SOUTH PACIFIC: TC 30P(MAILA) near CAT 4 US despite possible up-welling,intensification still possible next 24h/TC 31P (VAIANU) peaked at CAT 3 forecast to be a strong Subtropical Storm by 96h//071500 UTC

WDPS31 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (MAILA) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.7S 156.3E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 654 NM SOUTH OF KAPINGAMARANGI
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
DISCERNIBLE AND FULLY SYMMETRIC, CENTRAL EYE FEATURE OF TROPICAL
CYCLONE (TC) 30P (MAILA), RESULTING IN HIGH CONFIDENCE IN THE
INITIAL POSITION ASSESSMENT. THE TEMPERATURE OF THE EYE HAS WARMED
SLIGHTLY SINCE THE LAST WARNING OCCURRING BENEATH A PERSISTENT CANOPY
OF VERY COLD DEEP CONVECTION WITH CLOUD TOP TEMPERATURES NEAR -83
C. THE SYSTEM HAS UNDERGONE SUBSTANTIAL AXISYMMETRIZATION,
RESULTING IN A MORE UNIFORM AND ROBUST EYEWALL STRUCTURE NOW
EVIDENT ACROSS ALL QUADRANTS, INDICATING SLOW, BUT STEADY
INTENSIFICATION. SYNOPTIC ENVIRONMENT REVEALS LARGELY SUPPORTIVE
CONDITIONS, CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR,
AMPLE TROPOSPHERIC MOISTURE CONTENT, AND A WELL-ESTABLISHED,
PREDOMINANTLY WESTWARD, UPPER-LEVEL OUTFLOW CHANNEL. THE PRIMARY
ANTAGONISTIC FACTOR HOLDING A POTENTIAL FOR HALTING THE
INTENSIFICATION RATE IS THE OCEANIC FEEDBACK MECHANISM OF COLD
WATER UPWELLING, AS SIMULATED BY THE COUPLED OCEAN-ATMOSPHERE
MODELS HAFS AND HWRF. THE COOL WATER POOL DEPICTED BY THOSE
NUMERICAL PREDICTIONS IS DEPICTED RIGHT UNDERNEATH THE CURRENTLY
FORECAST TRACK. AT THE MOMENT, THE OBSERVED STRUCTURAL IMPROVEMENTS
SUGGEST THIS EFFECT IS CURRENTLY NEGLIGIBLE.  THE INITIAL INTENSITY
OF 110 KTS IS DETERMINED WITH MODERATE CERTAINTY, REFLECTING A
CONSENSUS OF AGENCY DVORAK ESTIMATES AND AUTOMATED SATELLITE-BASED
ALGORITHMS THAT UNANIMOUSLY INDICATE STRENGTHENING HAS OCCURRED.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE SOUTHWEST AND CENTERED OVER AUSTRALIA 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   ABRF: T6.5 - 127 KTS
   CIMSS ADT: 124 KTS AT 071130Z
   CIMSS AIDT: 120 KTS AT 071130Z
   CIMSS D-PRINT: 122 KTS AT 071300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 24-29 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 30P IS PROJECTED TO CONTINUE TRACKING
WEST-NORTHWESTWARD OVER THE NEXT 12-24 HOURS, AT VERY SLOW (3-4
KTS) TRANSLATIONAL SPEEDS. SLOW ACCELERATION TOWARD THE
WEST-SOUTHWEST UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE
POSITIONED TO ITS SOUTHWEST IS EXPECTED AFTER TAU 24. THIS
TRAJECTORY IS EXPECTED TO KEEP TC 30P ON A PATH JUST SOUTH OF THE
PAPUAN PENINSULA FOR THE DURATION OF THE FORECAST PERIOD. THE
CURRENT INTENSITY ASSESSMENT CONFIDENCE REMAINS LOW DUE TO 
THE AFOREMENTIONED UPWELLING POTENTIAL. THE COUPLED
MODELS DEPICT A REGION OF OCEANIC COLD WAKE (SUB -26C) IN CLOSE
PROXIMITY TO THE CURRENT LOW-LEVEL CIRCULATION CENTER AND EXTENDING
DIRECTLY IN FRONT OF THE PROJECTED PATH, POTENTIALLY INCREASES THE
CHANCES OF HALTED INTENSIFICATION. NEVERTHELESS, THE PERSISTENT
STRENGTHENING TREND SUGGESTS THAT EITHER THIS COLD POOL IS LESS
EXTENSIVE THAN MODELED, OR THE AMBIENT SEA SURFACE TEMPERATURES ARE
WARMER THAN SIMULATED. GIVEN THE OTHERWISE BENIGN ENVIRONMENTAL
PARAMETERS, CONTINUED INTENSIFICATION IS ANTICIPATED, WITH A PEAK
INTENSITY NEAR 120 KTS PROJECTED BETWEEN TAU 24 AND TAU 36.
