WDPN31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (SAUDEL) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS. 
   TYPHOON 19W (SAUDEL), LOCATED APPROXIMATELY 263 NM SOUTH
OF HONG KONG, HAS TRACKED WESTWARD AT 02 KNOTS OVER THE PAST SIX
HOURS. THE CURRENT POSITION IS BASED ON RECENT MICROWAVE SATELLITE 
IMAGERY, INCLUDING 230800Z SSMIS AND 231102Z NOAA-19 MHS PASSES, AND A 
231400Z PGTW SATELLITE FIX. THE INTENSITY OF 75 KNOTS IS CONSISTENT 
WITH A CONSENSUS OF SUBJECTIVE DVORAK AND AUTOMATED INTENSITY 
ESTIMATES. TY 19W IS TRACKING VERY SLOWLY WESTWARD UNDER THE STEERING 
INFLUENCE OF WEAK RIDGING CONNECTING TWO SUBTROPICAL RIDGE CENTERS 
SITUATED TO THE WEST AND TO THE EAST OF THE SYSTEM. PERSISTENT EASTERLY 
VERTICAL WIND SHEAR (15-20 KNOTS) IS DISPLACING DEEP CONVECTION TO THE 
WEST OF THE LOW-LEVEL CIRCULATION CENTER. HOWEVER, WARM SEA SURFACE 
TEMPERATURES (28-29C) AND MODERATE, WESTWARD UPPER-LEVEL OUTFLOW HAVE 
ENABLED THE SYSTEM TO MAINTAIN INTENSITY OVER THE PAST SIX HOURS.   
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. SUBTROPICAL RIDGING IS EXPECTED TO BUILD TO THE NORTH OF TY 19W 
OVER THE NEXT SEVERAL DAYS AS AN EXPANSIVE MID-LATITUDE TROUGH THAT 
PREVIOUSLY WEAKENED THE STEERING RIDGE PULLS AWAY. TY 19W WILL MOVE 
STEADILY WESTWARD TO WEST-SOUTHWESTWARD UNDER THE CONTINUOUS STEERING 
INFLUENCE OF THE BUILDING RIDGE THROUGH THE FORECAST PERIOD. STEADY 
WEAKENING IS LIKELY AS PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR 
CONTINUES TO IMPACT THE SYSTEM. HOWEVER, PASSAGE OVER WARM WATER AND 
SUPPORTIVE UPPER-LEVEL OUTFLOW SHOULD PREVENT DISSIPATION PRIOR TO 
LANDFALL IN CENTRAL VIETNAM, WHICH IS ANTICIPATED TO OCCUR IN ABOUT 54 
HOURS. THE SYSTEM IS EXPECTED TO FULLY DISSIPATE OVER LAND BY TAU 72. 
NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE OVERALL 
FORECAST SCENARIO, AND THE MODEL TRACK FORECAST CONSENSUS HAS BEEN 
STEADY FOR THE PAST SEVERAL RUNS. THEREFORE, THERE IS HIGH CONFIDENCE 
IN THE CURRENT JTWC TRACK FORECAST. 
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