WDXS31 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FABIEN) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 4.6S 82.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 598 NM EAST-NORTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST 6 TO 12 HOURS, TC 19S HAS QUICKLY CONSOLIDATED A LOW
LEVEL CORE AND REACHED TROPICAL STORM STRENGTH. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL AREA OF DEEP
CONVECTION WRAPPING TIGHTLY INTO THE ASSESSED LOW LEVEL CIRCULATION
CENTER (LLCC), WHICH REMAINS OBSCURED. THE MOST RECENT MICROWAVE
IMAGERY FROM 140036Z SHOWS A BROAD BAND OF DEEP CONVECTION
EXTENDING FROM THE SOUTHWEST TO NORTHWEST AND WRAPPING INTO A TIGHT
COMMA-LIKE FEATURE WHICH IS THE CORE OF TC 19S. THE INITIAL
POSITION IS ASSESSED WITH LOW CONFIDENCE DUE TO THE LACK OF RECENT
MICROWAVE IMAGERY, BASED SOLELY ON THE ANIMATED MSI AND AGENCY FIX
POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON A BLEND OF THE AVAILABLE AGENCY DVORAK CURRENT INTENSITY
ESTIMATES BETWEEN T2.5 AND T3.5. ENVIRONMENTAL CONDITIONS ARE
IMPROVING, WITH ANIMATED WATER VAPOR IMAGERY SHOWING THAT THE
UPPER-LEVEL OUTFLOW PATTERN HAS IMPROVED DRAMATICALLY SINCE
YESTERDAY, WITH HIGH-LEVEL CIRRUS NOW EXTENDING OUTWARD IN A
NEAR-RADIAL FASHION AND DECREASED OUTFLOW EXTENDING SOUTHWARD FROM
TC MOCHA IN THE BAY OF BENGAL. SHEAR IS LOW TO MODERATE (15-20
KTS), WHILE SSTS ARE VERY WARM (29-30C). THE SYSTEM IS TRACKING TO
THE WEST-SOUTHWEST ALONG THE NORTHERN SIDE OF A DEEP SUBTROPICAL
RIDGE (STR) TO THE SOUTH.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T2.5 - 35 KTS
   FMEE: T3.0 - 45 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 19S IS EXPECTED TO TRACK GENERALLY
WEST-SOUTHWESTWARD AT A RELATIVELY STEADY PACE, THROUGH THE
MAJORITY OF THE FORECAST PERIOD, ALONG THE NORTHERN SIDE OF THE
STEERING RIDGE CENTERED TO THE SOUTH. THE APPROACH OF A DEEP
MID-LATITUDE TROUGH FROM THE WEST WILL ERODE THE STEERING RIDGE
AFTER TAU 48, CREATING A BREAK IN THE RIDGE BY TAU 72, ALLOWING THE
SYSTEM TO PUSH MORE POLEWARD AFTER THIS POINT. HOW STRONG THE
TROUGH COMES, AND HOW MUCH TC 19S REACTS IN TERMS OF TRACK IS
HIGHLY UNCERTAIN, WITH VERY LARGE INCONSISTENCIES BETWEEN THE
VARIOUS MODELS. BASED ON CURRENT TRENDS AND ANALYSIS OF GLOBAL
MODEL FIELDS, IT IS ANTICIPATED THAT THE TROUGH WILL BE RELATIVELY
WEAK AND RIDGING WILL QUICKLY BUILD BACK IN, IN ITS WAKE AND TC 19S
IS NOT ANTICIPATED TO DIVE POLEWARD AT THIS TIME. HOWEVER, THE
TRACK WILL SLOW DOWN BY THE END OF THE FORECAST PERIOD AS THE
SYSTEM ENTERS A GENERALLY WEAK STEERING PATTERN. IN LIGHT OF THE
FAVORABLE ENVIRONMENTAL CONDITIONS THE SYSTEM IS FORECAST TO
STEADILY INTENSITY AT A 30 KNOTS PER DAY RATE, REACHING PEAK
INTENSITY OF 90 KNOTS BY TAU 72. AFTER THIS POINT, THE SYSTEM WILL
SLOWLY WEAKEN AS IT SLOWS DOWN, AND SUCCUMBS TO SLIGHTLY COOLER
WATERS UPWELLED ALONG ITS TRACK, DRY AIR ENTRAINMENT AND INCREASING
VWS. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGH ROUGHLY TAU 48, BUT THEN DIVERGES SHARPLY. BY TAU 48, THE
HWRF, GFS, AND GFS ENSEMBLE, ALONG WITH THE COAMPS-TC (GFS VERSION)
TURN TC 19S SHARPLY EASTWARD, TAKING THE SYSTEM AS FAR EAST AS 79E
BY THE END OF THE FORECAST AS WELL AS KEEPING THE SYSTEM NORTH OF
10S, GENERATING A SPREAD OF NEARLY 700NM BY TAU 120. THE REMAINDER
OF THE CONSENSUS MODELS INCLUDING NAVGEM, ECMWF, UKMET AND THE
UKMET AND ECMWF ENSEMBLE MEANS ON THE OTHER HAND TAKE THE SYSTEM ON
A FLATTER, SOUTHWESTWARD TRAJECTORY THROUGH THE REMAINDER OF THE
FORECAST PERIOD. THE ECENS AND GEFS ENSEMBLE PACKAGES HOWEVER ARE
IN BETTER AGREEMENT ON A TRACK TOWARDS THE SOUTHWEST, AT LEAST
THROUGH TAU 120, THOUGH THEY SHOW A LARGE SPREAD IN THE INDIVIDUAL
MEMBERS. THE JTWC FORECAST LIES CLOSE TO THE ECMWF DETERMINISTIC
TRACKER THROUGH THE FORECAST PERIOD, AND JUST EAST OF THE CONSENSUS
MEAN. HOWEVER, DUE TO THE LARGE SPREAD IN THE DETERMINISTIC AND
ENSEMBLES, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT ON A STEADY INTENSIFICATION, FOLLOWED
BY SLOW WEAKENING. HOWEVER, THE CTCX AND HWRF TRACKERS INDICATE A
RAPID WEAKENING AFTER TAU 48, AS THEY TURN THE SYSTEM SHARPLY
EASTWARD AND INTO THE FACE OF MUCH HIGHER SHEAR VALUES AS COMPARED
TO THE REST OF THE CONSENSUS MEMBERS. ADDITIONALLY, THE RICN AND
RIPA RAPID INTENSIFICATION AIDS HAVE BEEN TRIGGERED. THE JTWC
FORECAST LIES ALONG THE RIPA TREND THROUGH TAU 72, THEN CLOSELY
TRACKS THE DECAY-SHIPS FORECAST WITH MEDIUM CONFIDENCE. 

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