GOES-13 has been placed into Super Rapid Scan Operations (SRSO) mode today to support the OWLeS program over the eastern Great Lakes, providing periods of 1-minute interval imagery each hour. The extraordinary cold air over the eastern United States is producing heavy lake-effect snows over downwind of Lakes Erie (above) and Ontario (below). Storm total snowfall amounts were as high as 60 inches;  for additional information on this event, see the Wasatch Weather Weenies and Jim LaDue view blogs.

In a faster animation of GOES-13 SRSO visible images covering Lake Erie (below; click image to play animation; also available as an MP4 file), the motion of ice in the western portion of the lake could be seen; the formation and intensification of organized lake-effect snow bands occured over the ice-free open waters in the central and eastern parts of Lake Erie.

To supplement the GOES-13 SRSO images, a comparison of AWIPS images of Terra MODIS 0.65 µm visible channel and 11.0 µm IR channel data (below) showed the well-defined lake-effect snow (LES) bands streaming off of Lake Erie and Lake Ontario at 15:28 UTC (10:28 AM local time). At this time, surface visibility was restricted to 1/16 mile with heavy snow at Buffalo, New York (KBUF); other notable peak wind gusts included 46 knots at Waterton, New York (KART), 49 knots at Point Petre, Ontario (CQWP), and 50 knots at Long Point (CWPS) and Port Colborne (CWPC) Ontario. Metop ASCAT surface scatterometer winds were as high as 62 knots over Lake Erie and 46 knots over Lake Ontario. The coldest cloud-top IR brightness temperatures were -39º C immediately downwind of Lake Ontario, and -35º C immediately downwind of Lake Erie.

About 3 hours later (at 18:17 UTC or 1:17 PM local time), a similar comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (below) showed the 2 LES bands as they continued to organize and intensify. Surface visibility had dropped to 0 miles with heavy snow and blowing snow (and a peak wind gust of 41 knots) at Buffalo (KBUF). Other notable peak wind gusts included 41 knots at Watertown (KART) and 42 knots at Fort Drum (KGTB) in New York, 51 knots at Point Petre (CQWP), and 55 knots at Long Point (CWPS) and Port Colborne (CWPC) in Ontario. The Lake Ontario LES band had extended farther inland, with Saranac Lake, New York (KSLK) reporting visibility reduced to 1 mile with snow. Cloud-top IR brightness temperatures remained about the same: -39º C downwind of Lake Ontario, and -34º C immediately downwind of Lake Erie.

It is interesting to point out that there were a few cloud-to-ground lightning strikes downwind of Lake Ontario during the preceeding night-time hours; 1-hour lightning strikes are overlaid on a comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images at 06:54 UTC or 1:54 AM local time (below). In addition, note the small packet of gravity waves seen propagating southward (away from the area of lightning strikes) on the IR image. Isolated cloud-to-ground lightning strikes continued in this area until the early morning hours, as seen in an animation of GOES-13 IR images.

While not related to the OWLeS field experiment, it was interesting to examine GOES-13 SRSO visible channel images farther to the west over Lake Superior (below; click image to play animation; also available as an MP4 file), which displayed the following: (1) widespead multiple LES bands over much of the lake, which produced as much as 12 inches of snowfall near Deer Park (snowfall reports | Google maps), (2) a curious “solitary standing wave” feature that was oriented roughly parallel to the coastline of the eastern Upper Peninsula of Michigan east of Munising (station identifier KP53), and (3) packets of terrain-induced gravity waves both upwind and downwind of Isle Royale in the northwestern part of the lake (in addition to patches of lake ice both northwest and northeast of the island).

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Most users of water vapor satellite imagery interpret the patterns they see as variations in moisture within the middle to upper troposphere — and for the most part, this is often a good first-order assumption. However, one must keep in mind that the water vapor channel is essentially an InfraRed channel, which is sensing the average temperature of a layer of moisture — and the altitude and depth of the layer of moisture being detected can change significantly, based upon such factors as the temperature and/or moisture profile of the atmospheric column, and the viewing angle of the satellite.

