WDPS31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03P (RUBY) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.1S 161.0E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 374 NM NORTHWEST OF NOUMEA, NEW CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SLIGHT
WEAKENING TREND OVER THE PAST SIX HOURS WITH A PARTIALLY-EXPOSED
LOW-LEVEL CIRCULATION (LLC) POSITIONED ALONG THE WESTERN EDGE OF
THE CORE CONVECTION. A 130527Z SSMIS 91GH MICROWAVE IMAGE REVEALS A
PARTIAL EYEWALL SURROUNDING A DEFINED, ELONGATED CENTER WITH DEEP
CONVECTIVE BANDING OVER THE EASTERN SEMICIRCLE AND SHALLOW BANDING
OVER THE WESTERN SEMICIRCLE. DUE TO THE DE-COUPLING LOWER-LEVEL AND
UPPER-LEVEL CENTERS, THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE. THE SYSTEM HAS WEAKENED DUE TO AN INCREASE IN MID-LEVEL
SHEAR AS WELL AS SOME MID-LEVEL DRY AIR ENTRAINMENT. THE INITIAL 
INTENSITY OF 65 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A 
RANGE OF DVORAK DATA T ESTIMATES OF T3.5 (55 KNOTS) AND CURRENT 
INTENSITY ESTIMATES OF 4.0-4.5. POLEWARD OUTFLOW REMAINS ROBUST, 
ENHANCED BY A DEEP UPPER-LEVEL TROUGH TO THE SOUTHWEST.

INITIAL WIND RADII BASIS: PERSISTENCE OBJECTIVE BEST TRACK 

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


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: 4.0 - 65 KTS
   KNES: 4.5 - 77 KTS
   CIMSS SATCON: 69 KTS AT 132307Z
   CIMSS ADT: 82 KTS AT 130540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT.

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: TC 03P WILL TRACK EAST-SOUTHEASTWARD TO
SOUTHEASTWARD THROUGH THE FORECAST PERIOD ALONG THE SOUTHWESTERN 
PERIPHERY OF A DEEP-LAYERED STR. HOWEVER, THE SYSTEM WILL ACCELERATE 
AFTER TAU 12 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 RE-INTENSIFY BY TAU 24 TO A 
PEAK INTENSITY OF 75 KNOTS. BY TAU 48, THE SYSTEM WILL BEGIN TO 
INTERACT WITH THE SUBTROPICAL WESTERLIES AND TRACK OVER COOLER SST 
(25C). BY TAU 72, TC 03P WILL ENCOUNTER STRONG VERTICAL WIND SHEAR 
(25-35 KNOTS) WITH SIGNIFICANTLY COOLER SST (23-20C). 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 THROUGH 48.
ADDITIONALLY, THE 121800Z ECMWF ENSEMBLE (EPS) ALSO INDICATES A
TIGHT GROUPING OF ENSEMBLE MEMBERS AND A NARROW CONE OF HIGH STRIKE
PROBABILITY OVER AND JUST NORTH OF NEW CALEDONIA EXTENDING
SOUTHEASTWARD. THE JTWC INTENSITY FORECAST IS MORE UNCERTAIN WITH
RELIABLE INTENSITY GUIDANCE SPLIT INTO TWO DISTINCT GROUPINGS: HWRF
AND DECAY-SHIPS SUPPORT REINTENSIFICATION TO 75-80 KNOTS WHILE
COAMPS-TC AND GFS SUPPORT A GRADUAL WEAKENING TREND TO 55-60 KNOTS
OVER THE NEXT TWO DAYS BEFORE AGREEING ON A SHARPER WEAKENING TREND
THROUGH TAU 72. THE JTWC INTENSITY FORECAST IS PLACED CLOSER TO
THE HWRF, DECAY-SHIPS SOLUTIONS CONSERVATIVELY IN ANTICIPATION OF
SOME RE-CONSOLIDATION THROUGH THE UPCOMING CONVECTIVE MAXIMUM PERIOD.

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