WDPS33 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21P (SERU) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.9S 171.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 273 NM EAST OF NOUMEA, NEW CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTION SHEARING STRONGLY DOWNSTREAM (SOUTHEASTWARD) FROM A
NEARLY FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED CENTER EVIDENT IN VISIBLE SATELLITE IMAGERY AS WELL AS A
262108Z METOP-B ASCAT PASS. THE INITIAL INTENSITY OF 45 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAME ASCAT PASS AND IS
FURTHER SUPPORTED BY RECENT SUBJECTIVE AND AUTOMATED AGENCY FIXES
LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA (262108Z METOP-B ASCAT
PASS) 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGING (STR) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   PHFO: T3.5 - 55 KTS
   NFFN: T3.0 - 45 KTS
   CIMSS SATCON: 42 KTS AT 262256Z
   CIMSS ADT: 41 KTS AT 262320Z
   CIMSS AIDT: 38 KTS AT 262320Z
   CIMSS D-PRINT: 51 KTS AT 262340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG EASTWARD

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 21P IS EXPECTED TO TURN EASTWARD OVER THE
NEXT 24 TO 48 HOURS FOLLOWING THE REORIENTING FLOW ASSOCIATED WITH
THE STEERING RIDGE TO THE NORTHEAST. STRONG WESTERLY FLOW ALOFT
WILL PERSIST FOR THE NEXT TWO DAYS, DRIVING STEADY WEAKENING TO
DISSIPATION BY TAU 48. THE REMNANT CIRCULATION WILL REMAIN OVER
WARM WATER (GREATER THAN 26C), BUT REINTENSIFICATION APPEARS TO BE
VERY UNLIKELY AT THIS POINT DUE TO HIGHLY UNFAVORABLE UPPER-LEVEL
FLOW.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN EXCELLENT AGREEMENT
REGARDING FORECAST INTENSITY, WHICH IS CONSISTENT WITH BOTH THE
MULTI-MODEL CONSENSUS AND PREVIOUS JTWC FORECAST WITH HIGH
CONFIDENCE. NUMERICAL MODELS SUPPORT THE OVERALL TRACK FORECAST
SCENARIO BUT THERE IS NOTEWORTHY CROSS-TRACK SPREAD AS A FEW
SOLUTIONS INDICATE A POSSIBLE POLEWARD JOG AFTER TAU 24 IN RESPONSE
TO A BUILDING LOW TO MID-LEVEL RIDGE TO THE EAST. THE CURRENT TRACK
FORECAST LIES IN THE MIDDLE OF THE PACK, NEAR THE MULTI-MODEL
CONSENSUS, WITH MEDIUM CONFIDENCE.

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