WDPN31 PGTW 210900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING 
NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.8N 146.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 139 NM SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) ILLUSTRATES A
SOMEWHAT SHEARED DEPICTION, WITH THE OUTER BANDS OF THE LOW LEVEL
CIRCULATION CENTER (LLCC) EVIDENT IN THE SOUTHWESTERN QUADRANT AND
DEEP PERSISTENT CONVECTION ISOLATED TO THEN NORTHEASTERN QUADRANT.
A 210335Z AMSR2 89GHZ MICROWAVE IMAGE SHOWED THE CURVED CONVECTIVE
BANDS EXTENDING FURTHER AROUND THE WESTERN SIDE OF THE LLCC, PRIOR
TO THE ONSET OF SOME ADDITIONAL SOUTHERLY SHEAR, WHICH HAS SINCE
MOVED THE CONVECTION OFF THE CENTER TO THE NORTHEAST. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI AND
LOW-LEVEL CLOUD LINES OVER THE SOUTHERN QUADRANT, AS WELL AS
EXTRAPOLATION OF THE AMSR2 DATA. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW DVORAK ESTIMATES
OF T2.0 FROM BOTH PGTW AND KNES, AND AN ADT ESTIMATE OF T2.2, WHICH
ARE CONSISTENT WITH THE OVERALL STRUCTURE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 210540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: WHILE OVERALL VWS VALUES ARE LOW, THE PRESENCE OF
A MESOSCALE UPPER-LEVEL TROUGH IN THE VICINITY IS INDUCING
SUBSIDENT FLOW ON THE SOUTHWESTERN SIDE OF THE SYSTEM WHICH IS
SERVING TO ENHANCE THE IMPACT OF THE SOUTHERLY SHEAR AND INHIBIT
CONVECTIVE CONSOLIDATION NEAR THE CORE.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 06W IS FORECAST TO TRACK AROUND THE
SOUTHWESTERN PERIPHERY OF THE DEEP STR CENTERED FAR TO THE
NORTHEAST THROUGH TAU 36, THEN SLOW SLIGHTLY AS IT APPROACHES THE
RIDGE AXIS BY TAU 48. THE SYSTEM IS EXPECTED TO ROUND THE RIDGE
AXIS BY AROUND TAU 96, THEN BEGIN TO ACCELERATE NORTH-NORTHEASTWARD
THROUGH TAU 120. BY TAU 120, AS THE SYSTEM BEGINS TO MOVE
NORTHEASTWARD, IT WILL BEGIN TO INTERACT BOTH WITH THE MEIYU
BOUNDARY AND A MID-LATITUDE MAJOR SHORTWAVE TROUGH MOVING SOUTH
OVER HONSHU, AND BEGIN TO TRANSITION TO AN EXTRATROPICAL SYSTEM. IN
LIGHT OF THE POOR UPPER-LEVEL ENVIRONMENT AND THE SLOW DEVELOPMENT
OF THE CONVECTIVE CORE, THE SYSTEM IS EXPECTED TO ONLY SLOWLY
INTENSIFY OVER THE NEXT 24 HOURS. A PERIOD OF SLIGHTLY FASTER
INTENSIFICATION IS EXPECTED BETWEEN TAU 36 AND 48 AS THE SYSTEM
TRACKS OVER VERY WARM, HIGH OHC WATERS WITH A SIMULTANEOUS
IMPROVEMENT IN THE UPPER-LEVEL OUTFLOW PATTERN. AFTER TAU 96, THE
COMBINATION OF DECREASING SSTS, INCREASING NORTHERLY VWS AND
CONVERGENT FLOW ALOFT WILL CONSPIRE TO INDUCE STEADY WEAKENING
THROUGH THE REMAINDER OF THE FORECAST PERIOD.

MODEL DISCUSSION: OVERALL, DYNAMIC MODEL GUIDANCE SUPPORTS THE
OFFICIAL FORECAST TRACK, WITH THE CENTER OF TD 06W PASSING SOUTH OF
GUAM WITH A SPREAD OF 65NM AT TAU 24, INCREASING TO 125NM BY TAU
48. THE JTWC TRACK LIES ON THE POLEWARD SIDE OF THE GUIDANCE
ENVELOPE THROUGH TAU 36, CONSISTENT WITH THE PREVIOUS SIX HOUR
TRACK MOTION. FOR THE REMAINDER OF THE FORECAST PERIOD, THE JTWC
TRACK LIES CLOSE TO THE ECMWF SOLUTION, WHICH ITSELF CLOSELY
FOLLOWS THE MULTI-MODEL CONSENSUS MEAN. GUIDANCE SPREAD INCREASING
TO 645NM BY TAU 120, PRIMARILY DUE TO INCREASED ALONG TRACK ERRORS,
AS THE ECMWF FAR OUTPACES THE REMAINDER OF THE GUIDANCE AFTER TAU
96. THE GFS REMAINS A SLOW AND EASTWARD OUTLIER FOR THE DURATION OF
THE FORECAST.


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