MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (NOCK-TEN) WARNING NR 21// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 30W (NOCK-TEN), LOCATED APPROXIMATELY 73 NM WEST-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WEST- NORTHWESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED HIGH RESOLUTION VISIBLE SATELLITE IMAGERY INDICATES THAT TY NOCK-TEN HAS DRAMATICALLY WEAKENED AFTER PASSING OVER LUZON SOUTH OF MANILA, WITH THE SYSTEM BECOMING MUCH MORE ASYMMETRIC AND RAGGED. CONVECTIVE BANDING HAS BEEN VERY DIFFICULT TO IDENTIFY, THOUGH NOW THAT THE SYSTEM HAS REEMERGED OVER THE SOUTH CHINA SEA (SCS), THERE ARE HINTS THAT BANDING MAY BE TRYING TO REESTABLISH. A 26/0436Z AMSR-2 89 GHZ MICROWAVE IMAGE CONFIRMS THIS, SHOWING DEEP CONVECTIVE ACTIVITY CURVING INTO THE WESTERN SIDE OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON AVAILABLE SATELLITE IMAGERY, AS WELL AS COMPOSITE RADAR REFLECTIVITY DATA FROM THE DOPPLER RADAR AT TAGAYTAY. THE INITIAL INTENSITY IS BASED ON ANALYSIS OF FIX DATA FROM PGTW, WITH A CURRENT INTENSITY VALUE OF T4.5 (77 KNOTS) AS WELL ADVANCED DVORAK TECHNIQUE (ADT) AUTOMATED INTENSITY OF T4.1 (67 KNOTS). UPPER-LEVEL ANALYSIS INDICATES THAT TY 30W IS TRAVERSING THROUGH A WEAKLY FAVORABLE ENVIRONMENT WITH MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS) AND WEAK WESTWARD OUTFLOW. THE CYCLONE HAS BEGUN TO TRACK WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) WHICH EXTENDS FROM CENTRAL THAILAND ACROSS THE BASHI CHANNEL AND INTO THE PHILIPPINE SEA. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY NOCK-TEN IS FORECAST TO CONTINUE TRACKING GENERALLY NORTHWESTWARD AS THE STEERING RIDGE REORIENTS TO A NORTH-SOUTH AXIS VICE ITS CURRENT EAST-WEST AXIS. AFTER TAU 24, THE LLCC WILL START TO BECOME DECOUPLED FROM THE CONVECTION, COMPLETING THIS PROCESS BY TAU 48. CONCURRENTLY, THE LLCC OF TY 30W WILL TURN SOUTHWESTWARD AS IT BECOMES EMBEDDED IN THE BROAD NORTHEASTERLY FLOW ASSOCIATED WITH A COLD SURGE EVENT. AS TY NOCK-TEN EMERGES INTO THE SCS, THERE IS A 18-24 HOUR WINDOW FOR IT TO REMAIN AT TYPHOON STRENGTH, AS IT TAPS INTO MORE POLEWARD ORIENTED OUTFLOW AND BEFORE THE NORTHEASTERLY SURGE COMBINE TO SHEAR THE SYSTEM APART. AFTER TAU 24, TY 30W WILL RAPIDLY WEAKEN DUE TO INCREASED VWS (20-25 KNOTS) AND EXPOSURE TO THE STRONG COLD AND DRY NORTHEASTERLY SURGE IN THE SCS, FULLY DISSIPATING BY TAU 72. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH SOME ALONG TRACK SPREAD IN THE SCS AFTER THE DECOUPLING. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI- MODEL CONSENSUS AND REMAINS CONSISTENT WITH PREVIOUS FORECASTS, LEADING TO HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN