TC 17S(FILIPO) intensifying next 24H//INVEST 91S likely to develop next 48H// 1100utc updates

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 17S AND 3HOURLY SATELLITE BULLETINS ON INVEST 91S

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TC 17S WILL CONTINUE WESTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE SOUTH. AFTER TAU 24, A SECONDARY STR TO THE EAST WILL BUILD AND EXTEND WEST-NORTHWESTWARD, ASSUME STEERING AND DRIVE THE SYSTEM AROUND ITS WESTERN PERIPHERY SOUTHWESTWARD, INTO LANDFALL OVER CENTRAL MOZAMBIQUE SOUTH OF BEIRA JUST BEFORE TAU 36. AFTER TAU 48, TC 17S WILL CREST THE RIDGE AXIS THEN ACCELERATE SOUTHEASTWARD. THE MARGINALLY FAVORABLE ENVIRONMENT WILL FUEL A MODEST INTENSIFICATION TO 50KTS BY TAU 24 BEFORE LANDFALL. DRY AIR INTRUSION AND FRICTIONAL EFFECTS FROM THE RUGGED MOZAMBIQUE TERRAIN WILL ERODE THE SYSTEM DOWN TO 30KTS BY TAU 48. TC 17S WILL SPLASH BACK OVER WATER IN THE SOUTH INDIAN OCEAN AROUND TAU 60. MOISTURE INFUSION AND INCREASED POLEWARD OUTFLOW WILL FUEL A SECONDARY INTENSIFICATION TO A PEAK OF 50KTS AT TAU 96. CONCURRENTLY BY TAU 72, THE SYSTEM WILL UNDERGO SUBTROPICAL TRANSITION AND BY TAU 96, WILL ENTER THE BAROCLINIC ZONE AND COMMENCE EXTRA-TROPICAL TRANSITION. BY TAU 120, TC 17S WILL TRANSFORM INTO A STORM-FORCE COLD CORE LOW WITH AN EXPANDING WIND FIELD.

MODEL DISCUSSION: NUMERICAL FORECAST TRACK MODELS ARE SURPRISINGLY IN TIGHT AGREEMENT FOR A DEVELOPING SYSTEM, GRADUALLY AND EVENLY SPREADING OUT TO MERE 93NM BY TAU 72 AND 175NM BY TAU 120; HOWEVER, GIVEN THE UNCERTAINTIES ASSOCIATED WITH A FORMATIVE SYSTEM, ITS TRACK OVER LAND, AND ITS SUBTROPICAL AND EXTRA-TROPICAL TRANSITIONS, THERE IS ONLY MEDIUM CONFIDENCE IN THE NEAR- TO EXTENDED-PORTION OF THE JTWC TRACK FORECAST.

THE AREA OF CONVECTION (INVEST 91S) PREVIOUSLY LOCATED NEAR 12.1S 98.0E IS NOW LOCATED NEAR 12.2S 98.9E, APPROXIMATELY 112 NM EAST OF COCOS ISLAND. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 101203Z SSMIS 91 GHZ PASS DEPICT CONSOLIDATING LOW LEVEL CONVECTION CENTER (LLCC) WITH DEEP CONVECTION BUILDING OVER THE SOUTHERN AND CENTRAL REGION OF THE LLCC, STRENGTHENING THE CIRCULATION. SURFACE OBSERVATIONS FROM THE COCOS ISLANDS (YPCC) INDICATE STEADY SOUTHERLY WINDS AT 22-24 KTS GUSTING TO 30 KTS OVER THE PAST FEW HOURS. ENVIRONMENTAL ANALYSIS SHOWS A MARGINALLY FAVORABLE ENVIRONMENT WITH HIGH (30-40KTS) EASTERLY VWS OFFSET BY BROAD UPPER-LEVEL OUTFLOW AND WARM (29-30C) SEA SURFACE TEMPERATURES (SST). GLOBAL MODELS INDICATE AN EASTERLY TO SOUTHEASTERLY TRACK OVER THE NEXT TWO DAYS, WITH SLOW CONSOLIDATION. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS HIGH.

GLOBAL MODELS INDICATE AN EASTERLY TO SOUTHEASTERLY TRACK OVER THE NEXT TWO DAYS, WITH SLOW CONSOLIDATION.