September 1-9, 2011
Midwest Weekly Highlights - September 1-9, 2011
Record-Breaking Heat to Start September
Unseasonably hot weather was present over a majority of the Midwest for the first three days of September. Temperatures were at least 6°F above normal across the region, with the exception of western Minnesota and Iowa. A large area, which extended from central Missouri through Illinois, Indiana, Ohio, northern Kentucky, and Michigan, experienced temperatures that were 10°F to 14°F above normal (Figure 1).
Triple-digit heat was recorded in six of the Midwest states, with the exclusion of the three most northern states (Minnesota, Wisconsin, and Michigan). This extreme heat broke 201 daily high temperature records (66 tied), with at least one record being broken in each Midwest state.
The highest temperature recorded during the first three days of September was 105°F in Clinton, Missouri (Henry County) on the 1st, which tied the record for this date. On the same day, Clinton also tied the daily record for highest minimum temperature of 77°F.
Second Half Cool-Down
The second half of the week cooled down substantially, with the majority of the Midwest shifting from above normal temperatures to below normal temperatures (Figure 2). A majority of the region experienced an average maximum temperature from September 4-9 of 65°F to 78°F (Figure 3).
In contrast to the first few days of September, numerous locations broke their daily record for lowest maximum temperature after September 4th when below average temperatures took over the region (275 records set, 82 tied). There were 83 stations in the Midwest that broke or tied both highest maximum temperature daily records and lowest maximum temperature daily records within this nine-day period. For the period as a whole, temperatures ranged from 0°F to 3°F above normal from the northern to eastern fringes of the region to 3°F to 4°F below normal across the remainder for the region (Figure 4)
Dry Weather Persists
The first nine days of September were drier than normal for a large portion of the Midwest Parts of Minnesota, Missouri, and southern Illinois received only 2 to 25 percent of their normal precipitation. However, some regions received more than normal. Kentucky and Ohio received ample precipitation as the remnants of Tropical Storm Lee moved over the region (discussed in more detail below). Northeast Iowa, southwest Wisconsin, and northwest Illinois also received 150 to 300 percent of normal precipitation (Figure 5).
As of September 6 on the U.S. Drought Monitor, southeast Iowa, central Illinois, part of central Indiana remain in Severe Drought for the second week in a row, and not much precipitation relief was brought to these regions in the first nine days of September (Figure 6).
Tropical Storm Lee Drenches Kentucky and Ohio
The remnants of Tropical Storm Lee produced heavy rainfall for areas of Kentucky and Ohio from Sunday, September 4 until Wednesday, September 7 . Southeast Kentucky experienced the heaviest precipitation, with some locations receiving close to 7.00 inches of rain (Figure 7). The rainfall from Tropical Storm Lee broke an all-time precipitation record in Letcher, Kentucky (Letcher County) when 4.30 inches was recorded on September 6th. Overall, the heavy precipitation produced minimal flooded and was determined to be more beneficial than anything for Kentucky.
Severe Weather
Frontal lift and high temperatures produced severe thunderstorms that progressed through the Midwest on September 2nd and 3rd, producing high winds and hail throughout the region (Figure 8). High wind reports of over 74 miles per hour were recorded in Iowa and Wisconsin on September 2nd and large hail with a diameter of 2 inches was recorded in Centreville, Michigan (St. Joseph County) on September 3rd. Several college football games were interrupted by severe weather, notably the Notre Dame vs. South Florida game and the Michigan vs. Western Michigan game on September 2nd. The Notre Dame-South Florida game was delayed twice, with the longest delay at a little over two hours. The Michigan-Western Michigan games was cancelled after three quarters because of severe weather and lightning in the area. After the first few active days of September, it was fairly quiet around the Midwest in terms of severe weather.
-MW/SDH-