WDPS31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (THIRTYONE)    
WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3S 138.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 446 NM EAST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS EXPOSED LOW-LEVEL CLOUD 
LINES WRAPPING INTO AN EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), 
WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. ANIMATED RADAR 
IMAGERY FROM GOVE AIRPORT REVEALS RAINBANDS CURLING AROUND THE SOUTHERN 
AND WESTERN QUADRANTS OF THE LLCC. A 202051Z SSMIS 91GHZ MICROWAVE IMAGE 
INDICATES A SLIGHT IMPROVEMENT IN ORGANIZATION, WITH CURVED DEEP 
CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE AND WEAK, FRAGMENTED 
BANDING OVER THE NORTHERN QUADRANT. A 202343Z ASCAT-C BULLSEYE IMAGE 
ALSO SUPPORTS THE INITIAL POSITION AND SHOWS AN ASYMMETRIC WINDFIELD, 
WITH A SWATH OF 25-30 KNOT WINDS OVER THE SOUTHEAST QUADRANT ASSOCIATED 
WITH THE PRIMARY CONVECTIVE BAND. ENVIRONMENTAL CONDITIONS HAVE IMPROVED 
SLIGHTLY, WITH IMPROVED POLEWARD OUTFLOW. HOWEVER, THE VORTEX REMAINS 
TILTED AND THERE IS EVIDENCE OF MID- TO UPPER-LEVEL DRY AIR ENTRAINMENT, 
WHICH ARE HINDERING SIGNIFICANT DEVELOPMENT. THE INITIAL INTENSITY OF 30 
KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT DATA.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   ADRM: T2.0 - 30 KTS
   CIMSS SATCON: 47 KTS AT 202054Z
   CIMSS ADT: 41 KTS AT 202330Z
   CIMSS AIDT: 35 KTS AT 202330Z
   CIMSS D-MINT: 28 KTS AT 202053Z
   CIMSS D-PRINT: 28 KTS AT 210100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT, VORTEX TILT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 31P IS FORECAST TO TRACK
WEST-NORTHWESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR THROUGH
THE FORECAST PERIOD. TC 31P HAS CONTINUED TO STRUGGLE TO ORGANIZE
BUT IS STILL EXPECTED TO INTENSIFY SLIGHTLY WITHIN THE NEXT 24
HOURS AS IT TRACKS OVER WARM WATER AND MOISTENS GRADUALLY. HAFS-A
AND GFS INDICATE THE GRADUAL MOISTENING OF THE CORE AND A MORE
FAVORABLE VERTICAL ALIGNMENT THROUGH TAU 36, WHICH WILL ALLOW THE
SYSTEM TO SUSTAIN MINIMAL TROPICAL STORM STRENGTH NEAR 35 KNOTS.
AFTER TAU 36, TC 31P WILL WEAKEN DUE TO DRY AIR ENTRAINMENT AND 
INCREASING MID-LEVEL VERTICAL WIND SHEAR, WITH DISSIPATION ANTICIPATED 
BY TAU 48. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN FAIR AGREEMENT 
SUPPORTING THE JTWC TRACK FORECAST WITH MEDIUM CONFIDENCE. THE 201800Z 
ECENS AND GEFS RUNS ALSO SHOW A TIGHT GROUPING OF SOLUTIONS THROUGH TAU 
48, WITH A HIGH PROBABILITY OF A 30-40 KNOT SYSTEM. RELIABLE INTENSITY 
GUIDANCE REVEALS A MODERATE SPREAD, WITH COAMPS-TC (GFS), GFS AND HAFS-A 
PEAKING BETWEEN 30-35 KNOTS. ALTHOUGH THE SYSTEM IS NOT EXPECTED TO 
BRING MAJOR IMPACTS TO THE DARWIN AREA, ENHANCED GRADIENT WINDS MAY 
OCCUR AS THE SYSTEM PASSES NORTH OF DARWIN IN TWO DAYS. 

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