A very broad upper trough slowly traversed the Contiguous United States during the week of 12 Dec 2022, resulting in considerable and widespread winter weather impacts for the northern half of the United States, and severe weather impacts for the south. Satellite imagery captured various unique aspects of the storm system.
First, a hourly water vapor animation with RAP 500 mb height and wind speed captures the evolution of the broad storm system through the week (Fig 1). In the imagery, one can diagnose the significant shortwave troughs, deformation zones, jet streaks, and moisture features associated with the trough that would come and go throughout the week.
A similar but more qualitative animation of All-Layer Precipitable Water (ALPW) product, derived from vertical sounding measurements form polar sensors, shows us how moisture evolves throughout the atmosphere as the upper low deepens (Fig 1b). Early on, for example, low-level moisture originates from the GoM, while mid-upper level moisture comes from the East Pacific. Deep moisture came together over the central/northern US to result in heavy snowfall.
From late on the 12th through the afternoon of the 13th, one can leverage water vapor imagery to diagnose lee cyclogenesis along the eastern part of the broader trough in eastern Colorado, and combine RAP MSLP to see deepening low pressure ahead of the strengthening shortwave, and the storm system becoming vertically stacked as it enters mature stages and occludes over Nebraska (Fig 2). From the imagery alone, one can diagnose moisture wrapping around the circulation, and widespread cloud cover developing from southeast Texas north to the ND/MN/Canadian border, southwest across Wyoming and Colorado. A GLM FED overlay captures the development of thunderstorms during the overnight hours from central Texas through Oklahoma into Kansas. The following animation also includes a SWD overlay, to highlight blowing dust (coming out of the Chihuahua desert late on the 12th) as brown.
Taking a closer look at the blowing dust on the 12th, we leverage an experimental “Color Vision Deficiency” (CVD) Dust RGB in order to highlight the dust feature better than is done in the traditional Dust RGB, particularly for Color Blind folks (Fig 3). In this RGB, blowing dust shows up as bright green to yellow against the blue clear sky background. As with the Dust RGB, cloud microphysics properties can be gleaned as well.
Focusing on the overnight thunderstorms, numerous reports of severe hail and wind, plus a few tornados, were reported across Oklahoma and Texas, including many reports in the Dallas/Fort Worth area. Another water vapor animation overlays RAP 500 mb 60 knot wind speed (yellow), 850 mb 40 knot wind speed (blue), and 300K Isentropic surface 310K equivalent potential temperature (green; Fig 4). The animation allows one to view the thunderstorm development in relation to relevant environmental fields. Specifically, storms develop where the strong low level jet developed beneath the midlevel jet, within a surge of increasing low-mid-level moisture.
The deepening cyclone from the 12th to the 13th, specifically cloud evolution, can also be visualized in day/night transition RGB imagery (starting as the DCPD RGB during the day on the 12th, transitioning to the NightMicro RGB at night, and back to the DCPD RGB during the day on the 13th; Fig 5). The RGB imagery makes it simple to connect cloud features between the two RGBs, and to differentiate low clouds from upper clouds across the scene day/night, and to identify development of convection across a boundary interaction during the night in west Texas and later across central Oklahoma and north Texas. Other interesting features observed in the NightMicro RGB imagery overnight include the recent rainfall signature left behind thunderstorms in west Texas, the emergence of low clouds from beneath upper clouds as the low levels become saturated near the low pressure center in eastern Colorado, and the widespread low clouds ahead of the front marking an abundance of low level moisture. One may also notice the difference in appearance of low clouds ahead of and behind the front due to differing airmass, and therefore, different contributions from the 10.3 um IR “blue” component (less blue in cold environment behind front).
Focusing in on the severe thunderstorms that developed across the DFW area during the morning of the 13th, 1-min feature following VIS/IR sandwich imagery reveals rapid cloud top cooling of new storms, numerous OTs, and persistently cold cloud tops with great texture, all signs of strong updraft and strong-severe storm potential (Fig 6).
