Widespread rainfall leads to improved soil moisture and drought classification

We are in the third and final month of assessing SPoRT’s real-time version of LIS running the Noah land surface model. The assessment is being conducted at the NWS forecast offices in Huntsville, Houston, and Raleigh to determine the utility of SPoRT-LIS for monitoring drought and areal flooding potential. The past 1-2 weeks featured substantial rainfall that occurred over a large portion of the central and eastern U.S.  Much of this precipitation was associated with a deep trough that progressed from the Southern Plains to the U.S. East Coast from 13-16 October.  Fairly widespread rainfall amounts exceeding 5 inches occurred over portions of eastern Oklahoma, south-western Missouri, western Arkansas, and in a swath extending from southeastern Arkansas to the southern Appalachians (Fig. 1).

Fig 1.  Depiction of 7-day rainfall estimates from the Stage IV radar+gauge product, ending 1200 UTC 16 October 2014.

Figure 1. Depiction of 7-day rainfall estimates from the Stage IV radar+gauge product, ending 1200 UTC 16 October 2014.

One of the SPoRT-LIS fields that forecasters have found quite useful during the assessment is the one-week change in total column relative soil moisture (RSM, 0-2 m).  The RSM is the ratio of the current volumetric soil moisture between the wilting and saturation points for a given soil type, with values scaling between 0% (wilting) and 100% (saturation).  In response to the recent substantial rainfall over the Deep South, the LIS total column RSM increased by 8-24+% over a large area (Fig. 2) approximately corresponding to the areas that received 4 or more inches of rainfall in the past week given by the orange and red shading in Figure 1. This beneficial rainfall led to the improvement of the U.S. Drought Monitor classification by 1-2 classes over portions of Kansas, Oklahoma, Texas, extending into Alabama, Tennessee, and northern Georgia (Fig. 3).  The most recent U.S. Drought Monitor product issued on 14 October (Fig. 4) shows that all drought classes have been removed over northern Alabama, Tennessee, and Kentucky.

Fig 2.  SPoRT-LIS one-week change in total column (0-2 m) relative soil moisture valid 1200 UTC 16 October 2014.

Figure 2. SPoRT-LIS one-week change in total column (0-2 m) relative soil moisture valid 1200 UTC 16 October 2014.

Fig 4.  One-week change in the U.S. Drought Monitor classifications, from 7 to 14 October 2014.

Figure 3. One-week change in the U.S. Drought Monitor classifications, from 7 to 14 October 2014.

Fig 3.  U.S. Drought Monitor classification valid 14 October 2014.

Figure 4. U.S. Drought Monitor classification valid 14 October 2014.

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