WDPN32 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN) WARNING NR 
043//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.9N 130.7E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 176 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 06W (KHANUN) CONTINUES TO EXHIBIT MULTIPLE
VORTICES EMBEDDED WITHIN A LARGE, ROUGHLY 85NM WIDE CIRCULATION.
BASED ON ANIMATED JMA RADAR AND SHORTWAVE INFRARED (SWIR) IMAGERY
INDICATES THAT THE PRIMARY VORTEX CONTINUES TO WOBBLE AND FUJIWHARA
WITH ONE OR MORE SECONDARY VORTICES, LEADING TO A VERY ERRATIC
TRACK MOTION OVER THE PAST 12 HOURS. OVER THE PAST SIX HOURS, THE
PRIMARY VORTEX HAS TRACKED TOWARDS THE NORTH, BUT THE MOST RECENT
IMAGERY SUGGEST IT IS NOW MOVING TOWARDS THE WEST. HENCE PLACEMENT
OF THE INITIAL POSITION AND SUBSEQUENTLY, THE INITIAL MOTION
VECTOR, IS ASSESSED WITH ONLY MEDIUM CONFIDENCE. A 061637Z AMSR2
89GHZ IMAGE REVEALS SHALLOW BANDING ACROSS THE SOUTHERN HEMISPHERE
OF THE CIRCULATION, WITH ENHANCED CONVECTION IN THE NORTHERN
PORTION OF THE PRIMARY BANDING FEATURE. CONVECTION REMAINS
FRAGMENTED ACROSS THE MAJORITY OF THE CIRCULATION, STILL UNABLE TO
CONSOLIDATE EFFECTIVELY. AN EARLIER SENTINEL-1A SAR PASS REVEALED
MAXIMUM WINDS NEAR 65 KNOTS, WHILE THE AMSR2 WINDSPEED MEASUREMENT
FROM 061632Z SHOWED A MAX BETWEEN 50 TO 55 KNOTS IN THE NORTHEAST
QUADRANT, SUPPORTING THE INITIAL INTENSITY WITH HIGH CONFIDENCE. NO
SIGNIFICANT CHANGE IS NOTED IN THE ENVIRONMENTAL CONDITIONS; SHEAR
REMAINS LOW, SSTS WARM BUT THE LONGER THE SYSTEM LINGERS IN THIS
AREA THE COOLER THEY WILL GET DUE TO UPWELLING. THE ONLY MAJOR
CHANGE IS THE SLOWLY IMPROVING OUTFLOW. THE SYSTEM HAS STALLED DUE
TO THE DEVELOPMENT OF A SUBTROPICAL RIDGE (STR) NEAR 20N 140E,
WHICH IS BUILDING TO THE NORTH, EFFECTIVELY BLOCKING MUCH IN THE
WAY OF EASTWARD MOVEMENT.

INITIAL WIND RADII BASIS: AMSR2 WINDSPEED DATA.

