LightningCast in cold air

December 11th, 2021 |
RealEarth presentation of GOES-16 Clean Window infrared along with contours of LightningCast Probability (10 (blue), 25 (cyan), 50 (green) and 75 (purple) %). GLM Flash Extent Density is also shown. Data are every 5 minutes from 0700 – 1000 UTC on 11 December 2021 (Click to enlarge)

LightningCast probabilities are part of the ProbSevere portfolio, and they are available in RealEarth (link). This machine-learning product relates Band 13 and Band 15 observations to the probability of lightning occurrence (in daytime, Band 2 and Band 5 are also used). When your blogger was awakened by thunder (at 0826 UTC), as cold rain fell on the roof, he naturally thought: “I wonder what LightningCast is doing?” The animation above shows probabilities increasing as lightning developed over southern Wisconsin. Initial lead time for lightning from the probabilities is not big — but probabilities do expand and encompass the region that is experiencing lightning. The time of the lightning did match the closest approach of the surface low, as shown in this 0900 UTC surface analysis.

That lightning was produced in near-freezing surface temperatures reflects the vigor of this extratropical system that spawned a deadly tornado outbreak over the mid-Mississippi River Valley and lower Ohio River Valley (SPC Storm Reports).

Historic tornado outbreak affecting the Midwest and Southeast US

December 11th, 2021 |

GOES-16 “Clean” Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in cyan [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) include time-matched plots of SPC Storm Reports during a large outbreak of severe weather across parts of the Midwest and Southeast US from late in the day on 10 December to a few hours after midnight on 11 December 2021. The severe thunderstorms developed in advance of a strong cold front that was moving toward the Lower Mississippi Valley (surface analyses | VIIRS Infrared image). There were dozens of tornado-related deaths in 5 states — Kentucky, Arkansas, Tennessee, Missouri and Illinois — with most of those (at least 70) being in Kentucky. This event has become the deadliest December tornado outbreak in modern history.

Shown below is a closer look at the long-lived “Quad-State Supercell” thunderstorm that likely produced a  family of tornadoes that moved across northeast Arkansas, southeast Missouri, northwest Tennessee and western Kentucky. Note that a mesonet station 6 miles southwest of Mayfield, Kentucky reported a wind gust to 107 mph a few minutes before the tornado struck Mayfield — and after 0335 UTC, the Mayfield Airport (KM25) stopped providing data (presumably due to widespread tornado-related power outages). The pulsing of colder overshooting tops (highlighted by shades of white within black-enhanced cloud tops) was evident at the vertex of a prominent Enhanced-V signature — and this signature indicated that an Above-Anvil Cirrus Plume (reference | VISIT training) was likely present.

GOES-16 “Clean” Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in cyan [click to play animated GIF | MP4]

For the fatal tornado that struck Mayfield, Kentucky this pulsing of overshooting tops during the time from Tornado Warning issuance (0305 UTC) to its arrival in Mayfield (around 0325 UTC) was seen in 1-minute GOES-16 Infrared images viewed using RealEarth (below).

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animated GIF | MP4]

In addition to the severe weather produced by this event, farther to the west strong westerly winds — ahead of a pair of advancing cold fronts — lofted multiple plumes of blowing dust, whose source regions were in New Mexico and Texas. GOES-16 True Color RGB images created using Geo2Grid (below) highlighted the tan-colored dust plumes (along with a couple of brighter white wildfire smoke plumes).    

GOES-16 True Color RGB images [click to play animated GIF | MP4]

GOES-16 Dust RGB mages (below) showed the eastward/northeastward transport of airborne dust (brighter shades of magenta) past sunset. At some locations, peak wind gusts were in the 50-60 knot range and surface visibility was reduced to 3 miles or less.

GOES-16 Dust RGB images [click to play animated GIF | MP4]

Additional information about this severe weather event is available from: NWS Little Rock AR | NWS Memphis | NWS Paducah KY | NWS Louisville KY.  

GLM observations of a long-track tornado

December 11th, 2021 |
GOES-16 GLM Total Optical Energy, 2101 UTC on 10 December through 0600 UTC on 11 December 2021 (Click to enlarge)

Gridded GLM observations of Total Optical Energy, above, capture the tornado-producing long-lived storm that hit Mayfield KY (and others) on 10 December. This storm had its genesis in eastern Arkansas, and it moved northeastward through the bootheel of Missouri, then into western Kentucky. It was mostly isolated from a line of convection to its west until it approached Louisville at around 0600 UTC, when the cells began to join together.

GLM observations of Average Flash Area for the same time period are shown below.

GOES-16 GLM Average Flash Area, 2101 UTC on 10 December through 0600 UTC on 11 December 2