Advisories

WDPN32 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (CHAMPI) WARNING NR 035//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.7N 123.8E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 316 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPANDING
AND INCREASINGLY CLOUD FILLED EYE ENCLOSED BY DEEP CONVECTION THAT
HAS SHOWN A BRIEF RESURGENCE OVER THE PAST 6 HOURS. A 222339Z WSFM
89 GHZ MICROWAVE IMAGE CONFIRMED THAT THE DEEP CONVECTION HAS
NEARLY CLOSED OFF THE EYEWALL, SAVE FOR THE NORTHERN EDGE. A
222130Z PARTIAL RCM-3 SAR PASS CONFIRMED THE EXPANSIVE 50 KT WIND
RADII IN THE EASTERN SEMICIRCLE, WITH A 97 KT VMAX PEAK. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE IN
ANIMATED MSI. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE SAR ANALYSIS, T5.0-5.5 AGENCY DVORAK FIXES,
AND THE SPREAD OF CIMSS OBJECTIVE INTENSITY ESTIMATES. THE
ENVIRONMENT IS CHARACTERIZED AS MARGINAL WITH LOW VERTICAL WIND
SHEAR (VWS) AND EXCELLENT OUTFLOW BEING OFFSET BY COOLER SEA
SURFACE TEMPERATURES, LOWER OCEAN HEAT CONTENT, AND COLD WATER
UPWELLING.

INITIAL WIND RADII BASIS: PERSISTENCE SUPPLEMENTED BY A PARTIAL
RCM-3 SAR PASS

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTH OF HONSHU.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS ADT: 99 KTS AT 230010Z
   CIMSS AIDT: 86 KTS AT 230010Z
   CIMSS D-PRINT: 88 KTS AT 230010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: COLD WATER UPWELLING

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: TY 29W (CHAMPI) HAS TRACKED
NORTH-NORTHWESTWARD OVER THE PAST 6 HOURS AS IT APPROACHES THE AXIS
OF THE STEERING RIDGE CENTERED TO THE NORTHEAST. THE TRACK IS
FORECAST TO CONTINUE TURNING POLEWARD OVER THE NEXT 24 HOURS,
PASSING ABOUT 65 NM EAST OF TAIPEI AROUND TAU 18. THE TRACK TURNS
NORTH-NORTHEASTWARD THROUGH TAU 60 AS THE SYSTEM ROUNDS THE RIDGE
AXIS. AFTER TAU 60, THE TRACK ACCELERATES EAST-NORTHEASTWARD TOWARD
KYUSHU, WHERE LANDFALL IS EXPECTED APPROXIMATELY 50 NM SOUTH OF
SASEBO. THE INTENSITY IS FORECAST TO STEADILY WEAKEN THROUGH TAU
36, THEN WEAKEN RAPIDLY THROUGH THE REMAINDER OF THE FORECAST
PERIOD IN AN ENVIRONMENT OF INCREASING VWS AND COOLING SEA SURFACE
TEMPERATURES. EXTRATROPICAL TRANSITION (ETT) IS EXPECTED TO BEGIN
BETWEEN TAU 60 AND 72, BECOMING EXTRATROPICAL BY TAU 96. AS A
RESULT OF THE STEADY WEAKENING AND ETT, THE INTENSITY AS IT MAKES
LANDFALL OVER KYUSHU IS PROJECTED TO BE 30 KTS OR LESS.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT
ABOUT THE RECURVE SCENARIO, WITH A CROSS-TRACK SPREAD OF ABOUT 100
NM AT TAU 96, EXCEPTING ECMWF AND AND GFS AS NORTHERN OUTLIERS. THE
ALONG-TRACK SPREAD HAS IMPROVED SINCE THE PREVIOUS MODEL RUN, WITH
MOST OF THE AI MODELS NOW DEPICTING A SLOWER, MORE REALISTIC TRACK
SPEED IN THE LATER TAUS. THE JTWC TRACK FORECAST IS PLACED BETWEEN
THE MULTI-MODEL CONSENSUS AND THE GOOGLE DEEPMIND SOLUTIONS
THROUGHOUT THE FORECAST PERIOD. THE INTENSITY GUIDANCE IS IN GOOD
AGREEMENT ABOUT THE WEAKENING TREND THROUGHOUT THE FORECAST PERIOD
AND THE JTWC INTENSITY FORECAST IS PLACED SLIGHTLY HIGHER THAN THE
CONSENSUS. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: HIGH//
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