GOES-11 0.65 µm visible image (click to play animation)

McIDAS images of GOES-11 0.65 µm visible channel data (above) showed a persistent Tule fog event across much of the Central Valley of California on 05 January 2011. The northern portion of the fog eventually began to erode into the afternoon hours, but the remainder of the fog feature showed little change. A 1-km resolution MODIS Red/Green/Blue (RGB) true color image from the SSEC MODIS Today site (below) offered another view of the fog. The snow-covered Sierra Nevada Range can be seen to the east of the Central Valley.

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

Before the areal extent of the fog could be monitored using daytime visible images, a comparison of AWIPS images of the 1-km resolution MODIS fog/stratus product and the corresponding 4-km resolution GOES-11 fog/stratus product (below) demonstrated the clear advantage of improved spatial resolution for detecting the location of the fog edges. In addition, the portions of the fog that were deeper in vertical extent were highlighted with an orange to red color enhancement.

1-km resolution MODIS and 4-km resolution GOES-11 fog/stratus product images

The MODIS Cloud Top Temperature (CTT) product (below) depicted CTT values of +1 to +4º C (lighter red color enhancement) across the fog feature. Note that the CTT product incorrectly identified the cold, snow-covered Sierra Nevada mountains as cloud, with CTT values between 0 and -25º C (yellow to blue color enhancement).

MODIS Cloud Top Temperature product

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MODIS true color RGB image (viewed using Google Earth)

A strong Pacific storm system moved through the southwestern US in late December 2010, producing snowfall amounts as high as 30 inches in northern Arizona. On 01 January 2011, a 250-meter resolution MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth) from the SSEC MODIS Today site (above) showed the correlation of elevation and snow cover across the Grand Canyon region of northern Arizona. For example, while the lowest elevations of the Grand Canyon remained void of any snow cover, the snow depth at the North Rim of the Grand Canyon was 36 inches, while 16 inches of snow was on the ground at the South Rim of the Grand Canyon.

A comparison of AWIPS images of MODIS 0.65 µm visible channel data and a false color RGB image (below) shows a larger scale view of the snow cover across northern Arizona, southern Utah, and southern Nevada. Snow cover over the higher elevations — the brighter white areas on the visible image — shows up as the darker red areas on the MODIS false color RGB image. A band of supercooled water droplet clouds (the brighter feature on the RGB image) could be seen stretching southeastward across southern Utah into northern Arizona.

With deep snow cover in place across the region, the minimum temperatures that morning were quite cold: -12º F at the South Rim of the Grand Canyon (a new record low for the date), -29º F at Grand Canyon Airport (station identifier KGCN), and -30º F at Bellemont (near Flagstaff, Arizona, station identifier KFLG).

MODIS 0.65 µm visible image + MODIS false color Red/Green/Blue (RGB) image

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GOES-13 10.7 µm IR images (click image to play animation)

A tornado (which produced EF-2 damage at one point along its path) moved directly across the airport grounds and passed just south of the airport terminal at Jackson, Mississippi (station identifier KJAN) around 23:20 UTC on 31 December 2010 — being such a close call, it was cause for the staff at the National Weather Service forecast office at Jackson to shelter in place for several minutes while the tornado moved over the airport. This was part of a large severe weather outbreak across much of the south-central US.

AWIPS images of 4-km resolution GOES-13 10.7 µm IR data (above) showed the cold cloud top IR brightness temperatures associated with the storm, which reached a minimum value of -77º C at 22:10 UTC.

About 1.5 hours before the Jackson MS tornado, AWIPS images of 1-km resolution POES AVHRR 0.63 µm visible and 10.8 µm IR data (below) displayed IR cloud top brightness temperatures as cold as -82º C (violet color enhancement), as well as a prominent shadow that was being cast by that particular overshooting top on the visible image.

POES AVHRR 0.63 µm visible + 10.8 µm IR images

A comparison of the 1-km resolution POES AVHRR 10.8 µm IR image with the corresponding 4-km resolution GOES-13 IR image (below) is a good demonstration of the problem of parallax error associated with viewing tall storm top features from geostationary satellites. Note how far northward the cloud features are displaced on the GOES-13 IR image — with a POES satellite flying directly overhead, there is minimal parallax error and therefore a more accurate mapping of the cloud features.

POES AVHRR 10.8 µm IR + GOES-13 10.7 µm IR images

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GOES-13 6.5 µm water vapor images (click image to play animation)

An intense winter storm impacted a great deal of the eastern US on 26 December – 27 December 2010, producing blizzard conditions along much of the East Coast (with Blizzard Warnings issued from Virginia to Maine), total snowfall amounts as high as 32.0 inches at Rahway, New Jersey, and significant accumulations as far south as Mississippi, Alabama, and Georgia (HPC storm summary). AWIPS images of 4-km resolution GOES-13 6.5 µm water vapor channel data (above) showed that the storm exhibited a very well-defined dry slot (yellow to orange color enhancement) and comma head structure during the course of its development. Cloud-to-ground lightning strikes could be seen along the periphery of the dry slot, with isolated strikes noted over New Jersey and also Long Island, New York (where thundersnow was reported). An excellent summary of the storm can be found on the AccuWeather WeatherMatrix Blog.

On a series of 1-km resolution POES AVHRR 0.63 µm and MODIS 0.65 µm visible images (below) the shadowing and texture of a number of convective bands could be seen, which were responsible for enhancing snowfall rates. On a longer series of 1-km resolution POES AVHRR and MODIS IR images, IR cloud top brightness temperatures as cold as -40 to -50º C were evident along the East Coast of the US.

POES AVHRR 0.63 µm and MODIS 0.65 µm visible images

Night-time images of 4-km resolution GOES-13 3.9 µm shortwave IR images suggested the presence of a warm “eye-like” signature at the center of the storm, but the subsequent daytime 1-km resolution GOES-13 0.63 µm visible images showed that the presence of extensive low-level cloudiness prevented a well-defined “eye structure” from being seen (below).

GOES-13 3.9 µm shortwave IR and 0.63 µm visible images (click to play)

Once the bulk of the cloudiness had cleared in the wake of the storm by the afternoon on 27 December, a comparison of a 1-km resolution MODIS 0.65 µm visible channel image with the corresponding MODIS false-color Red/Green/Blue (RGB) image (created using the 0.65 µm visible channel as the Red and the 2.1 µm “snow/ice” channel as the Blue and Green components of the image) revealed that a rather large “snow hole” remained from central Pennsylvania to northern Virginia (below). Inland snow cover appeared as darker shades of red on the RGB image, in contrast to bare ground (cyan) and supercooled water droplet clouds (lighter shades of white).

MODIS 0.65 µm visible + MODIS false-color Red/Green/Blue (RGB) image

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