WDPN31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (SAUDEL) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS. 
   TYPHOON (TY) 19W (SAUDEL), LOCATED APPROXIMATELY 336 NM SOUTH-
SOUTHEAST OF HONG KONG, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS 
THE CENTRAL CONVECTION HAS BECOME MORE COMPACT AND SYMMETRICAL AS 
RAIN BANDS WRAPPED TIGHTER INTO THE LLC. THE INITIAL POSITION IS 
PLACED WITH GOOD CONFIDENCE BASED ON AN EVOLVING MICROWAVE EYE IN THE 
212308Z SSMIS PASS. THE INITIAL INTENSITY OF 65KTS IS BASED ON THE 
DVORAK ESTIMATES OF T4.0/65KTS FROM PGTW, KNES, AND RJTD. THE 
ENVIRONMENT REMAINS FAVORABLE FOR CONTINUED DEVELOPMENT WITH LOW 
(10-15KT) VERTICAL WIND SHEAR (VWS), WARM (29-30C) SEA SURFACE 
TEMPERATURES (SST) IN THE SOUTH CHINA SEA, AND RADIAL UPPER-LEVEL 
OUTFLOW. A SHORTWAVE TROUGH DIGGING INTO TAIWAN HAS WEAKENED THE 
STEERING SUBTROPICAL RIDGE (STR), PULLING THE CYCLONE POLEWARD INTO 
THE COL FORMED BETWEEN THE SPLIT STRS - ONE TO THE WEST AND ONE TO 
THE EAST.  
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. OVER THE NEXT 24-36HRS, TY 19W WILL TRACK VERY SLOWLY AND/OR 
BECOME QUASI-STATIONARY IN THE COL. AFTERWARD, THE STR TO THE EAST 
WILL BUILD AND EXTEND WESTWARD, BECOME THE DOMINANT STEERING 
MECHANISM, AND SLOWLY DRIVE THE CYCLONE WESTWARD TOWARD CENTRAL 
VIETNAM. BY TAU 72, TY 19W WILL HAVE REACHED A POINT APPROXIMATELY 
65NM SOUTH-SOUTHWEST OF HAINAN, CHINA. THE FAVORABLE ENVIRONMENT WILL 
FUEL INTENSIFICATION TO A PEAK OF 75KTS BY TAU 24; AFTERWARD, COOLING 
SST DUE TO UPWELLING IN THE COL AND INCREASING VWS AS THE CYCLONE 
TRACKS WESTWARD WILL GRADUALLY WEAKEN THE SYSTEM AND BY TAU 72, WILL 
BE DOWN TO 50KTS. NUMERICAL MODELS ARE IN AGREEMENT AS FAR AS 
RETAINING THE SYSTEM IN THE COL FOR A PERIOD OF TIME. HOWEVER, THEY 
OFFER VARYING SOLUTIONS AS TO WHEN THE CYCLONE WILL EXIT OUT OF THE 
COL WITH NVGM TAKING A MORE POLEWARD TRACK AND AFUM, UEMN, AND EGRR 
TAKING A MORE DELAYED LOOPING MOTION. IN VIEW OF THESE, THERE IS LOW 
CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. 
   C. BEYOND TAU 72, TY SAUDEL WILL TRACK MORE WEST-SOUTHWESTWARD AS 
THE STR TO THE WEST ASSUMES STEERING, MAKE LANDFALL JUST NORTH OF 
HUE, VIETNAM, BY TAU 78, THEN DRAG ACROSS LAOS AND INTO THAILAND BY 
TAU 120. THE RUGGED TERRAIN WILL PRIMARILY ERODE THE SYSTEM TO 
DISSIPATION BY TAU 120. THERE IS ALSO LOW CONFIDENCE IN THE EXTENDED 
PORTION OF THE JTWC FORECAST TRACK BECAUSE IT IS DEPENDENT OF THE 
NEAR-TO-MID TERM PORTION OF THE FORECAST TRACK.//
NNNN