Day 3: GOES-R Icing utility along the East Coast

Yesterday's icing focus was in two regions, the Southeast U.S. and the mid-Mississippi Valley northeast through the southern portion of New England. The GOES-R FIT algorithm was of particular use in the latter region.

Below are several screen captures of the 2115 UTC FIT (Fig. 1) and Cloud Phase (Fig. 2), both overlaid with the 2100 UTC icing forecast and PIREPs. Note the area of reds indication a high probability of moderate icing over WV and extending through northern VA and off the coast. While the regions over which AIRMETs are drawn are fairly wide and don't take advantage of the pixel by pixel detail of the FIT, forecasters did note the utility of the product in identifying forecast areas in which to focus. Particularly, they chose to key in on the areas of reds and yellows, the higher probabilities of icing conditions, as guidance for their AIRMET regions. PIREPs at 2100Z showed a number of moderate icing reports within these locations.

However, also take note of the two moderate icing PIREPs in NW GA, not in either of the forecast regions. Note both the higher probabilities of icing on the FIT as well as the presence of supercooled droplets indicated by the neon green color in the Cloud Phase display. Both of these provided evidence of icing conditions where the various model datasets did not, again showing the utility of having these products as analysis tools.

Figure1. 20130213 2115 UTC FIT and PIREPs; 2100 UTC icing forecast

Figure 2. 20130213 2115 Cloud Phase and PIREPS; 2100 UTC icing forecast

Also utilized at the icing desk yesterday afternoon were several other satellite based icing tools. Below are images of the 1845 UTC Supercooled Large Droplet (SLD) tool (Fig. 3) as well as the 2115 UTC Icing Bases (Fig. 4) and Icing Tops (Fig. 5), all three overlaid with the 2100 UTC forecast.

Recall from an earlier post that the SLD uses cloud retrievals to key in on supercooled water droplets and contains probabilities for snow/ice (cooler colors) and clear (warmer colors) surface conditions where size ranges from yellow/cyan = 13.5 - 16 um, orange/light blue = 16 - 19 um, red orange/blue 19 - 22 um, red/purple = 22 -25 um, and maroon/magenta = 25+ um. Forecasters thought this was a 'very neat tool' and were able to use it to further key in on potential areas of icing, particularly where surface conditions were snow and ice free (warmer colors). Also note the reds and oranges in NW GA where the two moderate icing PIREPs not in the forecast area occurred around 2100 UTC.

Figure 3. 20130213 2115 UTC SLD and 2115 UTC icing forecast

The icing bases (Fig. 4) and tops (Fig. 5) are a very new tool designed to provide icing bases and tops through the use of satellite cloud retrievals. With each icing AIRMET issuance the tops and bases of the expected icing layers are required. This satellite tool was able to provide additional guidance towards that end. The 2100 UTC forecast over WV and northern VA called for icing to occur between the surface and FL180. Note the satellite icing bases showing bottoms from the surface (purples) to around FL064, and tops extending to around FL150. PIREPs from 2100 UTC fell into these layers with several around FL110 and one lower at FL040.

20130213 2115 UTC icing bases and 2100 UTC icing forecast

20130213 2115 UTC icing tops and 2100 UTC icing forecast

While still a very new product, forecaster did indicate it's use in increasing situational awareness. Aside from providing the tops and bases of potential icing layers, it can also provide an idea of layer thickness. For example if bases are showing FL090 and tops are at indicated at only FL100, forecasters may not be as quick to issue an AIRMET for the area given the very thin layer. This tool will also provide information towards the development of a more CIP-like tool, supporting the GOES-R goal of putting together more NWP based products.