WDXS32 PGTW 111500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21S (GEZANI) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.9S 44.7E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 159 NM WEST OF ANTANANARIVO, MADAGASCAR
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: XX FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A POORLY
ORGANIZED AND VERTICALLY TILTED TROPICAL CYCLONE (TC) 21S (GEZANI) 
CURRENTLY OVER LAND, AS IT APPROACHES THE WESTERN COASTLINE OF 
MADAGASCAR. THE MID-LEVEL TURNING CAN BE OBSERVED TO THE NORTH AND 
NORTHWEST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). AS THE SYSTEM IS 
A COUPLE HOURS AWAY FROM RE-EMERGING OVER WARM WATERS OF THE 
MOZAMBIQUE CHANNEL, CONVECTIVE BANDING BEGINS TO DEVELOP. THE SYSTEM 
CONTINUES TO BE STEERED WEST-SOUTHWESTWARD BY THE STR CURRENTLY 
CENTERED TO THE SOUTH. THE INITIAL POSITION IS PLACED WITH MEDIUM 
CONFIDENCE BASED ON A 111127Z GPM GMI 37 GHZ MICROWAVE PASS DEPICTING 
THE LOW-LEVEL CENTER, WHILE THE 89 GHZ IMAGE SHOWS THE DEVELOPING 
CONVECTIVE BANDING. THE INITIAL INTENSITY OF 25 KTS IS ALSO ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON THE RAPID WEAKENING TREND OVER THE 
LAST 12 HOURS, ANTANANARIVO AIRPORT SURFACE BASED OBSERVATIONS 
REPORTING PEAK WIND SPEEDS OF 23 KTS AT 110300Z AND 110822Z OCEANSAT-3 
PASS SHOWING 10-15 KTS MAXIMUM WINDS OVER WATER TO THE WEST OF THE 
LLCC.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS D-MINT: 28 KTS AT 111127Z
   CIMSS D-PRINT: 30 KTS AT 111200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: OVER LAND
   OUTFLOW: WEAK WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC GEZANI IS ANALYZED APPROXIMATELY 30 NM AWAY 
FROM THE WESTERN COAST OF MADAGASCAR AND IS ON A TRAJECTORY FOR 
IMMINENT RE-EMERGENCE OVER VERY WARM (30-31 C) WATERS OF THE 
MOZAMBIQUE CHANNEL. WHILE TRAVERSING THE ISLAND, SIGNIFICANT 
OROGRAPHIC INTERACTION AND INCREASED SURFACE FRICTION RESULTED IN 
RAPID WEAKENING DOWN TO CURRENT ESTIMATE OF 25 KTS. WITHIN THE NEXT 
COUPLE HOURS, TC 21S WILL COMMENCE THE REORGANIZATION PHASE. UPON 
ENCOUNTERING A VERY FAVORABLE ENVIRONMENTAL REGIME OF HIGH SEA SURFACE 
TEMPERATURES (SST), LOW (5-10 KTS) VERTICAL WIND SHEAR, AND GOOD 
OUTFLOW CHANNEL ALOFT, A PERIOD OF STEADY RE-INTENSIFICATION IS 
ANTICIPATED. TC GEZANI WILL THEREFORE REACH 75-80 KTS PEAK INTENSITY 
AROUND BETWEEN TAUS 48 AND 72, FOLLOWED BY A WEAKENING PERIOD SOON 
AFTER. AS THE PRIMARY STEERING RIDGE RETROGRADES SOUTHEAST OF 
MADAGASCAR TC GEZANI WILL ROUND THE AXIS OF THE RIDGE AND TURN 
SOUTHWESTWARD AROUND TAU 72. THIS PROCESS WILL OCCUR COINCIDENTALLY 
WITH THE AMPLIFICATION OF A MID-LATITUDE BAROCLINIC TROUGH PROPAGATING 
TO THE SOUTH. THIS SYNOPTIC EVOLUTION IS EXPECTED TO FACILITATE A 
POLEWARD RECURVATURE OF TC 21S. FORECAST CONFIDENCE BEYOND TAU 72 IS 
LOW, DUE TO SIGNIFICANT UNCERTAINTY ASSOCIATED WITH NUMERICAL MODELS 
DEPICTIONS OF THE DOMINANT STEERING MECHANISM AFTER TAU 96.

MODEL DISCUSSION: THE NUMERICAL MODEL TRACK GUIDANCE HAS CONVERGED
TOWARD A HIGHER DEGREE OF CONSENSUS REGARDING THE LARGE-SCALE
SYNOPTIC EVOLUTION WITHIN THE INITIAL 72 HOURS AS WITNESSED BY A
100 NM CROSS-TRACK SPREAD AT TAU 72. AS MENTIONED ABOVE, SIGNIFICANT 
UNCERTAINTY PERSISTS IN THE EXTENDED FORECAST. A SUBSET OF GUIDANCE, 
NOTABLY NAVGEM AND ECMWF, CONTINUES TO DEPICT A LESS DISTINCT PHASING 
EVENT WITH THE ADVANCING LONGWAVE TROUGH. THIS SCENARIO WOULD RESULT 
IN A FAILURE OF THE CYCLONE TO RECURVE, PERMITTING A WESTWARD OR EVEN
NORTHWARD TRAJECTORY AND A POTENTIAL THREAT TO COASTAL MOZAMBIQUE.
ON THE OTHER SIDE OF THE ENVELOPE, UKMET, GFS AND GFS ENSEMBLE
INDICATE A SHARP INCREASE IN TRANSLATIONAL SPEEDS AND SOUTHWESTWARD
MOVEMENT, AS THE SYSTEM MOVES IN PHASE WITH THE UPPER-LEVEL LONGWAVE 
TROUGH. THE OFFICIAL JTWC FORECAST REMAINS ALIGNED WITH THE MULTI-
MODEL CONSENSUS RECURVATURE SOLUTION, ALBEIT WITH ONLY LOW CONFIDENCE
IN THE LONG-TERM TRACK FORECAST. WITH RESPECT TO INTENSITY, ALL
AVAILABLE GUIDANCE INDICATES SIGNIFICANT INTENSIFICATION OVER THE
NEXT 48 HOURS, FOLLOWED BY A 24 HOUR SLOW-DOWN, CULMINATING IN
STEADY WEAKENING AFTERWARDS. LONG-TERM INTENSITY FORECAST IS ASSESSED 
WITH MEDIUM CONFIDENCE, AS UNCERTAINTY ASSOCIATED WITH THE TRACK 
PREDICTION, AS WELL AS SPEED OVER WATER WILL DETERMINE THE RATE AND 
MECHANISM OF THE WEAKENING.

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