August 22-31, 2006
Midwest Weekly Highlights - August 22-31, 2006
A Wet, Cooler End to August
The
last ten days of the month were generally cool and wet, providing
relief to some of the hard-hit drought areas in Missouri, Iowa, and
Minnesota. Rainfall for the period was much above normal across the
central portions of the Midwest (Figure 1).
Torrential rains across
western Missouri into southern Iowa put a significant dent in the
summer precipitation deficits in those areas, although long-term
drought still persists.. Heavy rain also
fell
across central Minnesota and southern Wisconsin. A record 8.60 inches
of rain fell on the University of Minnesota St. Paul campus in August,
and near record amounts from eight to nine inches fell at other
southern Minnesota locations. The northern third of
Minnesota remained
dry. The August 29 edition of the U.S. Drought Monitor (Figure 2)
indicated some improvement in most areas except northern Minnesota.
There was some reduction in the areal extent of drought in western
Missouri, Iowa, and southern Minnesota, and elimination of abnormally
dry
conditions in the southern two-thirds of Wisconsin.
Temperatures
were 1°F to 3°F below normal from Illinois westward, and 0°F
to
1°F above normal from southern Michigan south through Indiana,
Kentucky, and Ohio (Figure 3).
Cool air penetrated well south, bringing
lasting relief to much of Missouri which had suffered through
triple-digit heat much of the the first half of the month. As
the
month came to a close an upper level low kept cool air in place and
temperatures were running well below normal in the northwestern half of
the region.
Severe Weather Results in Damage,
One Fatality
A
cold front pushed through the upper Midwest on August 23 (Figure 4),
and then stalled out. Upper level disturbances moving through the
Midwest combined with the front to produce severe weather across parts
of Minnesota, Wisconsin, Illinois, Indiana, and Michigan on August 23
and August 24. The first wave of storms erupted from west-central
Wisconsin southeast into northwestern Indiana during the afternoon and
evening of August
23.
The storms first developed over Lake Michigan during the afternoon but
remained nearly stationary. By late afternoon, the storms started
moving
toward northern Indiana. At 5:20 p.m. CDT a pilot reported a waterspout
over Lake Michigan about 28 miles east of Chicago. This radar image shows the complex of thunderstorm over Lake Michigan at the time the
waterspout was observed. As the storms moved ashore significant storm
damage, including that from a possible tornado, occurred in La Porte County, IN. Winds caused damage along a 30-mile path from
Gary to
La Porte. A wind gust of 106 mph was measured at the Great Lakes
Environmental Research Laboratory station in Michigan City, at the same
time a trained spotter reported a tornado on the ground.in the city,
about five minutes before this radar image at 7:10 p.m. EDT. Other wind gusts of at
least 75 mph were measured. Numerous trees were down, and
power
was out for more than 20,000 customers in northern Indiana.
In
Westville, IN the winds scattered a lumber company's entire stack of
wood across nearby railroad tracks. Heavy damage occurred at the
Washington Park Marina in Michigan City where boats were in place for
an annual boat show. The wind caused a sailboat pier and 20 boats
moored to it to shift about 100 feet, and other boats were reported
missing from the harbor. During the late evening a tornado briefly
touched
down in Sauk County, WI, but produced no damage.
Round
two
of the severe weather on August 24 began as a
second upper level disturbance began making its way across the Midwest
early on August 24 severe thunderstorms developed during the early
morning hours from southern Minnesota across southern Wisconsin and
northern Illinois. Severe hail (> .75 inch) was the most common
report in Minnesota and Wisconsin with this round of storms. High winds
and lightning knocked out power to more than 32,000 customers of
Commonwealth Edison in the Chicago metropolitan area.The storms caused
average delays of 20 to 40 minutes for both inbound and
outbound flights at Chicago O'Hare International Airport. A
third round of
storms developed in the late morning and afternoon over
Minnesota,
and by mid-afternoon most of southern Minnesota was in a tornado watch
as the storms intensified. Severe weather was concentrated in south
central Minnesota where hail the size of softballs and grapefruit (4
inches) was observed, causing significant damage. A car dealer in
Northfield, MN, south of Minneapolis-St. Paul, reported that his entire
inventory of 250 cars was a total loss. Buildings on the campus of St.
