Thursday, August 17, 2017

UKMET high-res model peforms well for SFO on Day 3

Unlike much of this week, day 3 at the SFO desk was a more typical fog and low stratus day around the terminal. Interestingly, not all of the models picked up on that 'normal' behavior. Below is a four panel capturing the various model solutions in the morning:
20170816 1300 UTC run of HRRR (top left) and GLAMP (top right) Ceiling Height grid at the 1-hour forecast, the 00 UTC run of the high res UKMET model (bottom left) Sky Cover grid, the 14-hour forecast, and GOES-16 visible satellite imagery at 1402 UTC.
Neither the HRRR or the GLAMP added much value to yesterday's forecast for clearing. Skies were already beginning to clear to the Southeast of SFO as shown on the satellite imagery, but the GLAMP still indicated fog at that time. The HRRR did have some clearing but didn't provide a particularly accurate picture of the cloud features themselves. For this reason, most of the focus was on the UKMET model, which ended up doing exceptionally well for the day.

The first positive point to its scorecard was in the way it seemed to pick up on the local orographic effects of the stratus layer.
20170816 00 UTC UKMET run, the 15-hour forecast of Sky Cover (right) and GOES-16 visible satellite imagery at 1502 UTC (left)
During a normal fog setup around SFO, the marine layer will funnel in through the San Francisco Bay and spread out through the Bay area. Additionally, it will advance onshore along the coast, but generally stops on the windward (west) side of the terrain. This was the setup yesterday, and the UKMET did an excellent job of capturing this terrain affect as seen in the image above.

Later in the afternoon, around 1800 UTC, cumulus clouds began developing over the SFO area and revealed a second positive point for the UKMET model. Below is the UKMET Sky Cover forecast and visible satellite imagery.
20170816 00 UTC UKMET run, the 18-hour forecast of Sky Cover (left) and GOES-16 visible satellite imagery at 1802 UTC (right)
Thanks to its higher resolution, the UKMET model actually was actually indicating that local cumulus development. Aside from picking up on such small scale detail and cloud features, the UKMET utilized for the experiment is the 00 UTC run. At this particular time, it was an 18-hour forecast picking up on the cumulus development.

All in all, a very good day for the UKMET model!

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