WDXS31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FYTIA) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.6S 54.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 188 NM SOUTH OF ST DENIS
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 19S (FYTIA) WITH A FULLY DECOUPLED AND EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). THE SYSTEM HAS SOMEWHAT UNEXPECTEDLY
REMAINED QUASISTATIONARY OVER THE PAST 6 HOURS. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC
IN ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 45 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL
ANALYSIS INDICATES THAT 19S IS IN AN UNFAVORABLE ENVIRONMENT
CHARACTERIZED BY STRONG POLEWARD OUTFLOW ALOFT GREATLY OFFSET BY
HIGH WESTERLY VERTICAL WIND SHEAR, SIGNIFICANT DRY AIR ENTRAINMENT,
AND MARGINAL SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) POSITIONED TO
THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   FMEE: T3.0 - 45 KTS
   CIMSS SATCON: 43 KTS AT 032127Z
   CIMSS ADT: 41 KTS AT 040000Z
   CIMSS AIDT: 41 KTS AT 040000Z
   CIMSS D-MINT: 31 KTS AT 040024Z
   CIMSS D-PRINT: 39 KTS AT 040000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 35-40 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT FROM THE WEST

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: 19S IS FORECAST TO CONTINUE ON A SOUTHEASTWARD
TRACK ALONG THE SOUTHWESTERN PERIPHERY OF THE STR TO THE EAST
THROUGH TAU 24. THE SYSTEM IS FORECAST TO SLIGHTLY WEAKEN OVER THE
NEXT 12 HOURS AS STRONG WESTERLY SHEAR AND DRY AIR IMPACT THE
VORTEX. 19S IS FORECAST TO BEGIN SUBTROPICAL TRANSITION AT TAU 12
WITH COMPLETION NEAR TAU 24 AS THE SHALLOW VORTEX BECOMES FURTHER
EMBEDDED WITHIN THE STRONG UPPER-LEVEL WESTERLIES. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT WITH CONSIDERABLE ALONG-TRACK SPREAD FOR SUCH A SHORT
FORECAST AT OVER 80 NM. GFS IS THE SLOWEST MODEL WHILE GALWEM IS
THE FASTEST. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
CONSENSUS WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE AGREES ON
GRADUAL WEAKENING THROUGH TAU 24. THE MAIN OUTLIER IS HAFS-A, WHICH
ACTUALLY INTENSIFIES THE SYSTEM THROUGH TAU 48 RATHER THAN WEAKENING
IT. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE CONSENSUS
WITH MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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