WDPN31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (TEMBIN), LOCATED APPROXIMATELY 225 NM SOUTHEAST
OF TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS
CENTRAL CONVECTION HAS SLIGHTLY WARMED AS THE OVERALL STRUCTURE
BECAME MORE ELONGATED, AN INDICATION OF INCREASED SHEAR. THE POLEWARD
OUTFLOW HAS SLIGHTLY DIMINISHED AS THE TUTT TO THE NORTH FILLED. THE
INITIAL POSITION IS BASED ON FIXES FROM MULTIPLE AGENCIES. THE
INITIAL INTENSITY IS BASED ON A MICROWAVE EYE ON A 212159Z AMSU-B
IMAGE AND FROM RADAR FIXES FROM TAIWAN CENTRAL WEATHER BUREAU WITH
HIGH CONFIDENCE. THE INITIAL INTENSITY IS AVERAGED FROM DVORAK
ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES
TY 15W HAS SUSTAINED A MESOSCALE ANTICYCLONE THAT CONTINUES TO
PROVIDE GOOD OUTFLOW DESPITE THE INCREASED SHEAR. THE SYSTEM IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE TO THE NORTH. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 15W IS FORECAST TO TRACK ON A MORE WESTWARD DIRECTION AS THE
STR FIRMLY ASSUMES STEERING OF THE SYSTEM AFTER TAU 12. THE
INTENSITIES WILL BEGIN TO DROP AFTER TAU 24 AS VERTICAL WIND SHEAR
INCREASES. TY 15W WILL MAKE LANDFALL ALONG THE CENTRAL EASTERN COAST
OF TAIWAN SHORTLY BEFORE TAU 36, WEAKEN DUE TO TOPOGRAPHIC EFFECTS,
CROSS THE TAIWAN STRAIT, AND MAKE A SECONDARY LANDFALL INTO CHINA
BEFORE TAU 72.
   C. AFTER TAU 72, TYPHOON TEMBIN WILL RAPIDLY DECAY DUE TO
TOPOGRAPHICAL EFFECTS, TRACK SOUTHWESTWARD WITH THE LOW LEVEL FLOW,
AND DISSIPATE AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND BY TAU 120.
THE AVAILABLE NUMERICAL MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT
UP TO TAU 72 WITH TWO DISTINCT OUTLIERS - AFTER TAU 24, EGRR IS
UNREALISTICALLY TRACKING THE VORTEX ABRUPTLY NORTHWARD INTO THE
STEERING RIDGE; GFS MAKES A COUNTER-CLOCKWISE LOOP AFTER TAU 36,
POSSIBLY INDICATING A BINARY INTERACTION WITH TYPHOON 16W, CURRENTLY
LOCATED SOUTHWEST OF IWO TO, JAPAN. THERE IS HIGH CONFIDENCE IN THE
TRACK FORECAST UP TO TAU 72, AFTER WHICH, THE CONFIDENCE IS LOW DUE
TO THE UNCERTAINTY OF THE LONG RANGE SYNOPTIC PATTERN.   //
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