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
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RSMC / TROPICAL CYCLONE CENTRE / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER : 8/4/20082009 1.A TROPICAL DEPRESSION 4 2.A POSITION 2008/12/17 AT 1800 UTC : WITHIN 30 NM RADIUS OF POINT 10.9S / 67.0E (TEN DECIMAL NINE DEGREES SOUTH AND SIXTY SEVEN DECIMAL ZERO DEGREES EAST) MOVEMENT : SOUTH 4 KT 3.A DVORAK ANALYSIS : 2.5/2.5 /D 0.5/24 H 4.A CENTRAL PRESSURE : 997 HPA 5.A MAX AVERAGE WIND SPEED (10 MN) : 30 KT RADIUS OF MAXIMUM WINDS (RMW) : 30 KM 6.A EXTENSION OF WINDS BY QUADRANTS (KM): 30 KT NE: 040 SE: 120 SO: 120 NO: 040 7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1008 HPA / 650 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM 1.B FORECASTS: 12H: 2008/12/18 06 UTC: 12.0S/66.6E, MAX WIND=035KT, MODERATE TROP. STORM. 24H: 2008/12/18 18 UTC: 13.0S/66.0E, MAX WIND=035KT, MODERATE TROP. STORM. 36H: 2008/12/19 06 UTC: 13.7S/65.2E, MAX WIND=030KT, TROP. DEPRESSION. 48H: 2008/12/19 18 UTC: 14.1S/64.1E, MAX WIND=030KT, TROP. DEPRESSION. 60H: 2008/12/20 06 UTC: 14.7S/62.9E, MAX WIND=030KT, TROP. DEPRESSION. 72H: 2008/12/20 18 UTC: 15.1S/61.6E, MAX WIND=030KT, TROP. DEPRESSION. 2.B OTHER INFORMATIONS: T=CI=2.5. AS USUAL BY NIGHTTIME, CONVECTION HAS STRENGHEN AROUND THE LLCC. A QUICKSCATT PASS AT 13:44Z SUGGEST SOME WINDS IN THE 30 KTS RANGE IN THE SOUTHERN SEMI CIRCLE (THE MAX NON CONTAMINATED WIND AT 43 KT IS SUSPECT). INTENSITY IS KEPT AT 30 KT AT THIS TIME (ALTHOUGH IT COULD BE A LITTLE BIT CONSERVATIVE ...) A WINDSAT PASS AT 13:30Z (FIX: 10.7S/67.0E) SHOWS THAT THE SYSTEM IS A LITTLE BIT MORE EASTWARDS THAN PREVIOUSLY ESTIMATED. IT SEEMS TO MAKE A SLOW DRIFT TOWARDS THE SOUTH. THIS SYSTEM EVOLVES WITHIN AN ENVIRONMENT WHICH IS NEUTRAL TO SLIGHTLY FAVOURABLE FOR THE MOMENT. LOCATED BENEATH THE WESTERN PERIPHERY OF THE UPPER RIDGE IT BENEFITS FROM WEAK VERTICAL WINDSHEAR, WHILE THE UPPER OUTFLOW IS RESTRICTED TO A MODERATELY POTENT POLEWARD CHANNEL (AHEAD OF AN UPPER TROUGH TO THE WEST). WHILE THERE IS A CONSENSUS AMONG THE DIFFERENT NUMERICAL MODELS FOR A GENERAL SOUTHWESTWARD MOTION OF THE SYSTEM THEY DISAGREE NOTICEABLY ABOUT THE FUTURE SPEED OF MOVEMENT. THE PRESENT TRACK, THAT TAKE INTO ACCOUNT THE LAST CONSENSUS FROM THE ECMWF ENSEMBLE PREDICTION SYSTEM AND THE 12Z TRACK FROM THE FRENCH LIMITED AREA FRENCH MODEL ALADIN, IS A LITTLE BIT TO THE LEFT AND SLOWER THAN THE PREVIOUS FORECAST. THE POTENTIAL FOR FURTHER INTENSIFICATION APPEARS LIMITED ALTHOUGH THERE IS A WINDOW FOR SOME MARGINAL IMPROVEMENT WITHIN THE NEXT 12 TO 24 HOURS BEFORE NORTHERLY TO NORTHWESTERLY WINDS START TO STRENGTHEN AND TO IMPINGE ON THE CLOUD SYSTEM AFFECTING IT THROUGH INCREASING VERTICAL WIND SHEAR.