MODIS true color and false color Red/Green/Blue (RGB) images)

A comparison of MODIS Red/Green/Blue (RGB) “true color” (created using Bands 1/4/3) and “false color” (created using Bands 7/2/1) images from the SSEC MODIS Today site (above) showed a well-defined single lake-effect snow (LES) band running down the length of Lake Michigan on 08 January 2011. On the false color image, snow cover, ice, and glaciated clouds appeared as cyan-colored features, in contrast to the brighter white supercooled water droplet cloud features.

A mesoscale vortex formed during the day along the southern end of the Lake Michigan LES band, which helped to enhance snowfall rates as the band moved inland across southwestern Lower Michigan and northern Indiana. With the heavy snow from this LES band and mesoscale vortex, South Bend, Indiana (station identifier KSBN) set a new record for both 1-day and 2-day snowfall — 26.0 inches and 36.6 inches, respectively. With the MODIS Sea Surface Temperature (SST) product showing mid-lake SST values over 40º F (+10º C) and the 12 UTC 850 hPa air temperatures at Green Bay WI and Gaylord MI around +4º F (-16º C), the delta-T values were certainly large enough to support the formation of intense LES bands.

A closer view of the southern end of the LES band and the mesoscale vortex using 250-meter resolution MODIS true color RGB images at 17:04 UTC and 18:46 UTC (below) also revealed the movement of small ice floes in the nearshore waters of Lake Michigan.

MODIS true color Red/Green/Blue (RGB) images

The evolution of the mesoscale vortex was evident on McIDAS images of 15-minute interval GOES-13 0.65 µm visible channel data (below; click image to play animation). Also note the numerous long, narrow streaks of snow on the ground across parts of northern Illinois into northern Indiana, left behind from previous events.

GOES-13 0.63 µm visible channel images (with surface weather) - click to play

AWIPS images of MODIS 0.65 µm visible channel data with overlays of MADIS 1-hour interval satellite winds (below) indicated that the LES band features were generally propagating southward at speeds of 20-30 knots.

MODIS 0.65 µm visible images + MADIS 1-hour satellite winds

A comparison of a 1-km resolution MODIS 11.0 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) showed that IR brightness temperatures within parts of the LES band feature were as cold as -25 to -30º C (cyan to darker blue color enhancement).

MODIS 11.0 µm IR and GOES-13 10.7 µm IR images

The 1-km resolution POES AVHRR Cloud Top Height (CTH) product (below) indicated that the LES feature exhibited CTH values which were generally in the 2-3 km range (darker violet color enhancement).

POES AVHRR Cloud Top Height product

The POES AVHRR Cloud Particle Effective Radius product (below) helped to highlight the glaciated portions of the LES band, where the radius of the larger ice crystals was in the 50-60 µm range (green color enhancement), compared to the supercooled water droplet clouds consisting of smaller particles in the 15-25 µm range (cyan color enhancement).

POES AVHRR Cloud Particle Effective Radius product

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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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