Temperature and Precipitation Anomalies.

May 2001 was the 16th wettest May for the Midwest as a whole (Figure 1). During the month, the main axis of rain shifted from the flood-prone northwestern portion of the region to the dry eastern part of the region. The copious rains in Iowa, Minnesota, and Wisconsin in the first half of the month (Figure 2a) caused a second flood crest to seriously impact Mississippi River towns from St. Paul to Hannibal. However, after mid-month the precipitation helped to ameliorate drought conditions in the southern and, especially, eastern Midwest (Figure 2b). Iowa received the heaviest precipitation during the first two-thirds of the month, and ended May averaging more than 3 inches above normal statewide, 7th wettest on record (Figure 3). Michigan was the wettest state for the whole month, ranking 5th wettest in 107 years.

A week after the switch of precipitation modes, around May 22, the first of a series of upper level lows brought cool, cloudy conditions to most of the Midwest. Temperatures went from 4-8°F above normal in the first two-thirds of the month (Figure 4a) to 6-12°F below normal in the last third (Figure 4b). Still, the Midwest ending up with its 37th warmest May in 107 years, and most locations were above normal for the month (Figure 5). No states had temperatures ranked in the top 25 warmest or coldest May's. However, some locations have set interesting marks for consecutive days of coolness since the third week of May. Chicago had 15 days with high temperatures below 70°F in late May and early June, setting an all-time record for the lateness in the year in which that happened. In addition, the Detroit WSO reported that they had only experienced 2 days with predominantly sunny conditions during May. In some areas, the lack of sunlight was more detrimental to some plants than the low temperatures themselves.

Climate and Agriculture.

Some of the drought stricken areas of the Midwest reached departures of 7 to 8 inches of precipitation below normal for the spring season by mid-May (Figure 26). In much of southeastern Missouri, southern Illinois, and southern Indiana, there was less than 50% of the normal precipitation for the March 1 to May 15 period. That same area experienced soil moisture levels at the fifth percentile (Figure 27, Climate Prediction Center) and stream flow values that were near or at record lows, except for the main stem of the Mississippi River, which carried a high flow level out of the flood region to the north (Figure 28, USGS). A number of crop districts in the drought area reported 75-90% of the farm land short or very short of soil moisture. In some places in Kentucky and Illinois, planting of soybeans stopped until there was some additional moisture in the topsoil. Corn that was planted earlier was not germinating well in these areas, and some that had germinated wilted and died. The overall severe and moderate drought areas in the Midwest expanded by mid-May to cover a large portion of the eastern and southern Midwest (Figure 29, National Drought Mitigation Center).

The rains of the following week caused the amount of farm land with soil moisture rated short or very short to decline 8% in Illinois, 25% in Indiana, 7% in Kentucky, 14% in Michigan and Missouri, and 31% in Ohio by May 20. While drought continued in the Ohio Valley, Kentucky, and southern Missouri, the northern and eastern reaches of the drought were curtailed, and the intensity of the drought was reduced, especially in the topsoil layer (Figure 30, National Drought Mitigation Center). Corn planting in the eastern and southern Midwest was already nearly completed before the heavy rains arrived. In these areas, some replanting will be necessary where rains washed out fields, and in places that suffered seed dry rot or plant death due to the previous dryness. In the western and northern Corn Belt, planting largely caught up with seasonal norms as farmers worked as fast as possible to plant seed in the newly accessible fields. However, some areas along the Mississippi River were still flooded, and may miss being planted this year.

Due to the spring drought, a panoply of bug infestations have attacked the drier areas of the Midwest. A significant outbreak of army worms seriously degraded wheat and hay in the drought areas of southern Missouri, Illinois, and Indiana. The most important insect impact may have unfolded in Kentucky, where $150 M in losses in the thoroughbred horse industry have been attributed to Mare Reproductive Loss Syndrome. The latest theory for the losses of pregnancies by mares and deaths of foals is that eastern tent caterpillars abandoned their normal place in black cherry trees and moved to the pasture grasses after a late April freeze damaged the tree vegetation. This occurred after a warm and early spring caused a greater than normal number of these insects to be present. These caterpillars concentrate cyanide from the leaves of the black cherry tree in their droppings, and have enough to kill a mouse in their bodies. Some of these caterpillars, and considerable amounts of their droppings, may have been ingested by pregnant mares and foals eating grass in the pastures. Meanwhile, in the overly wet zones of the Midwest, mosquitoes, gnats, and ticks are predicted to be a greater than normal nuisance this coming late spring and summer. In fact, Minnesota press reports indicate that they are already having a bad mosquito season in wet districts.

