WDXS31 PGTW 170300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FABIEN) WARNING 
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.5S 74.0E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 123 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A 162258Z
SSMIS 91 GHZ PASS DEPICTS A COMPACT SYSTEM WITH DISORGANIZED BANDS
OF CONVECTION WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER
(LLCC). IN ADDITION, A DRY AIR SLOT IS BEING INTRODUCED IN THE
WESTERN PERIPHERY. TC FABIEN IS IN A FAVORABLE ENVIRONMENT FOR
FURTHER TROPICAL DEVELOPMENT. THESE CONDITIONS ARE CHARACTERIZED BY
STRONG EQUATORWARD AND POLEWARD OUTFLOW ALOFT, A PRONOUNCED 850 MB
VORTICITY SIGNATURE, LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), AND
VERY WARM (28-29 C) SEA SURFACE TEMPERATURES (SST). THE LIMITING
FACTORS TO THESE FAVORABLE CONDITIONS WOULD BE THE DRY AIR
ENTRAINMENT AS MENTIONED ABOVE, AND UPWELLING OF COOLER (26 C) SST
AS THE SYSTEM PASSES OVER AN AREA OF RELATIVELY SHALLOW OCEAN HEAT
CONTENT (OHC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON MULTI-AGENCY FIXES AND THE ABOVEMENTIONED SSMIS IMAGERY.
THE INITIAL INTENSITY OF 95 KNOTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED OFF A BLEND OF MULTI-AGENCY AND AUTOMATED DVORAK
ESTIMATES, AS WELL AS THE AFOREMENTIONED LIMITING FACTORS HINDERING
FURTHER DEVELOPMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   FIMP: T5.5 - 102 KTS
   CIMSS SATCON: 99 KTS AT 162043Z
   CIMSS ADT: 104 KTS AT 170000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT AND UPWELLING

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 19S (FABIEN) IS PASSING BY THE NORTHWESTERN
PERIPHERY OF THE STR TO THE SOUTHEAST. DURING TAUS 12 THROUGH 24,
TC FABIEN WILL CONTINUE TO TRACK SOUTHWESTWARD AND STEADILY
DECREASE IN INTENSITY TO 80 KTS. BY THIS TIME, THE STR TO THE
SOUTHEAST WILL RECEDE AND THE STR OVER MADAGASCAR WILL BECOME THE
DOMINATE STEERING FEATURE. AS A RESULT, TC 19S WILL ADJUST TO A
WESTWARD TRACK THROUGH TAUS 36 AND 48, WHILE CONTINUING TO DECREASE
IN INTENSITY TO 75 KNOTS AS A RESULT OF ENTERING A MORE HOSTILE
ENVIRONMENT FOR TROPICAL DEVELOPMENT. THIS ENVIRONMENT IS
CHARACTERIZED BY DRY AIR ENTRAINMENT FROM THE SOUTH WRAPPING INTO
THE SYSTEM, AN INCREASE IN MID-LEVEL WIND SHEAR, AND CONTINUED
UPWELLING THE STORM WILL BE PRODUCING BRINGING RELATIVELY COOLER
(26 C) SSTS TO THE SURFACE AS INDICATED BY THE 170000Z HWRF MODEL
RUN. BETWEEN TAUS 72 AND 96, THE SYSTEM WILL CHANGE IN TRAJECTORY
TO THE WEST-NORTHWEST AND SLOW DOWN IN TRACK SPEED AS IT WILL
STRUGGLE BETWEEN THE STR OVER MADAGASCAR AND THE NEAR EQUATORIAL
RIDGE (NER) TO THE NORTHEAST. MOREOVER, THE INTENSITY WILL CONTINUE
TO STEADILY DECREASE TO 45 KNOTS BY TAU 120. 

MODEL DISCUSSION: THE DETERMINISTIC AND ENSEMBLE MODELS ALL AGREE
THAT TC 19S WILL CONTINUE TO TRACK SOUTHWEST THROUGH TAU 36, THEN
TRACK WESTWARD AFTERWARDS. HOWEVER, BY TAU 72 AND BEYOND THERE IS
SOME UNCERTAINTY IN THE TRACK SOLUTIONS. MOST DETERMINISTIC MODELS
SUGGEST A RECURVE SCENARIO BACK EASTWARD, WHEREAS THE ENSEMBLE
MODELS DO NOT SHOW THIS AT ALL. IN THE SHORT TERM, THE JTWC
FORECAST TRACK CONSENSUS MEMBERS ARE IN GOOD AGREEMENT SHOWING A 21
NM SPREAD AT TAU 12 THAT GRADUALLY INCREASES TO 50 NM BY TAU 48.
THE JTWC TRACK IS PLACED WITH MEDIUM CONFIDENCE CLOSE TO CONSENSUS
THROUGH TAU 72, AND LOW CONFIDENCE AFTERWARDS DUE TO THE SPORADIC
BEHAVIOR OF THE MODELS. AS SEEN IN THE PAST SEVERAL MODEL RUNS, THE
HIGH RESOLUTION COAMPS-TC AND HWRF TRACK SOLUTIONS SHOW TC 19S
HOOKING NORTHWARD, AND THEN BACK EASTWARD JUST SOUTH OF DIEGO
GARCIA IN THE LATER TAUS. THE JTWC INTENSITY CONSENSUS DISPLAY A 30
KNOT SPREAD THROUGH TAU 24, MORE THAN LIKELY DUE TO THE SMALL SIZE
OF THE SYSTEM. HOWEVER, THEY DO AGREE WITH A DECREASING SCENARIO
AFTER TAU 12. THE JTWC INTENSITY FORECAST IS SET WITH MEDIUM
CONFIDENCE UP TO TAU 72, AND LOW CONFIDENCE IN THE LATER TAUS DUE
TO THE UNCERTAINTY OF TRACK PROGRESSION.

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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