WDPS31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (ALFRED) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.1S 155.5E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 528 NM NORTH-NORTHEAST OF BRISBANE,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SYSTEM
FULLY ENCLOSED BY DEEP CONVECTION, WITH A RAGGED AND BROAD EYE. THE
OUTFLOW IS DOING THE MOST FOR THIS SYSTEM IN MAINTAINING ITS
ASSESSED INTENSITY, AS OBSERVED BY THE VIGOROUS RADIAL OUTFLOW
ESTABLISHED BY POLEWARD AND EQUATORWARD CHANNELS. A 271915Z SAR
PASS WAS USED TO ADJUST THE WIND RADII AND ANALYZE THE INTENSITY
WITH HIGH CONFIDENCE. THE OBJECTIVE AND SUBJECTIVE INTENSITY
ESTIMATES CORROBORATE THE ASSESSMENT. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
A DEEP-LAYER SUBTROPICAL RIDGE TO THE EAST AND WEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   CIMSS SATCON: 111 KTS AT 272317Z
   CIMSS ADT: 112 KTS AT 272340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 18P WILL REMAIN IN A COMPETING STEERING
ENVIRONMENT FOR THE FIRST 48 HOURS OF THE FORECAST PERIOD. THE
STEERING WILL BECOME MORE DOMINATED BY THE SUBTROPICAL RIDGE TO THE
NORTHEAST AFTER TAU 48, UNTIL THE LATER TAUS WHERE IT WILL ONCE
AGAIN BECOME LESS CERTAIN DUE TO RIDGING TO THE WEST. AS A RESULT,
THE TRACK MOTION WILL CONTINUE TO BE SLOW AND NEARLY
QUASI-STATIONARY. THUS, UPWELLING IS A FACTOR WORKING ACTIVELY
AGAINST ANY FURTHER INTENSIFICATION. INCREASING DRY AIR FROM THE
AIR MASS TO THE WEST WILL BECOME MORE OF A PROBLEM FOR ALFRED
THROUGHOUT THE LATER TAUS. THE HEALTHY EXHAUST MECHANISMS IN PLACE
WILL WORK TO SUSTAIN THE SYSTEM, RESULTING IN A FORECAST THROUGH
TAU 120 AND LIKELY BEYOND.

MODEL DISCUSSION: THE MODEL TRACK GUIDANCE IS IN FAIRLY GOOD
AGREEMENT CONSIDERING THE WEAK STEERING ENVIRONMENT, HOWEVER, TAU
120 AND BEYOND IS WHERE BIFURCATION INDICATORS START TO ARISE. THE
INTENSITY GUIDANCE IS IN MUCH BETTER AGREEMENT COMPARATIVELY,
SHOWING A STEADY DECLINE OF INTENSITIES. THE PACE OF WEAKENING IS
INVERSELY RELATED TO THE FORWARD SPEED, SUCH THAT WHEN THE FORWARD
SPEED ACCELERATES SLIGHTLY AFTER TAU 48, THE INTENSITIES ARE
SOMEWHAT MORE MAINTAINED THROUGH THE ACCELERATION PERIOD.

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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