WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MAYSAK) WARNING NR 
37//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 04W (MAYSAK), LOCATED APPROXIMATELY 139 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. MULTISPECTRAL SATELLITE IMAGERY (MSI)
SHOWS THE ASSOCIATED CONVECTION HAS BEGUN TO SEVER FROM THE LOW LEVEL
CIRCULATION CENTER THAT IS ABOUT TO MAKE LANDFALL INTO LUZON. THE
SUDDEN OROGRAPHIC LIFT INTO THE RUGGED MOUNTAIN RANGE CAUSED A
MOMENTARY BURST OF HEIGHTENED CONVECTION. THE INITIAL POSITION IS
BASED ON THE MSI ANIMATION AND ON A COMPOSITE RADAR LOOP FROM DOST
PHILIPPINES. THE INITIAL INTENSITY OF 45 KNOTS IS BASED ON AN OVERALL
ASSESSMENT OF DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER-LEVEL
ANALYSIS INDICATES THE SYSTEM IS TRACKING IN AN AREA OF MODERATE (15
TO 20 KNOT) VERTICAL WIND SHEAR (VWS) THAT IS PARTIALLY OFFSET BY
RADIAL OUTFLOW. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY
OF THE DEEP LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS MAYSAK, IMMINENTLY MAKING LANDFALL OVER SOUTHERN ISABELA,
WILL CONTINUE NORTHWESTWARD THROUGH TAU 48 UNDER THE STEERING
INFLUENCE OF THE STR. INCREASING VWS AND INTERACTION WITH THE RUGGED
TERRAIN WILL RAPIDLY ERODE THE SYSTEM. HOWEVER, TS 04W WILL EMERGE IN
THE SOUTH CHINA SEA AS A WEAK TROPICAL STORM. NEAR TAU 48, A
NORTHEASTERLY COLD SURGE EVENT THROUGH TAIWAN STRAIT WILL AID IN THE
DISSIPATION OF TS MAYSAK BY TAU 72 AS IT DIPS SOUTHWESTWARD WITH THE
LOW LEVEL FLOW. NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT,
LEADING TO HIGH CONFIDENCE IN THE JTWC FORECAST.//
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