WDPN31 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (SON-TINH) 
WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (SON-TINH), LOCATED APPROXIMATELY 197 NM
SOUTH-SOUTHWEST OF HONG KONG, HAS TRACKED WESTWARD AT 22 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS THAT TS 11W REMAINS A COMPACT SYSTEM WHICH CONTINUES TO RAPIDLY
TRACK WESTWARD. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON A 171104Z 91GHZ SSMIS MICROWAVE IMAGE WHICH SHOWS COMPACT
BANDING AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
INTENSITY OF 40 KNOTS IS HEDGED BETWEEN DVORAK INTENSITY ESTIMATES OF
T2.5 (35 KNOTS) FROM PGTW AND RJTD AND A DVORAK INTENSITY ESTIMATE OF
T3.0 (45 KNOTS) FROM KNES. ENVIRONMENTAL ANALYSIS REVEALS TS 11W IS
EXPERIENCING MODERATE (20 KNOT) VERTICAL WIND SHEAR. UPPER LEVEL
WINDS ARE PROVIDING MODERATE EQUATORWARD OUTFLOW BUT ONLY WEAK
POLEWARD OUTFLOW. SEA SURFACE TEMPERATURES REMAIN FAVORABLE, RANGING
BETWEEN 27 TO 28 DEGREES CELSIUS. TS 11W IS TRACKING WESTWARD AROUND
THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) WHICH IS
LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 11W WILL CONTINUE RAPIDLY TRACKING WESTWARD ALONG THE
SOUTHERN EXTENT OF THE STR LOCATED TO THE NORTHEAST. THE STR WILL
REMAIN IN PLACE AND CONTINUE TO BE THE PRIMARY STEERING INFLUENCE FOR
THE REMAINDER OF THE FORECAST. MARGINAL ENVIRONMENTAL CONDITIONS WILL
ALLOW FOR A BRIEF PERIOD OF INTENSIFICATION TO 45 KNOTS BY TAU 6.
HOWEVER, AFTER TAU 6, LAND INTERACTION WITH HAINAN ISLAND WILL
PREVENT ADDITIONAL DEVELOPMENT. WARM SEA WATER IN THE GULF OF TONKIN
WILL HELP TS 11W MAINTAIN AN INTENSITY OF 35 KNOTS THROUGH TAU 24. TS
11W WILL MAKE LANDFALL IN NORTHERN VIETNAM SHORTLY AFTER TAU 24 AND
DISSIPATE BY TAU 48 AS IT TRACKS INLAND. DYNAMIC MODEL GUIDANCE IS IN
TIGHT AGREEMENT, THEREFORE THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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