Skipping ahead to the evening of the 13th through much of the 14th, widespread heavy and blowing snow continued across the northern US plains, and the severe thunderstorm threat shifted east to the southern MS Valley area. A water vapor animation with 300K isentropic surface equivalent potential temperature contours (color) and pressure contours(white) help one to visualize the surge of ascending moisture northward along the MS River ahead of the upper low, and then cyclonically around the low over the northern plains (Fig 7).
VIIRS Day Night Band Near Constant Contrast Imagery overnight early on the 14th provided detailed “visible-like” imagery of thunderstorms over Louisiana and Mississippi (Fig 8). The gray/color colormap allows one to view clouds in grayscale, and bright lights associated with cities and lightning flashes (of which there are a few) in color.
Thunderstorms continued east during the day and into the evening, producing several strong tornados and severe wind gusts. One such storm produced a tornado in the New Orleans area. GOES-East 1-min VIS/IR sandwich imagery captured the details of the storm, which exhibited rapid cooling to very cold BTs and a OT with above anvil cirrus plume, indicated a particularly strong and dangerous storm had developed (Fig 9). Cloud tops warmed, and texture was lost, as the storm moved east of New Orleans, indicating a weakening of the updraft.
Further west, strong northerly winds developing on the backside of the surface low had resulted in blowing dust across far east-central CO and southwest Kansas. True Color imagery from Geocolor captures the blowing dust well, particularly from GOES-East as the sun sets to the west, and forward scatting increases to the sensor (Figure 10).
Now on the 15th as the system continued to slowly shift east, taking a broader look at the north-central part of the US, the DCPD RGB with RAP MSLP contours shows the massive circulation centered over Minnesota during the day, with widespread low clouds (light cyan) under, south and east of the low center, higher level clouds (red) and implied greater mid-upper level moisture wrapping around the northern and western parts of the low, where heavier precipitation (snowfall) would be occurring (Fig 11). Further west, where dry northwesterly flow had developed, clearing revealed the fresh snowpack (green). The tight pressure gradient and surface obs capture the widespread gusty conditions that had developed around the low, especially west.
The strong winds on the backside of the low resulted in widespread blowing snow, reducing visibility to less than a 1/2 mile in many areas. Where skies were clear, the blowing snow could be diagnosed in the experimental GOES-East blowing snow RGB (Fig 12). In the following animation, the subtle signal of blowing snow appears as a slightly lighter shade of red against the red, snow-covered background, and amongst the bright blue and gray color of liquid clouds, and even fainter red of upper/ice clouds. Bare ground is bright green. Blowing snow may also be present under the bright blue/gray HCR clouds, where plumes of blowing snow evolve into. An experienced user of this RGB could diagnose widespread blowing snow from Lusk, WY southeast through Alliance toward North Platte and Imperial in Nebraska. In the following animation, blowing snow is most apparent over and around Alliance, NE. Blowing snow resulted in car accidents and the closure of I-80W in Big Springs, NE, very near the northeast corner of CO.
The plumes of blowing snow were captured in even greater detail by VIIRS, in its version of the experimental blowing snow RGB (Fig 13).
Looking back to the warm side of the system, a 3-day animation from GOES-East shows the evolution of strong-severe thunderstorms during the period, transitioning between IR imagery at night and VIS/IR sandwich imagery during the day (Fig 15).
A NOAA 72-hr snowfall analysis ending the evening of the 15th shows a widespread region of 8+” of snow had fallen across the northern US (Fig 16).
On the 15th, the northeast was also impacted by winter weather associated with the system, including freezing rain from western Virginia north through Maryland and Pennsylvania into western New York. GOES-East DCPD RGB imagery showed the evolution of clouds in the area, including individual convective elements streaming north behind the main upper cloud shield 9Fig 17).
The VIIRS Snowmelt RGB on the 16th was able to capture signs of where the freezing rain had fallen, between still abundant cloud cover, including western Maryland and central PA (Fig 18). Recall, darker shades of blue represent ice cover in this RGB, while fresh snow cover will be lighter shades of gray, such as further to the west.
Continued strong winds and clear skies across the plains on the 17th resulted in continued blowing snow being observed in both GOES-East and VIIRS Blowing Snow RGBs over southeast South Dakota (Fig 19 and 20).
Bill Line, NESDIS/STAR
Satellite Liaison Blog 