Tropical Storm DAMREY Advisory Fri Aug 31

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (DAMREY) WARNING NR
13//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (DAMREY), LOCATED APPROXIMATELY 340 NM
SOUTHEAST OF SASEBO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 20
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS A FAST MOVING, WELL-DEFINED, LOW LEVEL
CIRCULATION CENTER (LLCC) WITH DEVELOPING CONVECTION ALONG THE
EASTERN SEMI-CIRCLE. THE CURRENT INTENSITY IS BASED ON A 311330Z
OSCAT PASS THAT INDICATED WINDS NEAR 45 KNOTS, AND BASED ON THE
RECENT IMPROVEMENT IN CONVECTION, THE INTENSITY WAS INCREASED TO 55
KNOTS. DVORAK ESTIMATES STILL INDICATE A WEAKER SYSTEM. UPPER LEVEL
ANALYSIS INDICATES THE POLEWARD OUTFLOW IS BEGINNING TO TAP INTO THE
MID-LATITUDE WESTERLIES LOCATED OVER NORTHERN JAPAN. THE LINKAGE
REMAINS WEAK, AND WITH DRY AIR ENTRAINING ALONG THE SOUTHERN
PERIPHERY FROM THE WEST, IT IS THE ONLY OUTFLOW MECHANISM. TS 11W IS
CURRENTLY STEERING ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING.
   B. TS 11W IS FORECAST TO STAY ON A STEADY TRACK TOWARD MAINLAND
CHINA, TRACKING WESTWARD UNDER THE INFLUENCE OF THE STR TO THE
NORTH. A SLOW INTENSIFICATION OVER THE NEXT 24 HOURS WILL BRING THE
SYSTEM TO TYPHOON STRENGTH AS IT MOVES OVER VERY WARM SEA SURFACE
TEMPERATURES ASSOCIATED WITH THE KUROSHIO CURRENT AND THE POLEWARD
CHANNEL OUTFLOW IMPROVES. THIS INTENSIFICATION WILL BE SHORT-LIVED
AS THE SYSTEM IS EXPECTED TO MAKE LANDFALL SHORTLY AFTER TAU 36. THE
UPPER LEVEL ENVIRONMENT REMAINS THE LIMITING FACTOR TO A GREATER
DEVELOPMENTAL POTENTIAL. ONE CONCERN IS THE IMPACT OUTFLOW FROM TY
10W IS PLAYING ON THE EQUATORWARD OUTFLOW OF TS 11W AND THE VERTICAL
WIND SHEAR. AS THE TWO SYSTEMS APPROACH EACH OTHER AN ANALYSIS OF
THE WATER VAPOR IMAGERY SHOULD BE ABLE TO ANSWER THIS QUESTION.
MODEL GUIDANCE REMAINS IN FAIR AGREEMENT AND THEREFORE THE OFFICIAL
JTWC TRACK FORECAST IS BASED ON THE MODEL CONSENSUS WITH HIGH
CONFIDENCE. THERE ARE OUTLIERS (JGSM AND WBAR) INDICATING A MORE
NORTHERLY SHIFT BY TAU 36 AND GFDN SHOWING A SHARP TURN TOWARD
TAIWAN. THE CURRENT FORECAST FAVORS NGPS, ECMWF, AND GFS.//
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