WDXS33 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 23S (HONDE) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.8S 49.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 699 NM SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 23S (HONDE) WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) AND CONVECTION SHEARING OFF TO THE EAST-SOUTHEAST.
EXTENSIVE DRY AIR CAN BE SEEN BEING PULLED INTO THE SYSTEM ALONG
THE NORTHWESTERN QUADRANT OF THE SYSTEM. ENVIRONMENTAL ANALYSIS
INDICATES THAT 23S IS IN A MARGINALLY UNFAVORABLE ENVIRONMENT
CHARACTERIZED BY THE PRESENCE OF DRY AIR, MODERATE TO HIGH (25-30
KTS) VERTICAL WIND SHEAR, AND BORDERLINE (25-26 C) SEA SURFACE
TEMPERATURES. THE ONLY REMAINING FAVORABLE FACTOR IS THE ROBUST
POLEWARD OUTFLOW CHANNEL. THE INITIAL POSITION AND INTENSITY ARE
BOTH PLACED WITH HIGH CONFIDENCE BASED ON THE 041757Z METOP-B ASCAT
IMAGE SHOWING DEFINED CENTER WITH 45-50 KNOT WINDS WITHIN THE
NORTHEASTERN QUADRANT. ADDITIONALLY, A PARTIAL 041541Z RCM-1 SAR
WIND SPEED IMAGE CAUGHT THE WESTERN PORTION OF THE CIRCULATION AND
REVEALED 50-55 KNOT WINDS WITHIN THE SOUTHWESTERN QUADRANT. OBJECTIVE 
INTENSITY ESTIMATES ARE ANALYZED TO BE TOO LOW DUE TO THE LACK OF 
CENTRAL CONVECTION AND THE EXPOSED NATURE OF THE LLCC.

INITIAL WIND RADII BASIS: 041757Z SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.0 - 30 KTS
   FMEE: T3.0 - 45 KTS
   CIMSS SATCON: 49 KTS AT 041631Z
   CIMSS ADT: 41 KTS AT 041800Z
   CIMSS AIDT: 40 KTS AT 041800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT ALONG THE WESTERN PORTION OF
THE SYSTEM.

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 23S IS FORECAST TO CONTINUE TRACKING
SOUTH-SOUTHEASTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR
THROUGH TAU 24. AFTER TAU 24, THE SYSTEM WILL BEGIN TO TRACK MORE
EASTWARD AS IT ROUNDS THE RIDGE AXIS AND ACCELERATES WITHIN THE
BAROCLINIC ZONE. EXTRATROPICAL TRANSITION IS FORECAST TO BEGIN AT
TAU 36 AND COMPLETE BY TAU 48 AS A SHARP LONGWAVE TROUGH ENVELOPS
THE VORTEX. FSU PHASE SPACE DIAGRAMS DEPICT 23S TRANSITIONING INTO
A COLD-CORE SYSTEM NEAR 070000Z. REGARDING INTENSITY, 23S IS
FORECAST TO BEGIN WEAKENING STARTING AT TAU 12 DUE TO THE QUICKLY
COOLING SEA SURFACE TEMPERATURES, HIGH VERTICAL WIND SHEAR, AND
SIGNIFICANT DRY AIR ENTRAINMENT. AS A RESULT, AN INTENSITY OF
AROUND 35 KTS IS ANTICIPATED AS THE SYSTEM TRANSITIONS INTO A
COLD-CORE LOW.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT REGARDING THE TRACK OF 23S WITH A MERE 38 NM CROSS-TRACK
SPREAD AT TAU 48. THEREFORE, THE JTWC TRACK FORECAST IS PLACED WITH
HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT ON
MAINTAINING INTENSITY THOUGH TAU 12 WITH A GRADUAL WEAKENING TREND
THEREAFTER. THE JTWC INTENSITY FORECAST IS ALSO PLACED WITH HIGH
CONFIDENCE.

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