Another challenging day in SFO for Day 2

This week has certainly been interesting for the participants at the SFO desk and yesterday was no exception. Ceilings had never really cleared the previous day and SFO awoke again with the airport rather socked in. HRRR was discounted almost immediately as it was noted to be far too dry compared to current satellite conditions. For this reason, it was decided that it would not be used for the day's clearing forecast.

20170815 1300 UTC HRRR run, 1400 UTC hour forecast (left) with GOES-16 high-resolution visible imagery at 1402 UTC (right). Satellite showed more cloud (i.e. moisture) than was seen in the HRRR initialization

GLAMP solutions from earlier runs hinted at clearing by 20 UTC and cleared it out completely by 21 UTC. The UKMET on the other hand had ceilings clearing by 1800 UTC. This was quite a significant difference between the two models, making it a more interesting challenge to decide which to go with.

20170815 1400 UTC UKMET (left) and GLAMP (right) runs, 20 UTC forecast hour. This was the first hour in which the GLAMP showed any clearing in the SFO arrival area

Compared with GOES-16 satellite, the UKMET appeared to have initialized better, capturing the current stratus coverage. For this reason participants were more inclined to go with an earlier clearing time than noted by the GLAMP.

20170815 0000 UTC UKMET run (right) of cloud cover, the 16, 17, and 18 hour forecasts, with GOES-16 high-resolution visible imagery (left) for verification

GOES-16 satellite showed clearing by 1700 UTC. This was fairly close to the UKMET solution, which had clearing starting at 1700 UTC and completely cleared closer to 1800 UTC. The high-resolution model also seemed more accurate in the details of the clouds themselves, showing the main stratus layer moving offshore and the small inland area of fog over Oakland burning off.