IFR probabilities for AWC GFE grid validation

Part of this year's summer experiment is exploring cloud and visibility grids using GFE. The idea is for the AWC to create a national grid of cloud and ceiling conditions, which would then be passed down to the various WFOs for further smoothing and tweaking in their respective local domains thereby creating a more consistent C&V forecast tool off of which to write the TAFs.

One of the potential grids being looked at in the testbed is for IFR probabilities. It is here where the GOES-R IFR probability product has been useful, not only for situational awareness as the grids are being created, but also as verification once they are completed. This morning participants looked back a forecasts created last Thursday at 18Z and compared them to the GOES-R products in the 03, 06, 09, and 12Z hour forecast periods. Below shows a sample of the 03Z and 06Z (i.e. Thursday at 21Z and Friday at 00Z). Please note that an issue with the verification script caused all clear sky values on the outside of the grid to appear as 100% IFR (the dark reds). Focus mainly close to the West Coast.

20150813 18Zf3 AWT GFE forecast and 2100 UTC IFR probabilities

20150813 18Zf06 AWC GFE forecast and 20150814 0000 UTC IFR probabilities

The AWC GFE 03Z forecast actually verified fairly well, particularly along the northern California and northern Washington coast. In between those two areas, the GOES-W IFR probabilities were about 20% lower than called for in the GFE forecast.

At the 06-hour valid time (00Z) the GOES-W IFR probabilities were much lower off the Washington coast, however upon closer examination it is clear (by the smooth texture of the data) that the satellite retrievals were unable to be used (likely due to higher clouds). Further south, the AWC GFE forecast called for IFR off the coast of SFO, but GOES-W IFR probabilities indicated clear skies.

Lastly, check out the 12-hour forecast, valid at 06Z on August 14th.

20150813 18Zf12 GFE AWC forecast and 20150814 0600 UTC GOES-W IFR probabilities

The GFE forecast captured the IFR conditions fairly well, but overdid them. This is particularly notable along the California coast south of SFO. Additionally, IFR conditions weren't as far inland as the AWC GFE forecast was suggesting.

Overall, the IFR probabilities have proved useful as a verification tool for the AWC GFE forecasts and will continue to be explored during this final week of the experiment.