WDXS31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FABIEN) WARNING NR 
022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.2S 69.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 249 NM SOUTHWEST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
DESPITE A RECENT BURST OF PERSISTENT CONVECTIVE ACTIVITY NEAR THE
ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC), THE OVERALL STRUCTURE
OF TC 19S (FABIEN) REMAINS RELATIVELY DISORGANIZED. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BURST OF STRONG
CONVECTION AND A RAGGED CENTRAL DENSE OVERCAST (CDO) FEATURE. A
191146Z GMI 37GHZ MICROWAVE PASS SHOWED A FALSE MICROWAVE EYE UNDER
THE STRONGEST CONVECTION, WHILE THE 89GHZ IMAGE SHOWED WELL DEFINED
LOW-LEVEL BANDING FEATURES, ANALYSIS OF WHICH LENT MEDIUM
CONFIDENCE TO THE INITIAL POSITION, PLACED ON THE NORTHWEST EDGE OF
THE DEEP CONVECTION. THE INITIAL INTENSITY IS HELD STEADY AT 45
KNOTS, IN LINE WITH THE FMEE AND FIMP CURRENT INTENSITY ESTIMATES
AND THE AIDT OF 45 KNOTS, THOUGH SLIGHTLY BELOW THE ADT AND SATCON.
THE SYSTEM CONTINUES TO MOVE SLOWLY TO THE SOUTHWEST IN A WEAK
STEERING PATTERN. OTHER THAN A RECENT DECREASE IN SOUTHERLY SHEAR,
THE ENVIRONMENT REMAINS RELATIVELY STATIC, WITH WARM SSTS AND
MODERATE POLEWARD AND EQUATORWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT WITH A
SUBTROPICAL RIDGE (STR) OVER NORTHERN MADAGASCAR AND A NEAR
EQUATORIAL RIDGE (NER) SOUTH OF SRI LANKA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   FMEE: T3.0 - 45 KTS
   FIMP: T3.0 - 45 KTS
   CIMSS SATCON: 51 KTS AT 190841Z
   CIMSS ADT: 55 KTS AT 191200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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: NO SIGNIFICANT CHANGES IN THE FORECAST TRACK
ARE EXPECTED WHEN COMPARED THE LAST SEVERAL FORECASTS. THE SYSTEM
WILL TRACK SLOWLY TO THE SOUTHWEST FOR THE NEXT 12 HOURS, BEFORE
TURNING SHARPLY TO THE SOUTH-SOUTHEAST AS THE NER TO THE NORTHEAST
STRENGTHENS AND MOVES WEST, AND BECOMES THE DOMINANT STEERING
INFLUENCE. A BRIEF PERIOD OF INTENSIFICATION TO 50 KNOTS IS
EXPECTED BETWEEN TAU 12 AND 24 AS THE SYSTEM BASKS IN THE LOW SHEAR
ENVIRONMENT AND THE ATMOSPHERE MOISTENS UP A BIT. THE GOOD TIMES
WILL BE SHORT-LIVED HOWEVER AND SOON AFTER TURNING SOUTHEAST, THE
SYSTEM WILL ENCOUNTER INCREASING SHEAR, COOLER SSTS AND DECREASING
OUTFLOW ALOFT WILL COMBINE TO STEADILY WEAKEN THE SYSTEM THROUGH
THE REMAINDER OF THE FORECAST. THE SYSTEM IS EXPECTED TO WEAKEN
BELOW TROPICAL STORM STRENGTH NO LATER THAN TAU 120. AS THE SYSTEM
STEADILY WEAKENS AND THE STEERING LEVEL LOWERS, IT WILL COME UNDER
THE STEERING INFLUENCE OF THE LOW TO MID-LEVEL ANTICYCLONE FAR TO
THE SOUTH, AND TURN ONTO A WESTWARD TRACK AFTER TAU 72. 

MODEL DISCUSSION: TRACK GUIDANCE CONTINUES TO SHOW A LARGE AMOUNT
OF UNCERTAINTY, WITH SPREAD INCREASING TO 400NM BY TAU 120 BETWEEN
THE NAVGEM TO THE NORTH AND ECMWF TO THE SOUTH. OVERALL, WITH THE
EXCEPTION OF THE ECMWF WHICH SHOWS A TRACK ALMOST DUE SOUTH THROUGH
THE FORECAST PERIOD, THE CONSENSUS MEMBERS AGREE ON THE S-SHAPED
TRACK BUT DIVERGE ON WHEN THE SYSTEM BEGINS TO TRACK WESTWARD.
NAVGEM TURNS WEST ALONG THE 11S LATITUDE, WHILE THE GFS TURNS
AROUND 13S AND THE EGRR AROUND 15S. THE JTWC FORECAST TRACK LIES
CLOSE TO THE GFS SOLUTION WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE HAS COME INTO BETTER AGREEMENT, WITH ALL CONSENSUS MEMBERS
AGREEING ON INTENSIFICATION TO 50-55 KTS THROUGH TAU 24, FOLLOWED
BY SLOW BUT STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST
PERIOD. THE JTWC FORECAST TRACKS THE CONSENSUS MEAN WITH MEDIUM
CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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