Midwest Weekly Highlights - May 18-24, 2011
A Mixed Bag of Spring Weather
The cool weather that began this period gave way to warmer weather much of the week. The central portion of the Midwest saw little rainfall, while rainfall reached 200 percent of normal around the periphery of the region (Figure 1). The rain in Ohio came on the tail end of the storm that was slowly moving out of the region at the start of this week, while the rain in the east and north came in systems the last half of the week. The last half of the week began with a major outbreak of severe weather.
Temperatures this week were within a degree or two of normal across the region (Figure 2). The warmest area was lower Michigan, which was 3°F to 4°F above normal, while the coolest was west-central Missouri at 1°F to 2°F below normal. There were only a handful of temperature records this week.
Spring Planting Accelerates Except for Ohio
The dry weather in the central Midwest helped the progress of spring planting. Illinois and Iowa were both ahead of the five-year average for corn planted as of May 22nd. Illinois, Iowa, and Missouri were ahead of their five-year average for soybean planting. There was little improvement in Ohio, with only 11 percent of the corn planted, compared to the average of 80 percent. Only four percent of Ohio soybeans have been planted, compared to an average of 54 percent.
Only minor flooding was occurring on the Mississippi River from Quincy, IL south to Cape Girardeau, with the exception of moderate flooding at Chester, IL (Figure 3). Only minor flooding was reported along the Ohio River from Shawneetown to Cairo, IL.
Severe Storms and Deadly Tornadoes
The first three days of this week were free of severe weather. Severe storms first developed in Iowa and Minnesota on May 21st, and by the end of the week the entire region had experienced severe weather (Figure 4), including a deadly EF5 tornado that devastated a large portion of Joplin, Missouri.
The weather map on the morning of May 22nd was typical of spring. Warm, humid air was streaming northward ahead of a strong low pressure system centered over the Dakotas (Figure 5). This was associated with a strong upper level low (Figure 6), and all the ingredients were in place for an outbreak of severe weather. During the morning the Storm Predication Center outlook indicated a moderate risk of severe weather extending from northeastern Oklahoma across Missouri, the northern half of Illinois, and parts of Wisconsin and Minnesota (Figure 7).
The first severe storms began developing in the early afternoon in Minnesota just ahead of the cold front. The first tornado touched down in Minneapolis, MN, killing one person and injuring 14 people, two critically. Storms continued to develop along the front from Iowa into Wisconsin. During mid afternoon a supercell thunderstorm developed in southeastern Kansas and moved east into Missouri. This storm spawned a large tornado that struck the south side of Joplin, MO around 5:40 p.m. CDT (Figure 8). The tornado struck on the south side of the city, producing a damage path seven miles long and 3/4 mile wide. The tornado obliterated whole neighborhoods and severely damaged one of the two hospitals in the city. As of May 24th 125 people have been confirmed killed by the storm and 750 injured. More than 200 people are still listed as missing.
The main low pushed northeast on May 23rd, dragging the cold front across the central Midwest and producing severe weather across southern Illinois, much of Indiana and Ohio, and parts of Kentucky. The front stalled across the southern Great Lakes on May 24th as another strong upper level system rode out of the southwestern U.S. toward the Southern Plains. The main outbreak of severe weather on May 24th was in Oklahoma and Kansas, though some severe storms occurred across Missouri, Iowa, and Illinois.