A flash flood from a lake-enhanced rainband

An analysis of a flash flood caused by a lake-enhanced rainband is presente d. The flood took place near Erie, Pennsylvania, on 17 September 1996. It w as found that the hood resulted from a complex interplay of several scales of forcing that converged over the Erie region. In particular, the flood oc curred during a period when 1) a lake-enhanced convective rainband pivoted over the city of Erie with the pivot point remaining quasi-stationary for a bout 5 h; 2) a deep, surface-based no-shear layer, favorable for the develo pment of strong lake-induced precipitation bands, passed over the eastern p ortion of Lake Erie; 3) the direction of flow in the no-shear layer shifted from shore parallel to onshore at an angle that maximized frictional conve rgence; 4) an upper-level short-wave trough contributed to low-level conver gence, lifting, and regional destabilization; and 5) a strong land-lake diu rnal temperature difference produced a lake-scale disturbance that locally enhanced the low-level convergence. Analysis of the Weather Surveillance Radar-1988 Doppler radar data from Buf falo, New York, and Cleveland, Ohio, revealed that most of the radar-derive d precipitation estimates for the region were overdone except for the regio n affected by the quasi-stationary rainband, which was underestimated. Reco nstruction of the conditions in the vicinity of the band indicate that clou d bases were considerably lower and equivalent potential temperatures highe r than for the areas of precipitation farther east over northwestern Pennsy lvania and southwestern New York State. It is postulated that, due to the l ong distance from the radar sites to the Erie area, the radar was unable to observe large amounts of cloud condensate produced by warm-rain processes below 4 km. Estimates of precipitation rates from a simple cloud model supp ort this interpretation.