A stationary front draped across the Midwest provided the focus for several days of strong springtime thunderstorms that delivered severe weather and heavy rains to the region. On May 21, 2004, a strong complex of thunderstorms known as an MCS or mesoscale convective system moved across southern Michigan, Ohio and into parts of the Appalachians leaving behind numerous reports of wind damage. Long-lived MCSs that generate wind damage over a wide area are also known as 'derechos' as was the case for this event. On May 22, there were numerous reports of tornados from Nebraska into Iowa. One woman was killed in Nebraska, and the town of Hallam, Nebraska was flattened by a tornado. On May 23, two children were swept away in Wisconsin as runoff from heavy rains drained into the Milwaukee river. And on May 24, there were more tornados, large hail and wind damage across parts of Iowa, Kansas, Missouri, and Illinois. In addition to tornados, hail and wind damage, strong thunderstorms can produce heavy rains and flooding especially when storms occur over the same area.
The Tropical Rainfall Measuring Mission satellite uses onboard sensors to measure rainfall from space. The TRMM-based, near-real time Multi-satellite Precipitation Analysis (MPA) at the NASA Goddard Space Flight Center monitors rainfall over the global tropics. MPA rainfall totals are shown for May 21-24, 2004 over the Midwest. Red areas indicate rainfall totals in excess of 10 inches across portions of northern Iowa, southern Minnesota, Wisconsin, eastern Michigan, northeast Ohio and southeast Ontario. Areas in between shaded in green received near 5 inches.
TRMM is a joint mission between NASA and the Japanese space agency JAXA.