During an unusually cold arctic outbreak over the north-central US during the 06 January – 07 January 2014 period, the outline of various portions of the Great Lakes (in particular, Lake Superior, Lake Michigan, and Lake Erie) could actually be seen on GOES-13 6.5 µm water vapor channel imagery (above; click image to play animation). So, how is it possible to see surface features on water vapor channel satellite imagery?

In helping to understand the vertical location and vertical extent of features seen on water vapor imagery, plots of the water vapor “weighting function” (or “contribution function”) can be generated by taking into account the temperature and moisture profile of that location, along with the satellite viewing angle (or “zenith angle”). For this example, plots of GOES-13 Imager 6.5 µm water vapor weighting functions for Green Bay, Wisconsin (below) showed how the altitude and depth of the moisture layer being sensed by the water vapor channel decreased from 12 UTC on 05 January to 12 UTC on 06 January as the core of the cold arctic air moved over the western Great Lakes region. After that time, both the altitude and depth of the moisture layer being detected (as seen on the water vapor channel weighting function plots) began to increase to approximately their pervious values as somewhat warmer and more moist air began to replace the arctic air mass.

Getting back to seeing the outlines of portions of northern Lake Superior, western Lake Michigan, and western Lake Erie: what was being seen on the water vapor imagery was not necessarily the actual surface per se, but the signal of the strong temperature gradient between the cold snow-covered land surfaces and the still-unfrozen waters — and the signal of this strong surface temperature gradient was “bleeding upward” through what little moisture was present in the atmospheric column, and reaching the GOES-13 Imager water vapor detectors.

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A strong winter storm affected much of the central and eastern US during the 02 January – 03 January 2014 period. A map of SSEC RealEarth 24-hour snowfall totals (above) shows how widespread the resulting snowfall was, with amounts as high as 24 inches in Massachusetts abd 22 inches in New York (WPC storm summary).

As the storm system departed over the Atlantic Ocean on 03 January, an AWIPS image comparison of the 17:53 UTC (12:53 PM Eastern time) Suomi NPP VIIRS 0.64 µm visible channel data and the corresponding false-color “snow vs cloud discrimination” Red/Green/Blue (RGB) product (below) showed the areal coverage of snow on the ground (varying shades of red on the RGB image). Some patches of supercooled water droplet clouds (varying shades of white on the RGB image) could be seen streaming off of Lake Erie and Lake Ontario; in fact, a closer look revealed mesoscale bands of “lake-effect snow” downwind of the Finger Lakes in western New York, and also downwind of Lake Champlain along the New York/Vermont border.

Cold air moving southward in the wake of the storm crossed the western Gulf of Mexico, moved through the Chivela mountain pass in southern Mexico, and eventually emerged over the Pacific Ocean in the Gulf of Tehuantepec — this type of mountain gap wind flow is known as a Tehuano wind event or a “Tehuantepecer”. An image of Metop ASCAT surface scatterometer winds at 02:36 UTC (below) showed that a large area of northerly gale force winds (red wind barbs) was present over the Gulf of Tehuantepec, with maximum remotely-sensed wind speeds of 41 knots. The tropical surface analysis (cyan) displayed the fractured cold frontal boundary that had advanced into southern Mexico; behind the cold front along the Gulf of Mexico coast at Veracruz (station identifier MMVR), the surface visibility at the time was reduced to 6 miles due to blowing sand (time series of MMVR surface reports). Surface reports at Ixtepec (station identifier MMIT) along the Gulf of Tehuantepec were sparse, but did show northerly winds gusting to 37 knots at 17 UTC (time series of MMIT surface reports).

Daytime images of GOES-13 0.63 µm visible channel data on 03 January (below; click image to play animation) showed the hazy plume of blowing dust and sand moving southwestward, with the boundaries of the strong Tehauno winds marked by long, narrow rope clouds.

A signature of the dry air (darker blue color enhancement) associated with the Tehuano winds could be seen on the MIMIC Total Precipitable Water product (below).

