WDPN32 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN) WARNING NR 
035//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.7N 126.4E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 104 NM NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS AN EXPANSIVE
(600 NM DIAMETER) SYSTEM WITH TIGHTLY-CURVED BANDING WRAPPING INTO
A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) THAT IS NEARLY DEVOID
OF DEEP CORE CONVECTION. A 041712Z NOAA-20 MICROWAVE PASS REVEALS THE
MOST PROMINENT CONVECTION IS LARGELY CONFINED TO A LARGE BAND OVER
100 NM FROM THE LLCC THAT ARCS ALONG THE EASTERN AND SOUTHERN
PERIPHERY. A PAIR OF EXCELLENT ASCENDING ASCAT PASSES OVER SIX
HOURS AGO CLEARLY DEPICT THE BROAD HOLLOW CENTER OF WEAK WINDS,
AND SET THE BASELINE FOR 34 KNOT WIND RADII. 10-MINUTE SUSTAINED
WINDS THROUGHOUT OKINAWA AND KUMEJIMA ISLAND APPROXIMATELY 100 NM
TO THE SOUTHEAST HAVE HOVERED AROUND 35-45 KNOTS. THE INITIAL
POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON RADAR FIXES AND
EXCELLENT MULTI-AGENCY FIX AGREEMENT ON THE WELL DEFINED LLCC.
INTENSITY ESTIMATES ARE WILDLY VARYING, WITH SUBJECTIVE AND
OBJECTIVE DVORAK ESTIMATES BEING UNREPRESENTATIVELY LOW. HOWEVER,
THE 56 KNOT SATCON ESTIMATE AGREES WELL WITH PRIOR ASCAT ANALYSIS
AND IS CONSISTENT WITH AIDT AND DPRINT, THEREFORE INTENSITY WAS
ASSESSED AT 55 KNOTS. ENVIRONMENTAL CONDITIONS REMAIN MARGINAL DUE
PRIMARILY TO THE UPWELLING OF 22-24 DEGREE WATERS IN KHANUNS WAKE,
BUT VALUES ALONG THE TRACK ARE IMPROVING. ADDITIONALLY, THERE IS GOOD 
OUTFLOW INTO A UPPER LEVEL SUB-TROPICAL LOW TO THE NORTHEAST AND LOW 
VERTICAL WIND SHEAR. TS 06W IS TRACKING TO THE EAST-NORTHEAST UNDER 
THE STEERING INFLUENCE OF A NEAR EQUATORIAL RIDGE TO THE SOUTH, AND 
FURTHER ENHANCED BY LOWER-LEVEL MONSOONAL FLOW.

INITIAL WIND RADII BASIS: PRIOR SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE ALONG CENTRAL
PHILIPPINES 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 56 KTS AT 041711Z
   CIMSS ADT: 32 KTS AT 041730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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, HOWEVER, THE EXTENDED TRACK
WAS ADJUSTED SLIGHTLY FURTHER WEST AND FASTER BASED ON TRENDING
GUIDANCE. 

FORECAST DISCUSSION: TROPICAL STORM (TS) 06W IS EXPECTED TO
CONTINUE A PREDOMINANTLY EASTWARD MOTION OVER THE NEXT 36 TO 48 
HOURS.
THE HWRF MODEL SUGGESTS THAT KHANUN WILL STRUGGLE TO RECOVER ANY
SEMBLANCE OF ITS FORMER GLORY DURING THIS TIME, AS THE MAX WINDS
REMAIN WELL DISPLACED FROM THE LLCC.  HOWEVER, AFTER TAU 48 RIDGING
IS EXPECTED TO BUILD TO THE EAST OF THE TRACK, COMBINED WITH A TROUGH
MOVING OVER THE KOREAN PENINSULA, RESULTING IN A POLEWARD SHIFT IN
MOTION AND THE START OF AN ACCELERATION IN FORWARD SPEED. AS IT
TRACKS NORTH, IMPROVING SST CONDITIONS AND POLEWARD OUTFLOW
CHANNEL SHOULD ALLOW FOR MODEST RE-INTENSIFICATION. HWRF SHOWS THE
WIND FIELD CONTRACTING, WITH REDEVELOPMENT OF CORE CONVECTION AS TS
06W BRIEFLY RETAINS TYPHOON STATUS PRIOR TO LANDFALL ALONG SOUTHERN
KYUSHU. KHANUN IS EXPECTED TO RE-EMERGE IN THE SEA OF JAPAN AND
REMAIN STORM FORCE AS IT BEGINS AN EXTRA-TROPICAL TRANSITION DUE TO
INCREASING BAROCLINIC INTERACTION. 

MODEL DISCUSSION: SHORT TERM MODEL AGREEMENT IS GOOD THROUGHOUT THE
FORECAST, WITH THE EXCEPTION OF GROWING OUTLIERS OF NAVGEM TO THE
EAST AND UKMET ENSEMBLE MEAN TO THE WEST AFTER TAU 24. TRACK
UNCERTAINTY HAS GRADUALLY SHIFTED WESTWARD, PLACING LANDFALL ALONG
THE SOUTHERN COAST OF KYUSHU, WITH THE CENTER REMAINING OVER THAT
ISLAND DURING PASSAGE, HOWEVER, THE WIND FIELD AND RESULTING
IMPACTS WILL REMAIN FAIRLY BROAD. THE UNCERTAINTY IS MORE IN THE
ALONG TRACK DIRECTION IN THE EXTENDED TAUS.

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