WDPN32 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (NARI) WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 24W (NARI), LOCATED APPROXIMATELY 544 NM EAST OF HUE, 
VIETNAM, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. 
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) INDICATES TY 24W 
HAS BEEN ABLE TO CONSOLIDATE THE LOW LEVEL CIRCULATION CENTER 
(LLCC), WITH A MAJOR BAND OF DEEP CONVECTION BUILDING ALONG THE 
WESTERN AND SOUTHERN PERIPHERIES INTO THE LLCC. THE CURRENT 
INTENSITY HAS BEEN INCREASED SLIGHTLY AS THE OVERALL ORGANIZATION 
HAS IMPROVED FROM THE PREVIOUS FORECAST. DVORAK ESTIMATES STILL 
INDICATE A SLIGHT WEAKENING TREND, BUT BASED ON CONSTRAINTS, HAVE 
YET TO REFLECT THE REORGANIZATION OVER THE PAST 18 HOURS. UPPER 
LEVEL ANALYSIS INDICATES BROAD DIVERGENCE ALOFT ASSOCIATED WITH AN 
UPPER LEVEL ANTICYCLONE TO THE NORTHEAST IS PROVIDING THE OUTFLOW 
MECHANISM FOR THE BUILDING CENTRAL CONVECTION; HOWEVER, IT IS ALSO 
PRODUCING MODERATE LEVELS OF VERTICAL WIND SHEAR (VWS) (15 TO 20 
KNOTS). TY 24W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP-
LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 24W IS EXPECTED TO TRACK GENERALLY WESTWARD THROUGH TAU 72 
UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED STR. AS THE 
SYSTEM TRACKS ACROSS THE WARM OPEN WATERS OF THE SOUTH CHINA SEA 
(SCS), TY 24W WILL INTENSIFY TO A PEAK OF 95 KNOTS BY TAU 24 AS 
FAVORABLE ENVIRONMENTAL CONDITIONS PERSIST. AFTER TAU 36, INCREASING 
LAND INTERACTION WILL BEGIN TO SLOWLY HAMPER THE SYSTEM AS TY 24W 
TREKS INTO THE MORE RESTRICTED WATERS OF THE WESTERN SCS. SLIGHTLY 
AFTER TAU 48 TY 24W WILL MAKE LANDFALL NEAR HUE, VIETNAM, AND BEGIN 
TO RAPIDLY ERODE DUE TO THE RUGGED TERRAIN.
   C. IN THE EXTENDED TAUS TY 24W WILL BE WELL INTO THE DISSIPATION 
PROCESS, WEAKENING DUE TO INCREASINGLY UNFAVORABLE LOW LEVEL 
ENVIRONMENT; NAMELY FRICTIONAL EFFECTS ASSOCIATED WITH A RUGGED 
TOPOGRAPHY OF SOUTHEAST ASIA. DYNAMIC MODEL GUIDANCE IS IN TIGHT 
AGREEMENT, WITH THE EXCEPTION OF ECMWF, WHICH CONTINUES TO INDICATE 
A TURN TO THE WEST-NORTHWEST AROUND TAU 12. THIS FORECAST FAVORS 
MODEL GUIDANCE SHOWING A MORE SOUTHERN TRACK AND IS VERY CLOSE TO 
THE CONSENSUS OF AVAILABLE GUIDANCE. BASED ON THE TIGHT GROUPING OF 
MODELS, PERSISTENT IN KEEPING THE TRACK ON A WESTWARD HEADING, THE 
CONFIDENCE IN THE FORECAST TRACK REMAINS HIGH.//
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