WDPS31 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06P (SIX) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4S 179.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 90 NM EAST-NORTHEAST OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: EASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS WARMING
CLOUD TOPS AND AN ABYSMAL APPEARANCE AS THE SYSTEM BEGINS TO
SHALLOW OUT DUE TO THE INTRODUCTION OF INCREASING MID-LEVEL DRYING.
WITHOUT BEING ABLE TO TAP INTO ANY UPPER LEVEL EXHAUST MECHANISMS,
NO APPARENT OUTFLOW IS OBSERVED AT THIS TIME. ANIMATED SCANS FROM
THE NEARBY NAUSORI RADAR TO THE WEST SHOW SIGNIFICANT CONVECTION IS
STILL PRESENT WITHIN THIS SYSTEM AS IT TRACKS EASTWARD. THE BRIEF
INTERACTION WITH LAND AS THE SYSTEM TRACKED ACROSS NORTHERN FIJI
IMPEDED THE APPLICATION OF ANY RECENT SCATTEROMETRY. A 291312Z ATMS
89 GHZ MICROWAVE IMAGE REVEALED THE SMALL STRUCTURE OF WHAT
REMAINED OF THE SYSTEM AFTER ITS DEPARTURE FROM FIJI. THE SPATIALLY
SMALL EXTENT OF THIS SYSTEM HAS BEEN ONE OF THE PRIMARY CHALLENGES
WITH ASSESSING THE INTENSITY AND HAS ALSO ALLOWED IT TO FLUCTUATE
INTENSITIES ON A SHORTER TIME SCALE. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON ANIMATED MSI AND SUPPORTED BY THE
CONVECTIVE SIGNATURES ON THE PREVIOUSLY MENTIONED RADAR. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH LOW CONFIDENCE BASED
ON A BLEND OF OBJECTIVE INTENSITY ESTIMATES: ADT OF 37 KTS, AIDT OF
38 KTS, AND DPRINT OF 25 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE AND SURFACE OBSERVATIONS

CURRENT STEERING MECHANISM: AN ELONGATED NEAR-EQUATORIAL RIDGE TO
THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS ADT: 37 KTS AT 291730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: ENVIRONMENTAL CONDITIONS WILL REMAIN LARGELY
UNCHANGED EXCEPT FOR UNFAVORABLY INCREASING VERTICAL WIND SHEAR AND
PRONOUNCED MID-LEVEL DRYING. SINCE THE SYSTEM IS FORECASTED TO
TRACK EASTWARD ALONG A MOISTURE BOUNDARY ASSOCIATED WITH THE SOUTH
PACIFIC CONVERGENCE ZONE (SPCZ), IT FOLLOWS THAT NATURAL PROCESSES
WILL GRADUALLY TAKE PLACE TO WRAP SOME OF THE DRY AIR IN FROM THE
DRY SIDE OF THE BOUNDARY. HOWEVER, IF THE SURFACE CONVERGENCE ALONG
THE SPCZ EXPERIENCES A MOMENTARY INCREASE AT ANY POINT DURING THE
NEXT 24-36 HOURS, THE CONVECTION ASSOCIATED WITH 06P HAS THE
POTENTIAL TO REINVIGORATE THE SYSTEM AND TAP INTO DIFFLUENCE ALOFT,
WHICH IS SITTING JUST OVERHEAD OF THE SYSTEM. SAVE FROM THAT
POSSIBILITY, A GRADUAL TRENDING DOWN OF THE INTENSITY IS EXPECTED,
WHICH WILL BEGIN THE DISSIPATION PROCESS AT TAU 24 AND COMPLETE THE
DISSIPATION OVER WATER BY TAU 36.

MODEL DISCUSSION: OVERALL, THIS SYSTEM HAS NOT BEEN HANDLED WELL BY
GLOBAL ENSEMBLE OR DETERMINISTIC MODELS, AND THERE HAS BEEN LITTLE
CONSISTENCY RUN-TO-RUN IN THE MESOSCALE MODELS AS WELL. ON THE PLUS
SIDE, STORM-SPECIFIC TRACK GUIDANCE IS IN TIGHT AGREEMENT WITH THE
EASTERLY TRACK, BASICALLY FOLLOWING THE POSITION OF THE TROUGH
ASSOCIATED WITH THE SPCZ. TRACK SPEEDS VARY SLIGHTLY, AND THE JTWC
FORECASTED POSITION AT TAU 36 LIES BETWEEN THE MULTI-MODEL TRACK
CONSENSUS AND THE ECMWF TRACK AID, WHICH HAS BEEN PERFORMING AMONG
THE BEST WITH THIS SYSTEM. INTENSITY AIDS HAVE REALLY STRUGGLED IN
THEIR HANDLING OF THIS SYSTEM, AND THE LOWER CONFIDENCE FORECAST IS
A REFLECTION OF THAT DEGRADATION. ALL INTENSITY GUIDANCE SHOWS THE
GRADUAL DECLINE THROUGH TAU 24, BUT THERE ARE DISCREPANCIES BEYOND
THAT WITH SOME OF THE HURRICANE-SPECIFIC MODELS HINTING AT A
RE-INTENSIFICATION LATER ON. THIS MAY SPEAK TO A TRANSITIONAL
PERIOD TO A NON-TROPICAL SYSTEM, WHICH IS BEYOND THE SCOPE OF THIS
PRESENT FORECAST.

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