WDPN33 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOMPASU) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.9N 123.1E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 285 NM NORTH-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY LARGE
(1100+ NM) MONSOON DEPRESSION WITH WIDE FEEDER BANDS REACHING UP TO
THE EAST CHINA SEA TO THE NORTH AND DOWN TO THE SULU SEA TO THE 
SOUTH. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED 
ON A COMPOSITE RADAR LOOP FROM PAGASA AND TRIANGULATED FROM NEARBY 
SURFACE WIND OBSERVATIONS. THE INITIAL INTENSITY OF 50KTS IS BASED 
WITH MEDIUM CONFIDENCE AND OVERALL ASSESSMENT AND AN AVERAGE OF 
AGENCY AND AUTOMATED DVORAK ESTIMATES AND SUPPORTED BY NEARBY 
OBSERVATIONS INCLUDING THOSE FROM THE BASCO RADAR SITE (100NM NNW) 
REPORTING NORTHEASTERLY WINDS AT 35KTS AND SEA LEVEL PRESSURE AT 
987MB, AND REFLECTS THE SUSTAINED 6-HR CONVECTIVE STRUCTURE. 
ENVIRONMENTAL ANALYSES INDICATE MARGINALLY FAVORABLE CONDITIONS FOR 
DEVELOPMENT CHARACTERIZED BY WARM SSTS IN THE LUZON STRAIT AND 
STRONG POLEWARD OUTFLOW ALOFT OFFSET BY MODERATE VWS AND LAND 
INTERFERENCE FROM LUZON AND TAIWAN. THE CYCLONE IS TRACKING ALONG 
THE SOUTHWESTERN PERIPHERY OF THE MID-LAYER STR TO THE NORTHEAST.

INITIAL WIND RADII BASIS: PERSISTENCE AND NEARBY SURFACE
OBSERVATIONS.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 47 KTS AT 110540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: UNDER THE STEERING STR, TS KOMPASU WILL 
CONTINUE TO TRACK GENERALLY WESTWARD INTO THE SOUTH CHINA SEA (SCS) 
AND ACROSS SOUTHERN HAINAN AND THE GULF OF TONKIN BEFORE MAKING 
LANDFALL SHORTLY AFTER TAU 72 IN NORTHERN VIETNAM. THE MARGINALLY 
FAVORABLE ENVIRONMENT WILL FUEL GRADUAL INTENSIFICATION TO A PEAK OF 
60KTS AT TAU 36 IN THE SCS WHERE THE ENVIRONMENT IS EXPECTED TO BE 
MORE FAVORABLE. AFTERWARD, INCREASING VWS WILL SLOWLY WEAKEN THE 
SYSTEM DOWN TO 40KTS AT TAU 72. AFTER LANDFALL, INTERACTION WITH THE 
RUGGED VIETNAMESE TERRAIN WILL RAPIDLY ERODE THE SYSTEM DOWN TO 
20KTS AFTER IT CROSSES CAMBODIA INTO THAILAND.   

MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN VERY TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72,
THEN MEDIUM CONFIDENCE AFTERWARD. COROLLARY TO THIS, THERE IS
MEDIUM CONFIDENCE IN THE INTENSITY FORECAST UP TO TAU 72, THEN LOW
AFTERWARD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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