GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (above) showed a cyclonically-rotating actinoform cloud feature that was moving west-southwestward across the East Pacific Ocean (about midway between Hawai’i and California) on 16 November 2021.

In GOES-17 Day Cloud Phase Distinction RGB images (below), the increasing shades of green exhibited by the curved bands of shallow convection suggested that those features were likely mixed-phase clouds — composed of a combination of liquid/supercooled water droplets and ice particles. 

Similarly, in a toggle between NOAA-20 VIIRS True Color and False Color RGB images viewed using RealEarth (below), darker shades of cyan suggested the presence of mixed-phase banded cloud elements within the core of the actinoform feature.

Other examples of actinoform clouds can be examined by scrolling through this link.

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MIMIC Total Precipitable Water, shown above, shows a narrow ribbon of rich moisture stretching from north of Hawaii northeastward to the Pacific Northwest. Rainfall associated with this Atmospheric Rivr resulted in widespread flooding over Washington State (USA) and British Columbia (Canada). The system also generated very strong winds.

CMORPH estimates of rain, below, from Real Earth, show substantial 24-h rain amounts on 14-15 November, with peak values on 15 November of 75 mm in southern British Columbia. (This automated gauge along the Nooksack River at North Cedarville WA showed >4″ of rain (graph)) The 7-day accumulation ending at 2359 UTC on 15 November shows a few values in excess of 200 mm. CMORPH estimates suggest that heaviest rains were just north of the US-Canada border.

The excess rain’s impact on Nooksack Falls, north of Washington’s Mt Baker are shown below.

Satellite estimates of flooding are available at this website. For example, the image below (from this direct RealEarth link) shows flood extent over northwestern Washington (note the US-Canada border in the image) on 16 November 2021.

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News videos of the impact of the flooding on the Sumas Prairie near Abbottsford are here, here, here and here. Click here for video footage from near Sumas, WA. Other Washington imagery is here. This storm was well-forecast, as noted here.

Measured streamflow on the Nooksack River reached historic or near-historic volumes, as shown in these streamflow plots at North Cedarville (graph), Everson (graph) and Ferndale (graph) (all from this site).

NOAA-20 true-color imagery, below, from 31 October and 16 November, taken from the VIIRS Today website, show silt from this flood event.

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The difference between the 16 November and 17 November Joint ABI/VIIRS Flood Extent product is shown below. The extensive flooding on the Sumas Prairie near Abbotsford in Canada is apparent.

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The polar orbiting satellite Metop-A was switched off on 15 November 2021, ending a very long career gathering information (the satellite was launched in 2006). The final ASCAT (ascending) imagery from Metop-A, from this site, is shown above (click here to see the descending data from that day). ASCAT scatterometery from satellites operated by EUMETSAT will now be limited to Metop-B and Metop-C (Click here for more information on Metop-A in the near future; click here for information on Metop satellites). ASCAT data is obviously important for defining wind features over the open ocean, where conventional data is sparse.

The loss of Metop-A ASCAT data means a 50% reduction in the scatterometery data assimilated into US Numerical models. Only Metop-B ASCAT data are now assimilated; work continues on incorporating Metop-C ASCAT data into assimilation schemes.

Metop-A also carried AVHRR, IASI, HIRS, AMSU and MHS instruments. Metop-C is Metop-A’s replacement.

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*Metop-A does continue to supply some (non-ASCAT) information to NESDIS (my thanks to Liam Gumley, SSEC, for this information!) as shown at this website. Not all instruments have (as yet) been switched off.

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The toggle above shows NEXRAD radar (source) inset during lake-effect precipitation with two versions of the GOES-16 Day Cloud Phase Distinction RGB, one with default values, and one with ‘Green’ (ABI Band 2 Visible imagery at 0.64 ?m) and ‘Blue’ (ABI Band 5 at 1.61 ?m) reduced from default values, from 79% to 60% for Band 2, and from 59% to 50% for Band 5 (by using the composite option feature in AWIPS). It can be advantageous to alter the bounds on some RGBs during periods of low light (i.e., sunrise and sunset) to accentuate features. However, make certain at some point to reload with the default value! As the sun rises higher into the sky, features will start to look unfamiliar if the modified RGB menu remains.

The radar/satellite comparison bears comment. First, note that the location of circled features is not quite the same, due to parallax (discussed here and here): The effect of parallax is that clouds are shifted away from the sub-satellite point in AWIPS. The effect is most pronounced for towering summertime thunderstorms, but even clouds producing lake-effect snow, clouds that are far more shallow, will be shifted.

The Day Cloud Phase Distinction RGB will show clouds with more of a yellow tint when those clouds glaciate, as might be expected in more intense lake-effect snow-producing clouds. As clouds glaciate, the ‘blue’ part of this particular RGB is reduced: ice crystals within the cloud absorb (rather than reflect) solar energy at 1.61 ?m. In the toggle above, clouds with a modest yellow enhancement in the RGB align well in three circled regions where radar suggests vigorous precipitation might be falling. This is a seasonal reminder, then, to use the Day Cloud Phase Distinction to highlight regions — during the day — where lake-effect might be most impactful.

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A similar example is shown above from 16 November. NEXRAD Radar (on the right) shows a single band with strongest returns stretching east-southeastward from just north of Rochester. Note the distinct color change to the cloud band in the RGB that overlays the strongest radar returns. Similar colors in the RGB are also present east of eastern Lake Ontario, where radar returns are also present.

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