WDPN31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.6N 123.1E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 269 NM NORTH-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 24W
(YINXING) APPROACHING THE NORTHEAST COAST OF LUZON. PEAK INTENSITY
IS ANALYZED TO HAVE OCCURRED AROUND 2100Z, BUT APPEARANCE HAS
SLIGHTLY DEGRADED SINCE THEN AS TERRAIN INTERACTION BEGINS. THE
NORTHWEST QUADRANT OF THE EYEWALL HAS STARTED TO BECOME A BIT MORE
RAGGED IN RESPONSE. THE POLEWARD OUTFLOW HAS CONTINUED TO REMAIN
ROBUST AS IT FLOWS INTO THE JET TO THE NORTH. ENVIRONMENTAL
ANALYSIS INDICATES THAT 24W IS IN A MARGINALLY FAVORABLE
ENVIRONMENT CHARACTERIZED BY TERRAIN INTERACTION OFFSET BY STRONG
POLEWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND
WARM (27-28 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE DEFINED EYE IN THE
ANIMATED MSI. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF AN EXTENSION OF A
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST-NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T6.5 - 127 KTS
   CIMSS SATCON: 117 KTS AT 070000Z
   CIMSS ADT: 127 KTS AT 070000Z
   CIMSS AIDT: 119 KTS AT 070000Z
   CISMS DPRINT: 114 KTS AT 070000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: TERRAIN INTERACTION WITH THE NORTHEASTERN COAST
OF LUZON.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: 24W IS FORECAST TO BEGIN TRACKING STRAIGHT
WESTWARD WITH LANDFALL ALONG THE NORTHEAST COAST OF LUZON WITHIN
THE NEXT 3 HOURS. 24W WILL THEN CONTINUE ON A WESTWARD PATH THROUGH
TAU 72. NEAR TAU 72, A RIDGE IS EXPECTED TO BUILD OVER THAILAND AND
LAOS AND EXTEND OVER INTO THE SOUTH CHINA SEA CAUSING THE SYSTEM TO
MAKE A SOUTHWESTWARD TURN. REGARDING INTENSITY, 24W IS FORECAST TO
BEGIN A WEAKENING TREND AS IT INTERACTS WITH THE COAST OF LUZON.
ADDITIONALLY, A COLD SURGE FLOWING TOWARD THE SOUTHWEST NEAR TAIWAN
WILL BRING IN COLD, DRY AIR AND AID IN WEAKENING THE SYSTEM.
HOWEVER, THE COLD SURGE IS EXPECTED TO WEAKEN AND ALLOW 24W TO
REMAIN STRONG AS IT TRAVERSES WESTWARD THROUGH THE SOUTH CHINA SEA.
ALL OTHER ENVIRONMENTAL VARIABLES ARE EXPECTED TO BE FAVORABLE
THROUGH TAU 72 WITH A 90 KNOT INTENSITY FORECAST AT THAT POINT.
AFTER TAU 72, THE ENVIRONMENT QUICKLY WORSENS DUE TO INCREASING
VERTICAL WIND SHEAR AND SIGNIFICANT DRY AIR ENTRAINMENT. AS A
RESULT, THE VORTEX WILL RAPIDLY WEAKEN AS IT BECOMES DECOUPLED AND
SHEARED APART NEAR THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 24W THROUGH TAU 72 WITH A 90 NM CROSS-TRACK
SPREAD AT THAT TIME. AFTER TAU 72, MODELS BEGIN TO DIVERGE,
ESPECIALLY THE JGSM AND ITS ENSEMBLE MEAN WHICH TRACK THE VORTEX
QUICKLY TO THE SOUTHWEST. DISREGARDING THOSE TWO OUTLIERS, THERE IS
A 218 NM CROSS-TRACK SPREAD AT TAU 120. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO THE AVERAGE OF THE REMAINDER OF GUIDANCE WITH HIGH
CONFIDENCE THROUGH TAU 72 AND MEDIUM THEREAFTER. INTENSITY GUIDANCE
REMAINS IN WORSE AGREEMENT WITH A LARGE SPREAD IN GUIDANCE. THE
MAIN TWO FACTORS BEING HOW MUCH THE VORTEX IS WEAKENED DUE TO LAND
INTERACTION AND THE ONGOING COLD SURGE. THE GFS REMAINS MUCH WEAKER
THAN THE MESOSCALE MODELS AND ECMWF, SUGGESTING A DROP TO BELOW
TYPHOON STRENGTH IN 24 HOURS. HAFS-A AND HWRF BOTH SUGGESTS A MORE
GRADUAL WEAKENING TREND THROUGH TAU 72 AND THEN RAPID WEAKENING
AFTERWARD. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE
MESOSCALE MODELS WITH OVERALL MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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