WDXS32 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21S (GEZANI) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.1S 50.1E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 156 NM EAST-NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT AND SYMMETRICAL TROPICAL CYCLONE (TC) 21S (GEZANI). CONVECTIVE 
BANDING FORMING A NEARLY UNIFORM CENTRAL DENSE OVERCAST (CDO) HAS 
TRANSITIONED INTO AN EYE FEATURE SCENE OVER THE LAST 12 HOURS 
INDICATING CONTINUOUS INTENSIFICATION. THE EYE HAS WARMED 
SIGNIFICANTLY (TO 18C AT 101200Z), WHILE THE CLOUD TOPS CONTINUE TO
REMAIN COLD (NEAR -78C). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE ANIMATED SATELLITE IMAGERY OF THE EYE, WHILE
THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON GOOD AGREEMENT AMONG THE OBJECTIVE AIDS AND SUBJECTIVE
AGENCY DVORAK ESTIMATES. AS TC GEZANI APPROACHES MADAGASCAR AND
BEGINS TO INTERACT WITH LAND, IT IS CURRENTLY REACHING PEAK INTENSITY, 
UTILIZING THE HIGHLY FAVORABLE ENVIRONMENT LEADING UP TO THIS MOMENT 
AND CHARACTERIZED BY ROBUST RADIAL OUTFLOW, WARM (28-29C) SEA SURFACE 
TEMPERATURES (SST), MOIST ATMOSPHERIC COLUMN, AND SUPPORTIVE, LOW 
(5-10 KTS) VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 108 KTS AT 101200Z
   CIMSS ADT: 112 KTS AT 101200Z
   CIMSS AIDT: 113 KTS AT 101200Z
   CIMSS D-MINT: 110 KTS AT 101200Z
   CIMSS D-PRINT: 101 KTS AT 101200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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: TC GEZANI IS QUICKLY APPROACHING LANDFALL OVER
EASTERN MADAGASCAR EXPECTED TO OCCUR WITHIN THE NEXT FEW HOURS.
DRIVEN BY HIGHLY FAVORABLE ENVIRONMENTAL CONDITIONS AND RAPID
INTENSIFICATION OVER THE LAST 12 HOURS, THE SYSTEM IS EXPECTED TO
REACH PEAK OF 115-120 KTS JUST PRIOR TO LANDFALL. AFTERWARDS, THE
SYSTEM IS FORECAST TO TRANSIT OVER THE ISLAND, WHILE INTERACTION
WITH THE MOUNTAIN RANGE AND FRICTIONAL EFFECTS OF THE TERRAIN WILL
RESULT IN RAPID WEAKENING AS REFLECTED BY INTENSITY DROP TO 30 KTS. 
THE TRANSIT IS EXPECTED TO LAST ABOUT 24 HOURS, FOLLOWED BY 
RECONSOLIDATION OCCURRING WITHIN THE MOZAMBIQUE CHANNEL. FAVORABLE 
ENVIRONMENT ENCOUNTERED BY THE SYSTEM ON THE OTHER SIDE OF THE ISLAND 
WILL RESULT IN STEADY INTENSIFICATION. A STEERING PATTERN SHIFT IS 
ANTICIPATED TO BEGIN AROUND TAU 48, WITH THE SUBTROPICAL RIDGE 
FORECAST TO RETROGRESS SOUTHEAST OF MADAGASCAR AND ATTENUATE. THIS IS 
EXPECTED TO OCCUR CONCURRENTLY WITH THE AMPLIFICATION OF A LONGWAVE 
TROUGH PASSING TO THE SOUTH, A COMBINATION OF FACTORS THAT WILL INDUCE 
A POLEWARD DEFLECTION OF TC 21S. IN REGARD TO INTENSITY, MULTI-MODEL 
CONSENSUS REFLECTS THE GENERAL AGREEMENT ON WEAKENING OVER LAND, 
FOLLOWED BY RECONSOLIDATION AND INTENSIFICATION AFTERWARDS. FAVORABLE 
CONDITIONS WILL RESULT IN SYSTEM ONCE AGAIN REACHING 65-70 KTS WIND 
SPEEDS.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE HAS COME TO A BETTER 
AGREEMENT IN REGARD TO THE GENERAL SYNOPTIC PATTERN, BUT UNCERTAINTY 
REMAINS, WITH SOME MODELS (NAVGEM, ECMWF) STILL INDICATING LESS OF AN 
IMPACT FROM THE LONGWAVE TROUGH AND POTENTIAL FOR THE CYCLONE TO 
CLOSELY APPROACH THE COASTAL MOZAMBIQUE. THIS LATTER SCENARIO RESULTS 
IN A FAILURE OF THE CYCLONE TO PHASE WITH THE ADVANCING BAROCLINIC 
TROUGH, THEREBY PERMITTING TC GEZANI TO MAINTAIN A MORE WESTWARD 
TRAJECTORY. THE OFFICIAL JTWC FORECAST ADHERES TO THE CONSENSUS 
RECURVATURE SCENARIO, BUT OVERALL CONFIDENCE IN THE TRACK FORECAST IS 
ASSESSED AS MEDIUM. CROSS-TRACK SPREAD AMONG THE MULTI-MODEL CONSENSUS 
MEMBERS IS ONLY 40 NM AROUND TAU 24, EXPANDING TO 120 NM AT TAU 72. IN 
TERMS OF INTENSITY, A LARGE INTENSIFICATION SPREAD (10-50 KTS) UPON 
THE RECONSOLIDATION WITHIN THE MOZAMBIQUE CHANNEL RESULTS IN LOW 
CONFIDENCE IN THE LONG RANGE INTENSITY PROJECTION.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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