May 17-24, 2006
Midwest Weekly Highlights - May 17-24, 2006
The third week of May was quieter than the second week, but still had its round of interesting weather conditions and climate anomalies. Headlines this week revolved around several record low temperatures, a few severe thunderstorms, and generally colder than normal conditions. The average daily temperature departures across the Midwest indicate that much of the region was significantly below average for this time of year, with a gradient from west to east (Figure 1). Average daily mean temperatures for the third week of May ranged from 6-10°F below normal across Kentucky, Indiana, Illinois, Michigan, and Ohio, to 2-6°F below normal across Wisconsin, and Minnesota. Missouri and Iowa were the warm states this week, where average daily temperature departures were near normal to 2°F above normal.
Precipitation for the
week was relatively spotty and light, thus many locations
received below
normal amounts of precipitation. Of course, unless you were one
of those who got stuck under a thunderstorm this past week,
precipitation deficits were rather common. This week much of
Wisconsin,
northern Minnesota, the Upper Peninsula
of Michigan, Illinois, Missouri, and Iowa
experienced precipitation deficits ranging from 0 to50% of normal (with
the near 0% across extreme north central Minnesota),
while parts of Indiana, Ohio, lower Michigan, and Kentucky,
saw
between 50 and 75% of the normal
precipitation (Figure 2).
The only spot this week to receive above average precipitation
was extreme northern lower Michigan, where residents there experienced
precipitation totals as much as 200% above normal. The lack of
significant precipitation resulted in little
change
in the drought status. However, long-term drought still
exists, with much of Missouri and southern Iowa experiencing a
"moderate" drought (Figure 3).
Sub-Normal Conditions Prevail
On May 17, a fast moving cold front sinking southward out of Canada, in combination with cold temperatures aloft and strong May sunshine, resulted in numerous severe thunderstorms across Wisconsin, Ohio, Indiana, Michigan, and Illinois (Figure 4). The severe weather consisted primarily of large hail reports, with an average size of about a half-inch (Figure 5). Behind the passage of the cold front, cooler conditions set in once again, but this was quickly reversed by a warm front which stalled across the region on May 20-21, producing some additional severe weather, primarily in the form of isolated large hail across Missouri and Kentucky.The extended rainy period experienced by a majority of Midwesterners this month has set or tied consecutive precipitation records. In Chicago, IL, precipitation of at least 0.01" fell on 9 consecutive days from May 10 to May 19. This is now tied as the 5th longest streak in Chicago's history, which dates back to 1871. Similarly, in Detroit, MI, precipitation of at least 0.10" fell on 9 consecutive days from May 10 to May 19. This is a new record number of rainy days, breaking the old record of just 6 days (set three times) in March, 1976; August, 1975; and December, 1966.
On Sunday, May 21, an area of high pressure slid across the northern portions of the Midwest, bringing clear skies and anomalously dry conditions (e.g. dewpoint temperatures in the low 30's and even low 20's in some areas). As the high moved overhead, ideal radiational cooling conditions set up across Wisconsin, Michigan, and northern Illinois. This allowed temperatures to drop to record cold levels for minimum temperatures on Monday, May 22 at the following locations: Chicago O'Hare, IL 36°F (was 37°F in 1997); Rhinelander, WI 26°F (was 29°F in 2003); Merrill, WI 25°F (was 26°F in 1967), Flint MI 33°F (tie 1961). The same area of high pressure settled further east on May 23, bringing a 30°F low temperature to Youngstown, OH, tying their record low which was set in 1967.
Above Normal Temperatures Spark Severe Thunderstorms
On Tuesday, May 23 to Wednesday May 24, an area of low pressure moving through the Dakota's with an associated cold front ignited several clusters of thunderstorms that first tracked across Iowa and Minnesota before heading east into eastern Iowa, much of Illinois and western Indiana (Figure 6). In Lac Qui Parle County County in west-central Minnesota, numerous towns were affected by large hail to the size of quarters and damaging straight-line winds which blew trucks off the highway, collapsed barn roofs, and destroyed at least one chain-link baseball dugout. In Calhoun County, IA, a mesonet observation measured a peak wind gust of 64 miles per hour as storms barreled through that region. On Wednesday, May 24, as temperatures warmed into the upper 80' in parts of the Midwest, several thunderstorms, many of which were severe, affected Wisconsin, Illinois, Missouri, Indiana, and Kentucky (Figure 7). Several reports of wind damage and large hail, and even a few tornadoes were common across this area (Figure 8). In Chicago, both O'Hare and Midway airports experienced departure delays of up to 2.5 hours because of the stormy weather. Despite the strong thunderstorms, remarkably, no large-scale impacts were felt across the Midwest, aside from the typical downed trees and power lines.
Going into the final week of May, the atmosphere appears to be in flux where anything can happen. Find out what occurs in next week's edition of the Midwest Climate Watch.
Kruk