WDPN32 PGTW 122100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05E (DORA) WARNING NR 050//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6N 176.4E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 810 NM WEST OF JOHNSTON ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
INCREASINGLY SHEARED SYSTEM, WITH UPPER-LEVEL CIRRUS STREAMING
TOWARDS THE LOW-LEVEL CIRCULATION CENTER (LLCC) OUT OF THE
SOUTHWEST. THE LLCC APPEARS TO BE LOCATED NEAR THE SOUTHWESTERN
EDGE OF THE DEEP CONVECTIVE MASS. IN THE ABSENCE OF RELIABLE
OBJECTIVE SATELLITE DATA, THE INITIAL INTENSITY IS LOWERED TO 65 KT
IN AGREEMENT WITH AGENCY DVORAK ESTIMATES. A POLEWARD OUTFLOW
CHANNEL REMAINS ESTABLISHED INTO THE EASTERN FLANK OF AN
UPPER-LEVEL TROUGH TO THE NORTHWEST WHICH IS IN THE PROCESS OF
PINCHING OFF INTO A CUTOFF LOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   CIMSS ADT: 94 KTS AT 121730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: DORA CONTINUES TO DECAY AS MODERATE
SOUTHWESTERLY VERTICAL SHEAR ERODES ITS INNER CORE. GRADUAL TO
STEADY WEAKENING IS LIKELY TO CONTINUE THROUGH AT LEAST THE NEXT 48
HOURS AS SHEAR HOLDS AT THIS MAGNITUDE DUE TO THE UPPER-LEVEL
TROUGH TO THE NORTHWEST. AS DORA TURNS NORTHWARD TO THE EAST OF
THIS TROUGH, THE TROUGH WILL PINCH OFF INTO A CUTOFF UPPER LOW AND
WEAKEN. AS THIS OCCURS, DORA MAY ENCOUNTER LOWER SHEAR DURING AT
LEAST A PORTION OF THE 72-120 HOUR PERIOD. ADDITIONALLY, THERE IS A
DEEP LAYER OF MOISTURE ON THE SOUTHEASTERN FLANK OF THE UPPER LOW
THAT MAY END UP POSITIONED ON THE UPSHEAR (SOUTHWEST) SIDE OF DORA
DURING THIS TIME, REDUCING THE AMOUNT OF DRY VENTILATION OF THE
VORTEX. THESE FACTORS COULD LEAD TO A REINTENSIFICATION OF DORA IN
THE LATTER PORTION OF THE FORECAST, A SCENARIO THAT IS NOW ESPOUSED
BY THE GFS, HAFS-A, HWRF, AND COAMPS-TC. HOWEVER, THERE REMAINS A
POSSIBILITY THAT DORA SIMPLY DISSIPATES PRIOR TO THIS WINDOW OF
OPPORTUNITY, ESPECIALLY IF IT TRACKS CLOSER TO THE UPPER-LEVEL LOW.
THE JTWC FORECAST SHOWS REINTENSIFICATION TO 50 KT AT 120 HOURS
AFTER WEAKENING TO A MINIMUM OF 45 KT DURING THE 72-96 HOUR
TIMEFRAME. ALONG-TRACK SPREAD EXPLODES TO LARGE VALUES AT 96-120
HOURS DUE TO UNCERTAINTY IN HOW QUICKLY DORA WILL REACH A FRONTAL
BOUNDARY TO THE NORTH AND GET USHERED NORTHEASTWARD ALONG THAT
BOUNDARY. TRACK FORECAST CONFIDENCE IS LOWER THAN AVERAGE DURING
THIS PERIOD. THE SAME FRONTAL BOUNDARY WILL ALSO INDUCE
EXTRATROPICAL TRANSITION BY 120 HOURS OR SO, BUT THIS TIMING COULD
CHANGE BASED ON THE AFOREMENTIONED UNCERTAINTY IN THE TIMING OF THE
FRONTAL INTERACTION.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS SLIGHTLY TO THE RIGHT
OF THE MULTI-MODEL CONSENSUS DUE TO THE WEAK REPRESENTATION OF DORA
IN SOME MEMBERS OF THE CONSENSUS, SUCH AS ECMWF, WHICH SHOW A
SHALLOW VORTEX THAT IS STEERED MORE WESTWARD, LIKELY
UNREALISTICALLY SO. THE JTWC INTENSITY FORECAST IS CLOSE TO THE
MEAN OF HAFS-A, HWRF, COAMPS-TC, AND GFS.

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