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN AS STEERING
INFLUENCE IS SHIFTING. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 47 KTS AT 061325Z
   CIMSS ADT: 35 KTS AT 061450Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: AS DISCUSSED ABOVE, THE EMERGENCE OF A
BUILDING STR TO THE SOUTHEAST OF TS 06W HAS EFFECTIVELY BLOCKED THE
SYSTEM FROM MOVING MUCH FURTHER TO THE EAST. RECENT IMAGERY
SUGGESTS THE PRIMARY VORTEX WILL PIROUETTE COUNTER-CLOCKWISE AND THEN
KICK OUT TO THE NORTHEAST OVER THE NEXT 12 HOURS, SUCH THAT THE
CENTER POSITION IS NOT EXPECTED TO MOVE MUCH FROM THE CURRENT
POSITION. BY TAU 12, THE STR TO THE SOUTHEAST IS EXPECTED TO
STRENGTHEN AND ORIENT TO A NORTH-SOUTH AXIS, AND PUSH TS 06W ONTO A
NORTHWARD TRACK. BY TAU 24, THE STRONG STR CENTERED FAR OUT INTO
THE NORTH PACIFIC WILL TAKE OVER AS THE PRIMARY STEERING MECHANISM,
AND PUSH TS 06W ONTO A NORTH-NORTHWEST TRACK, WHICH WILL CONTINUE
THROUGH THE REMAINDER OF THE FORECAST PERIOD. LANDFALL IS EXPECTED
TO THE WEST OF BUSAN AROUND TAU 84, WITH THE SYSTEM RAPIDLY MOVING
INTO NORTHEASTERN CHINA BY TAU 120. IN TERMS OF INTENSITY, THE
LARGE RADIUS OF MAXIMUM WINDS (RMW), WEAK UPWELLING, AND RESTRICTED
(THOUGH IMPROVING) OUTFLOW ALOFT ARE INHIBITING CONSOLIDATION AND
INTENSIFICATION AT THE MOMENT. AS THE SYSTEM BEGINS TO MOVE OFF TO
THE NORTH, IT WILL MOVE OVER THE DEEP, WARM WATERS OF THE KUROSHIO
CURRENT. AT THE SAME TIME, OUTFLOW WILL STEADILY IMPROVE, AND THESE
TWO FACTORS SHOULD COMBINE TO ENABLE INCREASED CONVECTIVE
CONSOLIDATION AFTER TAU 24, ALLOWING THE SYSTEM TO SLOWLY BUT
STEADILY INTENSIFY TO A PEAK OF 65 TO POTENTIALLY 70 KNOTS BY TAU
48. THE ULTIMATE INTENSITY WILL IN LARGE PART BE DRIVEN BY
INTERPLAY BETWEEN THE SIZE OF THE CIRCULATION AND THE PROXIMITY TO
KYUSHU. THE LARGER THE CIRCULATION AND CLOSER TO LAND THE SYSTEM
IS, THE LOWER THE PEAK INTENSITY WILL BE. AFTER LANDFALL, TS 06W
WILL RAPIDLY WEAKEN AS IT CROSSES OVER THE RUGGED TERRAIN OF THE
KOREAN PENINSULA, AND ULTIMATELY DISSIPATE OVER NORTHEASTERN CHINA
BY AROUND TAU 120. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS CONSISTENT WITH
THE PREVIOUS MODEL RUN, WITH NO MAJOR CHANGES IN THE CONSENSUS
TRACK OR THE ENVELOPE SIZE AND MAKEUP. THE NAVGEM AND UKMET
ENSEMBLE CONTINUE TO MARK THE EASTERN AND WESTERN OUTLIERS
RESPECTIVELY, THE REMAINDER OF THE CONSENSUS MEMBERS HOLDING FIRM
IN A TRACK ENVELOPE THAT MEASURES 95 NM ACROSS AT TAU 72. THE
ENVELOPE EXPANDS TO OVER 400NM BY TAU 120 THOUGH THE BULK OF THE
CONSENSUS MEMBERS LIE IN A MUCH SMALLER ENVELOPE OF JUST 125 NM. THE
JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND
LIES ON THE EASTERN SIDE OF THE GUIDANCE PACKAGE. WHILE CONFIDENCE
IN THE OVERALL TRACK IS FAIRLY HIGH, THE ERRATIC TROCHOIDAL MOTION
EXPECTED FOR THE FIRST 12 TO 24 HOURS INTRODUCES A MODEST AMOUNT OF
UNCERTAINTY IN THE EXACT FORECAST TRACK. INTENSITY GUIDANCE IS IN
GOOD AGREEMENT, WITH ALL AVAILABLE MODELS INDICATING
INTENSIFICATION AFTER TAU 12, WITH A PEAK INTENSITY RANGE BETWEEN
55-70 KNOTS. THE JTWC FORECAST IS ON THE HIGHER END OF THE GUIDANCE
THROUGH THE ENTIRE FORECAST PERIOD. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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