Showers over Wisconsin as viewed by GOES-16 Day Cloud Phase Distinction and Radar

April 21st, 2021 |

GOES-16 Day Cloud Phase Distinction RGB with 0.5 Reflectivity (Great Lakes Mosaic), 1836 UTC on 21 April 2021 (Click to enlarge)

The animation above toggles through the 1836 UTC GOES-16 Day Cloud Phase Distinction RGB with and without a Great Lakes Radar Mosaic of 0.5-degree Reflectivity.  There is an excellent correlation between green-tinted clouds in the RGB (signifying glaciated clouds) and radar echoes, so much so that it should be easy to say that clouds with the same color where radar data are missing, over north-central Wisconsin and the western Upper Peninsula, are also precipitating.  This relationship between the RGB and radar echoes has been noted before (here, very notably; see Figure 6!), and is most useful in cases of convective development without overlaying cirrus clouds.

(Added: Some of the snow showers in the Fox River Valley of Wisconsin were high-impact, as shown in this video)

Consolidation of ice within Green Bay

March 4th, 2021 |

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the wind-driven consolidation of ice within Green Bay during the 03 March04 March 2021 period. Northerly winds in the wake of a cold frontal passage on 03 March led to the fracturing of land-fast ice in the far northern portion of Green Bay — this ice then began drifting south-southwestward.

By sunrise on 04 March, GOES-16 Visible images indicated that the fractured ice had continued to drift farther southward overnight, eventually merging with the land-fast ice that had been covering the southern half of Green Bay; overnight low temperatures in the upper teens to low 20s F likely aided this merger process. Note that some filaments of ice had also migrated through gaps between islands, drifting southward across far western Lake Michigan (just off the coast of Wisconsin).

A toggle between 250-meter resolution Aqua MODIS True Color RGB images (source) on the 2 days is shown below.

Aqua MODIS True Color RGB images [click to enlarge]

Aqua MODIS True Color RGB images [click to enlarge]

As an aside, farther inland the tornado damage path from an EF3 tornado in northeastern Wisconsin was still evident, 13.5 years later (below).

Aqua MODIS True Color RGB images [click to enlarge]

Aqua MODIS True Color RGB images [click to enlarge]

Snow squalls in Montana

February 27th, 2021 |

GOES-16 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images (above) showed a cluster of convective features propagating south-southeastward over and to the east of Billings, Montana on 27 February 2021. The shades of green in the RGB images indicated that some of these cloud tops were glaciating, suggesting enough vertical development to produce significant precipitation — and the resulting snow squalls could have contributed to a multi-vehicle accident which closed down Interstate 90 (between Billings and the I-90/I-94 junction) shortly after 1900 UTC. A brief accumulation of 1.3 inches was reported just north of Billings around the time of the accident, and the 1900 UTC surface visibility dropped to 3/4 mile at Billings airport (but was likely lower where the more intense snow squalls were occurring farther east).

The corresponding GOES-17 (GOES-West) Visible/RGB animations are available here: GIF | MP4. A toggle between the 1901 UTC Day Cloud Phase Distinction RGB images from GOES-16 and GOES-17 is shown below. The satellite viewing angles are nearly equivalent from both satellites (around 60 degrees) — but the apparent location of the snow squall features is shifted, due to parallax.

1901 UTC Day Cloud Phase Distinction RGB images from GOES-16 and GOES-17 [click to enlarge]

1901 UTC Day Cloud Phase Distinction RGB images from GOES-16 and GOES-17 [click to enlarge]

VIIRS Imagery shows ice cover on Great Lakes

February 20th, 2021 |

Suomi-NPP VIIRS true-color imagery (1843 UTC) and GOES-16 Band 5 (1.61 µm) imagery (1841 UTC) on 20 February 2021 (Click to enlarge)

An uncommon somewhat clear day on 20 February 2021 allowed VIIRS on Suomi-NPP to provide a true-color image of all 5 Great Lakes. The true-color image above is shown in a toggle with GOES-16 “Snow-Ice” Band 5 near-infrared data (1.61 µm) that allows for discrimination between clouds made up of water droplets (bright white) and underlying snow/ice (darker grey).  Much of western Lake Superior shows ice:  highly reflective in the true color imagery and much darker in the snow/ice channel (but not quite as dark as open water).  Lake Superior has about 50% ice coverage (this figure, originally from this website).  Western Lake Michigan shows little ice coverage (except over Green Bay);  ice coverage on Michigan is less than 30%.   Lake Erie is the most ice-covered of the Lakes:  around 80% ice-covered.  Recent northwesterly winds have moved the pack ice away from the northern shore (except for the far western basin).