WDPS31 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (EIGHTEEN) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.3S 174.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 485 NM EAST-SOUTHEAST OF NOUMEA, NEW
CALEDONIA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS AN EXPANSIVE
SYSTEM WITH THE CENTRAL CONVECTION STRUGGLING TO STAY INTACT WITH
THE MODERATE WESTERLY VWS. THE LOW LEVEL CIRCULATION IS
BROAD AND PARTIALLY EXPOSED ON THE LEFT SIDE. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON LOW CLOUD TRACING IN THE
MSI LOOP. THE INITIAL INTENSITY IS BASED ON THE 022155Z PARTIAL
ASCAT PASS SHOWING 35-KT WIND BARBS ALONG THE NORTHEAST AND
SOUTHEAST QUADRANTS. ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH
MODERATE VWS OFFSETTING THE STRONG EASTWARD OUTFLOW AND WARM SST.
THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE NER TO
THE NORTH.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SMAP DATA. 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE 
NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG EASTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 18S WILL BECOME QUASI STATIONARY (QS) UP TO
TAU 24 AS THE NER RECEDES AND A WEAK SUBTROPICAL RIDGE (STR) BUILDS
TO THE EAST. AFTER TAU 24 THE STR WILL ASSUME STEERING AND DRIVE
THE SYSTEM WEST-SOUTHWESTWARD. THE MARGINAL ENVIRONMENT WILL FUEL A
SLIGHT INTENSIFICATION TO 40KTS BY TAU 12. AFTERWARD, INCREASING
VWS, EXACERBATED BY THE REVERSAL IN STORM MOTION, WILL RESULT IN
WEAKENING AS THE CONVECTION BECOMES DECOUPLED EASTWARD. BY TAU 48,
OR SOONER, THE SYSTEM WILL BE REDUCED TO 30KTS, BELOW JTWC WARNING
CRITERIA, AND DISSIPATE.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL AGREEMENT WITH
THE TRACK FORECAST; HOWEVER, GIVEN THE UNCERTAINTY DURING THE QS
MOTION, THERE IS LOW CONFIDENCE IN THE INITIAL JTWC TRACK FORECAST
ON THIS SYSTEM. 

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