An unusually intense (by early October standards) mid-latitude cyclone produced a variety of weather extremes across the parts of the north-central US during the 04 October to 05 October 2013 period. In the cold sector of the storm system, western South Dakota received record-breaking snowfall and prolonged blizzard conditions, with widespread power outages and livestock losses being two of the major impacts. The early evolution of the storm could be seen on 4-km resolution GOES-13 (GOES-East) Water Vapor (6.5 µm) images (above). Surface weather symbols (including precipitation type) are also plotted on the water vapor images. The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode during much of this time, providing images as frequently as every 5-10 minutes.

In the warm sector of the storm system, severe thunderstorms produced numerous tornadoes and hail as large as 2.75 inches in diameter (SPC storm reports), primarily across eastern Nebraska into Iowa. A very large tornado produced EF-4 damage in the Wayne, Nebraska area — the development of this storm could be seen on 1-km resolution 0.63 µm visible channel images (above) and 4-km resolution 10.7 µm IR channel images (below) from the GOES-15 (GOES-West) and GOES-13 (GOES-East) satellite perspectives. Wayne (station identifier KLCG) is located in the center of the visible and IR images; note that the hourly plotted weather observations for Wayne disappeared after 22 UTC, due to the fact that the airport weather instruments were damaged by the tornado.

GOES-13 0.63 µm visible channel images with overlays of the corresponding University of Wisconsin GOES-13 IR Cloud Top Cooling Rate (CTCR) product (below) indicated that CTCR values exceeded 30 degrees Kelvin per 15 minutes (darker blue color enhancement) at 20:45 UTC as the thunderstorm that produced the Wayne tornado was rapidly developing in northeastern Nebraska.

===== 07 October Update =====

High spatial resolution imagery from Low Earth Orbit (LEO) or “polar-orbiting” satellites can be useful for post-case analysis — with this particular storm, helping to determine the areal coverage of the resulting snowfall, and identifying a tornado damage path.

Once the large cloud shield associated with the storm system moved eastward, a comparison of 375-meter resolution (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images from 06 October (above) showed the widespread area of snow cover (which appeared as darker shades of red on the RGB image) over the western third of South Dakota as well as adjacent portions of Wyoming, Nebraska, North Dakota, and Montana. Terrain had an important influence in both the amount and the coverage of snowfall — it is especially interesting to note the areas of bare ground (shades of cyan in the RGB image) immediately downwind (south and southwest) of the Black Hills, where downsloping winds helped keep the precipitation type as rain (AWIPS-2 animation including topography). Aided by upslope flow, as much as 58 inches of snowfall was reported in the northern Black Hills of South Dakota. Note that much of the Black Hills appear darker on the visible and false-color images, due to the high density of coniferous trees — but there was still significant snow cover on the ground.

In addition, a comparison of before (28 September) and after (07 October) 250-meter resolution MODIS true-color RGB images from the SSEC MODIS Today site (below) revealed the southwest-to-northeast oriented damage path from the large tornado which produced EF-4 damage in the Wayne, Nebraska area (NWS Omaha news story).

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Tropical Storm Karen formed in the far southern Gulf of Mexico early in the day on 03 October 2013. About 2 hours after formation, AWIPS images of 1-km resolution POES AVHRR 12.0 µm IR channel and 0.86 µm visible channel data at 15:44 UTC (above) showed that areas of organized deep convection were displaced well to the east and north of the center of Karen.

A few hours later at 18:17 UTC, 375-meter resolution (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 11.45 µm IR data (below) revealed that a small convective burst had formed just to the northwest of the low-level circulation center (LLCC).

McIDAS images of 1-km resolution 0.63 µm GOES-13 visible channel data (below; click image to play animation) showed the exposed LLCC as it migrated slowly northwestward. Additional convective bursts near the LLCC werer seen to develop at the end of the animation. Another feature of interest was the well-defined low-level arcing convective outflow boundary moving northward away from the convective activity that was dissipating along the northern fringe of the Karen. Note that the GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes.

From the CIMSS Tropical Cyclones site, an animation of 4-km resolution GOES-13 10.7 µm IR channel imagery with an ovelay of the deep-layer wind shear (below) depicted about 20 knots of wind shear, which was acting to keep the most of the main convection away from the exposed LLCC.

 

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An AWIPS image of Suomi NPP VIIRS 0.7 µm Day/Night Band data (above) revealed a bright band of the aurora borealis that stretched from northern North Dakota and Minnesota into Quebec at 07:12 UTC (2:12 AM Central time) on 02 October 2013. This aurora display was caused by a coronal mass ejection from the Sun on 30 September.

The aurora borealis was faintly visible on a YouTube video (below; courtesy of Pete Pokrandt, UW-AOS) created using 10-second black and white images from the north-facing UW-SSEC/AOS rooftop camera.

A higher-quality digital camera photo taken from the roof of the UW-SSEC/AOS building (below) showed some of the green color of the aurora display (in spite of the high level of urban light pollution from the Madison area). Brighter green colors were seen on images taken further away from Madison, in Verona and Dodgeville in southern Wisconsin.

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An AWIPS image of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) data at 06:10 UTC or 2:10 AM local time on 30 September 2013 (above) revealed multiple signatures of mesospheric airglow waves over portions of the western Atlantic Ocean. There are three distinct packets of waves seen on the DNB image — two of which were likely generated by intense mesoscale convective systems associated with a strong occluding mid-latitude cyclone centered several hundred miles north-northwest of Bermuda. The impressive length of the third (southernmost) wave packet located southeast of Bermuda can better be seen in the full DNB swath image (courtesy of Kathy Strabala, SSEC); this feature is likely a high-altitude undular bore.

A comparison of the VIIRS DNB image (and cloud-to-ground lightning strike data) with the corresponding VIIRS 11.45 µm IR image (below) showed that there was no signature of these mesospheric airglow waves on the IR image.

A magnified comparison of VIIRS DNB and IR images (below) showed the difference between the short wavelength of cloud-top gravity waves propagating southwestward away from an overshooting top (located between the two lightning streaks) and the longer-wavelength mesospheric airglow waves seen along and south of the southernmost lightning streak. The DNB image lightning streaks are an artifact of sensor saturation by very bright cloud-top illumination resulting from intense lightning activity.

Other examples of mesospheric airglow waves were seen on 15 September 2013 and 05 April 2013.

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