GOES icing products in the Northeast

On the mock CAWS production desk this morning, forecasters examined the suite of icing products for the issuance of a CAWS. While these non-convective type CAWS are not currently issued operationally nor are they expected to be in the near future, the theory is that if/when it does, it would add value to the currently issued G-AIRMET forecasts. G-AIRMETs are a graphical, broad scale product, while the CAWS would be more small scale, honing in on areas that expect more MOG to SVR icing (or turb).

On this particular morning there are two areas of interest -the Great Lakes region and northern New England- the latter deemed an area more likely to experience MOG icing with patches of SVR. The image below captures the issued CAWS as compared to the operational icing G-AIRMET, both overlaid on the GOES-R Flight Icing Threat (FIT) index.

20160208 1545 UTC GOES-R Flight Icing Threat index with the experimentally issued CAWS (light blue), operationally issued G-AIRMET (neon green), and PIREP reports. Pink and red values in the FIT indicates high probability of MOG icing

Over the Great Lakes region the MOG area indicated by the FIT were quite consistent with PIREP reports, particularly in and around Chicago's airspace. There were numerous MOG greater reports in a wide swath of high probability MOG on the FIT index.

Fewer reports were made in the New England area, no doubt due in part to the numerous delays and cancellations currently being experienced because of winter weather. However reports were consistent with FIT index values. The CAWS area within the G-AIRMET covered the western end of an intense low spinning off of the coast within in domestic forecast boundaries (i.e. no areas beyond offshore zones included). The above FIT index image is not an animation, however a loop of the FIT product at this time showed a broad area of high MOG icing probabilities associated with this area slowly edging onshore.

In previous experiments it has been noted that utilizing a realtime satellite product like this can be difficult when issuing products for more than a few hours out. That was mentioned in discussion this morning, but it was also said that having the FIT, particularly for the initial diagnosis of icing conditions, was quite useful. Additionally, having an at-a-glance image of where icing may be and where a G-AIRMET may not be covering, or vice versa, would also be potentially helpful.

The Icing Cloud Bases/Heights were also examined for this case and captured images are here:

20160208 1545 UTC Icing Cloud Bases with experimentally issued CAWS (light blue), operationally issued icing G-AIRMETs (neon green), and PIREPS overlaid. Values run from 0 - 30+kft

20160208 1545 UTC Icing Cloud Tops with experimentally issued CAWS (light blue), operationally issued icing G-AIRMETs (neon green), and PIREPS overlaid. Values run from 0 - 30+kft

When a G-AIRMET or experimental (and operational) CAWS are issued, it is required that an estimated base and top of the icing layer is included. The icing bases and tops determines which clouds have icing potential bases on various cloud parameter thresholds and then estimated the base and top from the 'icing' clouds.

Similar to the FIT index, heights of both the bases and tops were generally consistent with PIREPs in both regions. The issued CAWS forecasted icing from FL040 to FL120. The estimated icing cloud bases at that time (darker green values equating to 3-5kft) were consistent and a PIREP report at 1600 UTC indicating icing at FL040 validated that forecast. Icing tops were estimated slightly higher (orange values equate to 15-20kft) than the CAWS forecast and another PIREP reported icing at FL160.

Despite the same concern of using real-time imagery for a 2+ hour forecast, forecasters were particularly enthusiastic about the icing cloud/bases tops. Again, it provides valuable information in the initial stages of G-AIRMET or CAWS generation. Furthermore, it is a valuable situational awareness tool during the issued period of both products, particularly if an amendment should be necessary.