WDPN31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 035//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 34.3N 128.0E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 72 NM SOUTHWEST OF BUSAN, SOUTH KOREA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 22 KTS
   SIGNIFICANT WAVE HEIGHT: 37 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND RADAR
IMAGERY DEPICT DEEP CONVECTIVE BANDING WRAPPING TIGHTLY INTO A
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH EXTENSIVE
BANDING AND HEAVY RAIN OVER THE NORTHERN AND EASTERN SEMICIRCLES.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EIR IMAGERY, RADAR IMAGERY AND SURFACE OBSERVATIONS. A 051718Z
AMSR2 89GHZ MICROWAVE IMAGE INDICATES EROSION OF THE WESTERN
PORTION OF THE EYEWALL WITH CURVED CONVECTIVE BANDING OVER THE
EASTERN SEMICIRCLE AND A DELTA RAIN REGION OVER THE NORTHERN
QUADRANT, INDICATIVE OF EXTRA-TROPICAL TRANSITION. A 051218Z
ASCAT-B BULLSEYE IMAGE WAS USED TO REFINE THE 34-KNOT AND 64-KNOT
WIND RADII AND LINED UP WELL WITH RECENT SURFACE OBSERVATIONS. THIS
IMAGE SHOWS EXTENSIVE GALE-FORCE WINDS AROUND THE SYSTEM AND ALSO
WEST OF SOUTHWEST KOREA AND EAST OF SOUTHEAST KOREA. THE MAXIMUM
WINDS OBSERVED OVER SOUTH KOREA THUS FAR (70 KNOTS) WERE REPORTED
AT GOSAN (ELEVATION 240 FEET) ON THE WESTERN SIDE OF CHEJU-DO
(47185) AT 051500Z. THE SYSTEM CENTER IS CURRENTLY WEDGED BETWEEN
TWO BUOYS (22188, 22104) AND IZUHARA (47800), WHICH INDICATE
SURFACE WINDS OF 33 KNOTS, 47 KNOTS AND 48 KNOTS, RESPECTIVELY.
BUSAN IS REPORTING EASTERLY WINDS AT 19 KNOTS WITH A SLP OF
983.8MB. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE HIGH END OF DVORAK CURRENT INTENSITY
ESTIMATES. A 051716Z AMSR2 WINDSPEED IMAGE INDICATED A SWATH OF 77
KNOT WINDS, SUGGESTING SOME UNCERTAINTY IN THE INITIAL INTENSITY
BUT WITHIN THE DVORAK CURRENT INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SURFACE
OBSERVATIONS 

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) WITHIN STRONG MIDLATITUDE SOUTHWESTERLY FLOW 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   CIMSS ADT: 69 KTS AT 051740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: INTERACTION WITH LAND, AND MID- TO UPPER-LEVEL DRY
AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: EXTRA-TROPICAL TRANSITION (ETT) HAS COMMENCED
WITH INCREASING SOUTH-SOUTHWESTERLY VERTICAL WIND SHEAR AND COLD
AIR ADVECTION EVIDENT IN EIR IMAGERY OVER THE YELLOW SEA, LIKELY
ENHANCING THE GALE-FORCE WINDS ALONG THE SOUTHWEST COAST OF KOREA.
TY 12W IS FORECAST TO ACCELERATE NORTH-NORTHEASTWARD ACROSS SOUTHEAST 
KOREA, COMPLETING ETT BY TAU 18 OVER THE CENTRAL SEA OF JAPAN AS IT 
GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED WITHIN A STRONG 
MIDLATITUDE SHORT-WAVE TROUGH NEAR THE JET.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH TAU 12 WITH A 40NM SPREAD IN SOLUTIONS AT TAU 12 DIVERGING
TO 125NM AT TAU 24 AS THE SYSTEM OCCLUDES OVER EASTERN RUSSIA. THE
051200Z ECMWF ENSEMBLE (EPS) AND GFS ENSEMBLE (GEFS) ARE IN
TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. 
RELIABLE INTENSITY GUIDANCE SUPPORTS THE RAPID WEAKENING FORECAST AND 
INDICATES SOME UNCERTAINTY IN THE TAU 24 INTENSITY WITH HWRF SHOWING 
55-60 KNOTS.  

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