The Effects of Extreme Precipitation Events on Climatology

Extreme weather events can drastically affect the local climate. For example, in September 2010, Albany, New York received 0.76 inches of rain over the first 29 days of the month. On 30 September, 2.68 inches of rain fell in association with a quasi-stationary boundary, resulting in a 0.13-inch precipitation surplus for the month. On paper, the total precipitation recorded for this month appears to be nearly normal. However, this “normal” month resulted from a singular extreme event. During May 2007 in Albany, NY, relatively small amounts of precipitation fell on 8 separate days, resulting in a cumulative monthly rainfall total of 3.51 inches, near the mean of 3.67 inches. Despite the extreme variation in these two monthly precipitation distributions, both of these months appear on paper to be “normal”. While statistical analyses were performed on ten geographically different cities across the United States, this presentation will focus only on Denver, Colorado and Tampa Bay, Florida. For each city, a 30 year summertime climatology of daily precipitation totals spanning 1981-2010 precipitation will be presented to show whether “normal” monthly cumulative precipitation is typically made up of several days of little precipitation, or a few days of extreme precipitation. Additionally, representative case studies will be highlighted illustrating how meteorological conditions can result in a “normal” month of precipitation comprised of an extreme precipitation event.