WDPN33 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (CHAN-HOM) WARNING
NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.5N 147.9E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 401 NM EAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED SHORTWAVE INFRARED (SWIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), ON THE
SOUTHEASTERN EDGE OF AN AREA OF INTENSE CONVECTION IN THE
NORTHWESTERN QUADRANT OF THE CIRCULATION. ANIMATED WATER VAPOR
IMAGERY AS WELL AS HIGH-RESOLUTION CIRA DERIVED MOTION VECTOR (DMV)
ANALYSIS DEPICTS A ROBUST UPPER-LEVEL LOW (ULL) CONTINUING TO DIVE
SOUTHWARD ALONG THE COAST OF JAPAN, NOW CENTERED ROUGHLY DUE EAST OF
YOKOSUKA, WITH TROUGHING EXTENDING EASTWARD ALONG THE SOUTHERN FLANK
OF TS 14W. THIS ORIENTATION IS PRODUCING ROBUST POLEWARD, DIVERGENT
OUTFLOW OVER AND NORTHWEST OF TS 14W, WHICH IS SUPPORTING THE RECENT
BURST OF CONVECTIVE ACTIVITY AND INTENSIFICATION. A 101114Z ASCAT-B
BULLSEYE REVEALED A WELL-DEFINED LLCC AND A COMPACT WIND FIELD WITH
MAXIMUM NON-FLAGGED WINDS OF 45 KNOTS, WITH SOME RAIN-FLAGGED WINDS
EXCEEDING 50 KNOTS IN THE WESTERN SECTOR OF THE CIRCULATION. THE
INITIAL POSITION AND INTENSITY WERE BOTH ASSESSED WITH HIGH
CONFIDENCE BASED ON THE ASCAT DATA. ENVIRONMENTAL CONDITIONS ARE
MARGINALLY FAVORABLE, WITH THE ROBUST POLEWARD OUTFLOW OFFSETTING
MODERATE SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) AND MARGINAL SEA
SURFACE TEMPERATURES (SSTS).

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A MID-LEVEL
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 48 KTS AT 101010Z
   CIMSS ADT: 45 KTS AT 101210Z
   CIMSS AIDT: 39 KTS AT 101210Z
   CIMSS D-MINT: 41 KTS AT 100948Z
   CIMSS D-PRINT: 44 KTS AT 101140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT ACROSS THE SOUTHERN FLANK OF
THE CIRCULATION.

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 14W IS BEGINNING TO GRADUALLY TURN MORE WEST-
NORTHWESTWARD AS IT BEGINS TO FEEL THE EFFECTS OF BUILDING MID-LEVEL
RIDGING TO THE NORTH. BY TAU 12, IT WILL BE TRAVELING WESTWARD AND
BEGIN A SLIGHT WEST-SOUTHWESTWARD JOG AS THE RIDGE CENTER MOVES INTO
A POSITION DUE NORTH OF TS 14W. LANDFALL ALONG THE EAST COAST OF
HONSHU NORTHEAST OF TOKYO IS EXPECTED NEAR TAU 24. THE SYSTEM THEN
TRACKS RAPIDLY ACROSS THE JAPANESE ALPS AND EMERGES INTO THE FAR
SOUTHERN SEA OF JAPAN (SOJ) SHORTLY AFTER TAU 36, CONTINUING WESTWARD
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THERE REMAINS
SIGNIFICANT UNCERTAINTY IN REGARD TO THE EXACT TRACK THE SYSTEM WILL
TAKE AFTER LANDFALL, WHICH WILL IN LARGE PART BE DETERMINED BY
LOCALIZED TERRAIN INTERACTIONS AS THE LOW-LEVEL VORTEX SEPARATES FROM
THE MID-LEVEL VORTEX. REGARDING INTENSITY, THE SYSTEM IS INTENSIFYING
AS EXPECTED DUE TO THE BURST OF CONVECTION SUPPORTED BY THE
DRAMATICALLY IMPROVED UPPER-LEVEL OUTFLOW ENVIRONMENT. THE ULL IS
FORECAST TO REMAIN IN A GENERALLY FAVORABLE POSITION RELATIVE TO TS
14W FOR ABOUT ANOTHER 6-12 HOURS, WHICH WILL ALLOW FOR A BIT MORE
INTENSIFICATION TO OCCUR THROUGH TAU 12. THE ULL CONTINUES TO DRIFT
SOUTHEASTWARD AND REPOSITIONS TO THE SOUTH OF TS 14W BY TAU 12,
INTRODUCING CONVERGENT EAST-NORTHEASTERLY FLOW ALOFT WHICH WILL
WEAKEN THE SYSTEM SLIGHTLY IN THE LEAD-UP TO LANDFALL. AFTER MAKING
LANDFALL, 14W WILL RAPIDLY DECOUPLE AND WEAKEN, EMERGING AS A WEAK
HYBRID LOW PRESSURE SYSTEM UNDERGOING SUBTROPICAL TRANSITION (STT).
BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL HAVE COMPLETED STT
AND DISSIPATED SIMULTANEOUSLY.

MODEL DISCUSSION: THE TRACK GUIDANCE PACKAGE, WHILE IN BETTER CROSS-
TRACK AGREEMENT COMPARED TO THE PREVIOUS MODEL RUN, HAS ONCE AGAIN
SHIFTED SOUTHWARD. THE GFS AND EC-AIFS CURRENTLY MARK THE NORTHERN
EDGE OF THE ENVELOPE, WHILE GOOGLE DEEPMIND'S GRAPHCAST AND EC-AIFS
MARK THE SOUTHERN EDGE, BRINGING THE SYSTEM OVER THE CENTER OF TOKYO.
WITH THE EXCEPTION OF THE ECMWF, WHICH NOW TRACKS THE REMNANT VORTEX
NORTHWESTWARD AFTER LANDFALL, THE REMAINDER OF THE CONSENSUS MEMBERS
DEPICT A WESTWARD TRAJECTORY POST-LANDFALL, TRACKING JUST OFF THE
NORTH COAST OF HONSHU AND NEAR OKINOSHIMA AND NISHINOSHIMA ISLANDS AS
THE SYSTEM DISSIPATES. THE EXPERIMENTAL JTWC SUPER ENSEMBLE CONTINUES
TO TIGHTEN UP, WITH INDIVIDUAL MEMBERS NOW SPREAD FROM SOUTH OF
SENDAI TO SOUTH OF YOKOSUKA AT TAU 24. THE JTWC FORECAST IS PLACED
NEAR THE AI CONSENSUS MEAN THROUGH THE FORECAST PERIOD WITH MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH THE BULK OF
MODELS INDICATING SLIGHT INTENSIFICATION THROUGH TAU 12, FOLLOWED BY
STEADY WEAKENING THROUGH TAU 60.

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