WDXS31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FABIEN) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 5.0S 80.1E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 471 NM EAST-NORTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
TIGHTLY COMPACT AND INTENSE SYSTEM, WHICH IS QUICKLY CONSOLIDATING
WITH BROAD OUTER BANDS WRAPPING INTO A SMALL, DEVELOPING CENTRAL
DENSE OVERCAST WHICH IS OBSCURING THE LOW-LEVEL CIRCULATION CENTER
(LLCC). A 141630Z ASCAT METOP-C IMAGE LENDS HIGH CONFIDENCE USING
EXTRAPOLATION FOR SETTING THE INITIAL POSITION AND INTENSITY. THE
COMPACT SYSTEM SHOWS EARLY SIGNS OF RAPID INTENSIFICATION (RI),
INCREASING TWO DVORAK T-NUMBERS IN LESS THAN 24 HOURS, AS INDICATED
BY MULTIPLE DVORAK AGENCIES AND OBJECTIVE DVORAK ESTIMATES FROM
CIMMS ADT, OPEN AIIR, AND THE NEW DEEP MIRCRONET (DMN). THIS IS DUE
TO THE FAVORABLE ENVIRONMENT TC19S LIES WITHIN, WITH LOW (5-10 KTS)
VWS, GOOD RADIAL OUTFLOW ALOFT, AND WARM SSTS (29-30C). THE SYSTEM
IS CURRENTLY TRACKING WEST-SOUTHWEST ALONG THE NORTHERN SIDE OF A
DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTH.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA FROM A 141630Z ASCAT
METOP-C IMAGE.

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.0 - 65 KTS
   FMEE: T3.0 - 45 KTS
   CIMSS ADT: 53 KTS AT 141500Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 19S (FABIEN) WILL CONTINUE TRACKING TOWARDS
THE WEST-SOUTHWEST ALONG THE NORTHERN SIDE OF A STR THROUGH THE
NEXT 48 HOURS. THE TIMING AND STRENGTH OF A PASSING UPPER-LEVEL
MID-LATITUDE TROUGH BY TAU 60 WILL DETERMINE IF FABIEN TURNS
POLEWARD, FINDING A POTENTIAL BREAK IN THE STEERING RIDGE.
SIGNIFICANT DIFFERENCES REMAIN BETWEEN THE US AND EUROPEAN MODEL'S
AS MENTIONED IN THE PREVIOUS FORECAST. THE STRENGTH OF THE TROUGH
AND THE INFLUENCE IT WILL HAVE ON FABIEN'S TRACK IS THE DECIDING
FACTOR, INDUCING LOW CONFIDENCE IN THE TRACK FORECAST AT THIS TIME.
IN THE ECMWF SOLUTION, THE TROUGH PASSES SAFELY TO THE SOUTH WITH
LITTLE INFLUENCE ON TC 19S OTHER THAN SLOWING THE TRACK SPEED AS IT
TRACKS SOUTHWEST THROUGH THE LATER PORTIONS OF THE FORECAST PERIOD.
BASED ON ANALYSIS OF THE CURRENT GLOBAL MODEL FIELDS, THE ECMWF
SOLUTION IS THE MORE LIKELY SCENARIO. HOWEVER, THE GFS ALTERNATE
SCENARIO INDICATES A DEEPER TROUGH, RESULTING IN TC 19S TAKING A
SHARPER TURN POLEWARD BY TAU 96, AS SHOWN IN PREVIOUS FORECAST
TRENDS. GOOD RADIAL OUTFLOW HAS HELPED THE SYSTEM RAPIDLY INTENSIFY
OVER THE LAST 24 HOURS. DURING THE NEXT 24-48 HOURS, THE
DEVELOPMENT OF A STRONG POLEWARD OUTFLOW CHANNEL WILL ONLY ENHANCE
FURTHER RAPID INTENSIFICATION, BRINGING THE PEAK INTENSITY OF THE
SYSTEM TO 105 KNOTS BY TAU 48. BY TAU 60, THE FORECAST CONFIDENCE
DECREASES DUE TO THE TRACK AND INTENSITY SHOWING SIGNS OF
DECREASING. TC 19S POTENTIALLY REACHES A POINT OF STAGNATION DUE TO
THE COMBINATION OF UPWELLING COOLER WATER, A WEAKENING EXHAUST
MECHANISM, AND AN INCREASE OF SHEAR IS LIKELY TO CAUSE THE SYSTEM
TO WEAKEN MORE RAPIDLY THROUGH THE FORECAST PERIOD. HOWEVER,
ALTERNATE SCENARIOS SUGGEST THE SYSTEM WILL MOVE MORE POLEWARD AND
REMAIN RELATIVELY INTENSE THROUGH TAU 120. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS HIGHLY UNCERTAIN, WITH A
SIGNIFICANT SPREAD OVER 400NM OF CROSS-TRACK SPREAD BETWEEN THE
UKMET ENSEMBLE AND GFS OUTLIERS. THE UKMET ENSEMBLE, UKMET, NAVGEM,
AND THE CONSENSUS MEAN REMAIN GROUPED ALTOGETHER ON A SOUTHWESTWARD
TRACK THROUGH THE FORECAST PERIOD AS SEEN ON PREVIOUS MODEL RUNS.
THE OTHER CONSENSUS MEMBERS ARE GROUPED ON A MORE POLEWARD TRACK
FURTHER TO THE EAST. HOWEVER, THE GFS AND GFS ENSEMBLE TRACKERS
SPLIT OFF FROM THIS GROUP AROUND TAU 48, TAKING THE SYSTEM SHARPLY
EASTWARD, THEN SOUTHEASTWARD THROUGH THE REMAINDER OF THE FORECAST.
THE GEFS AND ECENS ENSEMBLES ALSO SHOW A GREATER SPREAD AMONGST THE
MEMBERS, PARTICULARLY AFTER TAU 48, LEADING TO HIGH UNCERTAINTY IN
THE EXTENDED FORECAST. BECAUSE OF THIS, THERE IS ONLY MEDIUM
CONFIDENCE IN THE SHORT TERM FOR BOTH THE TRACK AND INTENSITY,
WHICH ARE HELD CLOSE TO MODEL CONSENSUS. DURING THE LATTER PORTION
OF THE JTWC FORECAST TRACK, CONFIDENCE WANES TO LOW DUE TO THE HIGH
UNCERTAINTY WITHIN THE MODELS. 

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