WDPN32 PGTW 312100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (KHANUN) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.1N 130.3E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 198 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER RAPIDLY INTENSIFYING OVER THE PREVIOUS 24 HOURS, TYPHOON
(TY) 06W (KHANUN) HAS PLATEAUED A BIT DUE TO A SLIGHT DETERIORATION
OF THE UPPER-LEVEL ENVIRONMENT, THOUGH IT REMAINS A POWERFUL
TYPHOON. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS
THAT THE SYSTEM HAS BEEN REMARKABLY PERSISTENT IN ALMOST EVERY
PARAMETER FOR AT LEAST THE PAST 12 HOURS; THE SYMMETRICAL, ROUND
EYE IS STILL 27NM WIDE, AND THE EYE TEMPERATURES HAVE FLUCTUATED
BETWEEN 15.5C TO 19.5C. A 311714Z AMSR2 89GHZ MICROWAVE IMAGE
HOWEVER, REVEALS A DETERIORATION OF THE EYEWALL ACROSS THE
NORTHWESTERN QUADRANT THOUGH THE 36GHZ IMAGE SHOWS A MUCH MORE
ROBUST LOWER-LEVEL STRUCTURE. THIS IS LIKELY DUE TO SOME
BELOW-ANVIL NORTHEASTERLY SHEAR AND ACCOMPANYING DRY AIR, WHICH IS
BEING INGESTED INTO THE CORE OF THE SYSTEM. THE MOST RECENT EIR
SHOWS A DISTINCT DETERIORATION OF THE EYEWALL STRUCTURE NORTHWEST
OF THE CORE INDICATIVE OF THE DRY AIR INTRUSION. THE INITIAL
INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON AGREEMENT OF
ALL AVAILABLE INTENSITY ESTIMATES, THOUGH THE LATEST D-MINT
ESTIMATED USING THE AMSR2 IMAGE NOTED ABOVE, WAS 126 KNOTS.
ANIMATED WATER VAPOR IMAGERY AND UPPER-AIR SOUNDINGS ACROSS JAPAN
SHOW THE PRESENCE OF A DEEP TROUGH CURRENTLY MOVING OVER WESTERN
HONSHU, A SHARP RIDGE JUST NORTH OF TY 06W AND AN UPPER-LEVEL LOW
JUST WEST OF SHANGHAI, WITH A WEAKENING OUTFLOW CHANNEL EXTENDING
FROM THE STORM INTO THIS UPPER LOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 116 KTS AT 311646Z
   CIMSS ADT: 115 KTS AT 311730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: WEAKENING OUTFLOW CHANNEL INTO UPPER-LEVEL LOW TO
THE NORTHWEST; UPPER-LEVEL NORTHEASTERLY SHEAR AND DRY AIR
INTRUSION. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THROUGH THE NEXT 24 TO 36 HOURS, AS THE
UPPER-LEVEL TROUGH PASSES JAPAN, IT WILL BREAK THE STEERING RIDGE
TO THE NORTHEAST. HOWEVER, A STRONG SUBTROPICAL RIDGE (STR) WILL
RAPIDLY MOVE EASTWARD BEHIND THE TROUGH AND SETTLE INTO POSITION IN
THE NORTHERN EAST CHINA SEA, ASSUMING THE PREDOMINATE STEERING
INFLUENCE, STEERING TY 06 ONTO A SLIGHTLY MORE WESTWARD TRACK AFTER
TAU 24. AFTER PASSING JUST SOUTH OF OKINAWA BY TAU 24, THE SYSTEM
WILL BEGIN TO SLOW DOWN, BECOMING QUASI-STATIONARY BY TAU 36, AS IT
NESTLES INTO A WEAK STEERING PATTERN TRAPPED BETWEEN A STR TO THE
NORTH-NORTHWEST, A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST AND
A STRONG STR FAR TO THE EAST. BY TAU 72, THE STR TO THE NORTHWEST
IS EXPECTED TO WEAKEN AND SLIDE TO THE WEST, WHILE THE NER BUILDS
AND PUSHES NORTH, TIGHTENING THE STEERING GRADIENT ON THE SOUTH
SIDE OF THE SYSTEM, ALLOWING IT TO SLOWLY PUSH NORTHEASTWARD
THROUGH TAU 120. HOWEVER, IT MUST BE NOTED THAT THE SYSTEM IS NOT
EXPECTED TO MOVE ALL THAT FAR AFTER PASSING OKINAWA, WITH THE
ENTIRE TRACK AFTER TAU 24 CONTAINED WITHIN A SMALL 200NM CIRCLE.
