Large hail and high winds in South Dakota and Nebraska

July 27th, 2018 |

GOES-16

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

A supercell thunderstorm which developed in southeastern Montana during the afternoon hours on 27 July 2018 produced damaging wind-driven hail as it moved southeastward across western South Dakota into far northern Nebraska (SPC storm reports | NWS Rapid City summary). 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the evolution of this storm.

The corresponding GOES-16 “Clean” Infrared Window (10.3 µm) images (below) revealed minimum cloud-top infrared brightness temperatures in the -60 to -70ºC range (darker red to black enhancement) with the strongest pulses of overshooting tops. The storm began to exhibit a well-defined enhanced-V signature once it crossed the South Dakota / Nebraska border after about 0200 UTC.

GOES-16

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

===== 30 July Update =====

Terra MODIS True Color and False Color RGB images [click to enlarge]

Terra MODIS True Color and False Color RGB images, with hail damage swath highlighted by red arrows [click to enlarge]

A comparison of 250-meter resolution Terra MODIS True Color and False Color Red-Green-Blue (RGB) images from the MODIS Today site (above) showed the northwest-to-southeast hail damage swath across southwestern South Dakota on 30 July.

Before/after (16/30 July) comparisons of MODIS True Color RGB images viewed using RealEarth and MODIS Today (below) further illustrate the appearance of the hail damage swath.

MODIS True Color RGB images from 16 July and 30 July [click to enlarge]

Terra MODIS True Color RGB images from 16 July and 30 July [click to enlarge]

Terra MODIS True Color RGB images from 16 and 30 July [click to enlarge]

Terra MODIS True Color RGB images from 16 July and 30 July [click to enlarge]

In a comparison between the 30 July Terra MODIS Visible (0.65 µm) image and the corresponding Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) products (below), within the core of the hail damage swath (near Oglala) LST values warmed into the 90s F and NDVI values were reduced to the 0.2 to 0.3 range (compared to cooler LST values in the 80s F and higher NDVI values of 0.3 to 0.6 over healthy vegetation areas immediately adjacent to the damage swath).

Terra MODIS Visible (0.65 µm) image and Land Surface Temperature and Normalized Difference Vegetation Index products [click to enlarge]

Terra MODIS Visible (0.65 µm) image and Land Surface Temperature and Normalized Difference Vegetation Index products [click to enlarge]

===== 31 July Update =====

MODIS True Color RGB images from Terra (14 July) and Aqua (31 July) [click to enlarge]

MODIS True Color RGB images from Terra (14 July) and Aqua (31 July) [click to enlarge]

In a better, more cloud-free before/after comparison of MODIS True Color images from 14 and 31 July (above), it can be seen that the NW-SE oriented hail damage swath extended into Nebraska (where hail as large as 3.0 inches was reported).

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