WDXS31 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (NINETEEN) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.6S 42.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 120 NM EAST-SOUTHEAST OF NACALA,
MOZAMBIQUE
   MOVEMENT PAST 6 HOURS: EASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 19S AS A QUICKLY CONSOLIDATING SYSTEM WITH SPIRAL BANDS OF
DEEP CONVECTION WRAPPING INTO THE CORE AND CIRRUS FILAMENTS  
ACCOMPANYING THE OUTFLOW. THE ENVIRONMENT IS HIGHLY FAVORABLE FOR 
DEVELOPMENT, CHARACTERIZED BY ROBUST EQUATORWARD AND POLEWARD OUTFLOW 
SUPPORTED BY THE TROUGH CENTERED TO THE SOUTHEAST AND A POINT SOURCE 
ALOFT NEAR THE CENTER, VERY WARM (29-30 C) SEA SURFACE TEMPERATURES, 
AND LOW (5-10 KTS) VERTICAL WIND SHEAR. 19S IS EXPECTED TO BE IN THE 
BEGINNING PHASES OF RAPID INTENSIFICATION (RI), GIVEN THE ENVIRONMENT 
AND THE QUICK CONSOLIDATION OF THE SYSTEM THUS FAR. THE INITIAL 
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON LOWER LEVEL CLOUD 
BANDING PRESENT IN ANIMATED EIR. THE INITIAL INTENSITY OF 35 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CIMSS OBJECTIVE ESTIMATE 
AND AGENCY DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SYSTEM IS IN A COMPETING STEERING
ENVIRONMENT WITH A NEAR EQUATORIAL RIDGE (NER) TO THE NORTHEAST, A
SUBTROPICAL RIDGE (STR) TO THE SOUTHWEST, AND A TROUGH CENTERED TO
THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   FMEE: T2.0 - 30 KTS
   CIMSS D-PRINT: 30 KTS AT 291900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 19S IS EXPECTED TO TRACK SLOWLY
EAST-SOUTHEASTWARD UNTIL LANDFALL IN MADAGASCAR JUST AFTER TAU 24.
19S IS EMBEDDED WITHIN A COMPETING STEERING ENVIRONMENT,
CHARACTERIZED BY A NEAR EQUATORIAL RIDGE (NER) TO THE NORTHEAST, A
DEEP LAYER SUBTROPICAL RIDGE (STR) CENTERED OVER SOUTHERN AFRICA,
AND A TROUGH CENTERED TO THE SOUTHEAST. AS 19S RAPIDLY INTENSIFIES
WITHIN THE MOZAMBIQUE CHANNEL, THE GRADIENT FLOW BETWEEN THE STORM
AND THE CLOSER NER WILL STRENGTHEN AND ALLOW THE NER TO ASSUME
STEERING INFLUENCE OVER 19S BEGINNING AROUND TAU 24. THIS WILL ALSO 
RESULT IN AN INCREASE IN TRACK SPEED AND CAUSING 19S TO ''MOVE IT MOVE 
IT'' ACROSS MADAGASCAR. THE DEEP LAYER TROUGH IS FORECAST TO BREAK 
DOWN BETWEEN TAU 36-48, ALLOWING THE NER TO BUILD AND EXTEND FURTHER 
SOUTHEASTWARD. AROUND TAU 48, THE NER WILL MERGE WITH A BUILDING STR 
CURRENTLY LOCATED FAR TO THE SOUTHEAST OF 19S, CREATING A SINGLE LARGE 
RIDGING COMPLEX THAT WILL CAUSE 19S TO TRACK SOUTHEASTWARD THROUGH TAU 
120. REGARDING INTENSITY, 19S IS FORECAST TO RI WITHIN THE MOZAMBIQUE 
CHANNEL AND MAKE LANDFALL AT OR STRONGER THAN 65KTS AFTER TAU 24. THE 
MOUNTAINOUS TERRAIN OF MADAGASCAR WILL SHRED THE LOWER LEVELS OF THE 
SYSTEM, CAUSING SIGNIFICANT WEAKENING FOR THE DURATION OF TIME 19S 
SPENDS OVER LAND. 19S IS FORECAST TO REEMERGE OVER WATER BETWEEN TAU 
48-72, ENTERING INTO A SECOND HIGHLY FAVORABLE ENVIRONMENT WHERE IT IS
EXPECTED TO QUICKLY RECONSOLIDATE WITH THE POTENTIAL FOR A SECOND
ROUND OF RI. 19S IS CURRENTLY FORECAST TO STEADILY INTENSIFY
THROUGH THE END OF THE FORECAST AT TAU 120.

MODEL DISCUSSION: RELIABLE DETERMINISTIC TRACK GUIDANCE IS IN
STRONG AGREEMENT IN THE NEAR-TERM TRACK FORECAST THROUGH TAU 36,
WITH MINIMAL CROSS-TRACK AND ALONG-TRACK SPREAD. THE GUIDANCE
ENVELOP WIDENS AS 19S TRACK OVER THE MOUNTAINS OF MADAGASCAR,
SLIGHTLY INCREASING THE UNCERTAINTY FOR THE FORECAST THROUGH TAU
72. ALL MODELS ARE IN GOOD AGREEMENT THAT 19S WILL TRACK
SOUTHEASTWARD ONCE REEMERGING OVER WATER AND MAINTAIN A
SOUTHEASTWARD TRACK THOUGH THE REMAINDER OF THE FORECAST PERIOD,
SUPPORTING THE JTWC LATE-TERM FORECAST WITH MEDIUM CONFIDENCE.
INTENSITY GUIDANCE IS IN GOOD AGREEMENT IN A QUICK INTENSIFICATION
BUT ALL DETERMINISTIC MODELS PREDICTS AN INTENSITY GREATER THAN 50 KTS 
PRIOR TO LANDFALL. THE RIDE RI MODEL IS THE ONLY GUIDANCE DEPICTING A 
PEAK INTENSITY ABOVE 50 KNOTS, REACHING AS HIGH AS 75 KNOTS. GIVEN THE 
HIGHLY FAVORABLE CONDITIONS DISCUSSED ABOVE, THE JTWC FORECAST 
DEVIATES FROM THE BULK OF THE GUIDANCE TO FORECAST FOR RI AND A PEAK 
INTENSITY OF 65 KTS PRIOR TO LANDFALL. THE INTENSITY GUIDANCE IS ALSO 
IN AGREEMENT IN A SIGNIFICANT WEAKENING OVER MADAGASCAR AND SUBSEQUENT 
RE-INTENSIFICATION. AS A RESULT, THE JTWC FORECAST IS PLACED WITH 
OVERALL MEDIUM CONFIDENCE.

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