WDPN31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (BOPHA) WARNING NR 42//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 26W (BOPHA) LOCATED APPROXIMATELY 280 NM SOUTHWEST OF 
MANILA, PHILIPPINES HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY 
SHOWS THE DEEP CENTRALIZED CONVECTIVE CLOUD COVER HAS EXPANDED 
WITHIN THE SOUTHWESTERN QUADRANT OVER THE PAST FEW HOURS BUT SHOWS 
SIGNS OF A SLIGHT ELONGATION OF THE LOW LEVEL CIRCULATION CENTER 
(LLCC). DVORAK ESTIMATES FROM PGTW, KNES AND RJTD RANGE FROM 55 TO 
77 KNOTS, WITH THE CURRENT INTENSITY MAINTAINED AT 65 KNOTS AS THE 
ORGANIZATION OF THE SYSTEM HAS SEEN LITTLE IMPROVEMENT OVER THE PAST 
SIX HOURS. UPPER-LEVEL ANALYSIS INDICATES TY 26W REMAINS TO THE 
SOUTHEAST OF A COL REGION BETWEEN THE SUBTROPICAL RIDGES (STR) 
CENTERED TO THE EAST AND WEST. VERTICAL WIND SHEAR (VWS) IS 
CURRENTLY LOW (05 TO 10 KNOTS) AND WATER VAPOR IMAGERY INDICATES A 
RECENT DECREASE IN THE POLEWARD CHANNEL AS THE MID-LATITUDE TROUGH 
CONTINUES TO PROGRESS EASTWARD. TY 26W IS CURRENTLY STEERING ALONG 
THE SOUTHWESTERN PERIPHERY OF THE EASTERN LOBE OF THE STR AND HAS 
STARTED TO SLOW AS IT APPROACHES THE COL REGION.
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY IN THE LATER TAUS HAS SHIFTED TO A 
WEAK TURN NORTHWARD BEYOND TAU 72, BUT REMAINS QUASI-STATIONARY FOR 
TRACK SPEEDS.
   B. TY 26W IS FORECAST TO SLOW DOWN AS THE SYSTEM TRACKS INTO THE 
COL REGION BETWEEN THE TWO LOBES OF THE STR, BECOMING QUASI-
STATIONARY BY TAU 24. AS THE SYSTEM REORGANIZES FROM ITS TRANSIT 
OVER PALAWAN, THERE IS A SLIGHT INTENSIFICATION EXPECTED WITH 
FAVORABLE SEA SURFACE TEMPERATURES AND UPPER-LEVEL OUTFLOW. AFTER 
TAU 48 THE LOW OCEAN HEAT CONTENT, COOL DRY AIR ASSOCIATED WITH A 
NORTHEAST MONSOON SURGE, AND INCREASING VWS WILL START TO IMPACT THE 
STRUCTURE OF THE SYSTEM, LEADING TO A STEADY WEAKENING TREND THROUGH 
TAU 72.  
   C. AFTER TAU 72, TY 26W IS EXPECTED TO INTERACT WITH THE STRONG 
NORTHEAST MONSOON SURGE AND REMAIN IN A VERY WEAK STEERING 
ENVIRONMENT UNDERNEATH THE UPPER LEVEL COL REGION. THE SYSTEM IS 
EXPECTED TO CONTINUE TRACKING SLOWLY AND ERRATICALLY WITH THE 
TRACKING TAKING ON A POSSIBLE LOOPING MOTION PRIOR TO DISSIPATION. 
MODEL GUIDANCE PERSISTS WITH A WIDE VARIATION OF SOLUTIONS IN THE 
EXTENDED TAUS. ALL THE MODELS INDICATE A STEADY WEAKENING TREND, 
WHICH LEADS TO THE LOOPING TRACK AS THE STEERING INFLUENCE SWITCHES 
FROM A DEEP LAYER FLOW TO GETTING CAUGHT WITHIN THE LOW LEVEL FLOW. 
IT APPEARS THE LARGE VARIATION IN THE MODELS IS BASED ON THE TIMING 
OF THIS STEERING TRANSITION. THE OFFICIAL JTWC TRACK FORECAST HAS 
SHIFTED SLIGHTLY FROM THE PREVIOUS FORECAST BY TAKING THE SYSTEM TO 
THE NORTH IN THE EXTENDED TAUS AS IT WEAKENS FURTHER. DUE TO THE 
LARGE SPREAD IN MODEL GUIDANCE, TRACK CONFIDENCE REMAINS LOW.//
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