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This effect can occur with onshore cyclonic flow of maritime air that is marginally unstable to sea surface temperatures.  At certain times SSTs can be higher close to coastlines than offshore.   In these cases the inshore sea surface temperature can be high enough for the convection scheme in IFS to trigger release of convection with high CAPE values.  Just upstream the lower sea surface temperatures offshore cannot overcome convective inhibition at low or mid-tropospheric levels.    The IFS convective scheme triggers Instantaneous shower development at each step but does not advect the showers down wind.  This results in repeated convective rainfall over the same inshore locations which can add up to large or very implausibly large implausibly record-breaking near-coast totals (Fig9.6.1-6).

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