WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (AERE) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0N 131.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 379 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATE MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), DISPLACED TO THE WEST
OF AN AREA OF ELONGATED FLARING CONVECTION. ATMOSPHERIC MOTION
VECTORS (AMVS) AND A 010600Z UPPER AIR SOUNDING FROM ISHIGAKI JIMA
INDICATE VERY STRONG (40-60 KTS) NORTHWESTERLY WIND FLOW ABOVE
300MB ALONG THE SOUTHWESTERN PERIPHERY OF A TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) CELL LOCATED JUST NORTH OF TS 05W. THIS
STRONG UPPER-LEVEL FLOW IS INDUCING SIGNIFICANT SHEAR OVER TOP OF
THE SYSTEM, AND LEADING TO A STRONG EASTWARD TILT IN THE VORTEX.
CONVECTION CONTINUES TO FLARE UP ON THE EASTERN SIDE OF THE CENTER
IN THE DIFFLUENT REGION OF THE UPPER-LEVEL OUTFLOW ON THE EASTERN
SIDE OF THE TUTT. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN THE ANIMATED MSI. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, SLIGHTLY
HIGHER THAN THE AGENCY DVORAK CURRENT INTENSITIES MIGHT SUGGEST,
BASED ON AN EARLIER 010027Z ASCAT PASS WHICH SHOWED A PATCH OF 40
KNOT WINDS ON THE EASTERN PERIPHERY OF THE CIRCULATION. THE SYSTEM
IS CURRENTLY MOVING SLOWLY NORTHWARD ALONG THE SOUTHWEST SIDE OF A
DEEP STR TO THE NORTHEAST. THE OVERALL ENVIRONMENT IS ASSESSED AS
MARGINALLY FAVORABLE, WITH THE DIFFLUENT OUTFLOW OFFSETTING THE
STRONG SHEAR TO A DEGREE.

INITIAL WIND RADII BASIS: PERSISTENCE WITH EARLIER SCATTEROMETER
DATA

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 40 KTS AT 010423Z
   CIMSS ADT: 34 KTS AT 010540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE PEAK INTENSITY HAS BEEN LOWERED
BY 10 KNOTS. 

FORECAST DISCUSSION: OVER THE PAST 24 HOURS, TS 05W HAS MOVED ALONG
A SOMEWHAT ERRATIC, BUT GENERALLY NORTHWARD TRACK. AS THE RIDGE TO
THE EAST BUILDS AND DRIFTS CLOSER TO TS 05W, THE STEERING GRADIENT
WILL TIGHTEN AND SHIFT THE TRACK OF TS 05W MORE NORTHWESTWARD WHILE
SIMULTANEOUSLY PICKING UP SPEED. BY TAU 36 HOWEVER THE STR WILL
BUILD, WITH AN EXTENSION OF THE RIDGE DEVELOPING OVER SOUTHERN
KOREA, WHICH WILL SERVE TO SLOW THE FORWARD MOTION OF TS 05W
THROUGH ABOUT TAU 60, AS IT MOVES SLOWLY NORTHWARD IN THE EAST
CHINA SEA. BY TAU 72, THE RIDGE TO THE NORTH WILL PINCH OFF INTO A
SEPARATE STR CENTER OVER NORTH KOREA, AND TS 05W WILL TRACK INTO
THE INDUCED WEAKNESS, MOVING ON TO A NORTHEASTWARD TRACK AFTER TAU
72. THE SYSTEM IS FORECAST TO TRACK RELATIVELY SLOWLY THROUGH THE
TSUSHIMA STRAIT BY TAU 96, AND ULTIMATELY EMERGE INTO THE SOUTHERN
SEA OF JAPAN BY TAU 120 AS IT WEAKENS AND COMES UNDER THE STEERING
INFLUENCE OF THE LOW-LEVEL FLOW FROM THE SOUTH. IN TERMS OF
INTENSITY, DUE TO THE HIGH SHEAR AND UPPER-LEVEL CONVERGENT FLOW
CURRENTLY ENTRENCHED OVER THE SYSTEM, NO ADDITIONAL INTENSIFICATION
IS ANTICIPATED IN THE FIRST 12 HOURS. SLOW INTENSIFICATION TO A
PEAK OF 50 KNOTS IS EXPECTED BETWEEN TAU 36 TO 48 AS THE TUTT
WEAKENS AND MOVES AWAY AND ALLOWS FOR A SHORT PERIOD OF MARGINALLY
IMPROVED OUTFLOW ALOFT. AFTER TAU 72 HOWEVER, THE SYSTEM WILL COME
UNDER THE INFLUENCE OF STEADILY INCREASING VWS, ENTRAINMENT OF DRY
MID-LEVEL AIR AND COOLING SSTS, LEADING TO A SLOW BUT STEADY
WEAKENING TREND. BY TAU 120 THE SYSTEM WILL BE CROSSING INTO MUCH
COOLER SSTS AND INTERACTING WITH AN APPROACHING 500MB TROUGH AND
THE RACE WILL BE ON TO SEE IF THE SYSTEM WILL FULLY DISSIPATE
BEFORE COMMENCING EXTRA-TROPICAL TRANSITION. 

MODEL DISCUSSION: WITH THE NOTABLE EXCEPTION OF NAVGEM, THE
REMAINDER OF THE CONSENSUS GUIDANCE IS IN GOOD AGREEMENT THROUGH
THE FIRST 72 HOURS OF THE FORECAST. NAVGEM IS A SIGNIFICANT
OUTLIER, TAKING THE SYSTEM INTO THE TEETH OF THE RIDGE AS IT IS
PRONE TO DO, AND TRACKING THE SYSTEM EAST OF KYUSHU THROUGH TAU 96.
IT SHOULD BE NOTED THAT THE JGSM ALSO TURNS THE SYSTEM SHARPLY
EASTWARD SOUTH OF KYUSHU BY TAU 72 WHILE IT REMAINS CLOSE TO THE
OTHER MEMBERS TO THAT POINT. THE BULK OF THE GUIDANCE IS IN A TIGHT
100NM SPREAD AT TAU 48, INCREASING TO 120NM AT TAU 72. SIGNIFICANT
DIVERGENCE OCCURS AFTER TAU 72 WITH SPREAD INCREASING TO 400NM BY
TAU 120, WITH NAVGEM AND JGSM ON THE EASTERN SIDE AND UKMET
ENSEMBLE ON THE WEST, TAKING THE TRACK OVER CENTER KOREA. THE JTWC
TRACK LIKES ON THE EASTERN SIDE OF THE TIGHTEST PACKING OF THE
GUIDANCE MEMBERS THROUGH TAU 72, THEN DEVIATES WELL NORTH OF THE
CONSENSUS MEAN THROUGH TAU 120, CLOSE TO THE GFS. THE BULK OF THE
INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH ALL BUT THE
COAMPS-TC KEEPING THE PEAK INTENSITY AT OR BELOW 50 KNOTS FOLLOWED
BY A SLOW WEAKENING TREND. THE JTWC FORECAST LIES BELOW THE MEAN
THROUGH TAU 12, THEN CLOSELY TRACKS THE MEAN THEREAFTER. 

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