Advisories

WDPN32 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (CHAMPI) WARNING NR 
041//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8N 123.3E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 253 NM WEST-NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
EXPANSIVE SWIRLING MASS OF LOW-LEVEL CLOUDS. A 241105Z SSMIS PASS
INDICATES RATHER SHALLOW CONVECTION ALONG THE OUTER EASTERN
PERIPHERY. TROPICAL STORM (TS) 29W HAS BEEN WITHOUT CENTRAL
CONVECTION FOR OVER 12 HOURS AND IS NOW MOVING OVER WATERS COOLER
THAN 26 DEGREES CELSIUS UNDER MODERATE TO HIGH NORTHEASTERLY
VERTICAL WIND SHEAR (VWS). FURTHERMORE, AN EXTENSIVE AREA OF DRY
AIR FROM THE ASIAN CONTINENT IS WRAPPING INTO THE CIRCULATION.
THESE FACTORS CONSTITUTE A HIGHLY UNFAVORABLE ENVIRONMENT FOR
DEVELOPMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE MOSTLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC).
THE INITIAL INTENSITY HAS BEEN LOWERED TO 50 KTS WITH LOW
CONFIDENCE BASED ON A BLEND OF THE SUBJECTIVE AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED SOUTHEAST OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.0 - 45 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 51 KTS AT 241106Z
   CIMSS ADT: 59 KTS AT 241130Z
   CIMSS AIDT: 50 KTS AT 241130Z
   CIMSS D-MINT: 37 KTS AT 241203Z
   CIMSS D-PRINT: 53 KTS AT 241130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 29W IS NOW ROUNDING THE RIDGE AXIS AND
BEGINNING TO TURN EAST, WHICH WILL CONTINUE OVER THE NEXT 36 HOURS,
ALONG THE NORTHWEST PERIPHERY OF THE STR AND GRADUALLY GAIN FORWARD
SPEED. THE ENVIRONMENT IS BECOMING EVEN MORE HOSTILE, WITH SEA
SURFACE TEMPERATURES (SST) DECREASING TO 25 DEGREES CELSIUS AND
VERTICAL WIND SHEAR (VWS) INCREASING TO 30-40 KTS BY TAU 24. THESE
CONDITIONS WILL RESULT IN CONTINUED WEAKENING AS THE SYSTEM ENTERS
THE BAROCLINIC ZONE, BEGINS EXTRATROPICAL TRANSITION (ETT) NEAR TAU
24, AND COMPLETES ETT BY TAU 48. AS THE SYSTEM SPINS DOWN, IT IS
QUITE POSSIBLE THAT THE LOW-LEVEL CIRCULATION WILL DEGENERATE INTO
A TROUGH, WITH MAXIMUM WINDS DECREASING TO 30 KTS, BEFORE
DISSIPATING PRIOR TO REACHING KYUSHU. THE FORECAST SPANS 60 HOURS
TO INDICATE THE PATH OF THE CIRCULATION CENTER IF IT REMAINS
INTACT.

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU
60, EXHIBITING A CROSS-TRACK SPREAD OF 90 NM AT THE CPA TO KYUSHU.
DYNAMICAL MODELS CONTINUE TO PREFER A LANDFALL POINT OVER CENTRAL
TO NORTHERN KYUSHU, WHILE AI GUIDANCE TAKES THE SYSTEM OVER
SOUTHERN KYUSHU. THE JTWC FORECAST TRACK IS VERY SIMILAR TO THE
PREVIOUS FORECAST AND IS SOUTH OF THE MULTI-MODEL CONSENSUS,
HEDGING TOWARD THE AI-MODEL MEAN. GOOGLE DEEPMIND IS SLIGHTLY SOUTH
OF THE JTWC TRACK. INTENSITY GUIDANCE IS IN EXCELLENT AGREEMENT,
WITH A 5-KT SPREAD THROUGH TAU 60. THE JTWC INTENSITY FORECAST IS
SET NEAR DEEPMIND AT TAU 12 AND LEANS TOWARD GFS AND ECMWF FROM TAU
24 TO TAU 60.

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