WDPN33 PGTW 281500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (KRATHON) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 125.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 500 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 20W (KRATHON) PRESENTS AN IMPROVING APPEARANCE ON ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY, MOST NOTABLY WITH THE
DEVELOPMENT OF A CENTRAL DENSE OVERCAST (CDO) FEATURE OVER THE LOW
LEVEL CIRCULATION CENTER (LLCC). OUTFLOW IN THE EQUATORWARD
DIRECTION IS BROAD AND RAGGED, AND THE WEAKER POLEWARD SIDE HAS A
SLIGHTLY IMPROVED, DIFFUSE OUTFLOW. WITH THE POLEWARD SIDE
APPEARING WEAKER IN THE UPPER LEVELS, IT IS EVIDENT THERE IS STILL
SOME PRESSURE PUSHING AGAINST THE SYSTEM ON THE NORTH SIDE AS A
RESULT OF A DEEP-LAYERED SUBTROPICAL RIDGE TO THE NORTHEAST.
SCATTERED CONVECTION IS PULSING THROUGHOUT THE SOUTHERN SEMICIRCLE,
WHICH HAS NOT QUITE ORGANIZED INTO RADIAL BANDS. A 280952Z RCM-3 SAR
PASS AND AN NRCS IMAGE FROM THE SAME PASS WERE USED TO PLACE THE
INITIAL POSITION WITH HIGH CONFIDENCE. THE SAR IMAGERY SHOWS A RAGGED 
CORE OF LIGHT WINDS WITH EXTENSIVE, ELEVATED WINDS WRAPPING AROUND 
THE SOUTHERN SEMICIRCLE. ADDITIONALLY, A 281210Z PARTIAL ASCAT IMAGE 
OF THE EASTERN SIDE WAS USED TO ASSESS THE INITIAL INTENSITY OF 45 
KTS WITH HIGH CONFIDENCE AND IS WELL-SUPPORTED BY THE RANGE OF 
CURRENT INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING BETWEEN SUBTROPICAL
RIDGES TO THE SOUTHWEST AND TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 45 KTS AT 281140Z
   CIMSS DPRINT: 48 KTS AT 281230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: THE SYSTEM HAS STALLED IN ITS SOUTHWARD
MOVEMENT AND SEEMS TO HAVE BEGUN ITS WESTWARD TURN, A FEW HOURS
EARLIER THAN ANTICIPATED. THE MOVEMENT WILL CONTINUE TO BE SLOW AND
POSSIBLY A BIT ERRATIC STILL AS IT IS ONLY DISTANTLY INFLUENCED BY
THE SUBTROPICAL RIDGE TO THE NORTHEAST. BY TAU 12, IT IS EXPECTED
THE SYSTEM WILL ADOPT A MORE SURE NORTHWESTWARD TRACK, CARRYING IT
PAST THE PHILIPPINES BUT WITH THE CORE REMAINING OFFSHORE TO THE
NORTH OF LUZON. THE FORWARD SPEED WILL REMAIN CLIMATOLOGICALLY
SLOWER THAN AVERAGE, ALLOWING FOR AMPLE OPPORTUNITY TO CONSOLIDATE
AND STRENGTHEN OVER THE WARM WATERS OF THE WESTERN PACIFIC. A PEAK
NEAR TAU 72 IS EXPECTED, EVEN THOUGH THE EXHAUST MECHANISMS ARE
EXPECTED TO IMPROVE BY THIS TIME DUE TO A POLEWARD OUTFLOW CHANNEL
OPENING UP INTO THE MID-LATITUDE WESTERLIES. THE PROXIMITY TO THE
EAST COAST OF TAIWAN WILL PRESENT THE BIGGEST CHALLENGE, WORKING
AGAINST ANY ADDITIONAL STRENGTHENING. ADDITIONALLY, INCREASING
VERTICAL WIND SHEAR WILL HELP TO WEAKEN THE SYSTEM BY TAU 120.

MODEL DISCUSSION: THE ECMWF ENSEMBLE (ECENS) DEPICTS THE SOUTHWARD
PROGRESSION TO SLOW AND MAKE THE WESTWARD TURN BETWEEN TAU 6 AND
TAU 12, AND ECENS GUIDANCE SPREADS DRASTICALLY THEREAFTER, BUT
SHOWING THE MAJORITY FAVORING A MORE NORTHWARD AND EVENTUALLY
NORTHEASTWARD TRACK IN THE LATER TAUS. THE GFS ENSEMBLE (GEFS)
AGREES WITH THE TIMING OF THE WESTWARD TURN, BUT DEPICTS BETTER
AGREEMENT FOR A NORTHWARD TRACK INITIALLY WITH ABOUT 80 PERCENT OF
MEMBERS. OVERALL, THE TRACKERS HAVE BEEN OSCILLATING BUT COMING
INTO TIGHTER AGREEMENT AROUND THE PLACEMENT OF THE PREVIOUS JTWC
TRACK FORECAST. THEREFORE, THE TRACK IS FORECASTED WITH MEDIUM
CONFIDENCE AND IS KEPT SLOWER THAN THE CONSENSUS MEAN, SIDING WITH
THE MORE RELIABLE MODEL GUIDANCE. THE INTENSITIES ARE FORECAST TO
TREND UPWARDS SLOWLY AS THE SYSTEM WORKS TO CONSOLIDATE, PEAKING
NEAR TAU 72, AND THIS FORECAST IS SUPPORTED BY IMPROVING AGREEMENT
AMONG THE INTENSITY GUIDANCE.

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