The primary mission of the Tropical Rainfall Measuring Mission or TRMM satellite is to measure rainfall over the global Tropics. It was placed into service in November of 1997. From its low-earth orbit, TRMM has been measuring rainfall over the global Tropics using a combination of passive microwave and active radar sensors. It can be used to calibrate rainfall estimates from other satellites. 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 here for the 7-day period 13 to 20 March 2008 for the central and southeastern United States. Rain extends from central Texas northeastward up into southern Pennsylvania. The highest rainfall totals for the period (shown in red) are about 200 mm (~8 inches) and are located over western Arkansas. A broad area of at least 100 mm (~4 inches, shown in yellow) covers most of southern Missouri, northwestern Arkansas and eastern Oklahoma with embedded higher amounts on the order 150 mm (~6 inches, shown in orange). Locally, there were reports of up to a foot of rain in parts of Missouri.

So far, at least 13 deaths are being blamed on the weather, and numerous rivers are at or above flood stage across the Midwest. The ongoing La Niña associated with cooler-than-normal ocean temperatures across the central Pacific maybe a contributing factor. La Niña and its famous counterpart El Niño can impact US weather patterns by altering the jet stream pattern especially in the northern hemisphere cold season. On average for this time of year, strong to moderate La Niña's are associated with above-normal rainfall from East Texas and northern Louisiana up through Arkansas and the Tennessee and Ohio Valleys.