WDXS31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FYTIA) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.4S 50.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 182 NM EAST-SOUTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 19S (FYTIA) WITH A QUICKLY CONSOLIDATING LOW-LEVEL
CIRCULATION CENTER (LLCC) AFTER ITS RECENT TREK THROUGH CENTRAL
MADAGASCAR. PERSISTENT CONVECTION HAS ONCE AGAIN DEVELOPED DIRECTLY
OVER THE LLCC, FULLY OBSCURING THE WELL-DEFINED SURFACE
CIRCULATION. CONVECTIVE BANDING HAS ALSO BEEN OBSERVED OVER THE
LAST FEW HOURS, EXTENDING DIRECTLY INTO THE NORTHERN AND
SOUTHEASTERN QUADRANTS. ALOFT, ROBUST POLEWARD OUTFLOW HAS AIDED IN
THE SYSTEMS RE-CONSOLIDATION IN THE SOUTHWEST INDIAN OCEAN AFTER
TRAVERSING OVER THE ANKARATRA MOUNTAINS 12 HOURS AGO. ENVIRONMENTAL
CONDITIONS REMAIN FAVORABLE OVER OPEN WATER, WITH WARM SEA SURFACE
TEMPERATURES BETWEEN 28-29 C, LOW VERTICAL WIND SHEAR (VWS) BETWEEN
10-15 KTS, AND THE AFOREMENTIONED UPPER-LEVEL POLEWARD EXHAUST. THE
INITIAL POSITION HAS BEEN PLACED WITH MEDIUM CONFIDENCE BASED ON
ANIMATED EIR SATELLITE IMAGERY. THE INITIAL INTENSITY HAS BEEN
ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AGENCY DVORAK
ESTIMATES AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A NEAR-EQUATORIAL
RIDGE (NER) CENTERED DIRECTLY TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS SATCON: 50 KTS AT 011053Z
   CIMSS ADT: 47 KTS AT 010900Z
   CIMSS AIDT: 42 KTS AT 011100Z
   CIMSS D-MINT: 38 KTS AT 011003Z
   CIMSS D-PRINT: 38 KTS AT 011130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TC 19S IS FORECASTED TO TRACK SOUTHEASTWARD
THROUGHOUT THE ENTIRETY OF THE FORECAST PERIOD. BETWEEN TAU 0 AND
TAU 12, THE CYCLONE WILL BE STEERED BY THE SOUTHERN PERIPHERY OF
THE NER CENTERED DIRECTLY TO THE NORTH. FOLLOWING TAU 12, THE SPEED
OF APPROACH WILL SLOW DURING A STEERING HAND-OFF TO A SUBTROPICAL
RIDGE (STR) TO THE SOUTHEAST. BETWEEN TAU 12 AND TAU 18, THE STR TO
THE SOUTHEAST WILL BUILD SLIGHTLY TO THE NORTHWEST, BECOMING THE
PRIMARY DRIVING FORCE FOR THE REMAINDER OF THE FORECASTED
SOUTHEASTWARD TRACK. FROM TAU 18 UNTIL THE END OF THE FORECAST
PERIOD, TC 19S WILL CONTINUE THE SOUTHEASTWARD TRACK ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE TO THE EAST AS THE
SYSTEM BEGINS SUBTROPICAL TRANSITION NEAR TAU 60. FOLLOWING TAU 60,
TC FYTIA WILL BEGIN INTERACTING WITH AN EQUATORWARD EXTENDING
LONGWAVE TROUGH, BECOMING EMBEDDED WITHIN THE MID-LATITUDE
WESTERLIES INTO TAU 96. REGARDING INTENSITY, TC 19S IS FORECASTED
TO MODERATELY INTENSIFY TO 55 KTS BY TAU 24 AS ENVIRONMENTAL
CONDITIONS REMAIN MOSTLY FAVORABLE. FOLLOWING TAU 24, VWS IS
FORECASTED TO INCREASE ABOVE 20 KTS AS DRY AIR BEGINS WRAPPING
AROUND THE CYCLONES NORTHERN SEMICIRCLE. FOLLOWING TAU 24, A
WEAKENING TREND IS EXPECTED AS THE ENVIRONMENT BECOMES INCREASINGLY
HOSTILE, WITH UNFAVORABLE VWS (25 KTS AND ABOVE) AT TAU 36 AND
AMPLIFYING DRY AIR ENTRAINMENT INTO THE SYSTEMS CENTRAL VORTEX. AS
THE CYCLONE BECOMES EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES
BETWEEN TAU 60 AND TAU 96, TC 19S IS FORECASTED TO GRADUALLY WEAKEN
TO 40 KTS UNTIL SUBTROPICAL TRANSITION NEAR TAU 96. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE AND ARTIFICIAL
INTELLIGENCE (AI) MODEL GUIDANCE CONTINUES TO REMAIN IN VERY GOOD
AGREEMENT THROUGH THE 96 HOUR FORECAST PERIOD, WITH A CROSS-TRACK
SPREAD OF 41 NM AT TAU 36. FOLLOWING TAU 36, SLIGHT TRACK
VARIATIONS ARE OBSERVED WITH GALWEM AND UKMET DETERMINISTIC
SOLUTIONS DUE TO THE EXPECTED STEERING MECHANISM HAND-OFF, HOWEVER,
ALL JTWC TRACK CONSENSUS MEMBERS REALIGN BETWEEN TAU 72 AND TAU 96,
ILLUSTRATED BY A CROSS-TRACK SPREAD OF 67 NM BY THE END OF THE
FORECAST PERIOD. THE JTWC TRACK FORECAST HAS BEEN PLACED WITH HIGH
CONFIDENCE THROUGHOUT ENTIRETY OF THE FORECAST AND ALIGNED CLOSELY
WITH THE JTWC MULTI-MODEL CONSENSUS. REGARDING INTENSITY, JTWC
INTENSITY CONSENSUS SOLUTIONS HAVE CONTINUED TO IMPROVE AND ALIGN
OVER THE LAST 12 HOURS, CHARACTERIZING 15 KTS IN INTENSITY SPREAD
AT TAU 24, WITH THE GFS DETERMINISTIC SOLUTION MAINTAINING LOWER
VALUES AND STATISTICAL-DYNAMICAL SOLUTIONS ILLUSTRATING HIGHER
VALUES NEAR A MAXIMUM OF 60 KTS. FOLLOWING TAU 12, MOST JTWC
INTENSITY CONSENSUS MEMBERS SHOW A GRADUAL WEAKENING PHASE, WITH
THE EXCEPTION OF COAMPS-TC, WHICH SHOWS A PERIOD OF
RE-INTENSIFICATION DURING SUBTROPICAL TRANSITION. THEREFORE, THE
JTWC INTENSITY FORECAST HAS BEEN ALIGNED CLOSELY TO THE MULTI-MODEL
INTENSITY CONSENSUS, LENDING MEDIUM CONFIDENCE TO THE INTENSITY
FORECAST AND REFLECTS THE GRADUAL WEAKENING PHASE THROUGH A LARGELY
UNFAVORABLE ENVIRONMENT TOWARD THE END OF FORECAST PERIOD.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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