July 1-10, 2003
Midwest Weekly Highlights - July 1-10, 2003
The first ten days of July 2003 have been quite eventful in the Midwest. On almost every day of the period, organized convective systems marched through the region, leading to a total of 1179 preliminary storm reports collected by the National Weather Service (Figure 1). Most of these reports are in a band extending from northwest to southeast across the region, coinciding with the location of a persistent trough that oscillated north to south across the central Midwest from July 3rd to the 9th. The persistent rains associated with these storms training over the same locations left a large region in Indiana and Ohio with more than 5 inches of rain (Figure 2), and a broader band across the Midwest from western Iowa to eastern Ohio with at least 3-4 inches of rain. Precipitation totals exceeded 200% over the wide band (Figure 3), with only western and southern Missouri and the Upper Peninsula of Michigan and adjoining Wisconsin having less than 50% of normal precipitation for the period. Official rainfall observations exceeded 10 inches in Rensselaer, Young America, Alexandria, Kokomo, and Marion, Indiana, while radar accumulation indicated even greater totals in places. Temperatures in the central latitudes of the Midwest were 3-5°F above normal for the ten days, except for parts of the Mississippi Valley (Figure 4). Drought recovery was noted on the U.S. Drought Monitor map for July 8 (Figure 5), National Drought Mitigation Center) in Wisconsin, Illinois, eastern Iowa, southern Michigan, and parts of northern Minnesota, and more should be noted in next week's map. Only in western Missouri did drought conditions worsen during the July 1-10 period.
July started with the passage of Tropical Storm Bill into the central Gulf Coast. While there were no notable precipitation events or storm reports in the Midwest on the 1st, a large flow of moisture laden air entered the Midwest. The first notable severe weather took place on the 2nd, when a mesoscale convective system (MCS) developed in northern Minnesota, crossing that state and moving southeastward in Wisconsin. Overnight, the storms passed though Minneapolis / St. Paul (Figure 6), and yielded many severe wind and hail event reports (Figure 7), Storm Prediction Center).
The core of the worst activity started on the evening of July 3rd, when a strong derecho, a line of fast moving thunderstorms with strong winds, entered Minnesota after doing tremendous damage in the Dakotas. The bow echo of the line is apparent in central south Minnesota at 2 AM on July 4 (Figure 8). The remnants of earlier severe thunderstorms can also be seen north of the bow echo. Wind speeds in excess of 60 mph were common in the area, as well as tree damage and minor power outages (Figure 9). Only 7 hours later, the same line of storms reached the eastern shore of Lake Michigan (Figure 10). The strong winds of these storms on the surface waters near the coast caused tremendous rip currents to form at some of the beaches in southwestern Michigan. Despite red flag warnings, seven people drowned in Lake Michigan within a few hours, the largest such one day loss since 1966. The line of thunderstorms strengthened once again with the day's solar heating, and continued southeastward through Ohio, exiting the region in mid-afternoon.
As the first derecho (straight-line wind storm) exited the region, the humid and hot environment left behind exploded in northern Indiana, with a huge cluster of thunderstorms forming in minutes (Figure 11). Within 2 hours, these cells had organized into another line of thunderstorms, but this one moved very slowly over northern and central Indiana, and was still active six hours later in the evening (Figure 12). This line of storms slowly slumped to the south, adding to the tremendous totals of severe weather event reports for July 4 (Figure 13). Within these two mesoscale storm clusters, one died in Indiana and two died in Ohio under falling tree limbs. However, the most widespread damage from this set of storms came in the form of torrential rains in northern and central Indiana. Despite having been below normal in river levels recently, small creeks and urban areas had substantial flash flooding, and major rivers started to rise. The cooperative observer at Kokomo, IN, reported 9.75 inches of rain the next day. Two persons drowned in Carroll County in Indiana on the morning of July 5th: one was swept into a drain pipe while trying to clear a culvert, and one drove into high water and was swept away. An inexperienced canoeist died in high waters in the Vermillion River in eastern Illinois. More than 100,000 lost power for one to two days in the central Indiana area, with not a small number of these customers needing electricity to run their sump pumps.
Even as the second mesoscale system of the day exhausted itself over Indiana, another cluster of thunderstorms was firing up in western Iowa (Figure 14). While the long line of storms collapsed southward, providing tremendous rain amounts to central Iowa, an outflow boundary on the eastern end of the cluster formed a bow echo (Figure 15) that raced eastward through Iowa, northern Illinois, and Indiana early in the morning on July 5th. The linear string of severe wind events in the July 4th severe events map (Figure 13) was caused by this bow echo, which was especially damaging to the cities of Rockford and Chicago in northern Illinois. The line of storms did not look especially strong on radar as it approached Rockford (Figure 16), but the storms had tremendous forward speed as well as strong microburst development. Winds over 100 mph were observed in Rockford. This line of storms and some others the next day caused 382,000 Commonwealth Edison customers to loose power in northern Illinois, of which 32,000 in Rockford were still without power two days later. In addition, Chicago lost more than 2000 trees, including the oldest living tree in Chicago. Transportation through Chicago's O'Hare Airport was disrupted and delayed for days during this period.
