August 15-24, 2003
Midwest Weekly Highlights - August 15-24, 2003
Hot and Dry Weather in the Midwest
The period August 15 to August 24 was very dry and warm in the Midwest. Some locations in the central Midwest received zero rain during this period, and even areas with some rain did not received enough to reverse a downward trend in crop quality or soil moisture status. Some locations around the outer rim of the Midwest have received near normal precipitation for the 10-day period, including northern Minnesota and Wisconsin, and large portions of Kentucky (Figure 1). Most of the Midwest received less than 50% of normal precipitation for the period, with only a few of the wetter spots just reaching normal (Figure 2). Temperatures were 6-10°F above normal for the period in the western half of the Midwest (Figure 3), with some cities like Kansas City and St. Louis visiting the 100°F mark repeatedly. Unlike earlier in the summer, high temperatures have persisted in the western half of the Midwest during this dry period, greatly accelerating drought development (Figure 4, National Drought Mitigation Center). The key stories for the period include the most intense heat wave in several summers in the Midwest, rapid intensification of drought with related crop damage, and some isolated severe events, including flash floods in Kentucky that took two lives.
Heat Wave
Starting on August 16th, and continuing until the end of the period (the 24th), a major heat wave blanketed the Great Plains and western Midwest. The first pulse of the heat wave abruptly intensified on the 17th, with record temperatures set at places in southwestern Missouri, and temperatures reaching 107°F in Cole Camp, MO, and Weir, KS. Kansas City, the largest city in the heat wave region, started a 6-day stretch on the 16th with maximum temperatures above 100°F, and exceeding 103°F between the 17th and 21st (Figure 5). Even International Falls, MN, tied its daily maximum temperature record of 95°F on August 19th. The heat most severely impacted Missouri and Iowa, closing non-air-conditioned schools and severely hampering crop growth in already dry conditions. The peak day of the heat wave was August 21, when the intense core of the heat spread all the way across Missouri (Figure 6a and Figure 6b). Record high temperatures were set in Kansas City (106°F), Columbia (105°F), St. Louis (104°F), Rolla (102°F), and Springfield (100°F). Fortunately, the dew point temperatures remained in the lower 70's during the warmest period of the day, capping the heat index at just over 110 in both Kansas City and St. Louis. St. Louis declared a heat emergency and opened more than 60 cooling shelters. Kansas City was also proactive in protecting its population. The electrical grid was able to deliver the record power levels needed in both cities to maintain air conditioning. Even though the low temperature for the day was 80°F in St. Louis, the city was able to get through the day with no reported heat related deaths, which is a tremendous credit to their heat wave action plan. Unfortunately, two elderly people in Kansas City were found dead in their non-air-conditioned homes after the peak of the heat wave, and their deaths have since been classified as heat-related.
Drought
The heat wave compounded the difficulties already ongoing in the region due to the recent lack of precipitation. Most of the Midwest had adequate and timely rains during May and June (Figure 7a), with conditions still favorable in most of northern Iowa and Illinois through July (Figure 7b). Unfortunately, in the last 30 days, precipitation was less than 50% of normal over the western and central Midwest (Figure 7c). The drought status increased substantially over the previous week in the August 19 US Drought Monitor map (Figure 4, NDMC), and conditions have continued to deteriorate through the end of the period. In the 18 leading states for corn and soybean production, the percentage of corn rated good or excellent has diminished 15% in the last two weeks, and soybeans have declined 14% over the same period. Prices for both commodities have been rising in response. Some of the worst impacts have been noted in northwest Missouri, where the area encompassing extreme drought on the USDM map expanded once again in the past week. This area has never fully recovered from last year's drought, despite good spring rains, and so it also has strong hydrological impacts such as lowering of water tables and drying of livestock ponds. Early tree leaf turning has been noted in the Kansas City, MO, area. Soils are so dry in Missouri and much of the Great Plains that not only are summer crops being severely impacted, but there are now grave concerns for the planting of winter wheat this fall. The federal government has approved emergency haying of conservation lands in 24 counties in northwestern Missouri, and the state has requested that an effort be made to generate a federal drought relief program. The losses due to last year's drought in Missouri were estimated to be $460 M in crops, livestock, and reduced economic activity, and climate anomalies this year will also generate considerable losses.
Elsewhere in the Midwest, drought impacts of various types were being observed and acted upon. In Minnesota, drought stressed soybeans were having difficulties with soybean aphids, and extra insecticides were sprayed over 1.5 million acres at a cost of $15 M. Early leaf turning was widespread in north-central and northeastern Minnesota. In Wisconsin, a state-wide drought emergency was declared by the governor's office. While this drought has had the benefit of reducing the mosquito population, there have been substantial reductions in crop yields, and losses of various tree and bush fruits. City officials in Milwaukee encouraged home owners to water street trees so as to reduce stress levels and keep them healthy. Local experts say that this is the worst drought in Wisconsin since 1988. In Iowa, crops declined rapidly: corn quality ratings of good or excellent descended from 76% on August 10th to 46% on August 24th, and soybeans fell from 74% to 43% good or excellent. In fact, in some of the worst affected areas in Iowa, corn yields are expected to reach only 50% of normal. The combined heat and lack of rain also severely impacted pasture and grass crops throughout the northwestern two-thirds of the Midwest.
Severe Storms
Despite the lack of general precipitation, there were a series of severe weather outbreaks as a cold front passed through the area slowly, from August 20 to 23. On the evening of the 20th, strong storms raked through the Duluth, MN, area (Figure 8, NWS) with 70 mph winds, causing power outages and knocking down trees, but with little damage to homes. Further south, 5000 customers lost power in Cedar Rapids, IA, and a 90-foot silo was knocked down by strong winds. More storms formed the following night along the cold front in Michigan (Figure 9, NWS). About 15,000 customers lost power, and many severe wind and hail reports were noted (Figure 10, Storm Prediction Center). Many funnel clouds were seen, and one confirmed tornado touched down in southeastern Michigan and knocked down a house and damaged some other buildings. Fortunately, none of the occupants of the house were injured.
The worst events occurred in Kentucky the following day, the 22nd. A persistent and long lived cluster of thunderstorms (Figure 11, NWS) dropped large amounts of rain over relatively small areas in two to four hours, accumulating local totals of up to 6 inches as estimated by radar (Figure 12, NWS). Near Frankfort, KY, a flash flood along Stony Creek undermined a house on its banks and collapsed the house into a 10-foot tall wall of rushing water. Two were confirmed dead in this incident. Some 57 homes were destroyed or damaged to the point they could not be occupied, leaving more than 150 people homeless. Many severe events were caused by storms throughout Kentucky (Figure 13, NWS), and damage was widespread but lighter away from flooded areas.