WDPS31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (ALFRED) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0S 154.0E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 818 NM NORTH OF BRISBANE, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS RADIAL
FILAMENTS BEING EJECTED FROM COMPACT, CIRCULAR, PULSING CONVECTION.
WARMING CLOUD TOPS WERE OBSERVED AT THE TIME OF THIS WARNING,
ASSOCIATED WITH A TEMPORARY STALL IN THE DEVELOPMENT. A POLEWARD
OUTFLOW CHANNEL WITH TRANSVERSE BANDING IS ESTABLISHED AND
CONNECTED WITH A SUBTROPICAL JET TO THE SOUTH. A 231915Z BULLSEYE
SAR IMAGE WAS USED TO ADJUST BEST TRACK POSITIONING AND WIND RADII,
AND IT ALSO REVEALED A FULLY ENCLOSED CENTRAL EYE FEATURE WITH
UPPER 50-KT WINDS WRAPPED AROUND THE NORTHWESTERN, SOUTHWESTERN,
AND SOUTHEASTERN QUADRANTS. THE RANGE OF OBJECTIVE INTENSITY
ESTIMATES VARIED BETWEEN 36 AND 71 KTS, THEREFORE THE SUBJECTIVE
AGENCY FIXES WERE RELIED UPON MORE HEAVILY TO ASSESS THE INITIAL
INTENSITY.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: A NEAR-EQUATORIAL RIDGE TO THE DISTANT
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   ABRF: T3.0 - 45 KTS
   CIMSS SATCON: 67 KTS AT 232318Z
   CIMSS ADT: 74 KTS AT 232330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 IN A UNIQUE POSITION OVER WARM SSTS,
AND WITH LIGHT VWS, DIFFLUENCE ALOFT, AND THE SUPPORT OF A POLEWARD
OUTFLOW CHANNEL WRAPPING INTO THE ENTRANCE REGION OF THE
SUBTROPICAL JET TO THE SOUTH. HOWEVER, IT WILL SUFFER A CONTINUAL
STRUGGLE WITH THE PRESENCE OF DRY AUSTRALIAN AIR TO THE WEST
ATTEMPTING TO WRAP INTO THE CIRCULATION. AS THE SYSTEM WORKS TO
BLOCK THIS INTRUSIVE FEATURE, THE INTENSITY MAY FLUCTUATE. OVERALL,
AN INTENSIFICATION IS EXPECTED THROUGH TAU 24 AND POSSIBLY BEYOND
IF AN EYE CAN ESTABLISH ITSELF. AFTER TAU 24 TO TAU 36, A GRADUAL
DECLINE IS FORECAST TO OCCUR DUE TO A SOUTHWARD TRACK CARRYING TC
18P INTO LESS FAVORABLE CONDITIONS. SLOW TRACK SPEEDS WILL CAUSE
OHC VALUES TO BECOME AN ISSUE, WORKING AGAINST ALFRED. THE BIGGEST
HINDRANCE WILL BECOME A NEARING PROXIMITY TO THE SUBTROPICAL JET. A
COMBINATION OF INCREASING WINDS ALOFT AND MID LEVEL DRYING WILL
WEAKEN THE SYSTEM TOWARDS THE END OF THE FORECAST PERIOD. NO
TRANSITION IS EXPECTED WITHIN THE SCOPE OF THIS FORECAST.

MODEL DISCUSSION: THE ECMWF TRACK AID FAVORS THE WESTERN BOUND OF
THE BULK OF RELIABLE MODEL GUIDANCE, WHILE THE GFS TRACK AID BOUNDS
THE EASTERN LIMIT. THEREFORE, THE JTWC FORECAST TRACK IS ALIGNED
WITH THE CONSENSUS MEAN. THE INTENSITY AIDS PREDICT A 40-KT SPREAD
BY TAU 24 DUE TO THE UNCERTAINTY OF RI POTENTIAL. IN LIGHT OF THE
FAVORABLE ENVIRONMENT, THE JTWC INTENSITY FORECAST IS MODESTLY
ABOVE THAT OF THE INTENSITY CONSENSUS YET WELL WITHIN THE RANGE OF
POSSIBILITIES INDICATED BY RI AIDS.

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