In the wake of a southward surge of arctic air across the central US — which produced surface temperatures as cold as -50ºF in Minnesota on 13 February — GOES-16 (GOES-East) Day Cloud Phase Distinction RGB images (above) showed the large areal extent of snow cover (brighter shades of green) across Oklahoma, New Mexico and Texas on 15 February 2021. In the RGB images, low-level supercooled water droplet clouds appear as pale shades of white.

As the Arctic chill continues to grapple the Plains, numerous new record lows were established this morning. Many of these locations will experience even lower temperatures by Tuesday morning, with additional record lows expected. pic.twitter.com/w3QifTxQkU

— NWS Weather Prediction Center (@NWSWPC) February 15, 2021

A closer view of GOES-16 Day Cloud Phase Distinction RGB images (below) showed the far southern extent of snow cover across northern Mexico and southern Texas. Precipitation briefly transitioned from rain to snow as far south as Brownsville, but there was no accumulation at that site.

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images (below) revealed a number of lake effect cloud plumes across northern and eastern Texas, as cold air moved across the warmer waters of small lakes.

Farther north over the Texas Panhandle, GOES-16 “Snow/Ice” images (below) showed a small cloud plume originating at the Xcel Energy Harrington Station power plant just north-northwest of Amarillo (KAMA). Note the drop in surface visibility to 5 miles at 17 UTC — this was likely due to snow flurries as the cloud plume drifted over the airport.

A timely overpass of Landsat-8 provided a 30-meter resolution False Color RGB image at 1721 UTC, as viewed using RealEarth (below) — as the cloud plume drifted over the KAMA airport, the 17 UTC METAR surface report indicated that the cloud base was at 1000 feet.

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On the following day, GOES-16 CIMSS Natural Color RGB images with plots of Metop-A ASCAT winds (above) showed how Tehuano gap winds had moved through Chivela Pass in southern Mexico (topography) and were spreading out across the Gulf of Tehuantepec (south of Ixtepec, station identifier MMIT). The highest surface scatterometer wind speeds were 24 knots near the coast.

With a low sun angle maximizing forward scattering, a plume of blowing dust could be seen right after sunrise in GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (below), moving southward across the Gulf of Tehuantepec.

? Starting a thread with records, stats, and other superlatives from the mid-February winter weather blitz. This may not be everything — there’s too much going on! — but these are the things that I’ve noticed. ?????

— Alex Lamers (@AlexJLamers) February 17, 2021

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Synthetic Aperture Radar (SAR) imagery can be used to produce very high resolution mapping of winds. Imagery is available in selected domains at this NOAA/OSPO website; OSPO is the Office of Satellite Product Observations. Data are available from three different satellites: Sentinel-1/Sentinel-2 (managed by the European Space Agency) and RADARSAT (managed by the Canadian Space Agency). These space-borne radars can operate in a mode that provides very small-scale wind information, as shown above.  Note the fine detail in the winds — elongated regions of winds in excess of 20 knots from north of Green Bay southeastward across Lake Michigan to North and South Manitou islands.  What does the ABI Imagery look like at the same time?

GOES-16 Band 7 (3.9 µm) imagery, below, similarly shows three parallel lines of colder cloud tops (the greyscale enhancement used is such that colder values are whiter). SAR data shows that convective bands over the lake have stronger surface winds than regions in between the convective bands.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Day Cloud Phase Discrimination RGB images (above) showed the development of a mesovortex over southern Lake Michigan on 12 February 2021. The surface flow supporting the mesovortex formation was well-depicted by hourly RAP40 model output. Note that there was a lack of GOES-16 Visible (Band 2) Derived Motion Winds created for this feature — this was likely due to high clouds drifting over the area, making it difficult for the algorithm to properly identify and track surface or near-surface cloud elements. In the western portion of the lake, a ribbon of ice was evident in the nearshore waters of Wisconsin and Illinois.

The GOES-16 Day Cloud Phase Discrimination RGB images indicated that convective cloud elements near the vortex center were becoming glaciated (as highlighted by brighter shades of green) — and light snow reduced the surface visibility to 2.5 miles at Holland, Michigan (KBIV) as the vortex moved inland. A toggle between GOES-16 Visible and Day Cloud Phase Discrimination RGB images at 1800 UTC is shown below.

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The animation above shows GOES-16 Band 4 (1.38 µm, “Cirrus Channel) Imagery along with GOES-16 Derived Motion Wind vectors and Turbulence observations. Significant and widespread turbulence occurred. Of particular interest is a arced feature that appears in the GOES-16 imagery from northern Mississippi through western Tennessee and into south-central Kentucky.  Turbulence occurs along this feature, where strong downward motion is likely present. Note this raw PIREP, for example, showing a very large vertical change!

UUA /OV RQZ/TM 1801/FL 410/TP C25M/TB SEV CAT/RM + OR - 1000 FT AND +60 KNOTS NO INJURIES NO DAMAGE

The curved structure is also prominent in the GOES-16 Band 8 (6.19 µm, Upper Level Water Vapor) infrared imagery shown below in a rocking animation.  It emerges out of convection along the Gulf Coast and subsequently races to the northeast.  The feature is less obvious in the Band 10 animation, suggesting that it is fairly high in the atmosphere. The 1200 UTC sounding from Jackson MS (link, from this website) shows a strong inversion at 500 mb; this might be the vertical boundary under which this feature is trapped. The weighting function for the Jackson sounding (here, from this site), shows peak values for all three water vapor channels very close to 500 mb.

Note that the arcing feature is apparent first in the upper-level water vapor imagery, then in the lower-level water vapor and cirrus channel imagery.

The mp4 animations below are also available as animated gifs: 6.19 µm, 7.34 µm and 1.38 µm)

GOES-16 6.19 µm (Band 8, “Upper-Level Water Vapor”) Infrared Imagery, 1236 UTC 11 February – 0001 UTC 12 February 2021 (Click to play mp4 animation)

 

GOES-16 7.34 µm (Band 10, “Low-Level Water Vapor”) Infrared Imagery, 1236 UTC 11 February – 0001 UTC 12 February 2021 (Click to play mp4 animation)

GOES-16 1.38 µm (Band 4, “Cirrus Channel”) near-infrared Imagery, 1401 UTC – 2201 UTC 11 February 2021 (Click to play mp4 animation)

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CIMSS scientists have recently upgraded a turbulence detection product that was developed using machine learning, combining Satellite Data, principally GOES-R Band 8 (6.19 µm, a “water vapor” band on GOES-R) and Band 13 (the Clean Window infrared, 10.3 µm) and trained on observations of EDR (Eddy Dissipation Rate). These mappings of Probabilities of Moderate or Greater (MOG) turbulence are available online at this website. How did this product fare on this day of active turbulence.

Animations below show predictions of MOG from 1200 to 2350 UTC on 11 February 2021. Predictions of MOG at 30000-31000 feet, 36000-37000 feet and 40000-41000 feet are shown.  The probability contours are shown on top of a grey-scaled 6.19 µm water vapor image, and observations of turbulence are included.

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