WDPS31 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03P (RUBY) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.8S 158.2E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 586 NM NORTHWEST OF NOUMEA, NEW CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 120-NM
DIAMETER CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL
CIRCULATION CENTER (LLCC). A 120817Z SSMIS 91GHZ MICROWAVE IMAGE
REVEALS A SMALL CORE OF CONVECTION WITH A MICROWAVE EYE FEATURE,
AND SPIRAL BANDING OVER THE SOUTHERN SEMICIRCLE. A 121049Z ASCAT-B
25KM BULLSEYE IMAGE SHOWS A CONSOLIDATED WINDFIELD WITH 45-50 KNOT
WINDS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE ASCAT AMBIGUITY IMAGE. THE INITIAL INTENSITY OF 50 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON AN AVERAGE OF THE DVORAK
ESTIMATES BUT IS ALSO SUPPORTED BY THE ASCAT DATA. THE 34-KNOT AND
50-KNOT WIND RADII HAVE BEEN ADJUSTED BASED ON A DETAILED ANALYSIS
OF ASCAT IMAGERY. THE RECENT RAPID CONSOLIDATION IS ATTRIBUTABLE TO
FAVORABLE ENVIRONMENTAL CONDITIONS, SPECIFICALLY, ROBUST POLEWARD
OUTFLOW INTO A DEEP UPPER-LEVEL TROUGH POSITIONED EAST OF
AUSTRALIA, LOW VERTICAL WIND SHEAR AND WARM SST VALUES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   ABRF: T3.0 - 45 KTS
   CIMSS SATCON: 59 KTS AT 120817Z
   CIMSS ADT: 57 KTS AT 121140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 03P WILL TRACK SOUTHEASTWARD THROUGH THE
FORECAST PERIOD ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED
STR. HOWEVER, THE SYSTEM WILL ACCELERATE AFTER TAU 36 WITHIN
ENHANCED FLOW BETWEEN THE AFOREMENTIONED STR AND A DEEP, HIGH
AMPLITUDE TROUGH. THIS STEERING PATTERN IS CLASSIFIED AS A HIGH
AMPLITUDE PATTERN AND IS COMMON EAST OF AUSTRALIA, AND GENERALLY
PRODUCES FASTER-THAN-CLIMATOLOGICAL TRACK SPEEDS WITH HIGH
CONFIDENCE TRACK CONFIDENCE. TC 03P WILL RAPIDLY INTENSIFY THROUGH
TAU 36 WITH A PEAK INTENSITY OF 85 KNOTS ANTICIPATED BY TAU 36. 
THERE IS SOME UNCERTAINTY IN THE ACTUAL PEAK INTENSITY WITH 
POTENTIAL FOR A HIGHER PEAK INTENSITY NEAR NEW CALEDONIA. BY TAU 60, 
THE SYSTEM WILL BEGIN TO INTERACT WITH THE SUBTROPICAL WESTERLIES 
AND TRACK OVER COOLER SST (25C). BY TAU 96, TC 03P WILL ENCOUNTER 
STRONG VERTICAL WIND SHEAR (30-40 KNOTS) WITH SIGNIFICANTLY COOLER 
SST (23-17C). THIS WILL SERVE TO RAPIDLY WEAKEN THE CONVECTIVE 
STRUCTURE AND LEAD TO SUBTROPICAL TRANSITION. HOWEVER, THE SYSTEM 
WILL REMAIN A STORM-FORCE SUBTROPICAL LOW AS IT APPROACHES NEW 
ZEALAND.    

MODEL DISCUSSION: AS MENTIONED EARLIER, THE HIGH AMPLITUDE PATTERN
TYPICALLY PRODUCES TIGHTLY-GROUPED FORECAST GUIDANCE AND,
CONSEQUENTLY, HIGH CONFIDENCE FORECAST TRACKS. THIS SYSTEM IS NO
EXCEPTION WITH A 100-110NM SPREAD IN SOLUTIONS FROM TAU 36 THROUGH
TAU 72. ADDITIONALLY, THE 120000Z ECMWF ENSEMBLE (EPS) ALSO
INDICATES A TIGHT GROUPING OF ENSEMBLE MEMBERS AND A NARROW CONE OF
HIGH STRIKE PROBABILITY JUST NORTH OF NEW CALEDONIA EXTENDING
SOUTHEASTWARD. THE JTWC INTENSITY FORECAST IS MORE UNCERTAIN WITH A
HIGH PROBABILITY FOR RAPID INTENSIFICATION OVER THE NEXT 36 HOURS
AS INDICATED BY THE TRIGGERING OF THE RAPID INTENSIFICATION
PREDICTION AID (RIPA). THE JTWC INTENSITY FORECAST IS PLACED ABOVE
MOST OF THE RELIABLE INTENSITY GUIDANCE AND THE JTWC INTENSITY
CONSENSUS (ICNW) DUE TO THE FAVORABLE ENVIRONMENTAL CONDITIONS
THROUGH TAU 48. 

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