NUCAPS sounding associated with strong winds over the central United States

December 15th, 2021 |
NUCAPS Sounding Availability, 1750 and 1932 UTC on 15 December 2021 (Click to enlarge)

NOAA-20 overflew the central United States twice in the afternoon of 15 December 2021 (NOAA-20 orbits that day shown here, from this website) as a potent weather system moved through. SPC‘s Convective Outlook showed a Moderate Risk of severe weather (link); There was widespread wind damage on this day (link). How could NUCAPS soundings (available in AWIPS as demonstrated here) on that day assist in understanding the state of the atmosphere? The toggle above shows where NUCAPS profiles were available. Blue boxes highlight profiles that are shown below. Note right away that the NOAA-20 orbits on the 15th allowed for multiple samplings of the atmosphere at the northern edge of the Moderate Risk. The soundings along the western edge of the ca. 1800 UTC NOAA-20 NUCAPS pass, below, show steep mid-level lapse rates, and MUCAPE values (as diagnosed by NSharp in AWIPS) increasing to the south.

NUCAPS soundings in central Iowa, location as indicated by the small blue circle within the blue polygon, around 1750 UTC on 15 December 2021. Computed MUCAPS is indicated for clarity — it’s also within the small readout below the sounding (Click to enlarge)

GOES-16 data can also be used to diagnose instability, and the Level 2 Product (Derived Stability Index) Lifted Index at 1751 UTC is shown below. The Level 2 product also shows stability decreasing to the south in Iowa. Keep in mind that southerly surface winds at this time (as shown in this visible image with surface observations in a toggle with the Dust RGB and NUCAPS Sounding Availability) were very strong with this dynamic system: advection could be very large.

NUCAPS Sounding at 41.3 N, 93 W, the location indicated by the light blue circle within the blue polygon, and GOES-16 Derived Stability (Liifted Index) at about the same time, 1750 UTC on 15 December 2021 (Click to enlarge)

Select vertical profiles from the subsequent NUCAPS swath shortly before 2000 UTC are shown below.

NOAA-20 NUCAPS Profiles at select point (indicated by blue boxes) at 1953 UTC. NUCAPS sounding availability is also shown above the GOES-16 Lifted Index at about the same time. Minimum Lifted Index values (bright yellow) are around -2. Click to enlarge)

Several profiles in the animation above deserve special mention. The first two comparisons, below, compare profiles from the two overpasses.

The sounding in southern Minnesota samples a region very close to a sounding location from 90 minutes earlier. The toggle below of sequential profiles shows a change in stability as diagnosed by NUCAPS. The mid-level lapse rate has steepened, and mid-level moisture has increased. Observations from sequential passes do not happen every day, but forecasters (north of about 41 N) can (and should!) take advantage of them, time permitting, when they do happen.

NOAA-20 NUCAPS Profile over southern Minnesota, 1815 and 1955 UTC on 15 December 2021 (Click to enlarge)

A similar comparison over southern Iowa is shown below, showing the ca. 1815 UTC profile first (the one with the highest diagnosed MUCAPE) toggled with two later adjacent profiles. Note how the mid-level lapse rates have destabilized in the later profiles

NUCAPS profiles at ca. 1800 UTC and 1930 UTC at the locations indicated over southern Iowa (Click to enlarge)

NUCAPS soundings that are in the moist air ahead of developing convection and within dry, dusty air behind the convective line at around 1953 UTC in Kansas are shown below. As with other soundings in the moist air, mid-level lapse rates show weak stability. The sounding closest to the developing convection shows abundant moisture in the lower troposphere. Soundings in the dusty air are very very dry : diagnosed total precipitable water is less than 0.3″. Visible imagery in the background image below shows the dusty air over western Kansas, it’s far more apparent in this toggle of visible imagery and the dust RGB at 1931 UTC!

NUCAPS Profiles at ca. 1953 UTC on 15 December 2021 across a developing squall line in Kansas, from moist air to a dust environment. Visible imagery with Derived Stability Index at 1931 UTC also shown (click to enlarge)

NUCAPS profiles over Kansas in front of the developing convection, below, show very steep lapse rates in the mid-troposphere! (Among the largest values this blogger has seen!) This suggests explosive development is possible if convection develops.

NUCAPS Profiles at the locations indicated just to the east of a developing convective line in Kansas, just before 2000 UTC on 15 December 2021 (Click to enlarge)

Gridded values of NUCAPS temperature and moisture (and of values derived from those fields) are available at this website. In addition, those values will shortly be available in RealEarth. Gridded 850-500 mb Lapse Rates derived from the two sequential NOAA-20 NUCAPS profiles are shown below. Much of the central/southern Plains has very low mid-tropospheric stability.

Gridded values of 850-500 mb Lapse Rate, 1805 and 1942 UTC on 15 December 2021 (Click to enlarge)

NUCAPS profiles give timely and independent estimates of atmospheric temperature and moisture in the mid-afternoon over the central United States; thus they are frequently useful for estimating convective potential.

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

Severe thunderstorms across the Northeast US

November 13th, 2021 |

GOES-16 “Red” Visible (0.64 µm) images, with SPC Storm Reports plotted in red [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) include time-matched plots of SPC Storm Reports — and showed severe thunderstorms moving eastward across parts of New Jersey, New York, Connecticut, Rhode Island and Massachusetts on 13 November 2021. These storms developed along and just ahead of a cold front (surface analyses), the position of which was highlighted by an “arc cloud” extending southward across the Atlantic Ocean.

The corresponding 1-minute GOES-16 “Clean” Infrared Window (10.35 µm) images (below) extended past sunset into the early evening hours; the low-topped convection only displayed coldest cloud-top infrared brightness temperatures in the -40 to -50ºC range (green to yellow enhancement).

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