SYSTEM. THESE SEEM UNLIKELY GIVEN THE FORECAST VERTICAL WIND SHEAR. FINALLY, BASED ON SHIP OBSERVATIONS ON THE PERIPHERY OF LUPIT, THE 34-KNOT WIND FIELDS HAVE BEEN EXPANDED TO SHOW A SLIGHTLY LARGER SYSTEM. C. THE REASONING FOR THE FORECAST TRACK BEYOND TAU 72 HAS CHANGED SIGNIFICANTLY. LUPIT IS STILL EXPECTED TO WEAKEN CONSIDERABLY AS IT SUCCUMBS TO THE EFFECTS OF DRY AIR ENTRAINMENT AND HOSTILE VERTICAL WIND SHEAR. HOWEVER, THE LOW LEVEL CIRCULATION CENTER OF THE SYSTEM IS NOW EXPECTED TO DRIFT WEST-SOUTHWESTWARD AS IT WEAKENS IN INTENSITY, DECOUPLES FROM THE UPPER-LEVEL CIRCULATION AND STARTS TO TRACK WITH THE LOWER-LEVEL NORTHEASTERLY FLOW AS A 700-MB RIDGE IS FORECAST TO BUILD EASTWARD OVER JAPAN. THE MODEL GUIDANCE AFTER TAU 72 IS HIGHLY DEPENDENT ON FORECAST INTENSITY. THE MODEL AIDS THAT MAINTAIN THE SYSTEM'S INTENSITY SHOW A MORE NORTHEASTWARD TRACK WHILE THOSE THAT DISSIPATE THE SYSTEM SHOW IT TRACKING ABRUPTLY BACK TO THE WEST.// NNNN