WDXS31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FABIEN) WARNING 
NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.0S 72.4E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 114 NM SOUTH OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICT AN UNRAVELLING,
SLOW-MOVING SYSTEM. THE CONVECTIVE STRUCTURE IS NEARLY NON-EXISTENT
AND REMAINS SOLELY ON THE SOUTHERN SECTOR OF THE LLCC AS INDICATED
ON THE 230041Z SSMIS 91GHZ IMAGE. THE INITIAL POSITION IS ASSESSED
WITH HIGH CONFIDENCE USING BOTH THE MICROWAVE IMAGERY FROM THE
230041Z SSMIS 91GHZ AND 37GHZ IMAGES, ALONG WITH THE MSI LOOP. THE
LACK OF CONVECTION IS MAINLY DUE TO THE SLOW PROGRESSION, COMBINED
WITH THE UPWELLING AND THE DRY-AIR AS DISCUSSED IN PREVIOUS
FORECASTS. THE INITIAL INTENSITY OF 65KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON MULTIPLE AGENCY DVORAK INTENSITY AND OBJECTIVE
AUTOMATED INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS REMAIN
MARGINALLY UNFAVORABLE WITH MODERATE (20-25KTS) VWS, WARM (28-29C)
SSTS, AND MODERATE POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE. 

CURRENT STEERING MECHANISM: COMPLEX STEERING FROM A SUBTROPICAL
RIDGE (STR) TO THE SOUTHEAST AND A BUILDING STR FROM THE WEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T4.0 - 65 KTS
   FMEE: T4.0 - 65 KTS
   FIMP: T3.5 - 55 KTS
   CIMSS SATCON: 66 KTS AT 172025Z
   CIMSS ADT: 55 KTS AT 180000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: UPWELLING AND DRY AIR ENTRAINMENT.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 (FABIEN) WILL SLOWLY MIGRATE UNDER THE
WEAK STEERING FROM THE STR TO THE SOUTH AND TRACK
WEST-SOUTHWESTWARD. THE CONVECTION WILL AGAIN DEVELOP SLIGHTLY AS
THE SUN RISES OVER THE INDIAN OCEAN AND TC 19S MOVES OVER WARMER
WATER. AS THE SYSTEM TRACKS TO THE WEST, IT WILL MAINTAIN THE 65KTS
INTENSITY UNTIL TAU 24. THEREAFTER, THE SYSTEM WILL WEAKEN STEADILY
AND TURN POLEWARD BY TAU 36 INTO A HIGHER WIND-SHEAR ENVIRONMENT.
THE SYSTEM WILL TRANSITION TO A NEW PRIMARY STEERING INFLUENCE FROM
A BUILDING STR OVER MADAGASCAR BETWEEN TAUS 24 AND 36. THE SYSTEM
WILL THEN MOVE INTO AN EVEN GREATER WIND SHEAR ENVIRONMENT, WHICH
WILL SIGNIFICANTLY DECREASE THE INTENSITY TO 35KTS BY TAU 120, IF
NOT SOONER.

MODEL DISCUSSION: EXCLUDING AFUM AND NAVGEM FROM THE MODEL GUIDANCE
ENHANCES THE CROSS-TRACK SPREAD. THE MODELS ARE NEAR IDENTICAL IN
THE CROSS-TRACK OUT TO TAU 36 AND ONLY HAVE A 16NM SPREAD. HOWEVER,
THE ALONG-TRACK TIMING FOR STORM TO TURN POLEWARD IS IN POOR
AGREEMENT. THE MEMBERS ARE STILL TRYING TO RESOLVE THE COMPLEX
STEERING PATTERN DISCUSSED ABOVE, AND FOR THIS REASON, THE JTWC
FORECAST TRACK IS PLACED WITH ONLY MEDIUM CONFIDENCE INITIALLY AND
WITH LOW CONFIDENCE IN THE EXTENDED TRACK FORECAST. THE MODEL
INTENSITY GUIDANCE IS IN FAIR AGREEMENT WITH A BULK OF THE
GUIDANCE. MOST MODELS GRADUALLY DECLINE THE INTENSITY FROM TAU 00
THROUGH TAU 120. HOWEVER, THE SYSTEM MAY DEGRADE FASTER THAN THE
JTWC INTENSITY FORECAST, WHICH IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH MEDIUM CONFIDENCE IN THE NEAR TAUS AND LOW IN THE
LATTER HALF.

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