Nearcast, CI, and CTC over ATL

With a cold front advancing into the Southeast U.S., the focus of attention at the GOES-R convective support desk was around Atlanta. Early Nearcast runs (Fig, 1) showed a boundary of instability associated with the cold front approaching ATL by 20Z. In advance of this front, another weaker area of instability moved through eastern Alabama, also with the potential to set off convection.

Figure 1. 20140811 1200 UTC Nearcast, 1-hour forecast

Note also the boundary of instability over western Kansas and Oklahoma. While there was in fact a lot of lower level moisture below higher level drying, no convection fired because other parameters conducive to convection weren't there. This is a good reminder that the Nearcast is not to be used as a standalone tool, instead another tool in the toolbox. 

To verify these areas of instability later in the day, the GOES-R CI and CTC were used. The GOES-R CI (Fig. 2) indicated increased probabilities of 50+% starting at 1545 UTC. Half an hour later, the CTC showed significant cooling signals (Fig. 3). Fifteen minutes after that, a line of convection formed just west of Atlanta.

Figure 2. 20140811 1545 UTC GOES-R CI and fronts

Figure 3. 20140811 1615 UTC Cloud Top Cooling

In this case participants were able to utilize the Nearcast model to better pinpoint areas of potential instability, and then verify these areas using real-time GOES-R products.