Status: Ongoing analysis Material from: Linus, Rebecca
1. Impact
On 5 February tropical cyclone Batsirai made landfall on Madagascar. The cyclone had earlier affected Mauritius and La Reunion.
https://www.bbc.co.uk/news/world-africa-60264389
2. Description of the event
3. Predictability
3.1 Data assimilation
3.2 HRES
The plot below shows surface winds from a SAR image from Sentinel (left) and a short (15-hour) HRES forecast. The data is valid for 4 February 15UTC.
Real (left) and simulated (right) infrared image valid for 4 February 15UTC (same as above).
Same as above but with the same zoom as the wind images.
The plots below show the ERA5 24-hour precipitation for 3 February, the HRES 24-hour precipitation at 1 day ahead (centre, reduced to 0.25deg), and the difference between HRES and ERA5 24-hour precipitation
The plots below show the GPM IMERG satellite precipitation for 3 and 5 February (left), the HRES 24-hour precipitation at 1 day ahead (centre), and the difference between HRES and GPM IMERG 24-hour precipitation (right)
3.3 ENS
The plots below show the tropical cyclone track for the operational ECMWF forecasts from 5 February 00UTC (first plot) to 26 January 00UTC (last plot). The symbols shows the position on 5 February 00UTC. HRES (red), ENS CF (blue), ENS PF (grey) and BestTrack (black).
The plots below show EFI and SOT for 1-day precipitation for 5 February, from different initial times.
The plot below shows the forecast evolution plot for 24-hour precipitation valid 5 February for the box outlined in the plots above. HRES –red, ENS blue box-and-whisker, Model climate – red box-and-whisker. Triangle marks the maximum in the model climate based on 1200 forecasts, The black square marks the ensemble/climate median and diamond ensemble/climate mean.
The plots below show the ENS probability of exceeding 300mm total precip from 4th to 7th February (inclusive), produced by Calum on 3rd February for the flood bulletins, and the IMERG precip totals indicating the area where precip exceeded 300mm over the same period.
Prediction of genesis
The plot below shows the probably of a cyclone passing within 300 km of the observed location of Batsirai on 27 January 12UTC (red). Cyclones from the 2020 Atlantic season in grey. The drop in probability around 25 January 00UTC is peculiar.
to investigate the feature on 25 January further, the plots below show the tropical cyclone track for the operational ECMWF forecasts from 27 January 00UTC (first plot) to 24 January 00UTC (last plot). The symbols shows the position on 27 January 12UTC. HRES (red), ENS CF (blue), ENS PF (grey) and BestTrack (black).
The plots below show the tropical cyclone (>17m/s) activity 28-29 January (48h) in observations (first plot) followed by forecasts from 27, 26, 25 and 24 January (all 00UTC).
Same as above but for 8 m/s threshold in the forecast.
3.4 Monthly forecasts
The plots below show the tropical storm activity during the week 31 January - 6 February from different initial times.
The plots below show the same a above but for probability of anomaly greater than normal activity.
The plots below show MJO forecasts from 31 January (left), 24 Jan (middle) and 17 January (right).
