Orographic banner cloud over Southern California

December 22nd, 2019 |

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm), Upper-level (6.2 µm) Water Vapor and

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm), Upper-level (6.2 µm) Water Vapor and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

A sequence of GOES-17 (GOES-West) Low-level (7.3 µm), Mid-level (6.9 µm), Upper-level (6.2 µm) Water Vapor and “Clean” Infrared Window (10.35 µm) images (above) showed a long-lived orographic banner cloud that formed in Southern California and extended about 200 miles to the northeast across southern Nevada on 22 December 2019. The banner cloud was formed by anomalously-strong southwesterly winds (925 hPa | 250 hPa) interacting with the high terrain of Southern California’s Transverse Ranges. At the surface, wind gusts as high as 86 mph were observed.

Within the banner cloud, the coldest GOES-17 Infrared brightness temperatures were in the -60 to -65ºC range — according to rawinsonde data from Vandenberg, California (below), those temperatures corresponded to altitudes in the 12-15 km range.

12 UTC rawinsonde data from Vandenberg, California [click to enlarge]

12 UTC rawinsonde data from Vandenberg, California [click to enlarge]