July 25-31, 2006
Midwest Weekly Highlights - July 25-31, 2006
The final week of July featured dangerous heat, damaging thunderstorms, and record breaking warm temperatures. The average daily temperature departures across the Midwest indicate that the entire Midwest was above average for this time of year (Figure 1), with localized areas of significantly above average temperatures. The northernmost portion of the Midwest, including locations from west-central Minnesota eastward into western Wisconsin were 7-10°F above average, while locations across Kentucky, southern Missouri, and southern Ohio were above average by only 1 to 2°F. The remaining portions of the Midwest fell between 4°F above average to 8°F above average, especially across locations in Iowa, northern Illinois, and much of Michigan.
Precipitation for the week was largely sporadic but exceptionally heavy in areas that saw strong to severe thunderstorms. The heaviest precipitation this week fell across drought-stricken areas of northern Wisconsin, northern Minnesota, and western Michigan into northern Indiana and Ohio where numerous flash floods were reported. In northern Wisconsin, locations received between an astounding 500 to 600% of normal precipitation, scaling back some drought concerns, while another band of 200 to 400% of normal precipitation stretched from northern Minnesota southeastward into lower Michigan (Figure 2). Some areas of the Midwest did not receive beneficial rains this past week, including much of Kentucky, western Missouri, western Minnesota, and southeastern Ohio, with most areas receiving between 2 and 25% of normal precipitation. Elsewhere, and generally along and north of the I-74 corridor, precipitation was between 75 and 125% of normal for the final week of July.
Drought Update
Prior to the arrival of significant precipitation
across northern Minnesota and especially north central
Wisconsin, the drought status in this area of the Midwest
remained unchanged from the previous week, as the Drought Monitor
indicated "extreme drought" across this region of the Midwest (Figure 3).
In fact, topsoil moisture values were well below average across
the northern portion of the Midwest, especially across Minnesota and
Wisconsin
(Figure 4), but these values responded quickly to abundant precipitation at the end of the week (Figure 5).
Fire danger across the northern woodlands of Wisconsin was rated
"very high" during the early portion of the final week of July.
In Sawyer County,
WI, the rainfall deficit was nearing six inches (as of July 28), and
there are numerous wildfires occurring in the county. The
Governor of Wisconsin has declared a state-wide drought emergency,
which effectively bans much outdoor burning, including all fireworks,
charcoal grills, and outdoor smoking on combustible surfaces.
In Minnesota, 85% of the landscape's topsoil moisture was rated
"short" or "very short", which is a 10% increase from the previous
week. Agriculturally, pasture conditions and alfalfa are
currently being significantly impacted by the drought.
Flooding Downpours
The final week of July began with numerous showers and thunderstorms across the Midwest, including the drought regions of northern Wisconsin and Minnesota. On July 25, a cold front sagged slowly southward across northern Wisconsin, bringing some much needed rain to the region (Figure 6). However, at the time, the rainfall was generally too widely scattered to make a dent in the long-term moisture deficits, and much of the thunderstorm activity was accompanied by large hail (July 25 storm reports). This same front continued southward on July 26, and interacted with a very moist atmosphere (characterized by precipitable water values greater than 2.00" across portions of the Midwest), to produce additional scattered heavy thunderstorms. Some thunderstorms rapidly became severe across central Illinois, producing at least three tornadoes (July 26 storm reports). These storms then "trained" over the same locales, producing flash flooding. Over 6.00" of rain was measured by a cooperative weather observer in central Piatt County, IL, which is considered a one in 50 year event. Heavy rains continued across east-central Illinois on July 27, prompting new flash flood warnings as storm total precipitation estimates by Doppler radar were in excess of 7.00" across portions of this area (Figure 7).Strong to severe thunderstorms also plagued the Chicago, IL metropolitan area on July 27, producing excessive rainfall totals, and stranded at least 1,000 travelers at Chicago's O'Hare International Airport. In fact, at both of Chicago's airports most passengers experienced delays of up to 3 hours during the height of the severe weather. Several funnel clouds were sighted across the southern suburbs, and very close to the National Weather Service Office of Chicago (located in Romeoville, IL). Further south, in Iriquois County, IL, a 10-mile stretch of I-57 was closed as a downburst snapped 30-40 power poles which were strewn over the interstate, blocking traffic.
