MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (GUCHOL) WARNING NR 17// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 05W (GUCHOL), LOCATED APPROXIMATELY 665 NM EAST- SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED JUST WESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM HAS FURTHER DEEPENED AND CONSOLIDATED AS A TRACE OF AN OUTFLOW CHANNEL HAS BECOME APPARENT ON THE NORTHWEST QUADRANT. THE MAIN CONVECTION REMAINS COMPACT AND DENSE WITH A SLIGHT WESTWARD TILT FROM BUT COMPLETELY OVERSHADOWS THE LOW LEVEL CIRCULATION CENTER. UPPER LEVEL ANALYSIS REVEALS THAT TY 05W IS JUST TO THE SOUTH OF A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) IN AN AREA OF LIGHT TO MODERATE (10-15 KNOT) EASTERLY VERTICAL WIND SHEAR (VWS), WHICH IS CAUSING THE STRUCTURE TILT. THE INITIAL POSITION WAS EXTRAPOLATED FROM A 142257Z SSMIS MICROWAVE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY WAS BASED ON THE DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD AND REFLECTS THE DEEPENING AND CONSOLIDATING TREND. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED LEAF OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 05W IS EXPECTED TO TRACK MORE NORTHWESTWARD AFTER TAU 12 AS IT REACHES THE SOUTHWEST EDGE OF THE STEERING STR. THIS IS IN RESPONSE TO A MID-LATITUDE TROUGH APPROACHING FROM THE NORTHWEST INTO TAIWAN THAT IS DIGGING INTO THE STR. OVER THE NEXT 12-72 HOURS, THE SYSTEM WILL TRACK POLEWARD INTO THIS BREAK IN THE RIDGE AND IS EXPECTED TO STEADILY INTENSIFY WITH POSSIBLE RAPID INTENSIFICATION TOWARD THE APEX OF THE TURN. THIS IS DUE TO CONTINUED FAVORABLE ENVIRONMENT - LOW VWS, VERY WARM SEA SURFACE TEMPERATURES (SST), AND RE-ESTABLISHMENT OF THE POLEWARD OUTFLOW CHANNEL. THERE IS GOOD CONFIDENCE IN THIS PORTION OF THE TRACK FORECAST AS THE AVAILABLE NUMERICAL MODEL GUIDANCE, WITH THE EXCEPTION OF WBAR AS THE SOLE LEFT OUTLIER, HAS COME INTO BETTER AGREEMENT. C. AFTER TAU 72, TYPHOON GUCHOL WILL BEGIN TO RECURVE NORTHEASTWARD TO JUST WEST OF OKINAWA, TOWARD KYUSHU AND INTO THE BAROCLINIC ZONE. BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL COMMENCE EXTRA-TROPICAL TRANSITION. ALTHOUGH THE MODEL GUIDANCE HAS COME INTO A BETTER AGREEMENT OVER THE PAST 24 HOURS, THERE IS, HOWEVER, STILL LOW CONFIDENCE IN THE EXTENDED TRACK DUE TO UNCERTAINTIES IN THE WESTWARD EXTENT OF THE STR AND DEPTH AND ORIENTATION OF THE MID-LATITUDE SHORTWAVE TROUGH EXPECTED TO DEEPEN OVER THE EAST CHINA SEA AFTER TAU 72. DURING THIS PORTION OF THE FORECAST, TY 05W IS EXPECTED TO GRADUALLY WEAKEN AS SSTS DECREASE AND VWS INCREASE, HOWEVER, THE SYSTEM WILL REMAIN A STRONG STORM-FORCE LOW AS IT ENTERS MAINLAND JAPAN.// NNNN NNNN