WDPN31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2N 119.3E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 237 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 24W
WITH A LARGE 30 NM EYE THAT STARTED TO FORM AROUND 2100Z. THE
OVERALL APPEARANCE HAS GREATLY IMPROVED SINCE DEPARTING THE COAST
OF LUZON WITH CLOUD TOPS IN THE SOUTHERN PORTION OF THE EYEWALL NOW
AROUND -76 C. HOWEVER, THE OUTFLOW, ESPECIALLY IN THE POLEWARD
DIRECTION, HAS WEAKENED AND IS NOW MORE LOCALIZED TO THE SYSTEM
RATHER THAN FLOWING INTO THE JET. ENVIRONMENTAL ANALYSIS INDICATES
THAT 24W IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE
RADIAL OUTFLOW, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE IN THE
ANIMATED MSI. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW. ADDITIONALLY, A 072147Z RCM-1 SAR
IMAGE SHOWS A MAX OF 80 KTS, AND 24W SEEMS TO HAVE INTENSIFIED
SINCE THEN.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 79 KTS AT 072243Z
   CIMSS ADT: 94 KTS AT 080000Z
   CIMSS AIDT: 79 KTS AT 080000Z
   CIMSS DPRINT: 86 KTS AT 080000Z
   CIMSS DMINT: 85 KTS AT 072243Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 CONTINUE TRACKING WESTWARD
THROUGH TAU 48 ALONG AN EXTENSION OF A STR POSITIONED TO THE
NORTHEAST. NEAR TAU 48, A RIDGE CENTERED OVER LAOS AND THAILAND
WILL TAKE OVER AS THE PRIMARY STEERING MECHANISM, CAUSING THE
SYSTEM TO TURN SOUTHWESTWARD. 24W IS THEN EXPECTED TO CONTINUE ON
THAT SOUTHWESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST
PERIOD. REGARDING INTENSITY, 24W IS FORECAST TO INTENSIFY OVER THE
NEXT 24 HOURS, REACHING A PEAK OF 100 KTS AT TAU 24. THE COLD SURGE
FLOWING SOUTHWESTWARD NEAR TAIWAN WILL BRING IN COLD DRY AIR THOUGH
AND PUT A CAP ON FURTHER INTENSIFICATION. AS A RESULT, THE SYSTEM
IS FORECAST TO MAINTAIN 100 KTS THROUGH TAU 36 IN RESPONSE TO AN
OTHERWISE CONDUCIVE ENVIRONMENT AS IT TRACKS WESTWARD. STARTING AT
TAU 48, THE ENVIRONMENT QUICKLY WORSENS DUE TO INCREASED WESTERLY
VERTICAL WIND SHEAR AND SIGNIFICANT DRY AIR ENTRAINMENT. 24W WILL
THEN BEGIN A RAPID WEAKENING PHASE AS IT DECOUPLES AND GETS SHEARED
APART WITH DISSIPATION NO LATER THAN TAU 120.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 24W THROUGH TAU 48. THE MAIN OUTLIER NOW IS
NAVEM WHICH TRACKS THE VORTEX NORTH-NORTHWESTWARD AFTER TAU 36
RATHER THAN WESTWARD. AFTER TAU 48, MODELS BEGIN TO DIVERGE AS THE
VORTEX QUICKLY WEAKENS. THE JTWC TRACK FORECAST IS PLACED CLOSE TO
CONSENSUS, AFTER DISREGARDING NAVGEM, WITH HIGH CONFIDENCE THROUGH
TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE PAINTS
A SLIGHTLY DIFFERENT PICTURE NOW WITH DTOP (A RAPID INTENSIFICATION
AID) NOW TRIGGERING. THE MESOSCALE MODELS SUGGEST A PEAK OF 95 TO
110 KTS AT TAU 36 WITH RAPID WEAKENING AFTERWARD. GFS CONTINUES TO
SHOW A MUCH WEAKER (AROUND 70 KTS) SYSTEM AT TAU 36. THE JTWC
INTENSITY FORECAST IS PLACED CLOSE TO THE MESOSCALE MODELS, WITHOUT
RAPID INTENSIFICATION (DUE MAINLY TO THE PRESENCE OF THE COLD
SURGE), 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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