WDPN31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MATMO) WARNING 
NR 03//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 10W (MATMO), LOCATED APPROXIMATELY 201 NM WEST-
NORTHWEST OF YAP, HAS TRACKED NORTHWARD AT 04 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE DEEP
CENTRALIZED CONVECTION HAS EXPANDED RADIALLY WITH AN EXPANSION OF THE
FEEDER BAND LOCATED ALONG THE SOUTHERN PERIPHERY TO THE WESTERN HALF
OF THE SYSTEM. THE POSITIONING OF THE SYSTEM REMAINS DIFFICULT DUE TO
THE DEEP CONVECTION, BUT A RECENT 172122Z SSMIS PASS HAS BEEN USED
FOR THE PLACEMENT OF THE LOW LEVEL CIRCULATION CENTER IN RELATIONSHIP
TO THE CONVECTION. THE CURRENT INTENSITY IS BASED ON THE COOLING
CLOUD TOPS WITH AN OVERALL EXPANSION OF CENTRAL CONVECTION OVER THE
PAST SIX HOURS. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED
IN A MARGINAL ENVIRONMENT WITH MODERATE (15 TO 20 KNOTS) VERTICAL
WIND SHEAR (VWS), WHICH IS PROVIDING EXCELLENT EQUATORWARD OUTFLOW,
EVIDENT IN ANIMATED WATER VAPOR IMAGERY. TS 10W IS SLOWLY TRACKING
NORTHWARD AND IS STARTING INTERACT WITH THE SUBTROPICAL RIDGE (STR)
TO THE NORTH OF THE SYSTEM.
3. FORECAST REASONING.
   A. THE TRACK PHILOSOPHY HAS SHIFTED SLIGHTLY FROM THE PREVIOUS
PROGNOSTIC REASONING MESSAGE AS MODEL GUIDANCE HAS COME INTO BETTER
AGREEMENT WITH THE INITIALIZATION OF TS 10W.
   B. TS 10W IS EXPECTED TO TRACK SLOWLY NORTHWARD, SHIFTING TO 
NORTHWESTWARD AS THE STR BECOMES THE DOMINANT STEERING INFLUENCE IN
THE NEXT 12 HOURS. TRACK SPEEDS WILL INCREASE IN RESPONSE TO THE 
IMPROVED INTERACTION AS WELL. VWS WILL REMAIN AT MODERATE LEVELS
THROUGH TAU 48, WHICH WILL INHIBIT STRONG INTENSIFICATION, BUT TS
10W IS EXPECTED TO STRENGTHEN WITH THE VERY FAVORABLE SEA SURFACE
TEMPERATURES (SST) AND HIGH OCEAN HEAT CONTENT ALONG THE FORECAST
TRACK. BEYOND TAU 48 THE VWS WILL DECREASE, ALLOWING FOR FURTHER
INTENSIFICATION. THE TRACK WILL REMAIN ON A GENERAL NORTHWEST TRACK
THROUGH TAU 72 ALONG THE SOUTHWESTERN QUADRANT OF THE DEEP LAYERED
STR.
   C. IN THE EXTENDED TAUS, A TRANSITORY MID-LATITUDE TROUGH WILL
CAUSE THE STR TO WEAKEN SLIGHTLY OVER SOUTHERN JAPAN, BUT WILL BE
SHORT LIVED AS THE TROUGH LIFTS TO THE NORTHEAST. THIS WILL ALLOW
THE STR TO BUILD BACK IN THE WEAKENED REGION, KEEPING TS 10W ON A
STEADY TRACK TO THE NORTHWEST. THE ENVIRONMENT WILL REMAIN FAVORABLE
FOR DEVELOPMENT THROUGH TAU 120, WITH THE MAXIMUM INTENSITY FORECAST
TO BE 95 KNOTS. DUE TO THE SLOW MOVEMENT IN THE NEAR TERM AND THE
RECENT SHIFT IN THE TRACK AT EXTENDED TAUS, THE CONFIDENCE IN THE
FORECAST TRACK REMAINS LOW.//
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