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Satellite signatures of widespread ice accretion

In a sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Day Snow-Fog RGB images (above), areas that received a significant accretion of ice — via sleet and/or freezing rain/drizzle from a significant winter storm — appeared as darker shades of gray to black in the 1.61 µm... Read More

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Day Snow-Fog RGB images [click to play animated GIF | MP4]

In a sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Day Snow-Fog RGB images (above), areas that received a significant accretion of ice — via sleet and/or freezing rain/drizzle from a significant winter storm — appeared as darker shades of gray to black in the 1.61 µm images and as darker shades of red in the RGB images on 04 February 2022

A toggle between Suomi-NPP VIIRS Visible (0.64 µm) and Near-Infrared (1.61 µm) is shown below, and provided a higher-resolution view of the darker ice accretion signature at 1942 UTC.

Suomi-NPP VIIRS Visible (0.64 µm) and Near-Infrared (1.61 µm) images [click to enlarge]

===== 05 Februray Update =====

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Day Snow-Fog RGB images [click to play animated GIF |MP4]

On the following day, clouds had cleared from much of the central US — enabling the areal coverage of this ice accretion signature to be seen across parts of Texas, Oklahoma, Arkansas, Tennessee, Kentucky (above). A comparison of GOES-16 “Red” Visible, Near-Infrared “Snow/Ice” and Day Snow-Fog RGB images at 1501 UTC (below) showed how this darker ribbon of ice accretion was located along the southern edge accumulating snowfall produced by the winter storm.

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Day Snow-Fog RGB images at 1501 UTC [click to enlarge]

A closer view centered on the Missouri-Illinois-Kentucky-Tennessee border region (below) showed (1) the subtle effects of topography on resultant snow/ice accumulation, and (2) the darker appearance on Snow/Ice and RGB images in some areas that appeared to be bare ground in the Visible images (due to the clear/translucent nature of any sleet and/or freezing rain on the surface). Unfortunately, a portion of that satellite scene was also affected by a major tornado outbreak about 2 months prior to this winter storm.     

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Day Snow-Fog RGB and Topography images at 1501 UTC [click to enlarge]

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Power outages over the mid-South

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)... Read More

NOAA-20 Day Night Band centered on Memphis, TN; click to enlarge

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!

NOAA-20 Day Night Band imagery on 3 January and 4 February 2022 (Click to enlarge)

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Cyclone Batsirai reaches Category 4 intensity

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... Read More

EWS-G1 Infrared Window (10.7 µm) images [click to play animated GIF | MP4]

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.

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

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) .

EWS-G1 Visible (0.63 µm) images [click to play animated GIF | MP4]

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Ice over the Great Lakes

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... Read More

GOES-16 True Color Imagery, 1601-1841 UTC on 1 February 2022 (Click to enlarge)

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.

RCM3 SAR imagery over eastern Lake Erie and Lake Ontario, 2307 UTC on 1 February 2022 (Click to enlarge)

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.

RCM3 NRCS imagery over eastern Lake Erie and Lake Ontario, 2307 UTC on 1 February 2022 (Click to enlarge)

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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