THEREAFTER, A GRADUAL WEAKENING TREND IS EXPECTED TO COMMENCE DUE
TO INCREASING MID-LEVEL VERTICAL WIND SHEAR (FORECAST TO REACH
30-35 KTS AROUND TAU 72) AND THE POTENTIAL FOR INCREASED FRICTIONAL
EFFECTS FROM TOPOGRAPHIC INTERACTION WITH THE OWEN STANLEY RANGE.

MODEL DISCUSSION: THERE IS ONLY MODERATE CONFIDENCE IN THE
NUMERICAL MODEL TRACK GUIDANCE, WHICH IS CENTERED ON THE
MULTI-MODEL GUIDANCE ENVELOPE. THIS CONSENSUS REPRESENTS A
COMPROMISE BETWEEN THE FASTER GFS AND NAVGEM SOLUTIONS, THE
MID-POINT ECMWF ENSEMBLE MEAN, AND THE SLOWER UKMET, GALWEM AND
DETERMINISTIC ECMWF TRACKERS. WHILE THERE IS GENERAL AGREEMENT ON
THE OVERALL STEERING REGIME AND THE EVOLUTION FROM A WESTWARD TO A
WEST-SOUTHWESTWARD TRACK, SIGNIFICANT UNCERTAINTY PERSISTS
REGARDING THE TIMING OF THE RATE OF ACCELERATION. AN ADDITIONAL
COMPLICATING FACTOR IS THE POTENTIAL FOR TOPOGRAPHIC ALONG-TRACK 
INTERACTION AND ASSOCIATED WEAKENING, SHOULD THE SYSTEM PROPAGATE 
CLOSER TO PAPUA NEW GUINEA. REGARDING INTENSITY, A RECENT SHIFT 
TOWARDS A MORE ROBUST INTENSIFICATION TREND, EVIDENCED BY THE IMPROVED
EYEWALL STRUCTURE, IS CORROBORATED BY NEARLY ALL AVAILABLE
GUIDANCE. CONFIDENCE IN THE OFFICIAL INTENSITY FORECAST REMAINS LOW
DUE TO THE HIGH UNCERTAINTY ASSOCIATED WITH THE LOOMING POTENTIAL
IMPACTS OF THE UPWELLING PHENOMENA AND A LARGE ALONG-TRACK SPREAD
IN THE MODEL GUIDANCE. FURTHERMORE, THE PERSISTENCE IN THE
TRIGGERING OF NUMEROUS RAPID INTENSIFICATION INDICES IN RECENT
MODEL CYCLE PROVIDES ADDITIONAL EVIDENCE SUPPORTING A CONTINUED
CONSOLIDATION AND INTENSIFICATION TREND.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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WDPS32 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (VAIANU) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.0S 175.9E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 182 NM SOUTHWEST OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS TROPICAL
CYCLONE (TC) 31P (VAIANU) PROPAGATING SOUTHEASTWARD ALONG THE
SOUTHWESTERN PERIPHERY OF A NEAR-EQUATORIAL RIDGE (NER) CENTERED TO
THE NORTHEAST. THE EYE FEATURE HAS BECOME FULLY OBSCURED AND CLOUD-
FILLED. WESTERLY VERTICAL WIND SHEAR HAS MARGINALLY SUBSIDED
OVER THE LAST 6 HOURS, BUT THE DRY AIR ENTRAINMENT IS STILL
PREVALENT RESULTING IN AN OVERALL MARGINALLY UNFAVORABLE ENVIRONMENT.
