At the National Weather Association conference back in October, we presented a poster examining the possibility of using output from the NASA Land Information System to assist with drought monitoring, winter weather forecasting, and hydrology. With an active southern stream pattern setting up across the Tennessee Valley and above-normal rainfall totals, hydrology became the focus over the last week. The same event that brought tornadoes to central Alabama resulted in widespread minor to moderate flooding in north Alabama, and concern was growing about the potential for additional flooding with another 1-3 inch system just three days later.
Heading into the event Wednesday, Huntsville Warning Coordination Meteorologist David Nadler sent out a note featuring Wednesday morning’s 0-10 cm relative soil moisture product, which can be an indicator for so-called “saturated” soils.
Recent experience has suggested that 65% RSM, combined with heavy rainfall, can be enough to produce several cases of flash flooding and river flooding in the Huntsville county warning area. As the image suggested, and David noted, the dark blue indicates 65% RSM across a large part of the Huntsville county warning area–but not all of it. In fact, the NASA LIS image suggested that the flooding threat may not be as bad as initially thought because several days of sunshine had depleted the 0-10 cm soil moisture more than expected.
Indeed, the combination of lighter rainfall (only about 1 inch instead of the feared 2-3 inches) and drier soils has resulted in little flooding. The rain has pushed RSM well above 65% across almost all of north and central Alabama once again, but this time, the forecast is dry for the next 5 or 6 days.