WDPS32 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 16P (KEVIN) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.3S 173.3E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 394 NM SOUTHEAST OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 24 KTS
   SIGNIFICANT WAVE HEIGHT: 55 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
UNRAVELING SYSTEM WITH CONVECTIVE BANDING BECOMING FRAGMENTED BEING
WRAPPED INTO THE LOW LEVEL CIRCULATION CENTER (LLCC). TC KEVIN IS
IN A MARGINALLY FAVORABLE ENVIRONMENT FOR FURTHER TROPICAL
ACTIVITY. THESE CONDITIONS ARE CHARACTERIZED BY CONSTANT POLEWARD
OUTFLOW ALOFT, MODERATE (20-25 KTS) VERTICAL WIND SHEAR (VWS), A
HEALTHY 850 MB VORTICITY SIGNATURE, OFFSET BY COOLER (24-25 C) SEA
SURFACE TEMPERATURES (SST). THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE AFOREMENTIONED EIR AND MULTI-AGENCY
FIX LOCATIONS. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE. IT IS SET BASED OFF A BLEND OF MULTI-AGENCY AND
AUTOMATED DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   PHFO: T6.5 - 127 KTS
   CIMSS SATCON: 136 KTS AT 040816Z
   CIMSS ADT: 112 KTS AT 041330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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 KEVIN CONTINUES ITS SOUTHEASTWARD TRACK AS
IT HUGS THE OUTER PERIPHERY OF STR TO THE EAST-NORTHEAST. BY TAU
12, TC KEVIN WILL CONTINUE TO ENTER A MORE HOSTILE ENVIRONMENT
CHARACTERIZED BY STRONGER VWS AND WILL DECREASE IN INTENSITY TO 95
KNOTS AS A RESULT. BY TAU 24, TC KEVIN WILL CONTINUE ITS
SUBTROPICAL TRANSITION AND WILL START TO FEEL THE EFFECTS OF DRY
AIR ENTRAINMENT FROM THE NORTHWEST BEING WRAPPED INTO THE CENTER.
BY TAU 36, THE SYSTEM WILL BECOME FULLY SUBTROPICAL.

MODEL DISCUSSION: THE JTWC TRACK CONSENSUS MEMBERS ARE IN EXTREMELY
TIGHT AGREEMENT SHOWING A CONTINUOUS SOUTHEASTWARD TRAJECTORY. THE
FORECAST MODEL ENVELOPE HAS A 45 NM SPREAD BY TAU 24 WHICH
PROGRESSIVELY INCREASES TO 129 NM BY TAU 36. AS A RESULT, THE JTWC
FORECAST TRACK IS SET WITH HIGH CONFIDENCE. THE JTWC INTENSITY
CONSENSUS MEMBERS ARE ALSO IN GOOD AGREEMENT SHOWING A DECREASING
TREND AS THE SYSTEM MAKES ITS SUBTROPICAL TRANSITION.

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