WDPN31 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 33//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (TEMBIN), LOCATED APPROXIMATELY 320 NM 
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED EASTWARD AT 05 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) INDICATES THE PRIOR WEAKENING TREND HAS LEVELED OFF AND 
CONVECTION IS RE-BUILDING OVER THE LOW LEVEL CIRCULATION CENTER 
(LLCC). ALTHOUGH THE NORTHEASTERLY VERTICAL WIND SHEAR (VWS) 
ASSOCIATED WITH EQUATORWARD OUTFLOW FROM TY 16W HAS EASED, ITS 
EFFECTS ARE STILL SEEN IN MSI AND ANIMATED WATER VAPOR IMAGERY. 
ADDITIONALLY, A MID-LATITUDE TROUGH APPROACHING FROM THE NORTH IS 
PUTTING PRESSURE ON THE POLEWARD OUTFLOW. THE INITIAL POSITION IS 
BASED ON ANIMATED MSI AND A 262212Z CORIOLIS 37GHZ MICROWAVE IMAGE 
WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 80 KNOTS 
BASED ON AN AVERAGE OF DVORAK INTENSITY ESTIMATES OF 77 KNOTS FROM 
PGTW AND RJTD, AND TAKING INTO ACCOUNT THE IMPROVING CONVECTION. TY 
15W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT BETWEEN A WEAK 
SUBTROPICAL RIDGE (STR) TO THE NORTH AND A BUILDING NEAR-EQUATORIAL 
RIDGE (NER) TO THE SOUTH. ADDITIONALLY, THERE MAY BE SOME WEAK 
INTERACTION OCCURRING WITH TY 16W, WHICH IS CENTERED APPROXIMATELY 
685 NM NORTHEAST OF TY 15W'S CENTER.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 15W IS FORECAST TO MOVE INTO A MORE PRONOUNCED STEERING 
ENVIRONMENT, ALONG THE NORTHWESTERN PERIPHERY OF THE NER, WHICH IS 
FORECAST TO BUILD TO THE EAST AS TY 16W TRACKS QUICKLY POLEWARD INTO 
THE YELLOW SEA. THIS WILL ALLOW TY 15W TO TURN POLEWARD AND 
ACCELERATE JUST EAST OF, OR POSSIBLY OVER TAIWAN. DYNAMIC MODEL 
GUIDANCE IS IN POOR AGREEMENT WITH A 250+ NM SPREAD AT TAU 72. THE 
JTWC FORECAST IS POSITIONED WEST OF THE MODEL CONSENSUS, FAVORING 
THE ECMWF AND JGSM SOLUTIONS, WHICH HAVE BEEN VERY CONSISTENT. THE 
GFS MODEL IS THE MAJOR EASTERN OUTLIER, WITH A NORTHEASTWARD TRACK 
INTO THE YELLOW SEA. TY 15W IS FORECAST TO GRADUALLY WEAKEN THOUGH 
TAU 36 DUE TO ONGOING INTERACTION WITH LAND. THE INTENSITY FORECAST 
IS BASED ON AN EAST-OF-TAIWAN FORECAST SCENARIO, HOWEVER, A SLIGHT 
WESTWARD SHIFT IN TRACK COULD FURTHER DEGRADE THE INTENSITY. THE 
SYSTEM IS FORECAST TO SKIRT THE COAST SOUTHEAST OF SHANGHAI, CHINA 
NEAR TAU 72.  
  C. AFTER TAU 72, TY 15W IS FORECAST TO TRACK NORTH-NORTHWESTWARD 
ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. DYNAMIC MODEL 
GUIDANCE IS IN POOR AGREEMENT, WITH A LARGE SPREAD AT TAU 120. GFDN 
IS THE WESTERN-MOST OUTLIER WHEREAS GFS REMAINS THE EASTERN-MOST 
OUTLIER, WITH A FASTER TRANSLATION SPEED RESULTING IN A 
NORTHEASTWARD TRACK OVER THE KOREAN PENINSULA. THE JTWC FORECAST 
FAVORS THE ECMWF SOLUTION AND REMAINS CONSISTENT WITH PREVIOUS 
WARNINGS. TY 15W IS EXPECTED TO WEAKEN SLOWLY DUE TO INTERACTION 
WITH LAND AND SHOULD DECREASE TO 30 TO 35 KNOTS BY TAU 120. BASED ON 
THE COMPLEX STEERING PATTERN, UNCERTAINTIES IN THE LAND INTERACTION 
WITH TAIWAN, AS WELL AS LARGE MODEL SPREAD, THERE IS LOW CONFIDENCE 
IN THE FORECAST TRACK.//
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