WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (GONI) WARNING 
NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 22W (GONI), LOCATED APPROXIMATELY 32 
NM SOUTH-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ENHANCED
INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM CONTINUED TO ERODE 
AS THE LOW LEVEL CIRCULATION DRAGGED ACROSS SOUTHERN LUZON, 
TRAILING THE FRAGMENTED MAIN CONVECTION THAT HAS NOW EXITED 
INTO THE SOUTH CHINA SEA (SCS). THE INITIAL POSITION IS PLACED 
WITH  HIGH CONFIDENCE BASED ON A COMPOSITE RADAR LOOP AND 
TRIANGULATED FROM MULTIPLE SURFACE WIND OBSERVATIONS. THE 
INITIAL INTENSITY OF 55KTS IS DEDUCED FROM THE NEARBY WIND 
AND MEAN SEA LEVEL PRESSURE OBSERVATIONS. UPPER LEVEL DYNAMICS
ARE MARGINAL WITH MODERATE (20-25KT) VERTICAL WIND SHEAR (VWS) 
PARTIALLY OFFSET BY GOOD RADIAL OUTFLOW. THE CYCLONE IS TRACKING 
ALONG THE SOUTHERN  PERIPHERY OF A SLIGHTLY WEAKENED DEEP-LAYERED 
SUBTROPICAL RIDGE (STR) TO THE NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. UNDER THE STR, TS 22W WILL CONTINUE ON ITS CURRENT TRACK 
INTO THE SCS, RE-CONSOLIDATE, THEN TRACK MORE WESTWARD AS THE 
STR REBUILDS. THE MARGINAL UPPER LEVEL DYNAMICS COMBINED WITH 
FRICTIONAL EFFECTS FROM THE ISLANDS WILL CONTINUE TO WEAKEN TS 
22W TO 50KTS BY TAU 24. AFTERWARD, THE ADDITION OF COOLING SEA 
SURFACE TEMPERATURES (SST) IN THE SCS AND INCREASED WESTWARD 
OUTFLOW WILL MODERATE THE ENVIRONMENT INTO A QUASI-EQUILIBRIUM
RESULTING IN GENERALLY SUSTAINED 50KT INTENSITY WITH A SLIGHT 
PEAK TO 55KTS AT TAU 48.
   C. BEYOND TAU 72, TS GONI WILL TRACK WEST-SOUTHWESTWARD AS 
THE STR FURTHER BUILDS, MAKE LANDFALL OVER SOUTHERN VIETNAM NEAR
QUI NOHN JUST BEFORE TAU 96. COOLING SST AND LAND INTERACTION
WILL PRIMARILY ERODE THE SYSTEM TO DISSIPATION BY TAU 120. 
NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT WITH GRADUAL, EVEN 
SPREADING TO 270NM AT TAU 120, LENDING FAIR CONFIDENCE TO THE 
JTWC TRACK FORECAST.//
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