Direction Interrégionale de LA REUNION
B.P.4    97491 Ste Clotilde Cedex
Téléphone                02.62.92.11.00
Fax exploitation      02.62.92.11.48
Fax direction           02.62.92.11.47

RSMC / TROPICAL CYCLONE CENTRE / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER : 4/12/20082009 1.A TROPICAL DEPRESSION 12 2.A POSITION 2009/04/05 AT 0000 UTC : WITHIN 20 NM RADIUS OF POINT 13.6S / 54.4E (THIRTEEN DECIMAL SIX DEGREES SOUTH AND FIFTY FOUR DECIMAL FOUR DEGREES EAST) MOVEMENT : SOUTH-WEST 9 KT 3.A DVORAK ANALYSIS : 2.5/2.5 /D 1.0/24 H 4.A CENTRAL PRESSURE : 997 HPA 5.A MAX AVERAGE WIND SPEED (10 MN) : 30 KT RADIUS OF MAXIMUM WINDS (RMW) : NIL 6.A EXTENSION OF WINDS BY QUADRANTS (KM): 30 KT NE: 020 SE: 040 SO: 040 NO: 020 7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1008 HPA / 700 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP 1.B FORECASTS: 12H: 2009/04/05 12 UTC: 14.8S/52.8E, MAX WIND=035KT, MODERATE TROP. STORM. 24H: 2009/04/06 00 UTC: 16.1S/51.4E, MAX WIND=045KT, MODERATE TROP. STORM. 36H: 2009/04/06 12 UTC: 17.8S/50.5E, MAX WIND=055KT, SEVERE TROP. STORM. 48H: 2009/04/07 00 UTC: 19.2S/50.1E, MAX WIND=065KT, TROPICAL CYCLONE. 60H: 2009/04/07 12 UTC: 21.0S/50.0E, MAX WIND=065KT, TROPICAL CYCLONE. 72H: 2009/04/08 00 UTC: 22.3S/50.3E, MAX WIND=060KT, SEVERE TROP. STORM. 2.B OTHER INFORMATIONS: T AND CI=2.5 DEEP CONVECTIVE ACTIVITY HAS CLEARLY IMPROVED, WITH TWO CURVED BAND BUILDING ON EACH PART OF THE CENTER. ENVIRONMENTAL CONDITIONS ARE FAVOURABLE FOR INTENSIFICATION WITH A EFFICIENT POLEWARD LOW LEVEL INFLOW ON THE NORTHERN EDGE OF THE SUBTROPICAL HIGH PRESSURES REBUILDING IN THE SOUTHWEST, TRANSEQUATORIAL MONSOON FLOW IS WEAK. UPPER LEVEL ENVIRONMENT IS FAVOURABLE WITH A WEAK VERTICAL WINDSHEAR IN THE AREA AND A GOOD POLEWARD UPPER LEVEL OUTFLOW AND A BUILDING EQUATORWARD ONE. SYSTEM IS EXPECTED TO BE DRIVED BY THE NORTHEASTERLY STEERING FLOW GENERATED BY THE MERIDIAN MID LEVEL RIDGE EXISTING EAST OF THE SYSTEM. AVAILABLE NWP MODELS ARE NOT IN AGREEMENT FOR THE EXPECTED TRACK. SOME OF THEM FORECAST A DIRECT SOUTHWESTWARDS TRACK TOWARDS THE NORTHEASTERN MALAGASY COASTLINE (LANDFALL WITHIN TAU 36) BUT DE MAIN PART OF THEM FORECAST NOW A SOUTHWARDS RECURVE TRACK ON AND AFTER TAU 24 AND A TRANSIT LINE BETWEEN MALAGASY AND LA REUNION. THIS SCENARIO IS STABLE SINCE SEVERAL RUNS OF ECMWF MODEL, THAT'S THE PHILOSOPHY FOLLOWING BY LA REUNION RSMC. ON AND AFTER TAU 60, SYSTEM SHOULD BE CONSTRAINTED BY NORTHWESTERLY VERTICAL WINDSHEAR.