WDPN31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W (CHAN-HOM) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 16W (CHAN-HOM), LOCATED APPROXIMATELY 280 NM
EAST-NORTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT
07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED 
SATELLITE IMAGERY DEPICTS FLARING CONVECTION WRAPPING AROUND A LARGE 
AND RAGGED 50NM DIAMETER EYE. THE INITIAL POSITION WAS PLACED WITH 
GOOD CONFIDENCE USING MULTISPECTRAL SATELLITE AND A 072325Z GMI 
37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY REMAINS ASSESSED AT 70 
KNOTS BASED ON AN AVERAGE OF PGTW/RJTD DVORAK INTENSITY ESTIMATES OF 
T4.0 (65 KNOTS) AND A KNES ESTIMATE OF T4.5 (77 KNOTS). VERTICAL 
WIND SHEAR IS GRADUALLY INCREASING (10-15 KNOTS), BUT OVERALL 
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH ENHANCED POLEWARD 
OUTFLOW, GOOD EQUATORWARD OUTFLOW, AND WARM (28-29 CELSIUS) 
SEA SURFACE TEMPERATURES. THE SYSTEM IS TRACKING ALONG THE 
SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO 
THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 16W CONTINUES TO TURN POLEWARD AND IS FORECAST TO TRACK 
TOWARD THE NORTH AND THEN NORTHEASTWARD BY TAU 24 TO 36. NUMERICAL 
MODEL GUIDANCE IS NOW SPLIT INTO SOMEWHAT OF A BIFURCATION SCENARIO, 
WITH THE GFS AND UKMET GLOBAL DETERMINISTIC AND ENSEMBLE MODELS 
SUGGESTING A SHARPER TURN TOWARD THE EAST-NORTHEAST AND THE OTHER 
MODELS INDICATING A TRACK CLOSER TO THE COAST OF JAPAN. THE JTWC 
FORECAST TRACK LIES CLOSER TO THE COAST OF JAPAN AND FALLS TO THE 
LEFT OF THE MULTI-MODEL CONSENSUS. AFTER TAU 36, THE SYSTEM WILL 
ACCELERATE NORTHEASTWARD AS IT INTERACTS WITH THE ZONAL MIDLATITUDE 
FLOW. AS VERTICAL SHEAR INCREASES, THE WINDOW OF OPPORTUNITY FOR TY 
16W TO INTENSIFY IS GRADUALLY CLOSING, SO THE PEAK INTENSITY 
FORECAST HAS BEEN SLIGHTLY LOWERED TO 75 KNOTS BY TAU 12. BASED ON 
THE ZONAL STEERING PATTERN AND SPREAD IN SOLUTIONS, THERE IS FAIR 
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, THE SYSTEM WILL CONTINUE TO ACCELERATE EAST-
NORTHEASTWARD AS IT MOVES AWAY FROM JAPAN. DUE TO HIGH VERTICAL 
WIND SHEAR, TY 16W IS EXPECTED TO WEAKEN STEADILY FOR THE 
REMAINDER OF THE FORECAST PERIOD TO AN INTENSITY OF 45 KTS BY TAU 
96. TY 16W WILL COMPLETE EXTRATROPICAL TRANSITION (ETT) BY TAU 96 AS 
IT GETS ABSORBED INTO THE BAROCLINIC ZONE. THE JTWC FORECAST 
TRACK LIES SLIGHTLY POLEWARD OF THE MULTI-MODEL CONSENSUS. DUE TO 
UNCERTAINTY IN THE TRACK AS THE SYSTEM UNDERGOES ETT, THERE IS FAIR 
CONFIDENCE IN THE JTWC FORECAST TRACK. ALL INTERESTS IN THE KANTO 
PLAIN REGION OF JAPAN SHOULD PAY CLOSE ATTENTION TO THE TIMING OF 
THE NORTHEASTWARD TURN AND EVOLUTION OF THE WIND FIELD, GIVEN THE 
AMBIENT NORTHEASTERLY ENVIRONMENTAL FLOW. THE POSSIBILITY EXISTS FOR 
A MINOR FORECAST TRACK SHIFT TOWARD THE WEST THAT WOULD BRING THE 
CORE OF TY 16W ASHORE.//
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