Advisories

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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