WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W WARNING NR 08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 27W (WUKONG), LOCATED APPROXIMATELY 170 NM 
SOUTH OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 11 KNOTS OVER 
THE PAST SIX HOURS. RECENT ENHANCED INFRARED (EIR) SATELLITE IMAGERY 
SHOWS CONVECTION HAS DECREASED IN INTENSITY AND AREAL COVERAGE AS 
THE SYSTEM TRACKS ACROSS THE PHILIPPINE ISLANDS. THE LOW LEVEL 
CIRCULATION CENTER IS DIFFICULT TO DISCERN IN RECENT MICROWAVE 
IMAGERY DUE TO PROXIMITY TO LAND AND DECREASING CONVECTIVE 
ORGANIZATION. THEREFORE THERE IS LOW CONFIDENCE IN THE INITIAL 
POSITION. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON 
DVORAK CURRENT INTENSITY ESTIMATES OF 35 KNOTS FROM BOTH RJTD AND 
PGTW. TS WUKONG IS LOCATED EQUATORWARD OF AN UPPER LEVEL RIDGE AXIS 
IN A REGION OF MODERATE (15-20 KNOT) VERTICAL WIND SHEAR. TS 27W IS 
TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE DEEP 
SUBTROPICAL RIDGE (STR) LOCATED OVER THE WESTERN NORTH PACIFIC OCEAN.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 27W IS FORECAST TO TRACK WESTWARD THROUGH TAU 24 AS IT
MOVES TOWARD THE WESTERN EXTENT OF THE STR. AS THE SYSTEM EMERGES 
OVER THE OPEN WATERS OF THE SOUTH CHINA SEA IN A AN AREA WITH 
INCREASED UPPER LEVEL OUTFLOW, THERE IS A NARROW WINDOW WHERE SLIGHT 
INTENSIFICATION MAY OCCUR. HOWEVER, THIS PHASE IS EXPECTED TO BE
SHORT-LIVED DUE TO INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH A
NORTHEAST SURGE EVENT. AS 27W WEAKENS AND BECOMES A MORE SHALLOW 
SYSTEM BETWEEN TAUS 24-36, THE PRIMARY STEERING MECHANISM IS 
EXPECTED TO SHIFT FROM THE STR TO THE STRONG NORTHEASTERLY WINDS. 
DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT, WITH THE EXCEPTION OF 
WBAR SHOWING AN UNLIKELY RECURVE INTO THE STRONG NORTHEASTERLY 
SURGE, ALL OTHER GUIDANCE INDICATES A WESTWARD TO EVENTUAL 
SOUTHWESTWARD TRACK, AND THERE IS HIGH CONFIDENCE IN THE JTWC 
FORECAST.//
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