## Nowcasting FLood Impacts of Convective storms in the Sahel (NFLICS) product guide

NFLICS exploits state-of-the-art research findings from satellite analysis to identify land surface drivers of extreme MCS rainfall, opening up the potential for probabilistic nowcasting of intense rain and flooding up to six hours ahead of these storms.

### Convective activity and land surface temperature patterns (latest)

### Convective activity and land surface temperature patterns (latest daily summary)

### Land Surface Temperature (LST) patterns on the current day with IMERG

Overplotted is a purple contour showing where the IMERG “early” rainfall product suggests that at least 5 mm fell in the period from 0600 UTC on the previous day up to 0530 UTC on the current day. Note that the IMERG product has a delay of 4-5 hours in being disseminated which means that the rainfall contour produced on images up to around 1200 UTC may miss data in the hours prior to 0600 UTC.

### Land surface state on the likelihood of convection

### Probability Nowcast of Convective Structures

Past nowcasts are available here

The nowcast plots have the forecast origin and lead-time in hours in the top right. The probabilities (0-100%) represent the chance of a convective structure occurring within a given spatial scale of the coloured pixel. The given spatial scale increases with lead-time, as shown by the black box in the top right of the plot. This distance has been optimised using past data and attempts to balance having useful forecast skill against the increased spatial uncertainties in storm locations at longer lead-times.

Method:

**Version 1** of the NFLICS probability nowcasts of convective structures only require IR10.8 MSG Cloud Top Temperature. Convective structures are identified from the IR10.8 image using a wavelet-transform method based on (Klein et al. (2018); Klein & Taylor (2020)).
A “conditional climatology” approach is used to produce the nowcasts. The nowcasts use the convective structures identified at the start of a nowcast to “look up” the likely future locations of convective structures based on a historical analysis over the period JJAS 2004-2019. The conditional climatology (i.e. what has happened in the next 6 hours given there is a convective structure at this location) is calculated for each time of day and across a grid of source area locations.
As a result, the NFLICS nowcasts can potentially allow for common decay and growth sequencies. The outputs are probabilities of convective structures occurring rather than ensembles of possible future storms. The NFLICS products do not explicitly infer or advect recent storm trajectories.

**Version 2 (used in the Testbed displays),** uses recent Land Surface Temperature anomalies to modify the Version 1 nowcast probabilities. The probability adjustments are based on historical analysis that shows cool/wet areas are less favourable for convection and heavy rain, whilst warm/dry areas are more favourable.

Latest nowcast animation

2 hour nowcast plot

6 hour nowcast plot

Probability time-series graphs