RSMC La Réunion activities regarding SWFDP Southern Africa

RSMC La Réunion activities regarding SWFDP Southern Africa Matthieu Plu (Météo-France, La Réunion), Philippe Arbogast (Météo-France, Toulouse), Nicole Girardot (Météo-France, Toulouse)

RSMC La Réunion • Since 1993, Météo-France La Réunion: WMO « Regional Specialized Meteorological Centre » (RSMC) for tropical cyclones in the South-West Indian Ocean (SWIO)

RSMC La Réunion • Cyclone activity in the SWIO : • 12% of the total worldwide cyclone activity (more than the North Atlantic) • Impacts : many human losses every year (particularly in Madagascar), and significant economical impact in the richer countries (example : Dina 2002  95 M€ losses in La Réunion) • Role of RSMC La Réunion for tropical cyclones : • Provide appropriate guidance information (analyses, forecasts) in real-time to the member countries of AR I • Climatology, database of TC • Training and R&D activities

OUTLINE : Contributions of RSMC La Réunion in SWFDP Southern Africa • Aladin-Reunion • Website of RSMC La Réunion • R&D activities

1. Aladin-Réunion • Since 2006, Météo-France (RSMC La Réunion) has been operating the ALADIN-REUNION model Main features : • 8km horizontal resolution • 3D-Var assimilation • 70 vertical levels • 3-days leadtime forecasts twice a day (at 00UTC and 12UTC)

1. Aladin-Réunion • ALADIN-REUNION = an adaptation of ALADIN for the tropical regions • 3D-wind bogus to improve tropical cyclones forecasts • The 3DVar errors are computed over the domain • Some specific physical parameters (convection, ocean fluxes) • Performance • Good skill for cyclone forecasts (tracks and intensity) • Very informative for wind and precipitation forecasts over La Réunion Island • Well appreciated by the meteorological services involved in SWFDP (according to the last SWFDP Technical meeting, Mauritius, July 2011) • SWFDP dissemination • Sent to Pretoria and displayed on RSMC Pretoria website • Displayed on RSMC La Réunion website

2. Website of RSMC La Réunion • Purpose : • Provide guidance in real-time regarding tropical cyclones, and extremewind and rainfall • A limited-access to the SWFDP and RA I national meteorological services • Available in twolanguages: French & English • Input data : • Aladin-Reunionforecastfields • For each cyclone, the official RSMC trackforecast • Deterministicmodels (Météo-France, ECMWF, UKMO) • Forecasttracksfrom ensembles (PEArp, ECMWF EPS, NCEP, CMC, MOGREPS) • Fields (mslp, wind, rainfall) from ensembles (PEArp, ECMWF EPS, NCEP, CMC)

2. Website of RSMC La Réunion • Permanent products: • Aladin-Réunion forecasts (00UTC and 12UTC, until 84h) • Probabilities and quantiles of strong winds and intense rainfall for 4 ensembles + multi-ensemble • mslp spaghettis forecasts (for cyclogenesis) for 4 ensembles + multi-ensemble • In case of a cyclone in the basin: • Official RSMC track forecast + uncertainty cone • Track forecasts from deterministic models • Tracks, live time, Strike probabilities, track for the 5 ensembles + multi-ensemble

2. Website of RSMC La Réunion

2. Website of RSMC La Réunion 90 kt 80 kt 85 kt Illustration : Bingiza (Feb. 2011)

2. Website of RSMC La Réunion Early detection of the cyclogenesis of Bingiza

Illustrations sur le cas de Bingiza (février 2011) Early detection of the cyclogenesis of Bingiza

2. Website of RSMC La Réunion Track forecasts from deterministic models Official RSMC forecast Uncertainty cone (derived from EPS)

2. Website of RSMC La Réunion Strike probabilities (PEArp)

2. Website of RSMC La Réunion Probability of high rainfall (PEArp)

2. Website of RSMC La Réunion Probability of high rainfall (EPS)

Probability of high rainfall (NCEP)

2. Website of RSMC La Réunion Aladin-Réunion forecast : mslp, rain and wind

2. Website of RSMC La Réunion Official RSMC forecast Uncertainty cone (derived from EPS) Track forecasts from deterministic models

2. Website of RSMC La Réunion

3. R&D activities • The evolutions of Aladin-Reunion (assimilation, physics) : a collaboration between RSMC La Réunion and CNRM (Météo-France, Toulouse)

3. R&D activities • Uncertainty cones • Based on ECMWF EPS: a case-dependent cone • At a givenlead-time, the circlethatcentered on the ensemble-mean and thatcontains 75% of the EPS membersiscomputed • This circleistranslated to the RSMC position forecast •  The ensemble dispersion of TC positions istranslated to the RSMC forecast • such a coneisproven to be able to discriminatebetween large and smallerrors ! • reference : Dupont et al, 2011, Weather & Forecasting, “Verification of ensemble-based uncertainty circles around tropical cyclone track forecasts”, in press.

3. R&D activities • Future R&D activities: • Comparison of the ensemble track forecasts from different ensembles, and from multi-ensemble • Calibration of the ensemble forecasts for wind and precipitation • A major difficulty: verification and calibration of ensemble forecasts where the observations are sparse • reference : Dupont et al, 2011, Weather & Forecasting, “Verification of ensemble-based uncertainty circles around tropical cyclone track forecasts”, in press.

RSMC La Réunion activities regarding SWFDP Southern Africa