Iowa, Michigan, Minnesota, Ohio, and Wisconsin exceeded 45% of farmland with surplus soil moisture ratings in USDA reports for May 27. Kentucky showed a great recovery, with a 65% short/very short rating in topsoil moisture becoming only 16% short/very short in one week. However, most of the driest areas in western Kentucky, southwestern Indiana, southern Illinois, and southeastern Missouri did not get much rain, less than 50% of normal in some areas during the period May 23-29 (Figure 31). Moderate drought persisted over this area, with some locations classified as in severe drought. The rain over the second half of May, though, really perked-up the corn and soybeans in previously dry areas. Corn emergence exceeded 75% and soybean emergence exceeded 50% in the southern and central Corn Belt, although emergence was well behind normal in Minnesota, Wisconsin, and the Dakotas. The chief problem at the end of the month was the lack of sunlight and warmth to dry the saturated soils and provide for healthy growth. Corn quality ratings on May 27 were generally above 60% good/excellent and soybeans exceeded 50% good/excellent in most states, but there were persistent reports of yellowing leaves and slow growth rates. The corn and soybeans were in a tenuous position at the end of the month, but could still recover to near-normal yields with a rapid return to warm and sunny weather with seasonable precipitation.

Extreme Events and Impacts.

The severe weather season in the Midwest had been fairly light up to the beginning of May. It appeared, however, that the Midwest might switch to a more active mode when there was a widespread severe weather outbreak on May 1. Severe storms along a stationary boundary had noteworthy impacts on northern Iowa, eastern Minnesota and adjacent parts of Wisconsin (Figure 32, Storm Prediction Center). An outbreak of 17 tornadoes affected this area in the afternoon and evening. The most significant tornado, an F-2 on the Fujita scale, damaged 40-50 buildings in Glenville, MN, including the local car wash and grocery store. Damages were estimated to exceed $2 M. Most of the 21 mile path of the storm was in open country, where several homes and farm buildings were also heavily damaged. Fortunately, there were no deaths and only a few minor injuries report.

Further north, the most damaging force was hail. A major severe hail storm traversed the Minneapolis-St. Paul area on the evening of May 1. The nearby community of River Falls, WI, reported massive damage to cars and house windows and roofs, as the large diameter hail (golf-ball sized) was whipped by 70 mph winds. Entire sides of dormitory buildings at the University of Wisconsin-River Falls had hundreds of windows broken out by hail, and the greenhouses on campus were destroyed. Power was also knocked out to the community, which is thought to have suffered more than $2 M in damage by local insurance brokers. However, the greatest financial toll will still be in the Twin Cities, where 1.5-2.0 inch hail brought in hundreds of insurance claims the day after the event. Allstate and State Farm insurance companies declared a "catastrophe" had occurred in order to bring in mobile claims offices. State Farm alone expects about 10,000 claims for houses and 5,000 for cars to be filed in the Minneapolis-St. Paul area.

Heavy rains in Michigan and Ohio on May 15-16 brought about extensive flash flooding and some river flooding. Some locations in Michigan around Grand Rapids received up to 8 inches of rain according to radar (Figure 33, NWS). Grand Rapids WFO received 5.25 inches over the two-day period. Ross County in south-central Ohio experienced more than $1 M in flood damage, and a number of counties in Michigan and Ohio were being considered for disaster status. Late in the week, on May 21, a severe weather outbreak produced at least 13 confirmed tornadoes in Michigan and 2 tornadoes in Ohio (Figure 34, Storm Prediction Center). While no one was killed, several were injured and extensive property damage occurred, especially with an F-2 tornado near Richland in Kalamazoo County, MI.

While isolated events of severe weather took place throughout the last 9 days of May, one significant outbreak of tornadoes struck the Fort Wayne, IN, area on May 26 (Figure 35, Storm Prediction Center). One tornado created a 500 yard wide damage path through some suburbs of Fort Wayne, peeling the roof off a retirement home, severely damaging houses in the Paper Mills Subdivision, and damaging a number of commercial buildings. While 45 people at the retirement home were evacuated and are temporarily homeless, only two injuries were reported. Otherwise, severe weather events were limited to isolated wind and hail damage. Unlike the pattern on May 1, the rest of May had much less severe weather activity than during a normal spring.