WDXS32 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (DINGANI) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.2S 71.9E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 907 NM SOUTH OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) LOCATED TO THE NORTH OF
A MASS OF CONVECTION WITH RAGGED FEEDER BANDS IN THE NORTHERN
PERIPHERY. A PARTIAL 131956Z AMSR2 IMAGE SHOWS THE LLCC BEGINNING
TO BE DECOUPLED FROM THE PARENT MASS OF CONVECTION TO THE SOUTH. A
PARTIAL 140439Z ASCAT-C PASS SHOWS 40-45 KNOT WINDS IN THE WESTERN
PERIPHERY APPROX 75 NM AWAY FROM THE ASSESSED LLCC. TC 13S IS IN AN
UNFAVORABLE ENVIRONMENT FOR FURTHER TROPICAL DEVELOPMENT WITH GOOD
(40-50 KTS) POLEWARD OUTFLOW ALOFT AND BORDERLINE WARM (26-27 C)
SEA SURFACE TEMPERATURES (SST), OFFSET BY STRONG (45-50 KTS)
VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED MSI. THE INITIAL
INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A
BLEND OF THE PGTW DVORAK ESTIMATE AND MULTIPLE AUTOMATED DVORAK
ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.5 - 55 KTS
   FMEE: T3.0 - 45 KTS
   CIMSS SATCON: 64 KTS AT 140304Z
   CIMSS ADT: 51 KTS AT 140630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 45-50 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 13S CONTINUES ITS SOUTH-SOUTHWESTWARD TRACK
AS IT RIDES THE WESTERN PERIPHERY OF THE STR. THE SYSTEM IS
EXPECTED TO REMAIN ON THIS TRACK UNTIL TAU 48. AFTER TAU 48, TC 13S
WILL MAKE A DRAMATIC TURN AND BEGIN TO HEAD SOUTHEASTWARD AS IT
FALLS UNDER THE INFLUENCE OF THE SUBTROPICAL JET THAT IS POLEWARD
OF APPROXIMATELY 30 DEGREES SOUTH. ENVIRONMENTAL CONDITIONS WILL 
CONTINUE TO DETERIORATE WITH INCREASED VWS, COPIOUS AMOUNTS OF DRY AIR
ENTRAINMENT, AND COOLER (25-26 C) SSTS. TC DINGANI WILL CONTINUE
ITS WEAKENING TREND AND COMPLETELY DISSIPATE BY THE END OF THE
FORECAST TRACK.

MODEL DISCUSSION: AS OPPOSED TO PREVIOUS MODEL RUNS, THE
DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE ARE IN BETTER AGREEMENT
THROUGH TAU 72. ALL MEMBERS AGREE ON THE SHIFT IN TRACK AFTER TAU
48 WITH AN OVERALL SPREAD OF 90 NM. OF THE CONSENSUS MEMBERS,
NAVGEM IS THE OUTLIER WITH A TRACK WELL TO THE WEST OF THE FORECAST
ENVELOPE. BECAUSE OF THIS, THE JTWC FORECAST TRACK IS PLACED
SLIGHTLY EAST OF CONSENSUS WITH MEDIUM CONFIDENCE. THE INTENSITY
GUIDANCE IS ALSO IN TIGHT AGREEMENT SHOWING AN OVERALL DECREASE DUE
TO THE DETERIORATING ENVIRONMENT. THE JTWC INTENSITY FORECAST IS
SET WITH HIGH CONFIDENCE. 

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