October 25-31, 2004
Midwest Weekly Highlights - October 25-31, 2004
A Warm, Wet End to October
The last week of October was a very
warm and wet one for most of the region. Temperatures this week
ranged from 2F above normal in northwestern Minnesota to 12F above
normal in southern Missouri (Figure 1).
The relatively warm
weather the last week to ten days of the month offset some of the cold
weather earlier in October. On October 29 temperatures soared to
near 80F as far north as central Iowa and Illinois (Figure 2), and a
number of locations tied or set high temperature records for the
day. Precipitation for the week was above normal across the
southern portions of the region, and also across most of Minnesota,
Wisconsin, and Michigan (Figure 3).
The were were some notable
dry pockets in western Iowa, the southern end of Lake Michigan, and
southern Ohio. In particular, western and southwestern Iowa have
been dry all month and received less than 50 percent of normal
precipitation for October.
Weather More Like Late Spring,
Not Late Fall
Most of the region enjoyed pleasant fall weather as the final week of
October began and a weak cold front pushed through the Midwest.
However, the weatehr deteriorated rapidly as warm moist air from the
Gulf of Mexico began to ride up and over the front which stalled across
northern Missouri and Illinois. Showers and thunderstorms spread across
Missouri and Illinois as the first of two waves of low pressure
traveled along the front on October 26. During the afternoon
severe weather developed across parts of southeastern Missouri and
southern Illinois, leading to tornado warnings for Cape Girardeau, MO,
Scott and Bollinger counties in Missouri and Alexander county in
Illinois. In New Hamburg, MO (Scott
County),
a tornado briefly touched down during the late afternoon
producing some structural damage and uprooting some trees. There
were no injuries reported.
Scattered showers and thunderstorms continued across southern Missouri,
Illinois, kentucky, and Ohio on October 27 as the low pressure wave on
the front exited the region. By October 28 another, much stronger
low pressure system began developing in the northern plains. The
strong circulation around this low produced strong southwesterly winds
across the Midwest, pushing a warm front north to a line from southern
Minnesota to central Wisconsin and into central Ohio (Figure 4, Unisys). The strong
winds transported Gulf warmth and moisture northward. As of
late-morning on October 29, dew point temperatures throughout the
southern one half of Minnesota were in the mid to upper 60's. At noon
CDT the dew point temperature at the Twin Cities International Airport
was 67 degrees, the highest dew point temperature ever recorded in the
Twin Cities on October 29. The previous record was 64 degrees, set in
1946.
The warm and moist air, combined with strong upper level winds over the
Midwest produced favorable conditions for severe weather. By
midday on October 29 parts of Iowa, Minnesota, Wisconsin, and Illinois
were included in an area of Moderate risk for severe weather (Figure 5 ,SPC). Storms
quickly erupted during the afternoon, and by early evening five tornado
watches covered an area from northern Wisconsin to southwestern
Missouri (Figure 6,
SPC). There were numerous reports of high winds and hail, and
unconfirmed reports of three tornadoes in central Minnesota.
Tornado touchdowns were also reported in Pettis
and
Johnson Counties in Missouri. The storms weakened by early
morning on Ocotber 30. The cold front swept through Illinois by
sunrise, and through the remainder of the region by noon. The
intense low pressure system over western Lake Superior generated strong
surface winds south to the Ohio Valley (Figure 7).
Sustained winds 20 to 25 mph with gusts to as high as 50 mph were
reported as far south as central Illinois. Trick-or-treaters
enjoyed generally pleasant weather on Halloween evening, with the
exception of much of Missouri where rain with the next approaching
weather system was spreading northeastward.