WDPS31 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (EIGHTEEN) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.4S 174.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 527 NM EAST-SOUTHEAST OF NOUMEA, NEW
CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A LARGE
SYSTEM WITH THE ASSOCIATED CONVECTION AND ITS CIRRI CANOPY
STRETCHED AND SHEARED EASTWARD, EXPOSING THE LOW LEVEL STRATUS
BANDS THAT ARE FEEDING INTO THE THE LOW LEVEL CIRCULATION (LLC).
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLC FEATURE IN THE 031630Z SSMIS 91GHZ IMAGE. THE INITIAL
INTENSITY OF 35KTS IS BASED ON THE PGTW DVORAK ESTIMATE AND
EXTRAPOLATED FROM RECENT PARTIAL ASCAT PASSES. ANALYSIS INDICATES A
MARGINAL ENVIRONMENT WITH STRONG EASTWARD OUTFLOW AND WARM SST
OFFSET BY STRONG (25KT+) VWS AND THE INFLUX OF DRY AIR IN THE LOWER
LEVELS, AS EVIDENCED BY THE COLD AIR STRATOCUMULUS BANDS IN THE EIR
LOOP. TC 18P IS TRACKING ALONG THE LOW REFLECTION OF THE STR TO THE
SOUTH.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   CIMSS SATCON: 44 KTS AT 031343Z
   CIMSS ADT: 39 KTS AT 031740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG 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 WILL CONTINUE ON ITS CURRENT TRACK
UNDER THE STEERING STR. THE MARGINAL ENVIRONMENT WILL FURTHER
DETERIORATE AS VWS INCREASES AND LOW LEVEL COLD DRY AIR INFLUX
PERSISTS, LEADING TO DISSIPATION BY TAU 24, LIKELY SOONER. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT;
HOWEVER, GIVEN THE WEAKNESS OF THE SHALLOW STEERING STR, AND THE
POSSIBLE EARLIER DISSIPATION OF THE CYCLONE, THERE IS OVERALL
MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS.  

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