A winter storm brought snowfall to much of southern Colorado on 11 November 2018. Behind the storm system on the 12th, a variety of low and high clouds lingered during the day after the snowfall had ended. Interrogating visible satellite imagery alone, it is difficult to differentiate the clouds from surface snow cover given both are highly reflective. The additional bands on the GOES-16 ABI compared to previous GOES imagers allows for the creation of RGB combinations that help differentiate various clouds from each other and from snow. This especially relevant to aviation forecasting when monitoring cloud cover near TAF sites.
The Day Cloud Phase Distinction has been described for this purpose in previous blog posts. The scene on the 12th was another great example of the advantages of using the Day Cloud Phase Distinction RGB over visible imagery alone. In the visible imagery (Fig 1), while it is apparent that there is widespread snow cover with clouds moving overhead, it is difficult to quickly diagnose clouds vs snow. The RGB (Fig 2) makes it clear where there is bare ground (dark blue), snow (green), liquid clouds (light blue), and ice clouds (red).
Figure 1: 12 November 2018 GOES-16 0.64 um VIS over southeast Colorado. Full res
Figure 2: 12 November 2018 GOES-16 Day Cloud Phase Distinction RGB over southeast Colorado. Full res
The Day Snow-Fog RGB can also be utilized for differentiating snow from low clouds and high clouds (Fig 3), but does not provide useful information over the Day Cloud Phase Distinction RGB. Further, it does not utilize the 0.64 um 500 m band, so it lacks the detail that is inherent in the Day Cloud Phase Distinction RGB, which does utilize the high resolution visible band.
Figure 3: 12 November 2018 GOES-16 Day Snow Fog RGB over southeast Colorado. Full res
Figure 4 provides a comparison of the visible channel with the two RGBs discussed along with labels for the various cloud and surface types.
Figure 4: 1732 UTC 12 November 2018 GOES-16 0.64 um VIS, Day Cloud Phase Distinction RGB, and Day Snow Fog RGB over southeast Colorado. Full res
Bill Line, NWS
A wildfire developed in northern California during the early morning hours of 8 November 2018. The “Camp Fire”, as it was named, spread quickly within very windy and dry weather conditions. GOES-16 captured the development and rapid spread of the fire best in the CONUS sector (5-min) 3.9 um shortwave IR channel, which is especially sensitive to heat from a wildfire (Fig 1).
Figure 1: 8 November 2018 GOES-16 5-min shortwave window IR imagery over northern California. Full res
With sunrise shortly thereafter, the 5-min visible imagery from GOES-16 revealed the impressive smoke plume emanating from the fire, and quickly spreading southwest within the strong flow (Fig 2).
Figure 2: 8 November 2018 GOES-16 5-min visible imagery over northern California. Full res
Comparisons can be made between the previous generation imager on GOES-15 and the new Advanced Baseline Imager on GOES-16 (Fig 3). GOES-15 is now at 128W, which is close to the longitude of northern California, meaning the IR pixel area won’t be too much larger than the 4 km found at nadir. GOES-16, however, at 75.2W will see pixel area increased considerably over northern California, from 2 km at nadir to around 8 km. However, GOES-16 provides significantly better temporal resolution of 5-min vs 15-30 min resolution of GOES-15.
Figure 3: 8 November 2018 GOES-15 (left) and GOES-16 (right) shortwave IR imagery over northern California. Full res
Similarly for the vis comparison (Fig 4), GOES-15 pixel area will be close to the 1 km found at nadir, and GOES-16 closer to 2 km (vs 0.5 km at nadir).
A GOES-16 1-min mesoscale sector was positioned over the region starting at 1830 UTC to support wildfire monitoring efforts (Fig 5).
Figure 5: 8 November 2018 GOES-16 1-min VIS. Full res
Bill Line, NWS
GOES-15 (GOES-West) began drifting from 135W on 10/29 to its new location at 128W, where it arrived today, 11/7, at 1910 UTC. During the drift, GOES-15 continued to transmit data in order to support NWS operations. Figure 1 shows 3-hourly GOES-15 Full Disk sector IR imagery from 10/29 – 11/7. The slow eastward shift of the sector is apparent in the imagery.
Figure 1: 29 Oct – 7 Nov 2018 GOES-15 (GOES-West) 3-hourly full disk IR imagery. Full res
GOES-17 continues to drift toward 137.2W, where it is expected to arrive on 11/13, and resume dataflow on 11/15. It is scheduled to become operational GOES-West on Dec 10. Thereafter, GOES-15 and GOES-17 will operate in tandem for at least 6 months.
Bill Line, NWS