July 2000
Temperature and Precipitation Anomalies.
The month of July was cooler and wetter than normal in the most of the Midwest. July 2000 was the 12th coldest in 107 years in the Midwest. The coolest state was Ohio, which had its 2nd coldest July on record. All states in the region averaged 1 Deg F or more below normal. However, the most unusual climate statistic was the lack of hot days. The pattern of high temperature departures in July (Figure 1) showed that almost the entire region was 3-6 Deg F below normal, while low temperatures (Figure 2) actually averaged somewhat above normal in most of the region. This indicates the importance of cloudy days and cool air masses from Canada in suppressing daytime temperatures. Many locations in the central Midwest reported the month of July was free of 90 F maximum temperatures for the first time in history. The Urbana, IL, coop station located at the MRCC has not reached 90 Deg F during the entire summer season through July 31 for the first time in 110 years of station history.
The Midwest as a whole experienced its 27th wettest July in 107 years. All states but Ohio and Kentucky were above normal in precipitation total, but no state ranked in the top 20 wettest years individually. The pattern of precipitation departures (Figure 3) indicates that northern and southern zonal bands of the Midwest were above normal, while a narrow band right through the middle of the Corn Belt from western Iowa to eastern Ohio was somewhat below normal, although usually by less than an inch. The northern part of the Midwest was frequently visited by low pressure areas moving through a persistent upper level trough over the Great Lakes. The southern portion of the Midwest was often at the frontal boundary between cool air masses from Canada and warm, moist subtropical air to the south. In both cases, clusters of thunderstorms were frequent events. While individual thunderstorms were often scattered, the precipitation map was gradually filled in due to the frequency with which they occurred in these preferred areas.
Growing conditions for corn were close to ideal in most of the Midwest during July, although in places it was a bit cool and wet for optimal soybean development. Drought still persists in west central and northwest Iowa, most of Nebraska, and in western and central Kentucky (Figure 4, Drought Mitigation Center). The month started off with three weeks of rather dry weather in much of the Corn Belt, but in the rarest of rare events, it was consistently cool, even though climatology most often associates dry weather with hot spells during the Midwestern summer. Given ample soil moisture, the cool and dry conditions were ideal for corn pollination, and a bumper crop in most of the Midwest was assured by the end of July. Soybeans, on the other hand, probably could have used more warmth, although drying soils helped in some regions that were saturated by the near record rains in June. Crop conditions peaked at the beginning of the third week of July, and declined the following week as the dry spell continued on just a bit too long. However, rain returned in the last ten days of July and the beginning of August, replenishing soil moisture to above normal levels in all of the Midwest except for a few locations in far northern Minnesota and Michigan, and the continuing drought areas in western Iowa and western Kentucky (Figure 5, Climate Prediction Center).
The month of July was very quiet overall, especially in the middle portion of the month when cool and dry air dominated. A wet first 10 days of the month brought some important severe events to the region. Flooding rains on July 3rd and 4th saturated much of Iowa, southern Wisconsin, northern Illinois, and northern Missouri before sweeping through the eastern states of the Midwest (Figure 6). Several inches of rain fell on saturated ground in northeastern Iowa, southern Wisconsin, and northern Illinois, causing widespread flash flooding and some renewed river flooding. Severe weather caused damage and flooding in Milwaukee. Mature trees were uprooted by winds approaching 90 mph, and several apartment buildings in a complex lost their roofs. In the Milwaukee metro area, 3-5 inches of rain fell in six hours, making this a 50-100 year event. In southeastern Wisconsin, 15,000 to 18,000 customer lost power. Governor Thompson will be requesting federal disaster assistance for the damages caused by this storm.
After a dry 7th, more heavy rain fell on the 8th and 9th with another movement of the frontal zone from north to south (Figure 7). Flash flooding caused significant damage in the Minneapolis, MN, area and in northern Wisconsin, and several more inches of rain fell in already wet areas of the north-central Midwest. In the St. Paul suburb of Eagan, 7.5 inches of rain fell at a station monitored by the National Weather Service, and even more fell in surrounding locations. Local officials estimated that 200 homes sustained major water damage, and many roads were submerged. In edition, severe weather and tornadoes also damaged homes and downed 1000 trees (Figure 8, Storm Prediction Center). The early estimate for damage in Eagan alone is $6 million. Northern States Power estimated that 190,000 customers lost power. Most tragically, an individual lost his life after being swept into a culvert in Lakeville while swimming in a flooded ditch with friends. In Wisconsin, Green Bay set its all-time 24-hour precipitation record for July, with 4.72 inches. Locations in the northern and eastern parts of the state experienced severe storms and flash flooding. Electricity was cut off to 18,000 customers in the affected areas of Wisconsin. Late on the 9th and early on the 10th the storms reached Iowa and Illinois. More than 3 inches of rain disrupted transportation and air travel in Chicago, and knocked out power to 17,000 in the metro area.
Severe weather affected a number of locations in the Midwest during the last week of the month. On the evening of July 25, severe thunderstorms along an advancing cold front brought a killer F4 tornado to Granite Falls, MN. One person was crushed to death under a pick-up truck, and 14 were seriously injured. Approximately 40 homes were completely destroyed, and several hundred more were damaged in a 12-block area of town. The mayor estimated that damage may exceed $7 million, and the governor has requested a federal disaster declaration for the area. A number of other tornadoes and sightings of severe winds and hail were also reported (Figure 9, Storm Prediction Center). Crop losses are also expected to be quite substantial, due mostly to hail damage in the central Wisconsin area affected by the storms. The following day, along the same front, a strong bow echo formed in western Iowa and traveled due south to rake the Kansas City metro area with fierce winds and strong rains (Figure 10, Storm Prediction Center). Approximately 100,000 customers lost power in the windstorm, and hundreds of reports of minor building and tree damage were received by the local police. Finally, the storms and rain produced by a stationary upper level low near Lake Michigan tremendously complicated air travel in both Chicago and Detroit, where major airline hubs are located. Hundreds of flights were canceled at both O'Hare and Detroit since July 28, and many more have been seriously delayed. On the beneficial side, though, electrical utilities are not being strained to supply excessive amounts of power as is happening in the West, and individual homeowners are not running air conditioning nearly as much as during a typical July in the Midwest.