WDPN31 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.1N 129.0E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 465 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM
HAS CONTINUED TO SLOWLY COALESCE AND INTENSIFY IN THE PHILIPPINE
SEA AS EVIDENCED BY FEEDER BANDS WRAPPING TIGHTER INTO A
SYMMETRICAL CENTRAL DENSE OVERCAST WITH DEEPENING AND OVERSHOOTING
CLOUD TOPS AND A PINHOLE FORMATIVE EYE. ADDITIONALLY, THE EIR LOOP
SHOWS AN EXPANDING SYSTEM WITH VIGOROUS POLEWARD AND A MODEST
EQUATORWARD OUTFLOW. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE FORMATIVE EYE, ADJUSTED FOR A SLIGHT
FORWARD TILT. THE INITIAL INTENSITY IS ALSO PLACED WITH HIGH
CONFIDENCE, ASSESSED HIGHER THAN THE RESTRAINED AGENCY DVORAK
ESTIMATES AND CLOSER TO THE AUTOMATED OBJECTIVE ESTIMATES. ANALYSIS
INDICATES A HIGHLY FAVORABLE ENVIRONMENT WITH LOW VWS, WARM
ALONG-TRACK SSTS, AND ROBUST VENTILATION FROM THE DUAL OUTFLOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 80 KTS AT 041659Z
   CIMSS ADT: 79 KTS AT 041730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 05-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD, MEDIUM EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON YINXING WILL CONTINUE ON ITS CURRENT
NORTHWESTWARD TRACK UP TO TAU 36; AFTERWARD, A SECONDARY STR
BUILDING IN FROM THE WEST NEAR HAINAN WILL SLOW DOWN THE SYSTEM
THEN ASSUME STEERING, DRIVING THE CYCLONE ON A MORE WESTWARD
TRAJECTORY THROUGH THE LUZON STRAIT AND INTO THE SOUTH CHINA SEA
(SCS). THE FAVORABLE ENVIRONMENT WILL PROMOTE A GRADUAL
INTENSIFICATION TO A PEAK OF 95KTS BY TAU 48, FUELED BY A JOLT OF
INCREASED POLEWARD OUTFLOW AS THE SYSTEM APPROACHES THE
SOUTHWESTERLY JETS AHEAD OF A TRANSITING MID-LATITUDE TROUGH. AFTER
TAU 48, THE RELATIVE VWS WILL INCREASE, SST AND OHC VALUES DECREASE
IN THE WAKE OF A PREVIOUS CYCLONE (23W), INTERACTION WITH LUZON,
THEN THE DRIFT INTO A COLD NORTHEASTERLY SURGE IN THE SCS WILL SLOWLY
THEN RAPIDLY ERODE THE SYSTEM DOWN TO 50KTS BY TAU 120. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY TIGHT AGREEMENT WITH
AN EVEN ACROSS SPREAD OF A MERE 55NM BY TAU 72; AFTERWARD, THE
MODELS SPREAD OUT TO 206NM AT TAU 120 WITH NVGM THE NOTABLE
RIGHT-OF-TRACK OUTLIER, LENDING HIGH CONFIDENCE UP TO TAU 72, THEN
LOW CONFIDENCE AFTERWARD, TO THE JTWC TRACK FORECAST. THERE IS
MEDIUM CONFIDENCE TO THE INTENSITY FORECAST UP TO TAU 72, THEN LOW
CONFIDENCE AFTERWARD. 

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