Monday, 10 January 2005
A comparison of lightning flash rate to rainfall over Florida
A wet season hourly lightning flash density climatology by flow regime (Stroupe et. al. 2002) provides a detailed account of lightning patterns over Florida. Watson et. al. (2002) describes a methodology for utilizing the lightning flash density climatology in the National Weather Service Graphical Forecast Editor (GFE). To demonstrate the utility of lightning flash density as method of estimating rainfall amount, lightning flash rate and rainfall were compared in 1 and 24 hour time intervals during the summer of 2004. The National Weather Service (NWS) Tampa Bay Area, Ruskin Florida WSR-88D radar estimated rainfall amount and lightning flash rates were overlaid and compared. In most cases higher flash densities were associated with areas of heavier rainfall, but some variability existed. Some cases had higher rainfall and lightning areas offset by 5 to 10 km. To account for this in GFE grids when lightning climatology data are used to provide a weather field, and a smart tool is used to derive rainfall from lightning flash density, some smoothing of the resulting rainfall grid is recommended. With the daily variability of lightning under different flow regimes and thermodynamic profiles, the lightning based weather grids should also be smoothed to account for the uncertainty.