An extratropical cyclone deposited a mesoscale snowband — a few counties wide — in south-central Kansas late in the day on 24 November 2020 (Click here to see the storm at 0300 UTC on 25 November). As is often the case, such bands have profound impacts on surface temperatures. It is therefore important to monitor their precise location. The animation above shows the Day Snow Cloud RGB; its use of the 1.61 µm band allows the RGB to distinguish easily between snow and clouds, both of which are bright in the visible, as shown in the image below, courtesy Mike Umscheid, NWS ICT, that shows the snow band and the similarly reflective clouds to the east. (Imagery created at this nifty website!)

GOES-16 Land Surface Temperatures (a baseline level 2 product) shows the effect of the snow on skin temperature, below. Shortly after sunrise, temperatures over the snowband are several degrees (Fahrenheit) cooler, as expected with clear skies and a fresh snowpack. (Warm lakes also shine through!)  Bare land in Kansas warms quickly, with Skin Temperatures reaching into the upper 60s and 70s by 1900 UTC, whereas the snow band remains in the 30s!

A comparison of GOES-R Land Surface Temperatures with METAR observations, below, underscores the notion that the skin temperature can be much warmer than the temperature 1.5 m above the ground, where METAR thermometers (or thermistors) measure the air temperature. The warmest METAR temperature at 2000 UTC is 57º F at Scott City, KS. Land Surface Temperatures there are in the mid-60s, with 70 just to the northeast.

Note that the default bounds of the colorbar range in Land Surface Temperature have been changed. Default values range from -10º to 110º F; values shown above range from 10º to 80º F. The toggle below compares the two, at 1501 UTC.

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Towards sunset, the Day Snow Fog RGB (or any RGB that relies on reflectances from visible, near-Infrared or infrared channels) can become dim. In that event, an AWIPS user can edit the Composite Options, reducing the upper bounds of all three RGB channels o that the image retains brightness and utility (in this case upper bounds were reduced for Red from 100 to 60; for Green from 70 to 40; for Blue from 30 to 19).

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US Space Force EWS-G1 Infrared (10.7 µm) images (above) showed Category 1 Cyclone Nivar making landfall along the southeastern coast of India on 25 November 2020.

EUMETSAT Meteosat-8 Infrared Window (10.8 µm) images with contours of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) indicated that Nivar was moving through an environment of low shear (and over warm water) — factors favorable for the storm maintaining its intensity.

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GOES-17 (GOES-West) Upper-level Water Vapor (6.2 µm) and Air Mass Red-Green-Blue (RGB) images (above) displayed a series of shear vortices migrating southward over the East Pacific Ocean (off the cost of the Pacific Northwest) on 24 November 2020. The ribbon of brighter orange to red hues on the RGB images highlight regions of dry, ozone-rich air where the tropopause was at a significantly lower altitude compared to adjacent areas.

GOES-17 Water Vapor images with isotachs of NAM40 model maximum wind speed (below) showed that these vortices were forming within a very tight gradient in wind velocity (which existed just to the left of a southward-moving polar jet streak) — so speed shear was a mechanism playing a role.

GOES-17 Air Mass RGB images with and without contours of NAM40 model PV1.5 pressure (below) indicated that the dynamic tropopause descended to the 500-600 hPa level in the vicinity of the most well defined shear vortices. Occasionally aircraft encounter turbulence near these types of vortices — but in this case, there were no pilot reports of turbulence in those areas.

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EUMETSAT Meteosat-11 High Resolution Visible (0.8 µm) images (above) showed a westward-moving medicane which developed a fairly distinct eye shortly before making landfall along the eastern coast of Tunisia on 22 November 2020.

A Suomi NPP VIIRS True Color Red-Green-Blue (RGB) image displayed using RealEarth (below) provided a higher-resolution view of the medicane’s eye and convective banding at 1152 UTC.

A plot of surface observations for Monastir’s Habib Bourguiba International Airport DTMB (below) showed that winds gusted to 43 knots as the system made landfall.

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