July 1-9, 2006
Midwest Weekly Highlights - July 1-9, 2006
The first week of July featured less than normal summer-time conditions, with a large deficit in precipitation amounts across much of the Midwest. The average daily temperature departures across the Midwest illustrate that much of the region was generally below average for this time of year (Figure 1), with a hint of an unusual north-south gradient. The northernmost portion of the Midwest, including locations from northern Minnesota eastward into northern Wisconsin and Michigan were actually 1-4°F above average for the first week of July. Meanwhile, locations further south, including all of Iowa, Illinois, Missouri, Indiana, Ohio, and Kentucky were all actually below average, generally 1 to 3°F below average, especially across southwestern Missouri and much of Ohio.
Precipitation for the
week was sporadic at times across the Midwest, with the heavier
precipitation falling across the Ohio River just east of Cincinnati,
OH. This week, parts of southeastern Ohio received between 125
and 175% of normal precipitation, while much of central Minnesota into
central Wisconsin had less than 10% of normal precipitation (Figure 2).
Much of Illinois, Michigan, Iowa, and Missouri saw precipitation
totals that were less than 50% of normal for the first week of July,
generating drought concerns across Missouri, Iowa, and western
Illinois. The lack of widespread, significant precipitation
across northern Minnesota has begun to affect topsoil moisture and
crops growing in this area. In fact, crops and native vegetation
are showing signs of wilting (University of Minnesota). Total
rainfall since May 1 across some areas of northern Minnesota, including
Alexandria, Hibbing, and Moorhead, is less than 50% of average (Figure 3),
whereas locations further south, including Minneapolis, is showing
roughly 60% of normal rainfall over the same period.
Consequently, these areas of the Midwest are currently
experiencing "Abnormally dry" conditions, or D0 on the Drought Monitor (Figure 4).
Drought is expanding in the north woods of Wisconsin as well, as
general streamflows in major rivers continue to slow.
Heat and Humidity Fuel Thunderstorms
On Saturday, July 1, a cluster of supercell thunderstorms erupted across central Wisconsin (Figure 5), producing 3.00 inch hail near Oconto, WI and damaging a number of vehicles and destroying corn crops in the area. As the evening progressed, a line of storms congealed and moved east-southeast into lower Michigan and southern Wisconsin. These storms formed at the leading edge of a cold front in the summer-like airmass that had engulfed the Midwest from July 1-3, and slowly retreated back towards the Gulf Coast states as the week progressed. High temperatures surged well into the 90's across the Midwest (Figure 6), and this continued through the holiday weekend. A stalled frontal boundary (Figure 7) was found across central Iowa, across northern Illinois, and into western Ohio during the early part of the week, resulting in continued rain and storm chances nearly each day, some of them becoming severe. On July 3, in Bloomington, IL, patriotic citizens attending a festive concert were forced to seek shelter at nearby concessions stands, before it was canceled, because of high winds, large hail, and heavy downpours. In Manitowoc, WI, crop damage was clearly evident as fields of corn were either stripped by hail or blown over by strong downburst winds on July 1. Hail up to one-inch in diameter fell in downtown Manitowoc, which littered the city with leaves and twigs. More detailed severe weather reports can be found at the Storm Prediction Center's website: July 1, July 2, and July 3.Quiet Weather to End the Week
Following the passage of the slow-moving cold front on July 4-5, cool high pressure filtered into the Midwest, ushering in noticeably drier Canadian air. This high pressure center settled over the Midwest for much of the remainder of the first week of July, bringing generally near, to slightly below average temperatures (Figure 8). The cool high pressure resulted in a few new record low temperatures on the morning of July 7: Springfield, IL 53°F (was 53°F in 1983), and Ottumwa, IA 52°F (was 53°F in 1979). There was also one record low maximum temperature, set at Jackson, KY on July 5 of 71°F (was 72°F in 1999). The cool temperatures were felt across a large portion of the Midwest, evident in the morning map from July 6, indicating locations with minimum temperatures at or less than 55°F (Figure 9). The airmass was also quite dry, especially across the drought areas of Missouri, including the Ozarks. In fact, dewpoint temperatures, an absolute measure of atmospheric water content, were in the middle 40's (°F) during the afternoon on July 6. Historically, this part of Missouri sees dewpoint temperatures this low less than 1% of all July days since 1948! The dry low-level airmass allowed for an ideal viewing of the space shuttle Discovery, which was docking with the International Space Station on the evening of July 6. However, observers across much of the Midwest had to peer through a smoke-filled sky. A large area of forest fires, burning some 900,000 acres across Saskatchewan province in Canada, were sending smoke high up into the troposphere, and upper level winds out of the north-northwest carried the smoke as far south as Kentucky during the day on July 6. The following two satellite images were assembled by the National Weather Service Office in Springfield, MO (Figure 10, Figure 11).
The first week of July ended with a cold front slicing through the upper-Midwest, across Minnesota, Wisconsin, and Michigan. The system brought some very heavy rain to parts of southern Wisconsin, including a whopping 3.68" storm total rainfall in West Allis, WI. In addition, Milwaukee, WI recorded it's 24-hour rainfall at 2.76", which set a new record for July 9. Radar images from 8pm on July 9 show a few isolated cells along the trailing cold front across southern Wisconsin (Figure 12). These cells moved very slowly to the east-southeast, which resulted in the large rainfall totals.There are signs that the second week of July could be quite warm across the western portion of the Midwest. Will this come to pass, and how will it affect residents across these areas? Find out in next week's edition of the Midwest Climate Watch.
Kruk