The wide-ranging high-impact storm that brought snowfall in a long band from the Southern Plains to the eastern Great Lakes and New England, as shown here (analysis from this website), and severe weather to Mississippi and Alabama, produced significant icing over the mid-south. With the icing came power outages, as shown in this screenshot (from 1410 UTC on 4 February 2022) from the Memphis (TN) Power and Light website. (You can also view state-wide maps, from this website, for Tennessee and Arkansas).

Day Night Band imagery on both NOAA-20 and Suomi-NPP can be used to determine the horizontal extent of Power Outages (as noted on this blog in the past numerous times; here and here for example). The NOAA-20 Day Night Band image above (NOAA-20 orbits for 4 February are shown here), centered on Memphis, and derived from the VIIRS Today Website, shows light emissions over Memphis and surroundings (note that the Moon on 4 February will not be providing lunar illumination at 0737 UTC; it is just 4 days past a New Moon, and the Moon set at 0224 UTC on 3 February). How can you judge the effect of power outages using the Day Night Band? This is typically done by comparing Day Night bands from before and during the Power Outages — with similar cloud cover. Finding similar cloud cover and similar lunar illumination is a challenge. A possible example is shown below, a toggle between NOAA-20 images on 4 February and from 32 days earlier, on 3 January.

Even with identical viewing geometry, and similar cloud conditions, it’s difficult to ascertain where lights are not present because of outages, and where they might be missing because of cloud cover. Regions to the east and south of Memphis show fewer light signals on 4 February — but clouds are also thicker there on 4 February!

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US Space Force EWS-G1 (formerly GOES-13) Infrared Window (10.7 µm) images (above) showed Cyclone Batsirai in the South Indian Ocean — just north of the island nations of Mauritius and Réunion — during the time period it was classified as a Category 4 intensity storm (00 UTC on 02 February to 15 UTC on 03 February 2022). Note that the small-diameter eye became notably larger by the end of the animation.

A DMSP-17 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) displayed evidence that Batsirai had recently completed an eyewall replacement cycle (ERC), with the faint signature of the original small-diameter eye surrounded by the new large-diameter eye. This ERC process — seen in a 48-hour MIMIC-TC animation — initiated Batsirai’s gradual  decline in intensity.

EWS-G1 Visible (0.63 µm) images (below) showed that the small eye was initially cloud-filled, but eventually cleared during the day on 02 February — to reveal the possible existence of eye mesovortices (although such features are difficult to diagnose using 30-minute images) .

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GOES-16 True-Color imagery from CSPP Geosphere (direct link to animation), above, shows high clouds over Lake Erie moving eastward as lake ice moves to the north. It is an unusual day that allows a (relatively) unobstructed view of the lake surface. Clouds are often present. Note that southern Lake Huron also seems ice-covered; western Lake Ontario is clear of ice.

The image below shows ice over eastern Lake Erie and Lake Ontario from Synthetic Aperture Radar (SAR) data from the RADARSat Constellation Mission 3 (RCM3) satellite on 1 February (after sunset) from this website. Ice is indicated over eastern Lake Erie, and over central Lake Erie south of Long Point, Ontario. RCM orbits produce overlaps every 4 days, so a similar view occurred on 28 January; this is useful to see how things change. With practice, your eye will differentiate ice structures from wind features. This is especially true if you view the imagery daily.

Synthetic Aperture Radar (SAR) data from RADARSAT Constellation Mission (RCM) satellites do give very high-resolution views of wind and ice over water. Wind roughens the open water surface, and the capillary waves that form on the water surface produce Bragg Scattering to which the SAR instruments are sensitive. Past blog posts that relate SAR observations to winds are here. (In the imagery above, plotted winds — in white — are from the GFS analysis) When ice starts to cover a lake, the roughness of the lake is damped, and it becomes more difficult for the wind to perturb the lake surface. In addition, a smooth ice surface will reflect microwave signals, not scatter them. However, frozen lake surfaces are not always smooth, and strong microwave signals can be reflected back to the SAR satellites, as suggested in the imagery above.

At the request of National Weather Service forecast offices, NOAA STAR’s SAR Team is creating a website that includes daily SAR imagery (when available) over the individual Great Lakes. The website is shown at bottom. Of particular interest for ice detection are the black and white NRCS (Normalized Radar Cross Section) images. The NRCS image that corresponds to the color image above is shown below. It has remarkable detail.

The Operational SAR website for the Great Lakes is shown below. Of special note are the individual Lake views that are available by clicking on the desired Great Lake. Click, and then scroll down and view all the recent SAR imagery available over that Lake, as shown below for Lake Erie.

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MIMIC Total Precipitable Water esimates over the Indian Ocean for the 24 hours ending at 2000 UTC on 1 February 2022, above, show the strong cyclonic circulation associated with Cyclone Basirai. Its forecast motion is westward towards Madagascar, as shown in the toggle below that also includes sea-surface temperatures and Window Channel (showing a well-structured storm; all images are from the SSEC/CIMSS Tropical Website). A wind shear analysis (also from the SSEC Tropical Website and valid at 1800 UTC on 1 February) for the Indian Ocean shows low shear values over the storm, but relatively high shear between the storm and the island of Madagascar.

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Batsirai’s path moves it close to Mozambique/Malawi, two countries that are still being flooded as a result of rains from Tropical Storm Ana a week ago. A VIIRS flood analysis (from this website), below, diagnoses active flooding occurring along the Shire River (south of Lake Malawi) and along the Zambezi River on 31 January 2022.

For more information on Batsirai, consult the RSMC at La Réunion (click ici) or the SSEC Tropical Website.

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