So far at least 9 people are dead and others are missing across the southeastern United States as a result of severe flooding brought about by several days worth of heavy showers and thundershowers. Normally at this time of year, slow moving or stalled out tropical storms or hurricanes bring the amounts of rainfall and flooding seen in this week’s event, but not this time.

Atlanta, Georgia was especially hard hit with reports of over 15 inches of rain in the metro region. The culprit was a persistent area of low pressure located over the lower Mississippi River Valley that pumped copious amounts of moisture up from the Gulf of Mexico northeastward over the Southeast, providing fuel and a trigger for the numerous showers and thundershowers. A stagnant upper-air pattern allowed the area of low pressure to persist for several days in the same location.

Armed with both a passive microwave sensor and a space-borne precipitation radar, the primary objective of the Tropical Rainfall Measuring Mission satellite (better known as TRMM) is to measure rainfall from space. For increased coverage, TRMM can be used to calibrate rainfall estimates from other additional satellites.

The TRMM-based, near-real time Multi-satellite Precipitation Analysis (TMPA) at the NASA Goddard Space Flight Center, Greenbelt, Md. is used to monitor rainfall over the global Tropics. TMPA rainfall totals for the 8-day period from September 14 to 22, 2009 for the southeastern U.S. and the surrounding region show the highest rainfall amounts in central Tennessee, central Alabama, north central Mississippi, and north central Georgia, around the Atlanta metropolitan area.

Nearly the entire southeastern U.S. from the Gulf Coast to the Ohio Valley and from the southern Mississippi Valley to the southern Appalachians received at least 50 mm of rain (~2 inches, medium green) with a good portion receiving at least 100 to 150 mm (4 to 6 inches, shown in light green and yellow areas, respectively). Embedded within these regions are locally higher amounts exceeding 250 to 300 mm of rain (~10 to 12 inches, shown in orange and red, respectively). The highest TMPA rainfall totals for the Atlanta region are on the order of 350 mm (~14 inches).

Tropical depression seventeen-e formed around 11 p.m. EDT Tuesday night and within twelve hours it strengthened into Tropical Storm Nora.

By 11 a.m. EDT today, Wednesday, September 23, Nora had maximum sustained winds near 45 mph, in the open waters of the eastern Pacific Ocean. Nora’s center was about 665 miles southwest of the southern tip of Baja California, near latitude 16.5 north and 117.5 west. Nora is moving west-northwest near 9 mph. Nora’s estimated minimum central pressure is 1002 millibars.

The Atmospheric Infrared Sounder (AIRS), instrument that flies aboard NASA’s Aqua satellite, captured an image of Tropical Storm Nora yesterday at 5:29 a.m. EDT, that showed she was still coming together. Eighteen hours after the image was taken, Nora formed as tropical depression 17-E.

She’s currently a small storm, as tropical storm-force winds only extend out to 40 miles from the center. Some strengthening is expected over the next 24 hours