September 22-30, 2006
Midwest Weekly Highlights - September 22-30, 2006
Temperature and Precipitation Trends
The final week of September was a brutal awakening to autumn, and temperatures for the fourth consecutive week were cooler than normal over a good chunk of the Midwest. The average daily temperature departure map for the Midwest shows that cool temperatures were found across the northwoods of Wisconsin, parts of Indiana, Illinois, and eastern Kentucky (Figure 1). Here, daily temperature departures were below normal by 3-4°F. A few locales experiences localized "warmer" pockets, though still below normal. Such examples include western Illinois, northern Minnesota, southern Missouri, and northeastern Ohio, where temperature departures were 0-1.5°F below normal for this time of year.
Precipitation for the week was widespread and exceptional in some locales, while other parts of the Midwest saw very little in the way of rainfall. The heaviest precipitation this week fell across southern Illinois, southeastern Missouri, nearly all of Kentucky, and southern Ohio (Figure 2). These locations saw precipitation totals that were 300 to 400% of normal for this time of year. Meanwhile, a stripe of rather dry conditions was found across much of Illinois, extending southwestward back into Missouri, and northeasward into southern Wisconsin. This dry stripe was characterized by precipitation totals that were only 10 to 25% of normal for the final week of September. Due to the copious rainfall across the southern Midwest, and near-normal rainfall across the north, drought conditions this week changed little from previous assessments (Figure 3).
Significant Tornado Outbreak
A very intense area of low pressure, measured at 985mb (29.08 inHg), spun across the Midwest from the 22nd through the 23rd (Figure 4). The low pressure system was actually deeper than Tropical Storm Ernesto at its peak intensity. Consequently, the wind field associated with this phenomenal low for early fall was exceptional, with jet stream wind speeds in excess of 150kts (172mph). The combination of strong wind fields, rapid northward return of low-level moisture, and some solar heating resulted in the explosive development of numerous severe thunderstorms on Friday, September 22. Storms initially fired across central Missouri (Figure 5), and rapidly became supercellular (i.e. containing rotating updrafts). These storms then quickly headed eastward while intensifying, prompting a number of tornado warnings across eastern Missouri and southern Illinois.
Further north, three distinct supercell thunderstorms moved across the Chicago area, north of I-80, on the evening of the 22nd. One storm produced a very recognizable"hook echo" on radar, prompting 2 separate tornado warnings near O'Hare International Airport (Figure 6). Fortunately, however, no tornadoes actually touched down, but a few funnel clouds were observed. Interestingly, the last two times a tornado warning was issued for the City of Chicago was April 20, 2004, and August 1, 2003.
The severe weather had tremendous impacts on the region, as over 37 tornado reports were relayed to the Storm Prediction Center (Figure 7). The most destructive tornado occurred in Perry County, MO, which was also hit by a dangerous tornado on March 11, 2006. Here, in a small town named Crosstown, MO, many residents were at the Perry County Community Fair when the eventual F-4 tornado struck. The tornado was the strongest in September to hit the Paducah, KY National Weather Service Office coverage area since at least 1880. Over 200 persons were displaced on the night of the 22nd, but fortunately, no deaths occurred, and the worst injury was a broken arm. One man's home, which had been built in 1875 with a whopping 18 rooms, was destroyed. The owner of the home sought shelter in his dining room, which was the only room of the 18 to remain standing. Firefighters, along with Red Cross personnel, and search and rescue teams concluded that over 80% of the homes in Crosstown, MO were uninhabitable on account of the damage sustained by the devastating tornado. Incredibly, over 30 tornado warnings were issued by Paducah alone during the event.
Further west, additional tornadic thunderstorms were found across south-central Missouri, spanning the NWS Offices of Springfield, MO, St. Louis, MO, each of which have detailed analyses of the tornado outbreak on their region. Fortunately, impacts across these areas, though still substantial, were not as drastic as those further east.
Finally, as the cold front swung through the Midwest on the 23rd, additional severe thunderstorms fired in Michigan, and southern Illinois once again. A tornado struck the small town of Caledonia, MI, late on the afternoon of the 23rd, as the cold front passed through the region. The tornado ripped roofs off of a cattle barn and golf cart business, and damaged several buildings along M-37. The tornado was later rated F-0 by the National Weather Service in Grand Rapids, MI, and had a path length of just over a half mile. Over 80 reports of severe weather were received (nationally) on the 23rd (Figure 8).
Incredible Rainfall
The severe weather outbreak also featured excessive rainfall totals across southern Illinois into southern Indiana and much of western and northern Kentucky. Parts of the Ohio River valley received in excess of 700% of normal weekly precipitation during the two-day event from September 22-24 (Figure 9). Radar images from around midnight on the 22nd (morning of the 23rd), reveal a nearly stationary band of strong thunderstorms stretching from southern Missouri northeastward into southern Ohio (Figure 10). At least 10 deaths were reported in Kentucky after the flooding rains sent creeks and rivers over their banks. Two of the deaths included a father and his 1-year-old daughter who were in their pick-up truck when it skidded on wet pavement on I-65 and plunged into floodwaters near Elizabethtown, KY. Additionally, two women were killed near Lexington, KY, after trying to cross a flooded roadway at night, when they were pulled under by the force of the water and then swept away. Another woman, located south of Lexington, KY, died when she drove her pick-up truck into high water. Two male passengers were able to escape before the vehicle overturned and got carried downstream. Yet another woman died in central Kentucky after she was ejected from her car when it hydroplaned and struck a guardrail. On account of the flooding rains and very high water which had submerged numerous roads, portions of I-65 were closed near Elizabethtown, KY, as well as portions of I-64 east of the city. Here are some random rainfall totals from the area: Paducah, KY NWS Office: 6.61"; Cadiz, KY: 8.34"; Mayfield, KY: 13.82"; Evansville, IN: 6.81"; Bernie, MO: 10.90".
More Cool Weather to End the Month
A cold front swept across the Midwest on the 27th, producing some showers and thunderstorms across Michigan, Indiana, southeastern Illinois, and southern Missouri (Figure 11). Behind it, much cooler weather filtered southward into the Midwest. Strong late-September sunshine, combined with cold air aloft, resulted in the formation of afternoon clouds and showers across much of the Midwest (Figure 12), helping to keep maximum temperatures on the cool side (Figure 13). Frost advisories and freeze warnings were posted for northeastern Wisconsin, and the Upper Peninsula of Michigan for the morning of the 29th, but cloud cover from the next approaching storm system prevented temperatures from falling too far, and were generally in the middle 30's.
Will the first week of October feature good harvesting weather, or will cool and damp conditions continue? Find out in next week's edition of the Midwest Climate Watch.
Kruk