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Tornado outbreak in Illinois

By Scott Bachmeier •

GOES-16

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

The largest December tornado outbreak on record for the state of Illinois occurred on 01 December 2018 (NWS St. Louis | NWS Lincoln | NWS Quad Cities). 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development of supercell convection which spawned the severe weather. in addition to the tornadoes, SPC Storm reports included hail as large as 1.75 inch in diameter and wind gusts of 75 mph.

GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed that cloud-top infrared brightness temperatures were as cold as -55ºC (darker shades of orange) with the more vigorous thunderstorm overshooting tops.

GOES-16

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

Plots of 18 UTC and 00 UTC rawinsonde data from Lincoln, Illinois (below) indicated that the coldest overshooting top brightness temperature of -55ºC seen in GOES-16 Infrared imagery was representative of a height just above the calculated air parcel Most Unstabe (MU) Equilibrium Level (EL).

Plot of 00 UTC Lincoln, Illinois rawinsonde data [click to enlarge]

Plots of 18 UTC and 00 UTC rawinsonde data from Lincoln, Illinois [click to enlarge]

A sequence of MODIS (from Terra and Aqua) and VIIRS (from Suomi NPP and NOAA-20) Visible and Infrared images (below) provided 2 higher-resolution views of the pre-storm environment, plus 3 views during/following convective initiation. Unfortunately, the thunderstorms in Illinois were located along the far eastern edge of the instrument scans in the final 2 images.

Terra/Aqua MODIS and Suomi NPP/NOAA-20 VIIRS Visible and Infrared images [click to enlarge]

Terra/Aqua MODIS and Suomi NPP/NOAA-20 VIIRS Visible and Infrared images [click to enlarge]

Even though the convection in western Illinois was near the limb of NOAA-20 (mis-labelled as Suomi NPP) VIIRS swath at 2007 UTC — degrading the spatial resolution and introducing some parallax error — the coldest detected Infrared brightness temperature (-52C) was still several degrees colder than that detected by GOES-16 (below). The two images are displayed in different projections, but the enhancements use the same color-vs-temperature breakpoints.

Comparison of GOES-16 ABI and NOAA-20 VIIRS Infrared Window images at 2007 UTC [click to enlarge]

Comparison of GOES-16 ABI and NOAA-20 VIIRS Infrared Window images at 2007 UTC [click to enlarge]

Categories: Aqua, GOES-16, MODIS, NOAA-20, Severe convection, Suomi NPP, Terra, VIIRS