WDPS31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (ALFRED) WARNING NR 
027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.3S 155.1E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 113 NM EAST OF BRISBANE, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A NEARLY
FULLY EXPOSED LOW-LEVEL CIRCULATION WITH FLARING CONVECTION
CONTAINED WITHIN THE SOUTHERN SEMICIRCLE OF TROPICAL CYCLONE (TC)
18P (ALFRED). THE SYSTEM IS MOVING VERY SLOWLY TOWARDS THE
AUSTRALIA COASTLINE. ENVIRONMENTAL CONDITIONS ARE GENERALLY
UNFAVORABLE FOR INTENSIFICATION, WITH VERTICAL WIND SHEAR (VWS)
REMAINING HIGH (30-35 KTS), COOL (25-26 C) SEA SURFACE TEMPERATURES 
(SST), DRY AIR ENTRAINMENT AND WEAK POLEWARD OUTFLOW. TC ALFRED IS 
CURRENTLY ASSESSED AS A TROPICAL SYSTEM WITH STRUCTURAL FEATURES 
CHARACTERISTIC OF BOTH TROPICAL AND MID-LATITUDE CYCLONES. PHASE 
CLASSIFICATION PLOTS INDICATE A DEEP WARM CORE, BUT THE SYSTEM REMAINS 
STRUCTURALLY ASYMMETRIC, WITH ITS LLCC LOCATED TO THE SOUTH OF THE 
SUBTROPICAL JET. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE LLCC PRESENT IN THE ANIMATED EIR IMAGERY. THE INITIAL 
INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE 
PERSISTENCE, AGENCY DVORAK ESTIMATES, AS WELL AS UPWARD TRENDING 
OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: EXTENSION OF A SUBTROPICAL RIDGE (STR)
OVER AUSTRALIA TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   CIMSS SATCON: 42 KTS AT 060808Z
   CIMSS ADT: 47 KTS AT 061130Z
   CIMSS AIDT: 41 KTS AT 061130Z
   CIMSS D-MINT: 34 KTS AT 060807Z
   CIMSS D-PRINT: 40 KTS AT 061200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: WEAK POLEWARD

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

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 TRACK WEST-SOUTHWESTWARD
OVER THE NEXT 12 HOURS. AS THE STR TO THE SOUTH BUILDS AND EXTENDS
FURTHER OFFSHORE, IT WILL STEER THE SYSTEM WEST-NORTHWESTWARD,
TOWARDS MORETON ISLAND. LANDFALL IS EXPECTED NORTH OF BRISBANE, 
BETWEEN TAUS 24 AND 36. SLOW TRANSLATION SPEED, COOLING DOWN SST
DUE TO UPWELLING, WEAK POLEWARD OUTFLOW AND STRONG VWS WILL LEAD TO
TC 18P BEGINNING TO WEAKEN JUST PRIOR TO LANDFALL, REACHING 45 KTS BY
TAU 24 AND DISSIPATING BY THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT WITH ALL MODELS FOLLOWING SIMILAR TRACK AS THE MULTI-MODEL 
CONSENSUS. THE CROSS-TRACK SPREAD IS JUST UNDER 20 NM THROUGHOUT THE 
FORECAST, WITH THE EXCLUSION OF THE DETERMINISTIC UKMET GUIDANCE, 
WHICH PREDICTS LANDFALL 20 NM NORTH OF THE MULTI-MODEL CONSENSUS 
ASSESSMENT. JTWC TRACK FORECAST IS THEREFORE ASSESSED WITH HIGH 
CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT WITH ALL 
MODELS SUGGESTING RAPID WEAKENING BEGINNING BETWEEN TAUS 12 AND 24, AS 
SOON AS THE SYSTEM STARTS INTERACTING WITH THE TERRAIN.

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