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 : 26/4/20072008 1.A TROPICAL DEPRESSION 4 (EX-CELINA) 2.A POSITION 2007/12/18 AT 1800 UTC : WITHIN 30 NM RADIUS OF POINT 21.5S / 59.5E (TWENTY ONE DECIMAL FIVE DEGREES SOUTH AND FIFTY NINE DECIMAL FIVE DEGREES EAST) 3.A DVORAK ANALYSIS : 2.0/2.5 /W 0.5/24 H 4.A CENTRAL PRESSURE : 996 HPA 5.A MAX AVERAGE WIND SPEED (10 MN) : 30 KT 6.A EXTENSION OF WINDS BY QUADRANTS (KM): 30 KT NE: 120 SE: 190 SO: 100 NO: 070 7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1006 HPA / 800 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM 1.B FORECASTS: 12H: 2007/12/19 06 UTC: 22.2S/58.4E, MAX WIND=030KT, TROP. DEPRESSION. 24H: 2007/12/19 18 UTC: 22.3S/57.3E, MAX WIND=025KT, TROP. DISTURBANCE. 36H: 2007/12/20 06 UTC: 22.3S/55.9E, MAX WIND=025KT, TROP. DISTURBANCE. 48H: 2007/12/20 18 UTC: 21.9S/54.4E, MAX WIND=020KT, FILLING UP. 60H: 2007/12/21 06 UTC: 21.6S/53.3E, MAX WIND=020KT, FILLING UP. 72H: 2007/12/21 18 UTC: 21.3S/52.2E, MAX WIND=020KT, FILLING UP. 2.B OTHER INFORMATIONS: T=2.0+ AND CI=2.5 THE EXISTENCE OF A WEAK LOW SOUTHWESTWARDS COULD EXPLAIN THE FACT THAT THE SYSTEM GOES ON TRACKING SOUTHWESTWARDS, WHITHOUT CURVING WESTWARDS AS IT IS FORECASTED BY MAIN NWP MODELS. SYSTEM HAS HOWEVER CLEARLY SLOW DOWN SINCE THE RECENT PAST HOURS. AFTER THE EVACUATION OF THIS WEAKNESS, HIGH PRESURE SHOULD REBUILD TO THE SOUTHWEST AND MAKE THE RESIDUAL VORTEX CURVE WESTWARDS, THEN NORTHWESTWARDS, TRACKING ROUND REUNION ISLAND TO THE SOUTH. THE NORTHWESTERLY VERTICAL WINDSHEAR IMPEDES SUCCESSIVE BURTS OF CONVECTION TO REBUILD ABOVE THE LLCC, AND REJECTS HEAVY RAINFALL SOUTHEAST OF THE SYSTEM. AS IT WILL TRACK WESTNORTHWESTWARDS, THE WINDSHEAR SHOULD WEAKEN, BUT DUE TO A POOR UPPER LEVEL OUTFLOW, DRY ENVIRNOMENT, AND POOR EQUATORWARD LOW LEVEL INFLOW, THE SYSTEM SHOULD NOT RE-INTENSIFY AND SHOULD FILL-UP PROGRESSIVELY. WINDS EXTENSION HAS BEEN MEASURED THANKS TO 1324Z QUIKSCAT SWATH.