MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (SONGDA) WARNING NR 12// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 23W (SONGDA), LOCATED APPROXIMATELY 310 NM NORTHEAST OF IWO TO, JAPAN HAS TRACKED AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A SMALL PINHOLE EYE STILL EVIDENT BUT APPEARS TO BE CLOSING. WATER VAPOR IMAGERY DEPICTS CONTINUED INTERACTION WITH THE MID-LATITUDE WESTERLIES AND ASSOCIATED MODERATE TO HIGH VERTICAL WIND SHEAR (VWS). A 102111Z SSMIS 91GHZ IMAGE REVEALS A DEEP CONVECTIVE INNER CORE STILL EVIDENT; HOWEVER, THE REMAINING CONVECTION HAS ELONGATED TO THE NORTHEAST DUE TO THE SOUTHWESTERLY VWS. THE CURRENT POSITION IS BASED ON THE PINHOLE EYE WITH HIGH CONFIDENCE. THE INTENSITY REMAINS AT 100 KNOTS BASED ON UNCHANGED DVORAK CURRENT INTENSITY ESTIMATES OF T5.5 (102 KNOTS). TY 23W IS TRACKING IN A MARGINALLY UNFAVORABLE ENVIRONMENT DUE TO MODERATE VWS OFFSETTING THE STRONG POLEWARD OUTFLOW WHICH IS CAUSING THE CONVECTIVE STRUCTURE TO WEAKEN. TY SONGDA HAS SLOWED FORWARD SPEED AND IS BEGINNING TO TURN TO THE NORTHEAST AS IT ROUNDS THE DEEP LAYERED SUB-TROPICAL RIDGE (STR) AXIS. 3. FORECAST REASONING. A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY SONGDA WILL CONTINUE TURNING TO THE NORTHEAST AS IT TRACKS NORTH OF THE STEERING STR AXIS. AFTERWARDS THE TYPHOON WILL RAPIDLY ACCELERATE NORTHEASTWARD AS IT EMBEDS WITHIN THE MID-LATITUDE WESTERLY FLOW. EXPECT ENVIRONMENTAL CONDITIONS TO CONTINUE TO DETERIORATE AS THE SYSTEM GAINS LATITUDE DUE TO VWS ABOVE 30 KNOTS AND SSTS DROPPING BELOW 26 CELSIUS NEAR TAU 36. TY 23W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 24 AS IT INTERACTS WITH THE BAROCLINIC ZONE AND COMPLETE ETT BY THE END OF THE FORECAST PERIOD AS A STRONG COLD-CORE LOW. THERE IS HIGH CONFIDENCE IN THE FORECAST DUE TO VERY TIGHT AGREEMENT IN ALL MODEL TRACKERS.// NNNN NNNN