WDXS32 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (DINGANI)   
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7S 75.5E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 1055 NM EAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
SYSTEM WITH A DEVELOPING 15NM DIAMETER EYE AND IMPROVED
ORGANIZATION, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH
CONFIDENCE. A 120326Z MHS 89GHZ MICROWAVE IMAGE REVEALS A MICROWAVE
EYE FEATURE ON THE EASTERN EDGE OF THE CORE CONVECTION WITH LIMITED
CONVECTIVE BANDING DISPLACED OVER THE NORTHEAST QUADRANT. ANIMATED
WATER VAPOR IMAGERY INDICATES ENHANCED POLEWARD OUTFLOW INTO A
SHARP UPPER-LEVEL SHORTWAVE TROUGH AND STJ POSITIONED TO THE
SOUTHWEST. THE INITIAL INTENSITY OF 65 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE KNES AND FMEE DVORAK INTENSITY ESTIMATES,
CONSISTENT WITH THE VISIBLE EYE.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   FMEE: T4.0 - 65 KTS
   CIMSS ADT: 55 KTS AT 120300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
REMAIN FAVORABLE WITH ENHANCED POLEWARD OUTFLOW AND LOW VERTICAL
WIND SHEAR (VWS) THROUGH TAU 24, CONSEQUENTLY, TROPICAL CYCLONE
(TC) 13S IS EXPECTED TO INTENSIFY SLIGHTLY TO 70 KNOTS BY TAU 12
AND MAINTAIN THAT INTENSITY THROUGH TAU 24. AFTER TAU 24, TC 13S
WILL WEAKEN STEADILY AS IT TRACKS SOUTHWESTWARD UNDER INCREASING
VWS AND COOLING SST WITH DISSIPATION ANTICIPATED BY TAU 120.  

MODEL DISCUSSION: DETERMINISTIC AND PROBABILISTIC MODEL GUIDANCE
CONTINUES TO INDICATE A LARGE SPREAD IN TRACK SOLUTIONS AFTER TAU
36. THERE IS CURRENTLY A 200 TO 400NM SPREAD IN DETERMINISTIC
SOLUTIONS FROM TAU 72 TO TAU 120, THEREFORE, THERE IS MEDIUM
CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU 72 AND LOW
CONFIDENCE IN THE EXTENDED PERIOD. RELIABLE INTENSITY GUIDANCE IS
IN IMPROVED AGREEMENT WITH ALL MODELS INDICATING STEADY WEAKENING
AFTER TAU 24. HWRF DOES PEAK SLIGHTLY HIGHER (75 KNOTS) THAN THE
JTWC PEAK (70 KNOTS), WHICH IS CERTAINLY POSSIBLE, BUT SHOWS A
SHARP DECREASE TO 35 KNOTS BY TAU 72. THE BULK OF THE INTENSITY
GUIDANCE INDICATES DISSIPATION NEAR TAU 120. 

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