WDPN31 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MINDULLE) WARNING NR 029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.9N 135.5E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 316 NM WEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 20W HAS CONTINUED TO HOLD TOGETHER FAIRLY WELL, THOUGH THE
HONEYMOON IS LIKELY ABOUT TO END. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS A 40-NM WIDE EYE FEATURE, SURROUNDED BY A
SOLID BAND OF DENSE, DEEP CONVECTION. HOWEVER, 291011Z AMSU-B 89GHZ
MICROWAVE IMAGE SHOWED A GAP IN THE EYEWALL DEVELOPING ON THE WEST
SIDE, AND CLOUD TOP TEMPERATURES HAVE WARMED SIGNIFICANTLY ON THE
EASTERN SIDE OF THE SYSTEM, INDICATIVE OF A LOOMING BREAKDOWN ON
THE EYEWALL TO THE EAST AS WELL. THE INITIAL POSITION IS ASSESSED
WITH HIGH CONFIDENCE, IN THE CENTER OF THE LARGE EYE. THE INITIAL
INTENSITY REMAINS HELD AT 115 KNOTS, IN LINE WITH THE AGENCY
CURRENT INTENSITY ESTIMATES AND THE SATCON, BUT A BIT HIGHER THAN
THE AGENCY DATA-T VALUES AND THE ADT, WITH MEDIUM CONFIDENCE. THE
OVERALL SYNOPTIC ENVIRONMENT REMAINS UNCHANGED SINCE THE PREVIOUS
FORECAST, WITH LOW VWS, WARM SSTS AND OVERALL GOOD OUTFLOW. CIMSS
UPPER-LEVEL WIND ANALYSIS REVEALS MODERATE SOUTHWESTERLY FLOW ALONG
THE WESTERN PERIPHERY OF TY 20W, RESTRICTING OUTFLOW IN THAT
SECTOR. THE BULK OF THE UPPER-LEVEL DIVERGENCE IS NOW RESTRICTED TO
A BAND TOWARDS THE NORTH, TURNING TOWARDS THE EAST AND THEN SOUTH,
WITH RADIAL OUTFLOW LIMITED TO AN AREA WITHIN 100 NM OF THE CENTER.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER THE NORTHERN MARIANAS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 112 KTS AT 291009Z
   CIMSS ADT: 104 KTS AT 291130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: RADIAL OUTFLOW IS CONFINED TO AN AREA WITHIN
APPROXIMATELY 100 NM OF THE CENTER. POLEWARD OUTFLOW EVENTUALLY
TURNS EQUATORWARD WELL TO THE EAST. 

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: TY 20W HAS TRACKED JUST SLIGHTLY EAST OF DUE
NORTH OVER THE PAST SIX HOURS, DIRECTLY DOWN THE FORECAST TRACK.
OVER THE NEXT 12 TO 24 HOURS, THE SYSTEM WILL GRACEFULLY TURN TO A
NORTHEASTWARD HEADING, STEADILY ACCELERATING AS IT MOVES INTO THE
STRONG GRADIENT BETWEEN THE STR TO THE EAST AND AN APPROACHING
MID-LATITUDE TROUGH, CURRENTLY EXTENDING FROM THE NORTH KOREA-CHINA
BORDER TO WEST-CENTRAL CHINA. THE ASSOCIATED SURFACE LOW OVER THE
WESTERN SEA OF JAPAN WILL MOVE NORTHEAST AND DRAG A COLD FRONTAL
BOUNDARY OVER HONSHU BY 24, WHERE IT WILL AWAIT THE ARRIVAL OF TY
20W. TY 20W HAS PEAKED AND FROM HERE ON OUT WILL STEADILY WEAKEN AS
IT MOVES INTO A PROGRESSIVELY LESS FAVORABLE ENVIRONMENT. THE
SYSTEM WILL BEGIN THE EXTRA-TROPICAL TRANSITION PHASE BY TAU 36 AS
IT BEGINS TO INTERACT WITH THE BAROCLINIC ZONE AND WESTERLY WINDS
ALOFT SERVE TO INCREASE MID-LEVEL SHEAR. BY ABOUT TAU 40, A STRONG
AND VERY DISTINCT TONGUE OF MID-LEVEL DRY AIR RIDING THE
NORTHWESTERLY FLOW WILL PUNCH ITS WAY INTO THE CORE OF TY 20W FROM
THE WEST, ERODE THE TROPICAL CORE OF THE SYSTEM AND LEAD TO VERY
RAPID WEAKENING. PHASE-SPACE AND THERMAL CROSS-SECTION FIELDS
INDICATE TY 20W WILL TRANSITION TO A STORM-FORCE WARM-SECLUSION
TYPE EXTRA-TROPICAL SYSTEM NO LATER THAN TAU 72 AS IT EMBEDS UNDER
A 500 MB TROUGH AND DEVELOPS STRONG THERMAL ADVECTION AND FRONTAL
CHARACTERISTICS. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN VERY GOOD AGREEMENT IN
BOTH ALONG- AND CROSS-TRACK SPREAD, GRADUALLY INCREASING TO
APPROXIMATELY 100 NM BY TAU 72. THE JTWC FORECAST REMAINS
CONSISTENT WITH THE PREVIOUS FORECAST WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE MEMBERS ALL AGREE THAT TY 20W HAS PEAKED AND
WILL STEADILY WEAKEN FROM HERE ON OUT. THE JTWC FORECAST LIES ABOUT
10 KNOTS HIGHER THAN THE CONSENSUS MEAN THROUGH TAU 24, THEN
CLOSELY TRACKS THE MEAN THEREAFTER, WITH HIGH CONFIDENCE. 

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