Midwest derecho

July 19th, 2017 |

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

A long-lived mesoscale convective system (MCS) known as a derecho produced swath of damaging winds — as well as some large hail and a couple of tornadoes — that stretched from north-central South Dakota to northwestern Indiana on 19 July 2017 (SPC storm reports | TWC summary). GOES-16 “Clean” Infrared Window (10.3 µm) images (above) showed the southeastward propagation of the storm system.

Closer views of the early stages of the derecho as it moved across central and eastern South Dakota are shown below, using GOES-16 “Red” Visible (0.64 µm) and Infrared Window (10.3 µm) images. The highest measured wind gust was 100 mph near Polo (1522 UTC), with 83 mph recorded at Huron (1636 and 1730 UTC). Hail of 2.50 inches in diameter fell near Cavour (1703 UTC). Note that most of the severe reports were in the general vicinity of the persistent cold overshooting top (black to white enhancement) seen on the Infrared imagery; due to parallax, the apparent location of this storm-top feature was shifted slightly north of its true location.

GOES-16 Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

1-km resolution Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images at (below) showed the MCS over the Huron (KHON) area at 1656 UTC. Since there is minimal parallax associated with polar-orbiter satellite imagery, the cluster of SPC storm reports (occurring within +/- 30 minutes of the time of the MODIS image) was much closer to the cold (-70 to -73º C, lighter gray enhancement) overshooting top. Another feature of interest seen on the Infrared image was a “warm trench” (exhibiting brightness temperatures as warm as -60º C, red enhancement) immediately surrounding the cold overshooting top — perhaps a result of compensating subsidence?

Terra MODIS Visible and Infrared Window (11.0 µm) images, with SPC storm reports [click to enlarge]

Terra MODIS Visible and Infrared Window (11.0 µm) images, with SPC storm reports [click to enlarge]

375-meter resolution Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1846 UTC (below) provided a detailed view of the MCS as it was centered near the South Dakota / Minnesota border. The coldest cloud-top IR brightness temperature was -83º C (violet enhancement).

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with SPC storm reports [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with SPC storm reports [click to enlarge]