July 2006
Midwest Overview - July, 2006
The month of July featured several new record temperatures near the end of the month, several important thunderstorm events, and a noteworthy drought across the upper Midwest. At the end of the month, the average daily temperature departures across the region for July were generally above normal, ranging from 4-7°F above normal across northern Minnesota and Wisconsin, to 1-3°F above normal across the remainder of the Midwest (Figure 1). Despite warmer than average temperatures to conclude the month, below normal temperatures were fairly regular across the Midwest during the early portions of the month, save Minnesota and Wisconsin, which helped balance out the month as a whole. As part of the intense heat and drought conditions across northern Minnesota, Duluth, MN recorded their warmest July since records began in 1870. The average monthly temperature in Duluth, MN for July 2006 was 71.9°F (6.4°F above average), which breaks the previous record of 71.7°F set in July 1881.
Precipitation for the month was generally near or above average for a good portion of the Midwest, except for much of Minnesota and western Wisconsin, who were drier than normal (Figure 2). "Extreme drought" was found across this region near the end of the month as streamflow analysis showed major rivers and streams with discharge rates less than 2% of normal. The heaviest precipitation fell across northern Indiana and into northern Ohio, where flooding rains were a common theme this month. In these areas, precipitation totals were 150 to 200% of normal for the month of July. In fact, South Bend, IN experienced their wettest July on record with over 8.60" of rain during the month, and Urbana, IL, who with 7.85" of rain recorded their 8th wettest July since records began in 1889. Further south, in Paducah, KY, the 8.02" of rain measured during July 2006 ranks them as the 5th wettest on record. Finally, in Toledo, OH, the total rainfall in July was 9.19", which ranks them as their wettest July on record. The previous record was 8.49" set way back in 1881.
Hot, Dry, and Destructive July
The month of July began with temperatures above normal, followed by a rather significant cool-down. This cool weather featured minimum temperatures several degrees below average, including some locations across the Midwest with morning low temperatures in the 40's (Figure 3). The upper level low responsible for the cool weather slowly pulled east by the end of the first week of July, forcing northwesterly flow aloft to take up residence. This allowed smoke from forest fires in Saskatchewan to filter south into the Midwest, resulting in very milky or hazy skies (Figure 4). Once the smoke cleared, high pressure settled in and allowed for return southerly flow to set-up across the Midwest. The ushering in of hot and humid air against departing cool weather resulted in numerous scattered thunderstorms that were prolific rain producers (Figure 5). The cloud cover and additional surface moisture tempered maximum temperatures from getting too extraordinarily hot over the second week of July, although drought-plagued regions of northern Minnesota and Wisconsin saw significantly above average temperatures on account of the dry soils.
The third week of July featured the most extreme weather of the month by far, with several bow echoes traversing the Midwest and striking major cities. Additionally, these thunderstorms fired in a very hot and humid environment, where daytime temperatures were recurrently over 90°F (and even 95°F in some locations). The most notable bow echo this month started out across southern Minnesota, producing numerous power outages, before diving east-southeast into northern Iowa and western Illinois. Once into Illinois, the storms were able to tap the extreme heat and humidity as they continued their path of destruction southward. Much of central Illinois was hard-hit by this complex of storms, including the capital city of Springfield, IL, which was devastated by a large tornado in March, 2006 (Figure 6, National Weather Service Lincoln, IL). As the late-afternoon progressed, the storms took a southwestward turn, and eventually made a direct hit on St. Louis, MO, during a Major League Baseball game (Figure 7). The bow echo caused concession stands to bounce around, blew down trees near the Gateway Arch, and was responsible for the collapse of at least three buildings. In all, over 30 persons were injured during the event, but the bigger story would follow in coming days as over 500,000 persons were without power during a long-lasting notable heatwave. At least seven persons died from excessive heat and no electricity, or were unfortunate victims of downed live power lines.Unfortunately for the residents of St. Louis, MO, just two days later another strong and damaging bow echo slammed into the city and then later trekked across southern Illinois, southern Indiana, and much of Kentucky causing widespread damage (Figure 8). Those who had electricity restored in St. Louis, MO from the previous storm were once again without it as the second bow echo caused even more damage to existing trees and infrastructure. Consequently, over 500,000 customers were once again without power, and it would take over a full week before electricity was fully restored.
Finally, as the month came to a close, intense heat moved eastward from the Rocky Mountains and took hold over the Midwest. Temperatures exceeded 100°F frequently during the final 3 days of the month, and over 20 new high maximum and high minimum temperature records were established, primarily across Wisconsin, Minnesota, and Michigan. On July 31, every state in the Midwest was involved in some sort of heat-related advisory from local National Weather Service Offices (Figure 9). For many, July of 2006 will be remembered as hot, dry/wet (location dependent), and destructive.
Kruk