WDPS31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (THIRTYONE) 
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.4S 141.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 384 NM NORTHWEST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES A MODEST 
IMPROVEMENT IN THE OVERALL CONVECTIVE STRUCTURE, WITH AN INCREASE IN 
CORE CONVECTION AND FORMATIVE CONVECTIVE BANDING. EIR ALSO SHOWS 
OVERSHOOTING TOPS WITH CLOUD TOP TEMPERATURES AS COLD AS -86C. A 
192107Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS A CURVED DEEP CONVECTIVE 
BAND OVER THE SOUTHWEST QUADRANT AND PERHAPS A WEAK, FORMATIVE BAND 
TO THE NORTH BUT NEGLIGIBLE BANDING OVER THE EASTERN SEMICIRCLE. 
HOWEVER, A 192313Z ASCAT-B IMAGE REVEALS A RELATIVELY SMALL REGION OF 
25-30 KNOT WINDS OVER THE SOUTHERN QUADRANT, WITH A WELL-DEFINED, 
SYMMETRIC CIRCULATION CENTER, WHICH SUPPORTS THE INITIAL POSITION AND 
INTENSITY WITH HIGH CONFIDENCE. VERTICAL WIND SHEAR HAS DECREASED TO 
10-15 KNOTS; HOWEVER, OVERALL ENVIRONMENTAL CONDITIONS REMAIN 
MARGINAL, WITH WEAK OUTFLOW, INTERACTION WITH LAND AND POSSIBLY DRY 
AIR ENTRAINMENT FROM CAPE YORK PENINSULA. ADDITIONALLY, THE SYSTEM IS 
SLIGHTLY TILTED, WITH THE UPPER-LEVEL CIRCULATION DISPLACED TO THE 
SOUTH. CIMSS OBJECTIVE INTENSITY ESTIMATES RANGE FROM 26 TO 45 KNOTS.

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

CURRENT STEERING MECHANISM: WEAK SUBTROPICAL RIDGE (STR) BUILDING
TO THE SOUTHWEST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   ADRM: T2.5 - 35 KTS
   CIMSS SATCON: 36 KTS AT 200000Z
   CIMSS ADT: 45 KTS AT 200000Z
   CIMSS AIDT: 36 KTS AT 200000Z
   CIMSS D-MINT: 26 KTS AT 192107Z
   CIMSS D-PRINT: 31 KTS AT 200000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK POLEWARD

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 LOCATED IN A WEAK 
STEERING ENVIRONMENT, WITH A STR BUILDING TO THE SOUTHWEST. 
THEREFORE, TRACK MOTION HAS BEEN VERY SLOW AND ERRATIC OVER THE PAST 
12 HOURS. HOWEVER, THE STR IS FORECAST TO STRENGTHEN WITHIN THE NEXT 
06-12 HOURS, WHICH WILL ACCELERATE THE SYSTEM WESTWARD. TC 31P SHOULD
BEGIN TO RE-INTENSIFY AFTER TAU 12 AS THE SYSTEM TRACKS AWAY FROM THE
CAPE YORK PENINSULA, WITH A MODEST INCREASE IN THE PEAK INTENSITY TO 
40 KNOTS BY TAU 24. AFTER TAU 48, TC 31P WILL TRACK WEST-
NORTHWESTWARD, WITH GRADUAL WEAKENING AND DISSIPATION ANTICIPATED BY 
TAU 96. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE HAS REMAINED IN FAIR 
AGREEMENT, WITH THE BULK OF THE GUIDANCE SUPPORTING THE JTWC TRACK 
FORECAST. PROBABILISTIC GUIDANCE FROM THE 191800Z GEFS AND ECENS
RUNS SHOWS A HIGH PROBABILITY OF THE SYSTEM TRACKING OVER WATER NORTH 
OF ARNHEM LAND. 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 THREE DAYS. THERE IS QUITE A BIT
OF UNCERTAINTY IN THE JTWC INTENSITY FORECAST, WITH GUIDANCE RANGING 
FROM 28 TO 43 KNOTS. COAMPS-TC (GFS) IS MORE OPTIMISTIC, WITH A PEAK 
INTENSITY VALUE OF 44 KNOTS AT TAU 24.     

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