OFFSETTING THESE CHARACTERISTICS ARE FAVORABLE AND WARM
(28-29 C) SEA SURFACE TEMPERATURES (SST) AND A WELL-DEFINED
POLEWARD UPPER-LEVEL OUTFLOW. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE UTILIZING THE ANIMATED INFRARED SATELLITE LOOP,
COMBINED WITH THE EXTRAPOLATION FROM A 070930Z METOP-C ASCAT PASS.
THE INITIAL INTENSITY OF 95 KTS IS ALSO ESTIMATED WITH HIGH
CERTAINTY, BASED ON A CONSENSUS OF AGENCY DVORAK CLASSIFICATIONS
AND OBJECTIVE SATELLITE-BASED INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: A 070701Z RCM-3 SAR PASS

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   PHFO: T5.5 - 102 KTS
   NFFN: T5.0 - 90 KTS
   CIMSS ADT: 97 KTS AT 071140Z
   CIMSS AIDT: 95 KTS AT 071140Z
   CIMSS D-PRINT: 88 KTS AT 071240Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 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 31P IS PROJECTED TO MAINTAIN ITS
SOUTHEASTWARD TRAJECTORY, STEERED BY THE AFOREMENTIONED
NEAR-EQUATORIAL RIDGE, THROUGH TAU 48. SUBSEQUENTLY, THE CYCLONE
WILL MIGRATE TO THE SOUTH OF THE SUBTROPICAL JET AXIS AND WILL ENTER A
REGION OF INCREASING UPPER-LEVEL TROUGHING. A DEEP-LAYER
ANTICYCLONE TO THE SOUTHEAST WILL THEN INDUCE A BRIEF SOUTHWESTWARD
TURN, A TRAJECTORY EXPECTED TO PERSIST UNTIL THE SYSTEM TRANSITS
THE RIDGE AXIS NEAR TAU 96. CONCURRENTLY, THE ONSET OF SUBTROPICAL
TRANSITION IS ANTICIPATED AS THE CYCLONE MOVES OVER MUCH COOLER
WATERS (BELOW 26 C). THIS TRANSFORMATION IS EXPECTED TO BE COMPLETE
JUST PRIOR TO TAU 120, AS THE SYSTEM MAKES LANDFALL OVER THE NORTH
ISLAND OF NEW ZEALAND, AND BECOMES POSITIONED UNDERNEATH THE JET
MAXIMUM. REGARDING INTENSITY, A CONSISTENT DECAY IS FORECAST AS
VERTICAL WIND SHEAR IS PROJECTED TO INCREASE SUBSTANTIALLY,
REACHING 40-45 KTS AS EARLY AS TAU 24 AND PERSISTING THROUGH AT
LEAST TAU 48.  AS THE SHEAR INTENSITY IS EXPECTED TO RELAX AFTER
TAU 48, THE RATE OF WEAKENING SHOULD DECREASE, AND THE SYSTEMS
INTERACTION WITH THE UPPER-LEVEL TROUGH IS EXPECTED TO HELP IT
SUSTAIN AN INTENSITY NEAR 45-55 KTS DEEP INTO ITS SUBTROPICAL
PHASE.

MODEL DISCUSSION: A HIGH DEGREE OF CONSENSUS EXISTS AMONG THE
NUMERICAL WEATHER PREDICTION MODELS REGARDING THE TRACK FORECAST,
LENDING HIGH CONFIDENCE TO THE OFFICIAL JTWC FORECAST TRACK.
SIMILARLY, THE INTENSITY CONSENSUS MEMBERS ARE IN STRONG AGREEMENT
CONCERNING THE OVERALL WEAKENING TREND. THE GUIDANCE SPREAD
INCREASES MARGINALLY TO 20 KTS BEYOND TAU 48, THEREBY REDUCING
CONFIDENCE IN THE LONG-RANGE INTENSITY FORECAST. OVERALL, BOTH THE
OFFICIAL TRACK AND INTENSITY FORECASTS ARE HEAVILY WEIGHTED TOWARDS
THE MULTI-MODEL CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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