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 the 21st of May 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 the 22nd, 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 the 23rd two children were swept away in Wisconsin as runoff from heavy rains drained into the Milwaukee river. And on the 24th there were more tornados, large hail and wind damage across parts of Iowa, Kansas, Missouri into 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 the period 21-24 May 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.

Flood Potential area for 72 hours Rainfall Accumulation May 24, 2004 0900 UTC

See LARGE [1.6 mb] QUICKTIME ANIMATION of May 21-24, 2004 Rainfall accumulation See SMALLER [.3 mb] QUICKTIME ANIMATION of accumulation See MEDIUM 3-D [.8 mb] MPEG ANIMATION of accumulation

TRMM is a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA).

Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).