Before the storms reached the Chicago, IL area, they pounded portions of southern and eastern Wisconsin. The city of Waukesha, WI, was hit particularly hard, and reported nearly 6 inches of rain from the event. An antique store in Waukesha, WI filled with customers and employees had to be evacuated as water began dripping down walls. Damage to antiques appeared likely, and according to initial estimates, damage costs could exceed $100,000. The storms also took their toll on the state capital of Madison, WI with up to 5 inches of rain, which resulted in the flooding of parts of the University of Wisconsin-Madison campus, leaving ponds of standing water nearly 5 feet deep. Lids from storm sewers popped off in several locations as well, allowing the water to rush over curbs and into nearby businesses and homes. Two buildings on the campus of the University of Wisconsin-Madison were severely damaged by the flood waters, and the damage was compounded by water main breaks and broken storm water pipes in the Computer Sciences and Veterinary Medicine buildings. Overall, the hardest hit counties were Waukesha, Racine, and Kenosha counties, along with Dane county, where Madison, WI is located.
In Eastlake, OH, flooding rains in excess of 9 inches filled rivers and streets in this northeastern Ohio town, and police were forced to respond to a day care center that was taking on water. In Painesville, OH, rising water resulted in the evacuation of at least four residential streets, and the Lake County, OH Administrator estimated that over 100 people were displaced from their homes due to the flooding rains. The Grand River, which runs near Painesville, OH, was already 4 feet above flood stage as of the morning on July 28, and it was expected to continue rising. Finally, in nearby Mentor, OH, more than 100 children were rescued from Ridge Pointe Child Care Center on July 27 as 3 to 4 feet of water, which had flooded the parking lot, began to seep into the building. Children were pulled out of the building through windows and were then bused to a nearby fire station where parents could pick them up.
Extreme Heat Returns to the Midwest
As the final week of July came to an end, the upper level ridge responsible for some 140+ heat-related deaths in California nudged eastward, engulfing much of the Midwest. Temperatures surged into the upper 90's across much of Minnesota on July 28 (Figure 8), while dewpoint temperatures remained in the upper 60's and lower 70's (°F). This resulted in peak afternoon heat index values well over 105°F, and into the "danger" category (Figure 9). Many heat advisories, excessive heat watches, and excessive heat warnings were in place for much of the Midwest during the final days of the month. In fact, on July 31, every state in the Midwest was under some sort of heat-related advisory (Figure 10, National Weather Service)! High temperatures on July 29 climbed into the low 100's again across the western Midwest, and this slowly spread eastward through the end of the month (Figure 11, Figure 12). Low temperatures made little effort in a reprieve from the heat, as they generally stayed in the middle and even upper 70's for several consecutive days. The hottest day was likely on July 31, when much of Missouri, central Minnesota, and western Wisconsin all saw temperatures above the century mark (Figure 13). Numerous record warm temperatures were set this week, and are summarized in Table 1.
The hot temperatures combined with high humidity values and several upper-level disturbances to ignite powerful thunderstorms across northern Minnesota, northern Wisconsin, and into lower Michigan during the final weekend in July. Thunderstorms began to develop across the Arrowhead of Minnesota late in the evening on July 29, and then these storms expanded and congealed into a large mesoscale convective system (MCS) with attendant bow echo at its leading edge (Figure 14). The storm produced numerous reports of wind damage, some in excess of 60mph, downing several trees across "God's Country" of northern Wisconsin, before sliding east-southeastward across the Oshkosh, WI, and Green Bay, WI areas. The storms then moved out over the waters of Lake Michigan, taking out seven of ten boats participating in a kayak race near Belmont Harbor, IL.
Will the first week of August see any new record temperatures, or will Mother Nature provide her own air-conditioning? Find out in next week's edition of the Midwest Climate Watch.
Kruk