A comparison of AWIPS images of Suomi NPP VIIRS Visible (0.64 µm) and False Color Red-Green-Blue (RGB) composite (above) showed a number of horizontal convective roll clouds over parts of eastern North Dakota and northwestern Minnesota that had formed in response to strong northwesterly winds in the wake of an arctic cold frontal passage on 19 January 2013. On the False Color image, snow cover appeared as shades of red, bare ground was cyan, and cloud features were varying shades of white.

McIDAS images of GOES-13 Visible (0.63 µm) visible data (below) showed the development and evolution of numerous long horizontal convective roll clouds. Although new snowfall amounts on this day were very light (generally 0.5 inch or less), the strong northwesterly winds — with wind gusts as high as 61 mph in northwestern Minnesota, 59 mph in North Dakota, and 53 mph in northeastern South Dakota — created significant blowing snow that was reducing visibility to 1/4 mile or less across parts of the region. The blowing snow (along with some brief, heavy snow showers) tended to be more focused and intense in the vicinity of the horizontal convective rolls and their associated cloud streamers.

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A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel data (above) showed a textbook example of a “baroclinic leaf” satellite signature associated with the large storm affecting much of the eastern US on 17 January 2013. The baroclinic leaf represents a region of ascending air that originates at low levels on the warm side of the primary surface cold front (18 UTC surface analysis).

4-km resolution GOES-13 6.5 µm water vapor channel images (below; click image to play animation) showed the development several important satellite signatures: (1) the baroclinic leaf; (2) the primary warm conveyor belt;, (3) the cold conveyor belt (which was helping to produce snow across parts of northern Mississippi and Alabama); and (4) a secondary warm conveyor belt after about 19 UTC. For additional information on conveyor belts, see this blog post from January 2011.

A McIDAS-V representation of the GOES-13 (GOES-East) water vapor image brightness temperatures as a topographical surface (below; click image to play animation; also available as a QuickTime movie) helps to visualize the descending intrusion of dry air (which exhibited warm brightness temperatures, yellow to orange color enhancement) and the ascending streams of moist air (which exhibited blue to white to green colors)  within the warm conveyor belt and baroclinic leaf structures.

Another McIDAS-V visualization (below; click image to play animation) shows the 3-dimensional structure of the various jet streams (cyan isosurface of 50 meters per second or higher winds) and the increasing values and ascending height of moisture (mixing ratio) within the primary warm conveyor belt as the cross section slice is moved from south to north. McIDAS-V images courtesy of Joleen Feltz and Mike Hiley (CIMSS).

Early in the day, a SIGMET was issued (below) to outline an area of risk for severe turbulence due to wind shear near the axis of the strong jet stream associated with this developing system.

===== 18 January Update =====

A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and the corresponding VIIRS false-color Red/Green/Blue (RGB) image (below) aided in the discrimination of the resulting snow cover from the storm (shades of red) versus clouds (shades of white).

 

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A sequence of AWIPS images of Suomi NPP VIIRS 11.45 µm IR data from 13 January to 15 January 2013 (above; click image to play animation) revealed a great deal of motion of the sea ice in the Arctic Ocean off the north coast of Alaska. Surface stations along the Alaskan coast were reporting strong easterly winds during this time period, with gusts in excess of 40-50 knots — these strong winds were helping to push the sea ice westward. Also evident in the images was the relatively warm signature (cyan to yellow color enhancement) exibited by numerous “cracks” in the sea ice — it is unclear whether these features are simply weaknesses in the thick ice pack, or actual leads of open water.

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A Mesolow developed over Lake Superior today and moved rapidly northeast towards Ontario. As the system moved near Pukaskwa, ON (48.6 N, 86.3 W), winds there shifted from northwest at 3 knots at 1800 UTC to northeast at 5 knots at 1900 UTC to west at 7 knots, gusting to 16 knots at 2000 UTC. (An animation of surface plots overlain on the satellite imagery is here). The mesolow seems to have developed as an interaction with the topography on Isle Royale. Lake Surface temperatures are in the mid-30s, as is typical this time of year, and 850-mb temperatures (as measured at International Falls at 1200 UTC) were around -18 C.

GOES-West provided an oblique view of the system development, shown above.

Hat tip to the National Weather Service in Marquette Michigan for first alerting us to this system’s presence!

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