In a classic case of "atmospheric dominoes", the outflow of cold air from the latest MCS fired up storms over northern Indiana again during the afternoon of July 5th. While severe weather was not as widespread as on other days during the period (Figure 17), more storms formed over already soaked areas of central Indiana (Figure 18). One of these storms spawned an F1 tornado with an 8.5 miles path through Huntington and Wells counties. Several houses were extensively damaged and two high voltage power towers were destroyed, but no deaths or injuries were noted. By the end of the evening on July 5, most of northern Indiana and northwestern Ohio had received at least 5 inches of rain in the previous 48 hours (Figure 19), with many places approaching 10 inches for the 2-day period.
Storms on July 6 were not highly organized, but did train over saturated areas of Indiana once again (Figure 20). These storms were quite potent, resulting in a number of severe weather event reports (Figure 21). On the morning of July 7, a new and significant bow echo formed over northern Illinois and raced across Indiana in a matter of a few hours. The radar pattern of the storms formed a classic bow echo arc over northern Indiana(Figure 22). The bow echo was responsible for about two hundred severe wind event reports (Figure 23), which slowed the recovery in northern Illinois from the previous windstorm on the 5th. Radar estimated precipitation totals for July 6 through 1 PM on July 7 reached 3-6 inches over most of Indiana, with some isolated zones above 8 inches in northwestern Ohio (Figure 24). By this time, flash flooding would occur commonly with any passing storms, as creeks and rivers had reached flood stage and surfaces were saturated. Major rivers had risen over well over flood stage in northern and central Indiana and western Ohio, including the Wabash, White, and St. Mary's rivers in Indiana.
Precipitation continued to be the most important aspect of the major weather events of the period on July 8 and 9. The stationary boundary shifted slightly southward and became more west-east oriented, allowing wave after wave of upper air disturbances to destabilize the warm and moist environment and organize mesoscale convective systems. By mid-afternoon on the 8th, three waves of thunderstorms were visible from western Illinois, to the Illinois/Indiana border, and in eastern Indiana/western Ohio (Figure 25a) and (Figure 25b). Severe weather was common in these thunderstorm clusters (Figure 26). The final evening of extreme precipitation for the period occurred on July 9. A wave like pattern formed along the boundary again, but was much more complete than the previous evening, tracing a path of heavy storms from Kansas to Pennsylvania (Figure 27). A close-up of the storms in Illinois (Figure 28) reveals a complex arrangement of thunderstorm cells blowing up and then dying, and triggering other storms with the outflow from the original storms. Some of this activity reached the East Coast, as can be seen in the severe weather reports for the 9th (Figure 29).
On July 10, a strong high pressure center entered the northern Midwest and converted the stationary front to a cold front, which moved fairly quietly out of the region. Only the far eastern side of Kentucky was affected by severe weather on the 10th, except for some cold air funnels behind the front (Figure 30). The precipitation accumulated in the last three days of the period was very substantial in Iowa (Figure 31), Iowa/Illinois (Figure 32), Illinois (Figure 33), and Indiana (Figure 34). These radar maps show precipitation that fell from July 8 to 10, and do not include the previous totals. The weather radar covering eastern Indiana and western Ohio presented an accumulated precipitation total for July 4 to July 10, revealing the tremendous magnitude of the events in Indiana and Ohio (Figure 35). While the radar indicates precipitation totals over 15 inches over a very wide area north of a line from Indianapolis to Dayton, there are only a few ground measurements in that range. It is probable that periods of extreme rain rates combined with an extra boost to the signal return from water covered hail stones would lead to a radar total being somewhat overestimated. However, it is certainly indicative of the extreme precipitation and the flooding that ensued during the period.
The river stages in most of the central Midwest were in the top 10 percent of flows for the day at the end of the period (Figure 36), and most gauge stations in Indiana established a new record flow for the time of year (Figure 37). Major flooding proceeded down the largest river in Indiana, the Wabash, causing major flooding which has peaked in Lafayette (Figure 38), Covington (Figure 39), and Montezuma (Figure 40); the flood wave continues southward through parts of Indiana that did not experience the heaviest rains. Substantial losses occurred in parts of Lafayette and Montezuma and in many of the smaller, rural communities along the river. For instance, in the same area, the small town of Delphi was flooded by record levels on Deer Creek, which overtopped the levees protecting the town. The White River flooded parts of Noblesville north of Indianapolis (Figure 41). In northeastern Indiana, much of Decatur was flooded by the St. Mary's River (Figure 42), and some of New Haven was flooded by the Maumee River (Figure 43). While it is too early to form a conclusion regarding the total losses in the region, the figure of $100 M in damage was estimated by a FEMA administrator for Indiana alone. More than 3,600 homes and businesses have already been listed as damaged, with only half of the state information accumulated. Substantial agricultural losses from river flooding, ponding in farm fields, and wind and hail damage were expected. Fortunately, new flood controls put in place in the last 20 years prevented worse damage in some of the large cities such as Lafayette and Fort Wayne, even though water levels reached heights last exceeded in the 1950s, with devastating results at that time. Due to the substantial damages caused by the storms and floods during the period, a federal disaster declaration covering 25 counties in Indiana has been issued(Figure 44). Ohio has also requested federal disaster status for counties in western Ohio, and Iowa and Illinois are suffering crop losses from field flooding but have not determined yet if a federal disaster declaration will be requested. This has certainly been a noteworthy event on the 10th anniversary of the Great Flood of 1993.