Satellite Liaison Blog

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

The GOES-17 drift to the GOES-West 137.2W position will begin on Wednesday, October 24. Information about the GOES-17 and GOES-15 drifts can be found here, with a more detailed schedule here. In this blog post, the drift is summarized with NWS folks in mind, so please refer to the linked pages for more details.

• GOES-15 (current GOES-West): drifting from 135W to 128W
  • Drift period: 10/29 – 11/7
  • Imagery will remain available before, during, and after the drift
• GOES-17 (Future GOES-West): drifting from 89.5W to 137.2W
  • Drift period: 10/24 – 11/13
  • Imagery not available: 1345 UTC on 10/24 through 11/14
  • Dataflow resumes on 11/15
  • GOES-17 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

Figure 1: 22 October 2018 GOES-17 Full Disk Imagery from 89.5W GOES checkout position. Full res

Bill Line, NWS

By the morning of 10 October 2018, Hurricane Michael was a category 4 storm set to make landfall on the Florida Panhandle coast later in the day. GOES-16 had been providing 1-min satellite imagery over the storm during the days leading up to landfall, and collected 30-second imagery of the storm on the 10th to help support operations.

The VIS/IR sandwich product has been discussed in previous blog posts, and involves combining visible and IR imagery into one display to take advantage of both. The VIS provides high spatial detail, while the IR provides the quantitative brightness temperature information. In the past in AWIPS, users would overlay semi-transparent IR on the VIS to make this product. Recently, the OPG in collaboration with NWS created an RGB that combines the VIS and IR imagery into one. This allows for the high spatial detail of the VIS to show within the IR information noticeably better. The RGB is currently being tested in a few offices and tweaked to best fulfill forecasters needs.

Below is 40 minutes of 30-sec VIS/IR Sandwich RGB imagery over Hurricane Michael (Fig 1) on the 10th, along with corresponding VIS (Fig 2) and IR (Fig 3) imagery.

Figure 1: 10 October 2018 GOES-16 30-sec VIS/IR sandwich RGB. Full res

Figure 2: 10 October 2018 GOES-16 30-sec VIS. Full res

Figure 3: 10 October 2018 GOES-16 30-sec IR. Full res

Zoomed in view on Hurricane Michael center of circulation just prior to landfall (Fig 4).

Figure 4: 10 October 2018 GOES-16 30-sec VIS/IR sandwich RGB. Full res

GOES-16 Derived Motion Winds (DMW’s) were available every 2.5 minutes within the 30-sec meso sector (Fig 5). As one would expect, most of the winds were in the upper levels (0-250 mb = pink). Low level winds (blue) were computed around the outside of the storm.

Figure 4: 10 October 2018 GOES-16 2.5-min VIS, Derived Motion Winds. Reds = upper level, Blues = lower level. Full res

A daylong animation of the storm, including landfall, from GOES-16 5-min CONUS imagery (Fig 5). Note the eye holds together pretty well after landfall before filling in towards sundown.

Figure 4: 10 October 2018 GOES-16 5-min VIS/IR sandwich RGB. Full res

Bill Line, NWS

A compact shortwave trough skirting across the norther-central US/Canada border sent a cold front racing south down the central US plains during the day/evening of October 3, 2018.

GOES-16 15-min full disk water vapor imagery depicted the progression of the shortwave east along the US/Canada border (Fig 1). Since NWS/AWIPS does not display GOES-R full disk imagery at full resolution, I prefer to do my long, large scale water vapor analysis time-matched to the full disk imagery with the full resolution CONUS imagery overlaid. The cold front can also be diagnosed in water vapor imagery surging south through the plains, is especially apparent over the high plains, and forcing the development of convection from Kansas to Michigan.

Figure 1: 3-4 October 2018 GOES-16 15-min water vapor imagery. Full res

IR-Window imagery provides a highly detailed, both spatially and temporally, depiction of the cold air advancing through the plains (Fig 2).

Figure 2: 3-4 October 2018 GOES-16 15-min IR window imagery. Full res

The Land Surface Skin Temperature (Fig 3) and Total Precipitable Water (Fig 4) baseline derived products depict the cold and very dry airmass pushing south into the northern plains behind the front.

Figure 3: 3-4 October 2018 GOES-16 15-min Land Surface Temperature. Full res

Figure 4: 3-4 October 2018 GOES-16 15-min Total Precipitable Water. Full res

Bill Line, NWS

The NWS National Hurricane Center has requested GOES-16 1-min mesoscale imagery to support monitoring of Hurricane Florence since September 5. Previous blog posts have discussed the value of 1-min satellite imagery for analyzing tropical cyclones, particularly for identifying a center of circulation and for monitoring thunderstorm evolution. The Florence center of circulation appeared to have briefly revealed itself in 1-min VIS during the morning of 9 September (Fig 1). Thunderstorms in the vicinity of the storm center quickly obscured the view.

Figure 1: 9 September 2018 GOES-16 1-min visible imagery focused on Hurricane Florence. Full res

By 5 AM Monday, Florence had strengthened to a category 2 storm, with an eye apparent in satellite imagery. The storm was also quite large, as depicted in Figure 2, which shows the storm with respect to the full 1000 x 1000 km (at nadir) 1-min mesoscale sector. The westward shift of the sector is captured in the middle of the animation. Bermuda was well to the north of the forecast path.

Figure 2: 10 September 2018 GOES-16 1-min mesoscale sector 2 visible imagery, over Hurricane Florence. Full res

A little later in the morning on September 10, the NHC requested 30-second imagery over Florence (Fig 3). As a reminder, two sectors of 1-min imagery can be collected, OR one sector of 30-second imagery, from an ABI.

Figure 3: 10 September 2018 GOES-16 30-second visible imagery centered over eye of Hurricane Florence. Full res

Bill Line, NWS