A Very Wet Spring For Northern Ohio
The National Scene
Residents of northern Ohio will remember the extraordinarily wet and gloomy spring of 2011 for many years. Ohio was located in a large area extending from the lower Midwest northeast up the Ohio valley that experienced record breaking precipitation and flooding during April and May. The images in the two panels below show the observed precipitation for April and May (left-hand side) and the departure from normal for each month (right-hand side). In April, the total precipitation across much of the lower Ohio valley was in the range of 15 to 20 inches, an amount that was nearly 600% of the long-term average. Many long-standing records fell during the period and rivers across the region and the lower portion of the Mississippi River reached historic levels.
The pattern of precipitation in May was remarkably consistent with April. While the total precipitation received across this region in May was less than April, it was still significantly above normal.
The Local Scene: Northern Ohio
From January 1 through May 31, 2011 the total observed liquid precipitation at Cleveland-Hopkins Airport was 25.35”, a whopping 10.77” (73.9%) above normal. The precipitation during April and May was particularly heavy, with a new record of 6.89” being set in April; an amount more than twice the long-term average of 3.37". The previous record for April of 6.61" had persisted since 1961. As might be expected, there were wide variations in the April precipitation totals at other locations across northern Ohio. Akron-Canton, the farthest south of the cities examined received only 4.94", an amount only 1.55" above normal. The observations for Toledo, Ohio and Erie, Pennsylvania were similar to Cleveland at 6.33" and 6.38" respectively. The totals at Toledo and Erie were above normal, but well below their records.
At least a trace amount of precipitation was observed at Cleveland-Hopkins on twenty-two of the thirty days (73%) in April. Significant rain fell from showers and thunderstorms on April 4 (1.3"), April 19 (.95") and April 25 (1.70"). These three days alone contributed approximately 57% of the total precipitation received in April. In spite of the abundant rain and overall gloomy conditions, the average monthly temperature was 50° F which was 2.4° F above normal.
The record for precipitation at Cleveland-Hopkins for May is 9.14" which was set in 1989. While the total for May 2011 (7.74") did not exceed this amount, it was nearly 4.25" higher than the long-term average of 3.5". This places it second on the list of wettest Mays. Similar to April, the precipitation across northern Ohio was uneven with Akron-Canton recording 7.25" and Toledo and Erie accumulating 5.88" and 8.54" respectively. The total precipitation at Erie was 5.2" above their May average of 3.34".
At least a trace of precipitation fell at Cleveland-Hopkins on all but six days (80%) in May. The rainfall on just four days; May 14 (.82"), May 18 (.89"), May 23 (.84") and May 25 (1.22") produced nearly 50% of the rain for the entire month.
What prompted the record rainfall? To answer that question, we must examine the atmospheric conditions a few miles above the surface and several hundred miles to both our west and east.
|Special Note: The analysis presented on the following pages requires an understanding of surface and upper-air weather charts. If you are unfamiliar with these resources or need a refresher, please review this instructional page.|