September 1-10, 2004
Midwest Weekly Highlights - September 1-10, 2004
Frances Visits the Eastern Midwest
The Midwest experienced a rare visit of a tropical system during the first ten days of September.
Frances moved northward along the eastern borders of Kentucky and Ohio on September 7-9,
bringing flooding rains to the region (Figure 1, College of DuPage - COD). In fact, Frances was
responsible for most of the moisture in the region during the period, except for a strong low
pressure center and cold front that brought heavy rains to northern Minnesota. Much of the rest
of the Midwest was dry during September 1-10, while the Frances-affected area received 3-6
inches of rain (Figure 2). The central two-thirds of the Midwest was well below normal in
precipitation during the period, receiving no rain except for isolated events (Figure 3). Because
of the predominantly dry and sunny conditions in the region, temperatures tended to be warm
during the day and cool at night. Overall, average temperatures were 2-4°F warmer than normal
in the northern Midwest, and 2-4°F cooler than normal in the southwestern Midwest (Figure 4).
The rains in northern Minnesota removed abnormally dry conditions in that region, leaving only
northeastern Wisconsin with this designation in the Midwest (Figure 5, National Drought
Mitigation Center). Generally seasonable to warmer than normal conditions also helped crop
progress in the Midwest that was slowed by very cold conditions in August.
Severe Weather and Heavy Rain
The first days of September were quiet in the Midwest, with only a few isolated heavy rain
storms in Indiana and Michigan on the 3rd. In Monon, IN, 5.25 inches of rain was measured by a
cooperative observer, although this was one of only several isolated heavy soakers in the area
(near Rensselaer, IN, on (Figure 6, NWS). On the 5th, a large low pressure center over South
Dakota began to slowly move northeastward across the northern portion of Minnesota (Figure 7,
COD). Ahead of the low and a strong cold front (Figure 8, COD), a large plume of moist air
entered the western Midwest. Numerous supercell thunderstorms developed (Figure 9, USWRP-ROC Radar Archive), leading to an outbreak of 12 reported tornadoes in the Iowa, Minnesota,
and Wisconsin area (Figure 10, Storm Prediction Center). Iowa set a new record for the number
of tornadoes in a single year, 110, subject to slight changes as tornado records are finalized. The
tornadoes caused damage to farm buildings and killed livestock, but did not kill any people.
Wind damage to crops was also common in the area. Since the front stalled and the low lifted
into Canada, only the northern Midwest experienced heavy rain. The abnormally dry area of
northern Minnesota received copious rain totals exceeding 4 inches in places (Figure 11a and Figure 11b, NWS), leading to the removal of this region from the US Drought Monitor for
September 7 (Figure 5, NDMC).
Frances
Hurricane Frances was a particularly large and slow moving storm as it reached and crossed Florida (Figure 12, NWS). After reentering the state of Florida at the Panhandle, the low pressure center that was Frances marched northward on the 6th, reaching southeastern Kentucky on the 8th (Figure 13, COD). Both eastern Kentucky and Ohio were subjected to more than 36 hours of heavy rain as moisture lifted over the Appalachians (Figure 14, COD). Rainfall amounts exceeded 4 inches during the 24-hour period ending on the morning of the September 9 (Figure 15, NWS). Flash flooding was widespread in the hilly region, and river flooding was common in Ohio, where many roads were closed (Figure 16, USGS: black dots indicate record river heights for the day of the year). Tragically, 4 people were killed by flood waters in Ohio: 2 were drowned in a car driving on a flooded road, one died of a heart attack pumping water from his basement, and a child died crossing a flooded pedestrian bridge on her way home from school. Hundreds of homes and businesses were also impacted by the floods, and roads were closed for several days in many locations in eastern and southeastern Ohio. A state of emergency was declared by Governor Taft in ten counties in Ohio, and a federal disaster declaration will be requested for at least one of these counties. The progress of Ivan is of great concern in the region, as these wet areas in the eastern Midwest would not be able to sustain another storm with a similar or greater amount of rain