WDPN32 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) 
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.1N 145.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 490 NM SOUTH-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL 
CLUSTER OF FLARING CONVECTION SHEARED TO THE SOUTH OF THE LLCC, WHICH 
ACCOUNTS FOR THE RECENT FULL-EXPOSURE OF THE LLCC. VIGOROUS 
EQUATORWARD OUTFLOW WITH TRANSVERSE BANDING AROUND THE EASTERN AND 
SOUTHERN PERIPHERIES AIDED IN THE SYSTEM REACHING A PEAK INTENSITY OF 
35 KTS AT 050000Z; HOWEVER, THE INTENSITY WEAKENED TO 30 KTS AT 
050600Z ONCE THE SYSTEM DECOUPLED. TD 13W IS LOCATED UNDERNEATH A 
TUTT CELL AND IMMEDIATELY ADJACENT TO AN EXTENSIVE AREA OF DRY AIR 
AND SUBSIDENCE TO THE WEST OF ITS CURRENT POSITION AND FORECAST 
TRACK. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
ANIMATED VISIBLE SATELLITE IMAGERY SHOWING A FULLY EXPOSED LLCC. THE 
INITIAL INTENSITY OF 30 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE 
BASED ON SUBJECTIVE AGENCY DVORAK ESTIMATES IN GOOD AGREEMENT AND 
RECENT SCATTEROMETRY WINDSPEEDS RANGING FROM 25-35 KTS.

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

CURRENT STEERING MECHANISM: DEEP LAYER STR TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 050220Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 13W HAS A FEW ADVANTAGES IN THE SHORT TERM,
INCLUDING THE VIGOROUS EQUATORWARD OUTFLOW MENTIONED ABOVE, A
WELL-WRAPPED LOW LEVEL CLOUD SYSTEM, AND WARM SSTS OF 27-28C
THROUGHOUT THE FORECAST PERIOD. ALTHOUGH THE INTENSITY WEAKENED
SLIGHTLY (BY 5 KTS) AFTER THE SYSTEM BECAME DECOUPLED, THE MARGINALLY
FAVORABLE ENVIRONMENTAL CONDITIONS WILL ALLOW THE INTENSITY TO
FLUCTUATE UPWARDS TO 35 KTS AGAIN NEAR TAU 12. HOWEVER, THE
POSITION IN RELATION TO THE TUTT CELL OVERHEAD IS PROBLEMATIC DUE
TO A WEAK CONVERGENT INFLUENCE ALOFT, WHICH WILL INHIBIT FURTHER
DEVELOPMENT. TD 13W HAS A STRONG STEERING INFLUENCE WHICH WILL
RECURVE IT AROUND THE STR AXIS AND CAUSE IT TO ACCELERATE
NORTHEASTWARD AS IT NEARS THE MID-LATITUDE WESTERLIES. THE 
ENVIRONMENT WILL BECOME INCREASINGLY HOSTILE WITH UNFAVORABLE VWS 
(30-34 KTS) BY TAU 24 AND BEYOND. BY TAU 36, THE SYSTEM WILL VENTURE 
INTO MID-LATITUDE TERRITORIES WHERE A STRONG SHARED ENERGY JET MAX
EXISTS POLEWARD. A BAROCLINIC INFLUENCE IN THE HIGHER LATITUDES
WILL LEAD TO THE EXTRATROPICAL TRANSITION OF TD 13W BY TAU 48.

MODEL DISCUSSION: THE DYNAMICAL MODEL GUIDANCE REMAINS CONSISTENTLY
IN VERY TIGHT AGREEMENT FOR THE TRACK OF TD 13W, THEREFORE THE JTWC
TRACK FORECAST ALIGNS CLOSELY WITH THE CONSENSUS MEAN. NUMERICAL
MODEL GUIDANCE IS ALSO IN GOOD AGREEMENT CONCERNING A GRADUAL
DECREASE IN THE INTENSITY, BUT WHEN ACCOUNTING FOR THE OVERALL PACE
OF THE SYSTEM, THE JTWC FORECAST IS HEDGED AT OR ABOVE THE
INTENSITY CONSENSUS. CONFIDENCE IS HIGH FOR BOTH THE JTWC TRACK AND 
INTENSITY FORECASTS.

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