Model evaluations at the SFO desk

The 2017 Summer Experiment features a new desk focused around the San Francisco terminal. A visiting scientist from the UKMET office has provided high resolution UKMET data in a mesoscale domain over the SFO area, and participants have been comparing it with various other models. Specifically, they have been examining when the models are suggesting the fog and low ceilings will clear out, and how the high resolution UKMET is performing as compared to the others.

Shown below is the HRRR ceiling field from late morning yesterday:

HRRR Layer Cloud Cover forecast for the morning and early afternoon of August 8th

Immediately notable was how smoothed out the clouds features are in the HRRR. Though it showed clearing, it wasn't particularly useful given the lack of identifiable cloud features. The smoothed out area of clouds is not realistic for an area like SFO, where mesoscale climates often have fog and low stratus following the bay and other terrain features.

GLAMP ceilings were also examined:

GLAMP Ceiling Height from the morning and afternoon of August 8th

The GLAMP noted ceilings lifting later, not until around 1900 UTC, and did provide better detail in the cloud features as compared to the HRRR.

UKMET Cloud Cover field from August 8th, the 1700 UTC forecast from the 00 UTC run

The Cloud Cover field from the UKMET office showed clearing much earlier, around 1700 UTC and provided a much more realistic looking cloud field. Given satellite imagery at the time as well as observed winds, however, 1700 UTC was thought to be too early. Below is the GOES-16 0.64 um visible satellite image from 1752 UTC over SFO.

GOES-16 0.64 um visible image at 1752 UTC on August 8th

GOES-16 visible imagery showed clearing by just shy of 1800 UTC. Though this was in fact later than the UKMET predicted at 1700 UTC, the cloud features of the visible were far more accurate with the high resolution model than either of the others.