![GOES-16 Upper-level Water Vapor (6.2 µm) images [click to play MP4 animation]](https://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2018/09/mcs_wv8_waves-20180901_131218.png)
GOES-16 Upper-level Water Vapor (6.2 µm) images [click to play MP4 animation]
A series of large Mesoscale Convective Systems (MCS) developed across Nebraska and Iowa during the nighttime hours before sunrise on 01 September 2018, which produced large hail and damaging winds (
SPC storm reports). Storm-scale anticyclonic outflow aloft around the periphery of the decaying convection acted as a short-term barrier to the upstream southwesterly winds within the middle/upper troposphere, creating quasi-stationary gravity waves along their rear
(westward) edges which persisted for several hours. These waves were most evident over eastern Nebraska and northeastern Kansas on GOES-16 Upper-level Water Vapor (
6.2 µm) images
(above).
6.2 µm Water Vapor images with plots of GOES-16 Derived Motion Winds (below) intermittently showed these high-altitude anticyclonic winds along the western edges of decaying convection — for example, at 0842 UTC, 0922 UTC, 0957 UTC, 1127 UTC, 1212 UTC and 1312 UTC.
![GOES-16 Upper-level Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to play MP4 animation]](https://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2018/09/mcs_wv8_winds-20180901_131218.png)
GOES-16 Upper-level Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to play MP4 animation]
The quasi-stationary waves appeared to coincide with a few pilot reports of high-altitude turbulence: Clear Air Turbulence (CAT) was mentioned over northeastern Kansas at
37,000 feet and
39,000 feet, and “mountain wave action” was reported over southeastern Nebraska at
43,000 feet.
![Pilot reports of turbulence [click to play animation]](https://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2018/09/180901_1648utc_NE_FL430_MTN_WAVE_ACTION.jpeg)
Pilot reports of turbulence [click to play animation]
Higher resolution views of the convection were provided by VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from Suomi NPP at 0755 UTC and NOAA-20 at 0845 UTC
(below). With ample illumination from the Moon
(in the Waning Gibbous phase, at 67% of Full), the “visible image at night” capability of the Day/Night Band was well-demonstrated. The coldest cloud-top infrared brightness temperature associated with the MCS in western Iowa was -84ºC — and the effect of a similar “blocking wave” along the western/northwestern edge of that storm could be seen, which was effectively eroding the approaching high-altitude anvil cloud material from the Nebraska MCS. Note that the 0845 UTC NOAA-20 VIIRS images are incorrectly labeled as Suomi NPP.
![Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, with plots of SPC storm reports [click to enlarge]](https://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2018/09/180901_0755utc_suomiNPP_viirs_DayNightBand_InfraredWindow_anim.gif)
Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, with plots of SPC storm reports [click to enlarge]
![NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]](https://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2018/09/180901_0845utc_noaa20_viirs_DayNightBand_InfraredWindow_anim.gif)
NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]