Is anyone using sub-hourly radar QPE to drive urban flood alerts? I’m piloting a 5-minute rainfall ensemble over a 3 km2 catchment and can extend lead time about 12 minutes, but false alarms spike along convective edges; I’m weighing hysteresis on depth proxies versus exposure-weighted thresholds to keep actions focused. What calibration change cut nuisance alerts for you without dulling sensitivity in the first hour?
I cut edge false alarms by adding an ‘M-of-N’ gate: require 2 of 3 consecutive 5‑min bins and at least two neighboring pixels over threshold, and suppress hits where a 3×3 rain‑rate texture/gradient flag trips. It kept the about 12‑min lead and, with a small decay hysteresis on depth proxies for ramp‑down, trimmed nuisance alarms; caveat: it can miss razor‑thin cells that just graze the catchment. Want to try the knock‑twice trick before exposure‑weighting?