National composites of radar reflectivity were converted to rainfall rate using Z=300R^1.5, where Z is reflectivity factor in mm⁶m^-3 and R is rainfall rate in mm h^-1. The latitude averaging interval for the time-longitude diagrams was 30-48 N, while the averaging interval for the time-latitude diagrams was 115-78 W.
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methodology

These diurnally-averaged time-longitude plots show the percentage of time that the area-averaged rainfall rate met or exceeded 0.1 mm h^-1 for each longitude and time-of-day, averaged from 33 to 48 N, unless otherwise noted in the figures. Some plots are associated with animations showing the hourly frequency of precipitation over the full lat-lon domain. more info