WDPS31 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (THIRTYONE) 
WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.9S 135.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 281 NM EAST-NORTHEAST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
CONVECTION REBUILDING AND NOW COVERING THE CENTER OF WHAT WAS
PREVIOUSLY A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OVER
THE DURATION OF THE LAST SIX HOURS. HOWEVER, UPPER-LEVEL CLOUD
TEMPERATURES ARE WARMING, THEREBY INDICATING STAGNATION OF
INTENSIFICATION. WATER VAPOR IMAGERY REVEALS WEAK POLEWARD OUTFLOW.
AN EARLIER 211646Z GCOM W1 AMSR2 IMAGE REVEALING BANDING ON THE
NORTHERN PERIPHERY OF THE CIRCULATION CENTER WITH BUILDING DEEP
CONVECTION OVER CENTER. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED EIR AND MICROWAVE
IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON LOCAL SURFACE OBSERVATIONS OF 28-30KTS AND A
20-30KTS REVEALED IN A 211646Z GCOM W1 AMSR2 WIND SPEED IMAGE.

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

CURRENT STEERING MECHANISM: AN ELONGATED SUBTROPICAL RIDGE CENTERED
OVER WYNDAM, AUSTRALIA, AND EXTENDING NORTHWESTWARD OVER THE TIMOR
SEA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T1.5 - 25 KTS
   ADRM: T2.0 - 30 KTS
   CIMSS SATCON: 40 KTS AT 211553Z
   CIMSS ADT: 41 KTS AT 211720Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 UNDER THE STEERING INFLUENCE OF A NEAR
EQUATORIAL RIDGE TO THE SOUTH WHICH SPANS FROM NORTHERN AUSTRALIA
OVER THE TIMOR SEA. THE SHALLOW NATURE OF THE SYSTEM MAY RESULT IN
TRACK VARIATION MORE NORTHWARD OR SOUTHWARD DEPENDING ON HOW
SIGNIFICANTLY THE VERTICAL EXTENT OF THE SYSTEM REBUILDS. THE
SYSTEM IS FORECAST TO SLIGHTLY INTENSIFY OT 35KTS WITHIN THE NEXT
24 HOURS FOLLOWED BY A PERIOD OF STAGNATION. THE EARLY-TERM
ENVIRONMENT WILL BE FAVORABLE WITH 29-30C SEA SURFACE TEMPERATURES,
10-15KT VERTICAL WIND SHEAR, AND STRONG UPPER-LEVEL DIVERGENCE
UNTIL TAU 36 WHEN THE UPPER-LEVEL ENVIRONMENT BECOMES UNFAVORABLE.
DUE TO THE CONVERGENT NATURE OF THE CIRCULATION, THE SYSTEM WILL
DISSIPATE BELOW WARNING CRITERIA BY TAU 48.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT THE SYSTEM WILL TRAVEL WEST-NORTHWESTWARD FOR THE REMAINDER OF
THE FORECAST. AFTER TAU 24, THE MODEL SOLUTIONS SPREAD SLIGHTLY DUE
TO VARIATION OF THE VERTICAL EXTENT OF THE STORM DRIVING THE
STEERING AT SLIGHTLY DIFFERENT LEVELS BETWEEN DIFFERENT CONSENSUS
MEMBERS. ON THE NORTHERNMOST EXTENT, NAVGEM REVEALS A MORE
NORTH-NORTHWESTWARD TRACK BY TAU 48, AND GFS DEPICTS A DUE
WEST-NORTHWESTWARD TRACK ON THE SOUTHERN BOUNDARY OF THE GUIDANCE.
THE JTWC INTENSITY MULTI-MODEL GUIDANCE IS SPLIT, WITH GFS, AND
SHIPS INDICATING SLIGHT INTENSIFICATION WITHIN THE NEXT 24 HOURS,
WHILE HAFS-A AND COAMPS-TC INDICATING A NEAR-TERM WEAKENING TREND. 
HOWEVER, THE ENVIRONMENT PROVES TO BE OVERALL FAVORABLE, WHICH IS WHY 
THE FORECAST REFLECTS A SLIGHT INCREASE OF INTENSITY TO 35KTS.

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