The above bar chart shows the hourly incremental rainfall values in inches for the epic rainfall event of May 1st and 2nd 2010 at Nashville, Tennessee. Bar charts are used by meteorologists to study rainfall events such as this one on a temporal scale. Saturday's (May 1st) rainfall at Nashville totaled 6.32 inches while 7.25 inches fell on Sunday (May 2nd) for an event total of 13.57 inches. There was a 12 hour period Saturday night in which very little rain fell at Nashville. The chart shows 7 hours of heavy rainfall on Saturday ( May 1st) and 9 hours on Sunday (May 2nd) for an event total of 16 hours of heavy rainfall at Nashville. Also note how the rain began Saturday morning (May 1st) in Nashville. Other than the spike in the rain between 6 and 7 am the rain basically ramped up during the morning hours to a crescendo between 1 and 2 pm in the afternoon before quickly falling off. The rainfall on Sunday (May 2nd) started in earnest between 6 and 7 am and continued heavy throughout the morning and into the afternoon before ending in the early evening. Rainfall of this magnitude and duration is unprecedented in the record books that date back to November 1870 for Nashville, Tennessee.
National Weather Service