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A train derailment occurred about one mile west of Casselton, North Dakota at 20:10 UTC (2:10 PM local time) on 30 December 2013 — ten cars of a westbound train transporting grain initially derailed, which then caused an eastbound train transporting crude oil to also derail. A large fire and multiple explosions erupted from the engine and 18 cars of the derailed eastbound train, which were carrying crude oil from the Bakken oil shale field region in northwestern North Dakota. McIDAS images of GOES-13 0.63 µm visible channel and 3.9 µm shortwave IR data (above; click image to play animation; also available as a QuickTime movie) showed the dark smoke plume beginning with the 20:15 UTC visible image, which then quickly fanned out to the south-southeast by 21:45 UTC. On the corresponding shortwave IR images, a darker gray fire “hot spot” accompanied the initial visible image signature of the smoke plume at 20:15 UTC, which later became very hot (dark black) on the 21:15 UTC image.

A comparison of GOES-15 (GOES-West, positioned at 135º West longitude) and GOES-13 (GOES-East, positioned at 75º West longitude) 0.63 µm visible channel images (below; click image to play animation) showed how the dark smoke plume appeared from the very different viewing perspectives of the two geostationary satellites. On both sets of images the eastern portion of the smoke plume appeared to have drifted over Interstate 29 (I-29) south of Fargo (FAR), but due to the low sun angle it is likely that this was actually the shadow from the dark smoke plume. Note that the low cloud features cast similar shadows during the late afternoon hours toward the end of the animation.

The corresponding comparison of GOES-15 vs GOES-13 3.9 µm shortwave IR images (below; click image to play animation) also showed differences in the apparent intensity of the fire hot spot, which were dependent upon satellite viewing angle, viewing time, and the opacity of the dense smoke plume overhead. On the GOES-13 21:15 UTC image (which was actually scanning the fire area at 21:17 UTC), a notable increase in IR brightness temperature was seen, with the hot spot exhibiting a brightness temperature of 322 K (48.9º C or 120º F). This was likely the near the time of one of several explosions (video 1 | video 2). GOES-15 was not scanning the fire area at that particular time, so a fire hot spot of that intensity was not evident in the imagery.

===== 31 December Update =====

The intense oil-fueled fire continued to burn into the following night; an AWIPS image of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) data at 09:07 UTC or 3:07 AM local time on 31 December (below) showed the bright glow of the fire near Casselton, as well as the smoke plume which was still drifting to the southeast. The glow of lights from cities and towns appeared somewhat blurry on the DNB image, due to scattering of the light through a thin veil of cirrus clouds that was drifting over the region (VIIRS 11.45 µm IR channel image). Since the Moon was nearly in the New phase, there was very little moonlight to illuminate the smoke plume — airglow and lights from nearby cities and towns helped to make this feature visible on the DNB image. Note that the navigation of the DNB image was slightly off, with the image being shifted a few miles to the southwest; in addition, this particular DNB image was enhanced to provide a darker contrast, eliminating “noise” from the glow of the regional snow cover (which was generally in the 5-13 inch range) to help highlight the smoke plume. A subtle signature of the fire hot spot (a darker gray pixel) could still seen on the corresponding VIIRS 3.74 µm shortwave IR image.

Due to air quality concerns from the toxic smoke plume, residents immediately downwind of the crash site were urged to evacuate. At Fargo’s Hector International Airport (located about 25 miles to the east of Casselton), the surface visibility dropped to 2 miles with haze at 06:53 UTC (12:53 AM local time) on 31 December, as winds shifted to the southwest (time series of surface reports); it is unknown whether this drop in visibility was due to smoke being transported from the accident site, or simply from local sources (such as the widespread burning of firewood in the city, given that the ambient air temperature at the time was -15º F). A WDAY News tower camera photo (below) showed that the dark smoke plume could be seen from downtown Fargo — the tower camera is looking to the west, and the smoke plume is drifting southward (to the left).

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