WDPN31 PGTW 160300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (MEKKHALA) WARNING 
NR 11//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 01W (MEKKHALA), LOCATED APPROXIMATELY 617 NM 
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER 
(LLCC) WITH DEEP CONVECTIVE BANDING OVER THE WESTERN SEMI-CIRCLE. A 
152230Z SSMIS IMAGE REVEALS IMPROVED SHALLOW BANDING WRAPPING INTO A 
WELL-DEFINED LLCC, THEREFORE, THERE IS GOOD CONFIDENCE IN THE 
INITIAL POSITION. UPPER-LEVEL ANALYSIS INDICATES CONTINUED EASTERLY 
VERTICAL WIND SHEAR (15-20 KNOTS) WITH WEAKENED POLEWARD OUTFLOW AS 
EVIDENT IN WATER VAPOR IMAGERY. THE INITIAL INTENSITY IS ASSESSED AT 
40 KNOTS AND IS HEDGED SLIGHTLY HIGHER THAN THE DVORAK ESTIMATES OF 
35 KNOTS FROM ALL AGENCIES. TS MEKKHALA IS 
CURRENTLY TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A LOW- 
TO MID-LEVEL SUBTROPICAL RIDGE (STR).     
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 01W WILL CONTINUE TO TRACK WESTWARD TO WEST-NORTHWESTWARD 
UNDER THE STR LOCATED TO THE NORTH THROUGH TAU 72. TS 01W IS 
FORECAST TO MAKE LANDFALL IN THE CENTRAL PHILIPPINES NEAR TAU 36. TS 
01W IS FORECAST TO SLOWLY INTENSIFY PRIOR TO MAKING LANDFALL DUE TO 
STRONG DIVERGENCE ALOFT AND FAVORABLE SST, OFFSET BY MODERATE 
EASTERLY VERTICAL WIND SHEAR. TS 01W IS FORECAST TO CONTINUE 
TRACKING WESTWARD TO WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE 
OF THE STR.
   C. AFTER TAU 72, TS MEKKHALA WILL RAPIDLY WEAKEN DUE TO LAND 
INTERACTION AND INCREASED VWS. THIS WILL CAUSE THE SYSTEM TO TURN TO 
THE WEST-SOUTHWEST UNDER THE STEERING INFLUENCE OF THE NORTHEASTERLY 
SURGE. GFS, JGSM, ECMWF AND EGRR RECURVE THE SYSTEM NORTHWARD, 
HOWEVER, AFTER CONDUCTING A MODEL ANALYSIS, THEY ARE ERRONEOUSLY 
JUMPING VORTICITY MAXIMUMS TO AN AREA WITHIN THE STRONG WESTERLIES. 
THE OFFICIAL JTWC FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS, 
HOWEVER, DUE TO THE BIFURCATION MENTIONED ABOVE, THERE IS LOW 
CONFIDENCE IN THE FORECAST TRACK.//
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