WDXS32 PGTW 202100 AMD
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15S (EWETSE) WARNING NR 
001A AMENDED//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
 
SUMMARY:
   INITIAL POSITION: 25.1S 41.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 186 NM SOUTH-SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET
 
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 15S (EWETSE) HAS RAPIDLY DEVELOPED OVER THE
LAST 24 HOURS, AFTER EMERGING INTO THE SOUTHERN MOZAMBIQUE CHANNEL.
THE SYSTEM IS SITUATED ALONG THE TAIL END OF A REMNANT SHEAR LINE
WHICH EXTENDS FAR TO THE SOUTHEAST, OFF THE SOUTHERN COAST OF
MADAGASCAR. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS A SMALL CENTRAL DENSE OVERCAST (CDO) FEATURE, WITH WEAK
ROTATION EVIDENT IN THE OVERSHOOTING TOPS ALONG THE NORTHERN SIDE
OF THE CDO. A LATE-BREAKING ASCAT PASS FROM 201850Z DEPICTS A SMALL 
AND SYMMETRICAL LLCC AND REVEALS MAXIMUM WINDS OF 45-50 KNOTS IN THE
SOUTHWESTERN PERIPHERY OF THE LLCC. LATE RECEIPT OF A 201448Z SMOS
PASS ALSO SUPPORTS AN INTENSITY CLOSER TO 50 KNOTS THAN 40 KNOTS. THE 
INITIAL POSITION AND INTENSITY ARE ASSESSED WITH HIGH CONFIDENCE BASED 
ON THE ASCAT PASS NOTED ABOVE. ENVIRONMENTAL CONDITIONS ARE
FAVORABLE FOR ADDITIONAL INTENSIFICATION, WITH LOW TO MODERATE
DEEP-LAYER SHEAR, WARM SSTS AND ROBUST POLEWARD OUTFLOW.
 
INITIAL WIND RADII BASIS: SCATTEROMETER DATA
 
CURRENT STEERING MECHANISM: LOW-LEVEL WESTERLY FLOW ON THE
EQUATORWARD SIDE OF A LOW-LEVEL SHEAR LINE WHICH EXTENDS SOUTHEAST
TO THE SOUTH OF MADAGASCAR.
 
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.0 - 45 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS D-PRINT: 38 KTS AT 201800Z
 
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
 
ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: LOW
 
3. FORECAST REASONING.
 
SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.
 
FORECAST DISCUSSION: TC 15S QUICKLY CONSOLIDATED OVER THE LAST 12
HOURS, AND RAPIDLY INTENSIFIED OVER THE PAST SIX HOURS, AS IT MOVES
QUICKLY EASTWARD. THE SYSTEM WILL CONTINUE TO TRACK EASTWARD, ALONG
THE NORTHERN SIDE OF A BAND OF LOW-LEVEL WESTERLY FLOW ON THE
EQUATORWARD SIDE OF A REMNANT SHEAR LINE, WHICH IS ITSELF PUSHING
EASTWARD. THE SYSTEM IS FORECAST TO MAKE LANDFALL ALONG THE
SOUTHWESTERN COAST OF MADAGASCAR AROUND TAU 12 AND WILL THEM MOVE
INLAND AND NORTHWARD ALONG THE SPINE OF THE CENTRAL MOUNTAINS OF
MADAGASCAR THROUGH THE REMAINDER OF THE FORECAST PERIOD. IN TERMS
OF INTENSITY, THE SYSTEM IS FORECAST TO INTENSIFY ANOTHER 5-10
KNOTS PRIOR TO MAKING LANDFALL, WITH THE FORECAST SPECIFICALLY
CALLING FOR LANDFALL AS A 55 KNOT TROPICAL CYCLONE. ONCE THE SYSTEM 
MAKES LANDFALL, IT WILL QUICKLY DISSIPATE OVER THE RUGGED TERRAIN OF 
SOUTHERN MADAGASCAR, DISSIPATING OVER LAND BY TAU 36.
 
MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG
AGREEMENT, SUPPORTING AN EASTWARD TRACK AND LANDFALL ALONG THE
SOUTHWESTERN COAST OF MADAGASCAR WITHIN THE NEXT 12-15 HOURS. AFTER
LANDFALL, THE MODEL PACKAGE SHOWS SIGNIFICANT DIVERGENCE, WITH THE
TRACKERS QUICKLY DISPERSING, SOME MODELS SHOWING THE SYSTEM
RETURNING TO THE MOZAMBIQUE CHANNEL, WHILE OTHERS CUT STRAIGHT
ACROSS MADAGASCAR AND MOVE INTO THE SOUTH INDIAN OCEAN. THE
MAJORITY OF THE GUIDANCE DEPICTS A SLOW TRACK NORTHWARD ALONG THE
MOUNTAIN SPINE, THEN A SLOW TURN BACK TO THE WEST. THE JTWC TRACK
IS PLACED NEAR THE MULTI-MODEL CONSENSUS MEAN WITH HIGH CONFIDENCE.
INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT, DEPICTING A SLIGHT
INTENSIFICATION OR STEADY INTENSITY THROUGH LANDFALL FOLLOWED BY
RAPID WEAKENING AND DISSIPATION BY TAU 36.
 
FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH

4. JUSTIFICATION FOR AMENDMENT: UPDATED INITIAL INTENSITY AND 
FORECAST INTENSITY.//
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