The May Day Weekend Floods: How it Happened


The May Day Weekend Floods of 2010: How it Happened

The incredible amounts of rainfall that inundated the region over the weekend were a result of a complex weather setup. Below, you will find and image explaining how so much Gulf of Mexico moisture was able to find its way into the Ohio Valley, and why it stayed for such a prolonged period of time. Many locations in south central Kentucky along the Tennessee border received 8 to 10 inches of rainfall from early Saturday morning (May 1) to late Sunday evening (May 2). The copious rain that fell caused widespread and dangerous impacts across the region, including flash flooding, areal flooding, mudslides, dam failure, road closures, evacuations, and swift water rescues. Almost all streams and rivers in southern Indiana and central Kentucky have already or are forecast to reach some sort of flooding. Areas along the Green River in south central Kentucky were forecast to reach Major flood criteria, which will have significant impacts on local communities. Dunham Lake Dam on the south fork of the Little Barren River  in Metcalfe County was put at a high risk of failing due to flood waters eroding the barrier. The Dunham Lake Dam has since been stablized.

Nearly the entire southern Indiana and central Kentucky warning area was put in a flood emergency Sunday and Sunday night. Below, you will also find a map of the total rainfall for the entire event and some flood pictures from around the region.

Above is the meteorological setup that allowed plentiful amounts of Gulf of Mexico moisture into the region. The strong high pressure anchored off the mid Atlantic coast helped to stall the frontal boundary over the mid Mississippi River Valley. This also tightened the pressure gradient between the two systems, which strengthened the near surface winds. A 50 to 60 knot low level jet of winds was able to quickly and efficiently transport the incredible amounts of moisture. Waves of low pressure at the surface, combined with waves of energy aloft help kick off showers and thunderstorms. With so much moisture to work with, the showers and thunderstorms produced incredible rainfall rates of 1 to 2 inches per hour in some spots!

Above is an image of total rainfall received from early Saturday morning through late Sunday evening. Notice the large swath of 8 to 10 inches across south central Kentucky. Southern Warren county received just over 10 inches!

Above is an image from NESDIS showing the intense plume of moisture advecting northward from the Gulf of Mexico to our region early Saturday morning. The darker colors indicate higher moisture content.


Pictured above is the Dunham Lake Dam in Metcalfe County. As so much water rushed over the spillway, the base of the dam was eroded. The dam has since been stabilized.

Pictured above: Flood waters affecting a home in Monroe County.

Turn Around Don't Drown!!! Four Fatalities occurred in central Kentucky over the weekend due to the flooding.


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