Olaf College suffered roof and window damage. A number of people
suffered minor injuries in Northfield as a result of breaking
windshields while they were in their cars. Later in the afternoon, at
least one and possibly as many as three tornadoes touched down in Nicollet and Le Sueur Counties. The most significant tornado, with a
track of 30 miles and at one point a half mile wide, produced
F3
damage across the two counties. The tornado caused one fatality when an
elderly man was killed in his house near Kasota, MN. A hook echo is
evident on this radar image at 5:53 p.m. CDT. Five minutes later
there were multiple reports of a tornado near St. Peter, MN.
In
addition to the hail, tornadoes, and wind, heavy rain from the storms
caused urban and street flooding in Minnesota and Wisconsin. Daily
rainfall records were set at Rochester, MN with 2.77 inches (old record
1.79 inches in 1975) and in Madison, WI with 2.25 inches (old record
1.11 inches in 1892).
Front Stalls, Missouri Soaked
The
frontal system in the Midwest pushed slowly south into Missouri,
Illinois, and Indiana on August 27, but stalled as a wave of low
pressure began moving along the front out of Oklahoma and Kansas
(Figure 5). The
disturbance triggered heavy thunderstorms during the afternoon and
evening, dumping as much as seven inches of rain in the Kansas City and
Independence, MO areas. Three to five inches of rain were common
throughout eastern Kansas and western Missouri. At the Kansas City
International Airport 3.33 inches of rain was a new daily record,
breaking the old record of 2.43 inches set in 1989. However, that
amount paled in comparison to other amounts reported. In the Watts Mill
area south of Kansas City 7.16 inches of rain fell, and 7.04 inches was
measured by a raingauge on Stadium Drive in Kansas City. The Kansas
City Fire Department responded to more than 100 people stranded after
trying to drive though flooded streets, and in some areas the water was
up to the tops of car roofs. The thunderstorms also spawned two
tornadoes, one near Atherton, MO in Jackson County, and another north
of Independence Center. No damage or injuries were reported.
As
the storms diminished in western Missouri, they began to rapidly
develop over eastern Missouri and western Illinois in response to the
wave of low pressure (Figure 6).
The slow-moving storms produced
two to three inches of rain in Jersey and Macoupin Counties in Illinois
causing flash flooding, with some roads reported being covered by up to
four feet of water.
Severe storms developed ahead of
the advancing cold front late in the afternoon of August 28 in eastern
Indiana and western Ohio (Figure 7).
The storms produced several
tornadoes but only one occurrence of severe hail and one high
wind event. Damage surveys indicated that all of the tornadoes
produced F0 damage.
Cloudy, Cool End
Midwest
weather the last four days of August were dominated by a upper level
low pressure system that moved slowly through the region (Figure 8).
The low produced scattered light showers and an
extensive
area of cloudiness. The cool, unstable air on August 29 led
to the development of at least three waterspouts and several
funnel
clouds over the nearshore waters of Lake Michigan east of Racine and Kenosha Counties, WI. The waterspouts formed along a land
breeze front
that extended from the Racine-Kenosha County line out over Lake
Michigan 10 to 15 miles. The waterspouts moved slowly to the southwest,
but none reached land.
High temperatures on August
29 were mostly in
the 60s and 70s, with the warmest readings (mid 80s) in eastern
Kentucky (Figure 9). Springfield, IL set a new record low high
temperature of 68°F, breaking the old record of 69°F set in
1915. Temperatures the last four days of the month
ranged from 3°F to 5°F below normal across the western two thirds of
the region (Figure 10).
Temperatures were near to slightly above normal in northern Minnesota,
and 1°F to 2°F above normal over southeastern Ohio and Kentucky.
SDH