WDPS31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (ALFRED)     
WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.3S 156.7E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 198 NM EAST OF BRISBANE, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED, TIGHTLY WRAPPED LOW-LEVEL CIRCULATION (LLC), WITH DEEP
CONVECTION SHEARED OVER THE SOUTHEAST QUADRANT. THE SYSTEM HAS
TRACKED ERRATICALLY OVER THE PAST 12 HOURS WHILE EXECUTING A TIGHT
CYCLONIC LOOP. RECENT EIR IMAGERY AFTER 051200Z INDICATES THE
SYSTEM HAS RETURNED TO A SLOW WESTWARD TRACK. A 051138Z MHS 89GHZ
MICROWAVE IMAGE AND RECENT TOTAL PRECIPITABLE WATER IMAGERY
INDICATE AN IMPROVED, MORE SYMMETRIC CONVECTIVE STRUCTURE AS THE
SYSTEM'S CORE RE-MOISTENS. ENVIRONMENTAL CONDITIONS HAVE IMPROVED
SLIGHTLY WITH DECREASING UPPER-LEVEL WESTERLIES OVER THE SYSTEM AND
SLIGHTLY LOWER VERTICAL WIND SHEAR (VWS). HOWEVER, OVERALL
CONDITIONS REMAIN MARGINAL, WITH MODERATE EASTWARD OUTFLOW AND WARM
SST (25-26C) VALUES OFFSETTING THE HIGH VWS. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE EIR IMAGERY AND A
051144Z ASCAT-C BULLSEYE IMAGE REVEALING A DEFINED CENTER, WITH
EXTENSIVE GALE-FORCE WINDS OVER THE EASTERN AND SOUTHERN
SEMICIRCLES. SURFACE OBSERVATIONS AT CAPE BYRON (28.64S 153.60E)
CONTINUE TO INDICATE PERSISTENT GALE FORCE WINDS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
WESTERN AUSTRALIA WITH A NARROW RIDGE EXTENDING SOUTH OF THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS SATCON: 44 KTS AT 050922Z
   CIMSS ADT: 29 KTS AT 051130Z
   CIMSS AIDT: 44 KTS AT 051130Z
   CIMSS D-MINT: 27 KTS AT 050820Z
   CIMSS D-PRINT: 34 KTS AT 051200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30+ KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE EASTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 18P IS FORECAST TO RESUME A WESTWARD TRACK
UNDER THE STEERING INFLUENCE OF THE DOMINANT STEERING RIDGE TO THE
SOUTH. TRACK SPEEDS ARE EXPECTED TO REMAIN CLIMATOLOGICALLY SLOW
DUE TO THE COMPETING NEAR-EQUATORIAL RIDGE TO THE NORTH. TC 18P IS
FORECAST TO INTENSIFY TO 60 KNOTS PRIOR TO MAKING LANDFALL JUST
NORTH OF BRISBANE AT TAU 48. AFTER TAU 48, THE SYSTEM WILL TRACK
INLAND AND WEAKEN SIGNIFICANTLY BY TAU 72. DUE TO THE SLOW TRACK
MOTION, THIS SYSTEM IS EXPECTED TO PRODUCE HEAVY RAINFALL OVER THE 
COASTAL REGION OF EASTERN AUSTRALIA.  

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN FAIR
AGREEMENT SUPPORTING THE JTWC TRACK FORECAST WITH MEDIUM CONFIDENCE. 
RELIABLE INTENSITY GUIDANCE IS IN FAIR AGREEMENT, WITH HAFS-A 
INDICATING A PEAK INTENSITY OF 61 KNOTS AT TAU 12 AND COAMPS-TC (GFS) 
PEAKING AT 58 KNOTS AT TAU 24. THE LATEST GEFS AND EPS ENSEMBLE 
GUIDANCE SUPPORTS THE JTWC TRACK FORECAST WITH MEDIUM CONFIDENCE.  

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