September 22-30, 2005
Midwest Weekly Highlights - September 22-30, 2005
Wet and Warm End to September
During the last 9 days of September, large amounts of rain fell due to frontal activity in the region and yet another tropical system reaching the Midwest. Precipitation totals exceeded 3 inches in southern Minnesota, northern Iowa, and central Michigan due to repeated frontal passages and convective systems, while a swath of 2-4 inches of rain followed the path of Hurricane Rita through southern and eastern Missouri, southern Illinois, central Indiana, and northern Ohio (Figure 1). Most of the Midwest received more than 200% of normal precipitation for the September 22-30 period, with only northern Minnesota and eastern Kentucky missing the action (Figure 2). Temperatures were only slightly above normal in the northern Midwest, oscillating back and forth from warm to cool as cold fronts passed through on the 22nd, 25th, and 28th. For the most part, however, the southern Midwest stayed in the warm sector, and was 5-8°F above normal for the nine days (Figure 3). The large amounts of rain helped to ameliorate drought conditions in Wisconsin, Illinois, Indiana, and Michigan (Figure 4, National Drought Mitigation Center). However, the core of extreme drought in Illinois only received near-normal amounts of rain. The month of September was the 5th warmest for the region since 1895, and was wetter than normal overall, with the area and magnitude of drought reduced from levels at the beginning of the month.
Severe Weather Outbreak in the Northern Midwest, September 21-22
The Minneapolis metro area was rocked by a series of severe thunderstorms late on the 21st as a cold front passed through the region (Figure 5, National Weather Service - NWS). A few tornadoes were present and caused serious damage to the towns of Andover, Blaine, and Coon Rapids (an F-2 on the Fujita Scale) north of the city. However, most of the damage was due to downburst winds that exceeded the speed of small tornadoes (Figure 6, Storm Prediction Center - SPC). Winds were measured up to 78 mph and estimated to be considerably worse in places. One man was killed by a falling tree limb in north Minneapolis as he was running from his car to his house to get out of the storm. There were no other deaths, despite the destruction of numerous houses in the tornadoes, and the toppling of tens of thousands of trees by the straight-line winds. In the neighborhood of Brooklyn Park alone, it was estimated that 10,000 trees were downed. About 200,000 electricity customers were without power initially after the storm, with 44,000 still without power more than 48 hours later. Wind and hail damage to crops was also significant, as much of the corn and soybeans had not yet been harvested. Finally, a number of locations received more than 3 inches of rain (Figure 7, NWS) in a short amount of time, causing localized flash flooding in the northern Metro area and elsewhere in the region outside Minneapolis.
The cluster of storms weakened while dumping heavy rains across Wisconsin (Figure 8, NWS), but were still strong enough for more than 13,000 utility customers in the Milwaukee area alone to loose power. The same frontal boundary triggered additional intense thunderstorms in central Michigan on the 22nd (Figure 9, NWS), bringing about severe weather events across the state (Figure 10, SPC), and 2-3 inches of rain in a swatch from Grand Rapids to Flint.
Another Tropical System Visits the Midwest
Hurricane Rita crashed into the Gulf Coast at the Texas/Louisiana border region early on the morning of the 24th, and its cloud shield was already shadowing southern Missouri by that afternoon (Figure 11, College of DuPage - COD). A warm front across Iowa and Illinois was triggering showers and thunderstorms at the time, and Rita providing even more moisture to that system, as well as retaining its own precipitation shield. By the morning of the 25th, the rain shield of Rita had reached central Illinois (Figure 12, COD), and heavy rain was also falling to the north where a strong cold front pushed against the tropical air. The core of the remnants of Rita followed a path through southeastern Missouri, southern Illinois, central Indiana, and northern Ohio before exiting the region along with the cold front on the 26th. Because of the rapid motion of Rita, as compared to Katrina, maximum tropical rain totals in the swath along its path were only 2-4 inches (Figure 1).
The month ended with 4 days of high pressure and fair weather sandwiched around a frontal passage late on the 28th. A 25°F temperature change existed across the front, with 55°F air trailing the front and 80°F air ahead of the front (yellow dashed lines in (Figure 13, COD). While most of the front was not triggering severe weather, a line of strong thunderstorms developed from Texas to southern Missouri (Figure 14, COD). A number of severe weather reports occurred in this area (Figure 15, SPC), but no deaths or injuries were reported due to direct storm effects in southern Missouri. However, it is thought that the heavy rains of the storms triggered a rock slide that caused an Amtrak passenger train to derail on the 29th near De Soto, MO, injuring 26, two of whom needed to be hospitalized. The last two days of the month were quite cool compared to recent warmth, with first frosts in normally colder location in Iowa, Minnesota, and Wisconsin on the morning of the 29th.