THE SYSTEM IS EXPECTED TO INTENSIFY SLIGHTLY OVER THE NEXT 12 HOURS
BUT WILL BEGIN TO GRADUALLY WEAKEN FROM TAU 24 TO TAU 48 DUE TO
INCREASED NORTHERLY SHEAR AND SLIGHTLY CONVERGENT FLOW ALOFT WHICH
WILL SERVE TO CONSTRICT UPPER-LEVEL OUTFLOW. AS THE SYSTEM SLOWS
DOWN AND BECOMES QUASI-STATIONARY IN THE EAST CHINA SEA,
SIGNIFICANT UPWELLING OF COOLER WATERS WILL LEAD TO A MUCH MORE
RAPID PACE OF WEAKENING AFTER TAU 48. HOWEVER, DUE TO THE VERY
LARGE SIZE OF THE SYSTEM AND THE CLOSE PROXIMITY TO OKINAWA THROUGH
THE ENTIRE FORECAST PERIOD, THERE IS A HIGH PROBABILITY OF A
SIGNIFICANT PERIOD OF GALE TO STORM-FORCE WINDS ACROSS OKINAWA,
ESPECIALLY IF THE SYSTEM DRIFTS CLOSER WITHIN THE WEAK STEERING
PATTERN. 

MODEL DISCUSSION: THROUGH THE FIRST 48HOURS, DETERMINISTIC TRACK
GUIDANCE IS IN TIGHT AGREEMENT, WITH A 50NM SPREAD AT TAU 36
INCREASING SLIGHTLY BY TAU 48, LENDING HIGH CONFIDENCE THROUGH THIS
PORTION OF THE FORECAST. BY TAU 48 HOWEVER, BOTH THE DETERMINISTIC 
AND ENSEMBLE GUIDANCE BEGINS TO DIVERGE FAIRLY RAPIDLY. THE UKMET
AND UKMET ENSEMBLE CONTINUE TO PERSIST IS TRACKING THE SYSTEM
STRAIGHT INTO EASTERN CHINA BY TAU 120 WHILE THE REMAINDER OF THE
GUIDANCE SHOW A SHARP TURN TO THE NORTHEAST AFTER TAU 72, WITH A
FAIRLY WIDESPREAD IN THE SHARPNESS AND EXACT TIMING OF THE TURN.
THE GFS, NAVGEM AND ECMWF HAVE NOW COME INTO AN AGREEMENT, SHOWING A
VERY SHARP TURN TO A POSITION NEAR AMAMI OSHIMA ISLAND BY TAU 120.
THE GFS ENSEMBLE, HAFS-A, HWRF AND COAMPS-TC (GFS) ALSO TURN THE
SYSTEM SHARPLY NORTHEASTWARD BUT LIE FURTHER WEST BY TAU 120.
HOWEVER, DUE TO THE WEAK STEERING PATTERN, A HIGH PROBABILITY OF A
SLOW, ERRATIC TRACK MOTION, LENDING LOW CONFIDENCE TO THE JTWC
FORECAST AFTER TAU 48. INTENSITY GUIDANCE IS IN FAIRLY GOOD
AGREEMENT, WITH MOST MESOSCALE GUIDANCE INDICATING SLIGHT
INTENSIFICATION THROUGH TAU 12, FOLLOWED BY GRADUAL WEAKENING
THROUGH TAU 72 AND MORE RAPID WEAKENING THEREAFTER AS THE SYSTEM IS
IMPACTED BY STRONG UPWELLING. 

FORECAST CONFIDENCE:
   TRACK 0 - 48HR: HIGH
   TRACK 48-120 HR: LOW
   INTENSITY 0 - 48HR: MEDIUM
   INTENSITY 48-120 HR: MEDIUM//
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