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.

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.

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.

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West Pacific Typhoon Jebi underwent a period of very rapid intensification on 30 August 2018 (ADT | SATCON), reaching Category 5 Super Typhoon intensity. Himawari-8 rapid-scan (2.5 minute interval) “Clean” Infrared Window (10.4 µm) images (above) showed that Jebi began to exhibit an annular appearance with a nearly symmetric eyewall as it moved through the Northern Mariana Islands (north of Guam). The eye passed just south of the uninhabited volcanic island of Pagan around 16 UTC on 30 August.

Himawari-8 “Red” Visible images (below) revealed mesovortices within the eye of Jebi.

Toggles between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (below) showed more detailed views of (1) the well defined eye, (2) surface mesovortices within the eye, and (3) storm-top gravity waves that were propagating away from the eyewall region. With the Moon in the Waning Gibbous phase (at 77% of Full), ample illumination was available to provide detailed “visible images at night” using the VIIRS DNB.

Convective Rain Rate and Surface Rain Rate products derived from GCOM-W1 AMSR2 data (below) showed the heavy rainfall occurring within the eyewall region and a primary feeder band to the west. VIIRS and AMSR2 images courtesy of William Straka, CIMSS.

As Jebi tracked west-northwestward across the West Pacific, products from the CIMSS Tropical Cyclones site showed that it had been moving over waters having high values of Sea Surface Temperature and Ocean Heat Content (below).

A 48-hour animation of the MIMIC-TC product (below) showed the evolution of the Jebi from 29-31 August. The storm was completing an eyewall replacement cycle near the end of the animation, with the eye becoming distinctly larger.

In a comparison of DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images at 1900 UTC (below), the Microwave data helped to better visualize the structure of the large eyewall in addition to a long, narrow feeder band wrapping inward toward the eye.

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Pacific Hurricane Norman, a potent storm with sustained winds of 150 mph, exists outside of GOES-16’s CONUS (Contiguous United States) domain. In fact, on 30 August 2018, both GOES-16 Meso sectors were placed over the tropics to provide 1-minute imagery of tropical systems, both Norman over the Pacific, and a strong tropical easterly wave over the Atlantic and Caribbean. The toggle above shows the two positions (using visible imagery at 0.64 µm) along with the CONUS domain (using the clean window, band 13 at 10.3 µm).

The Mesoscale Sector allows 1-minute imagery over Norman. Otherwise, full-disk imagery with a time cadence of every 15 minutes would be used. The hour-long animation, below, shows the evolution of the storm and its environment.

A closer view of the eye, below, (Click to play animated gif), shows a well-developed eye with embedded low clouds. Because Norman is near 120 W, the view angle is oblique and only the western edge of the eyewall can be viewed.

Norman appears to be at the northern edge of deep tropical moisture, based on the toggle below of GOES-16 Clear Sky Total Precipitable Water and the GOES-16 infrared Low-Level Water Vapor image (7.34 µm). The projected path of Norman is mostly Westward so the storm will remain within deep tropical moisture for the next several days. It is forecast to remain a strong hurricane.

For more information on Norman, please consult the website of the National Hurricane Center or the SSEC/CIMSS Tropical Weather Website.

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* GOES-17 images shown here are preliminary and non-operational *

A comparison of Visible images from GOES-15 (GOES-West), GOES-17 and GOES-16 (GOES-East) (above) showed an isolated thunderstorm that developed in the Nebraska Panhandle late in the day on 29 August 2018. The storm produced hail (SPC storm reports), and also exhibited an Above Anvil Cirrus Plume. The images are displayed in the native projection of each satellite, with no re-mapping.

One other feature that was seen north of the thunderstorm was smoke which was being transported eastward from the Britania Mountain Fire in southeastern Wyoming. The smoke was more apparent on the GOES-17 and GOES-16 images as forward scattering increased toward sunset.

Shortwave Infrared imagery from the 3 satellites revealed important differences affecting fire detection: namely spatial resolution and viewing angle. The 3.9 µm detector on the GOES-15 Imager has a spatial resolution of 4 km (at satellite sub-point), compared to 2 km for the GOES-16/17 ABI. Given that the fire was burning in rugged mountain terrain, the view angle from each satellite had an impact on the resulting bire brightness temperature values. For example, the first indication of very hot (red-enhanced) pixels was at 1527 UTC from GOES-16/17, vs 1715 UTC from GOES-15; at the end of the day, the very hot fire pixels were no longer seen with GOES-15 after 2300 UTC, but continued to show up in GOES-17 imagery until 0042 UTC and in GOES-16 imagery until 0122 UTC.

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