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

1. Aladin-Reunion

2. Website of RSMC La Réunion

3. 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 extreme

wind and rainfall– A limited-access to the SWFDP and RA I national meteorological services– Available in two languages: French & English

Input data :– Aladin-Reunion forecast fields– For each cyclone, the official RSMC track forecast– Deterministic models (Météo-France, ECMWF, UKMO) – Forecast tracks from 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 kt85 kt80 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

Illustrations sur le cas de Bingiza (février 2011)

Early detection of the cyclogenesis of Bingiza

Illustrations sur le cas de Bingiza (février 2011)

Early detection of the cyclogenesis of Bingiza

Illustrations sur le cas de Bingiza (février 2011)

Early detection of the cyclogenesis of Bingiza

Illustrations sur le cas de Bingiza (février 2011)

Early detection of the cyclogenesis of Bingiza

Illustrations sur le cas de Bingiza (février 2011)

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

Official RSMC forecastUncertainty cone (derived from EPS)

Track forecasts from deterministic models

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 forecastUncertainty cone (derived from EPS)

Track forecasts from deterministic models

2. Website of RSMC La Réunion

2. Website of RSMC La Réunion

2. Website of RSMC La Réunion

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

reference : Dupont et al, 2011, Weather & Forecasting, “Verification of ensemble-based uncertainty circles around tropical cyclone track forecasts”, in press.

– At a given lead-time, the circle that centered on the ensemble-mean and that contains 75% of the EPS members is computed

– This circle is translated to the RSMC position forecast

The ensemble dispersion of TC positions is translated to the RSMC forecast

such a cone is proven to be able to discriminate between large and small errors !

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.