WDPS31 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (THIRTY) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.0S 169.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 108 NM SOUTHEAST OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A MORE CONSOLIDATED,
SYMMETRIC CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL
CIRCULATION CENTER. ANIMATED WATER VAPOR IMAGERY INDICATES IMPROVED
OUTFLOW ESPECIALLY OVER THE WESTERN QUADRANT, WITH STRONG EQUATORWARD
AND POLEWARD OUTFLOW CHANNELS EVIDENT. A 142223Z ASCAT-C BULLSEYE 
IMAGE SHOWS A SWATH OF EXTENSIVE GALE-FORCE WINDS OVER THE EASTERN 
SEMICIRCLE, WITH MAXIMUM WINDS OF 45 KNOTS, WHICH SUPPORTS THE 
INITIAL INTENSITY WITH HIGH CONFIDENCE. THE 142225Z ASCAT-C 
AMBIGUITIES IMAGE SHOWS AN ELONGATED BUT DEFINED CENTER, WHICH 
SUPPORTS THE INITIAL POSITION WITH MEDIUM CONFIDENCE. DESPITE SOME 
PRESSURE OVER THE WESTERN PERIPHERY, ENVIRONMENTAL ANALYSIS CONTINUES 
TO INDICATE A FAVORABLE ENVIRONMENT WITH WARM SST VALUES AND LOW 
VERTICAL WIND SHEAR.    

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER 
SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   NFFN: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 57 KTS AT 150010Z
   CIMSS AIDT: 47 KTS AT 150010Z
   CIMSS DPRINT: 44 KTS AT 150140Z
   CIMSS SATCON: 50 KTS AT 150110Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TROPICAL CYCLONE (TC) 30P IS FORECAST TO TRACK
SOUTHWARD THROUGH THE FORECAST PERIOD, ALONG THE WESTERN PERIPHERY OF 
THE STR. TC 30P WILL MERGE WITH A LARGE MIDLATITUDE LOW, WITH A TIGHT 
GRADIENT OVER THE SOUTHEASTERN PERIPHERY FORECAST TO PRODUCE STORM 
FORCE WINDS REACHING 50-55 KNOTS. AS THE SYSTEM TRACKS SOUTHWARD, IT 
WILL QUICKLY TRANSITION INTO A SUBTROPICAL LOW AS IT TRACKS UNDER THE 
SUBTROPICAL JET AND INTERACTS WITH THE BAROCLINIC ZONE.  

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT 
WITH A 135 NM CROSS-TRACK SPREAD AT TAU 24 AND MINIMAL ALONG-TRACK 
SPREAD BETWEEN TRACKERS. THE 141800Z ECENS AND GEFS ENSEMBLES ARE IN 
GOOD AGREEMENT ON THE TRACK FORECAST THROUGH TAU 24 AND SHOW HIGH 
POTENTIAL FOR STORM FORCE WINDS AS THE SYSTEM TRACKS TOWARD NEW 
ZEALAND.   

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