GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images

A tornado was observed and photographed near Mt. Evans in north-central Colorado around 2:51 PM local time or 20:51 UTC (Local Storm Report) on 28 July 2012. A comparison of McIDAS images of 4-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 10.7 µm IR channel data (above) showed that the thunderstorm which produced the tornado developed fairly rapidly just to the east of Copper Mountain (station identifier KCCU), but was relatively small in size and did not exhibit particularly cold cloud top IR brightness temperatures (-40º C at 20:45 UTC, and -52º C at 21:15 UTC).

AWIPS images of 1-km resolution MODIS 0.6 µm visible channel and 11.0 µm IR channel data at 20:28 UTC (below) showed that the storm was beginnng to produce a few negative cloud-to-ground lightning strikes, with a minimum IR brightness temperature around -50º C at that time.

MODIS 0.65 µm visible and 11.0 µm IR channel images (with cloud-to-ground lightning strikes)

The CIMSS Cloud Top Cooling Rate product (below) did flag the storm at 20:32 UTC as it was beginning to develop in north-central Colorado.

GOES-13 instantaneous Cloud Top Cooling Rate product

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GOES-13 0.63 µm visible channel images

McIDAS images of GOES-13 0.63 µm visible channel data (above) showed the hazy signature of a dense veil of airborne Saharan dust over South Florida and the adjacent offshore waters of the Gulf of Mexico and the Atlantic Ocean on 25 July 2012. This particular major pulse of Saharan dust began to move westward across the Atlantic Ocean during mid-July.

A closer view using an AWIPS image of Suomi NPP VIIRS 0.64 µm visible channel data (below) also showed the hazy signature of the dust over the southeastern portion of the satellite scene. A pilot reported flight visibility of 4 to 5 statute miles within the dust layer over the Florida Keys.

Suomi NPP VIIRS 0.64 µm visible channel image + Pilot reports

A comparison of the VIIRS 0.64 µm visible image with the corresponding VIIRS 11.45 µm IR image (below) demonstrated that there was no dust signal at that particular IR wavelength, due to the fact tht an elevated dust layer is generally transparent to thermal radiation from the land and ocean surfaces below.

Suomi NPP VIIRS 0.64 µm visible channel + 11.45 µm IR channel images

The VIIRS Aerosol Optical Thickness product (below) showed a strong signal (yellow to red color enhancement) over that region due to the presence of the airborne dust. Yet another strong pulse of Saharan dust could be seen exiting  the coast of Africa and moving westward across the Atlantic Ocean,

Suomi NPP VIIRS Aerosol Optical Thickness product

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Suomi NPP VIIRS 0.64 µm visible channel images

Even though most of Hudson Bay in Canada was essentially ice-free on 24 July 2012, there were still some ice floes consisting of thick first year ice that remained in the far southwestern part of the Bay. AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (above) showed the motion of these ice floes (along with the other cloud features in the region) between 17:50 and 19:29 UTC.

A comparison of a VIIRS 0.64 µm visible channel image with the corresponding 3-channel Red/Green/Blue (RGB) image created by using 0.64 µm, 1.61 µm, and 11.45 µm data (below) demonstrated the utility of using RGB imagery to help discriminate between ice features (darker purple color enhancemnt) and clouds (varying shades of white).

Suomi NPP VIIRS 0.64 µm visible channel + false-color Red/Green/Blue (RGB) image

Similarly, a comparison of a MODIS 0.65 µm visible channel image with the corresponding RGB image created using 0.64 µm and 2.1 µm data (below) showed the ice features as darker red, compared to supercooled water droplet clouds (lighter shades of white) and glaciated clouds (lighter pink color enhancement).

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

The MODIS Sea Surface Temperature (SST) product (below) showed SST values in the middle 30s F (darker blue color enhancement) over the ice floe features, compared to SST values in the low-middle 40s F over the adjacent open waters of Hudson Bay.

MODIS Sea Surface Temperature product

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MODIS Estimates of Lake Surface Temperature

Persistent heat over the upper Midwest and Eastern United States for the first half of 2012 have helped warm Great Lakes surface water temperatures. MODIS estimates of Lake Surface temperature, above, show only a small region of temperatures cooler than 60 F in the entire Lake system in a very small region near Isle Royale in Lake Superior. (Click here for maps of Lake Superior temperatures. You can also find data for Lakes Huron, Michigan, Erie and Ontario). All other temperatures exceed 60 F. The 8-day average of MODIS SSTs over the lake, from Terra and from Aqua, obtained from this interactive site also shows the warmth. An SST image from AVHRR (the image doesn’t include all of Lake Superior) also shows warm temperatures.

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