WDPN31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (GUCHOL) WARNING 
NR 10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 05W (GUCHOL), LOCATED APPROXIMATELY 70 NM 
EAST-NORTHEAST OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 09 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
SHOWS AN INCREASE IN THE OVERALL HORIZONTAL EXTENT OF THE RAINBANDS 
AND AN INCREASE IN THE TIGHTLY CURVED BANDING OVER THE EASTERN SEMI-
CIRCLE OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 130545Z AMSU-B 
MICROWAVE IMAGE DEPICTS DEEP CONVECTION AROUND THE MAJORITY OF THE 
LLCC WITH A SLIGHT BREAK OVER THE NORTHWESTERN QUADRANT. THE 
INITIAL POSITION WAS BASED ON THE AMSU-B IMAGE ALONG WITH ANALOGOUS 
CENTER FIXES FROM PGTW AND RJTD WITH GOOD CONFIDENCE. THE INITIAL 
INTENSITY WAS INCREASED SLIGHTLY TO 40 KNOTS BASED ON THE IMPROVING 
STRUCTURE OF THE LLCC AND THE PGTW DVORAK ESTIMATE OF 45 KNOTS. 
UPPER-LEVEL ANALYSIS INDICATES A POINT SOURCE OF DIVERGENCE HAS 
FORMED A COUPLE OF DEGREES EAST OF THE LLCC. THIS FEATURE IS 
PROVIDING FOR WEAK VERTICAL WIND SHEAR AND EXCELLENT DIVERGENCE 
ALOFT. WATER VAPOR IMAGERY DURING THE PAST 24 HOURS CONFIRMS THE 
GREATLY IMPROVED OUTFLOW AND ALSO SHOWS A DEVELOPING OUTFLOW 
CHANNEL INTO A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO 
THE EAST. TS 05W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY 
OF A MID-LEVEL SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 05W IS EXPECTED TO CONTINUE TRACKING ALONG THE SOUTHERN TO 
SOUTHWESTERN PERIPHERY OF THE STEERING STR. THE SYSTEM SHOULD 
CONTINUE TO TRACK WEST-NORTHWESTWARD TO NORTHWESTWARD THROUGH TAU 
72 AS THE STR WEAKENS AHEAD OF AN APPROACHING MID-LATITUDE TROUGH, 
CURRENTLY DIGGING SOUTH OF CHINA. THE SYSTEM SHOULD CONTINUE TO 
INTENSIFY UNDER THE FAVORABLE OUTFLOW AND WARM SEA SURFACE 
TEMPERATURES. MODEL GUIDANCE IS IN TIGHT AGREEMENT TROUGH TAU 48; 
THEREFORE, THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK.
   C. AFTER TAU 72, TS 05W IS FORECAST TO ROUND THE SOUTHWESTERN 
PERIPHERY OF THE WEAKENING STR AND TURN MORE POLEWARD. IN THE 
EXTENDED FORECAST, MODEL GUIDANCE SPREADS WITH NOGAPS AND GFDN 
MAKING THE FASTEST TURN POLEWARD SOUTH OF OKINAWA, JAPAN. UKMO AND 
GFS MAINTAIN A MORE NORTHWESTWARD TRACK AND SLOWLY TURN THE SYSTEM 
POLEWARD. THIS LATEST MODEL RUN SHOWS THE ECMWF NOW PORTRAYING A RE-
CURVE SCENARIO WHEREAS BEFORE IT MAINTAINED A NORTHWESTWARD TRACK 
TOWARDS SOUTHEASTERN ASIA. THERE IS LOW CONFIDENCE IN THE RE-
CURVATURE TIMING AND POSITION DUE TO THE MODEL SPREAD IN THE 
EXTENDED FORECAST. HOWEVER, THE JTWC FORECAST FAVORS A RE-CURVATURE 
SCENARIO BASED ON THE DEEPENING MID-LATITUDE TROUGH. TS GUCHOL 
SHOULD CONTINUE TO STEADILY INTENSIFY AS IT TRACKS OVER WARM WATER 
AND AS OUTFLOW INCREASES INTO THE MID-LATITUDE TROUGH.//
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