GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

Strong winds of 50-60 mph (with a peak gust of 74 mph at Fort Stanton, New Mexico) in the wake of a cold frontal passage caused widespread areas of blowing dust from New Mexico to Kansas on 28 February 2012. One notable feture that was apparent on both GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel images (above; click image to play animation) was a long plume of blowing sand originating from the White Sands National Monument located in southern New Mexico. Note how the plumes of blowing dust/sand became easier to identify later in the day on the GOES-13 imagery, as the forward scattering angle increased during the afternoon hours.

A 250-meter resolution Aqua MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below; viewed using Google Earth) revealed how the gypsum sand from White Sands appeared white in color (full-resolution view), in contrast to the light brown colored blowing dust that was seen across the Texas and Oklahoma panhandle regions into southwestern Kansas.

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

The interaction of the strong winds with the terrain could be seen in a comparison of 1-km resolution MODIS 6.7 µm and 4-km resolution GOES-13 6.5 µm water vapor channel images (below), which revealed a complex pattern of mountain waves across the region.

MODIS 6.7 µm and GOES-13 6.5 µm water vapor channel images

The strong surface winds in tandem with very dry air were creating conditions favorable for wildfire activity — one such fire could be seen in the southern Texas panhandle region in a comparison of 1-km resolution MODIS 3.7 µm and GOES-13 3.9 µm shortwave IR images (below).

MODIS 3.7 µm and GOES-13 3.9 µm shortwave IR images

Additional information and imagery from this event can be found on the Wide World of SPoRT blog.

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Web Map Service mapping of radar returns, watches/warnings, and satellite-detected cloud features

Unseasonably strong thunderstorms in the Piedmont on the East Coast produced a variety of severe weather on February 24th. (Storm reports are here.) The image above was produced by the SSEC/CIMSS web map service at 2006 UTC on 24 February and includes radar reflectivities, watches/warnings, storm reports, and satellite-detected cloud features (black circles indicate overshooting tops; pink circles indicate convective initiation) over the Eastern United States.

0.86 micron imagery from AVHRR and auto-detection of Overshoots from GOES-13

GOES-13 infrared data can be used to detect overshooting tops (see here) that are well-correlated with severe weather at the surface. The loop above shows 0.86-micron imagery from AVHRR at 1914 UTC, with satellite-detected overshooting tops designated by the green thunderstorm icon. As seen here, the tops do overlap a thunderstorm that, at 1915 UTC, was likely producing severe weather. 12-micron brightness temperatures on this top were as cold as -77 C. The automated overshooting top detection algorithm also identified the storm over central South Carolina at 1815 UTC that was producing a tornado in central South Carolina.

GOES-13 11-micron enhanced imagery with auto-detected Thermal Couplet (Enhanced V) indicated by white arrow

More than an hour later, at 2040 UTC, automated satellite detection suggested the presence of a thermal couplet — that is, a warm trench downwind of an overshoot — as shown above. This storm was part of a complex of warned severe storms over eastern Georgia. This storm continued to display tornadic features as it moved northeastward into coastal eastern South Carolina.

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GOES-15 6.5 µm water vapor channel images (click image to play animation)

AWIPS images of GOES-15 6.5 µm water vapor channel data (above; click image to play animation) displayed a signal of strong subsidence around the eastern periphery of a middle-tropospheric ridge of high pressure located over the eastern North Pacific Ocean on 22 February 2012. Note the rapid warming of water vapor brightness temperatures just off the coast of California, reaching abnormally high values of 14º C (darker orange color enhancement) by 21:00 UTC. This rapid middle-tropospheric drying created the appearance of a very strong moisture gradient on the water vapor imagery, being adjacent to the clouds and higher levels of moisture associated with the polar jet stream that was moving southeastward across the Pacific Northwest region of the US.

The magnitude of the dry air within the middle to upper troposphere was very apparent on rawinsonde data from Oakland, California (below).

Oakland, California rawinsonde reports

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

A comparison of AWIPS images of  MODIS 0.65 µm visible channel data with the corresponding MODIS false-color Red/Green/Blue (RGB) image (above) showed a large swath of snow on the ground on 20 February 2012, in the wake of a winter storm that moved across the Mid-Atlantic region the previous day.  The snow cover appears as shades of red on the false-color image, in contrast to the patches of supercooled water droplet clouds that persisted over the western half of the snow swath.

Farther to the west, strong winds (gusting to 60-70 mph) behind a cold front were causing an outbreak of blowing dust across parts of far eastern New Mexico and the Texas Panhandle. A comparison of a MODIS 0.65 µm visible channel image with the corresponding 1.3 µm “cirrus detection channel” image (below) demonstrated how the near-IR cirrus channel can be used to better identify the areal extent of the blowing dust (which might not be apparent on the visible channel imagery). The cirrus detection channel is sensitive to particles that are good scatterers of light, such as ice crystals, dust, volcanic ash, and smoke/haze.

MODIS 0.65 µm visible channel + MODIS 1.3 µm "cirrus detection channel" images

A comparison of the MODIS 0.65 µm visible channel image with the corresponding MODIS 11-12 µm IR difference product (below) demonstrates how 11-12 µm difference values of 1-2 degrees C (yellow color enhancement) highlighted areas where the dust concentration was highest. Airborne dust particles have different emissivities at the 11 µm and 12 µm wavelengths, which allows such an IR difference product to be used to locate and track blowing dust. Recall that the older series of GOES satellites (GOES-8 through GOES-11) had a 12.0 µm IR channel that allowed the creation of a similar IR difference product — but on the latest satellites (GOES-13 through GOES-15) the 12.0 µm IR channel was replaced with a 13.3 µm channel.

MODIS 0.65 µm visible channel image + MODIS 11-12 µm IR difference image

A closer view of the blowing dust cloud can be seen using 250-meter resolution MODIS true-color RGB images from the SSEC MODIS Today site (below). Some of the primary source regions of the blowing dust (located in New Mexico) can be seen on the earlier Terra image at 17:56 UTC.

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

In the southeastern Texas Panhandle, a multiple-vehicle accident occurred along Highway 287 around 20:00 UTC (3:00 pm local time), causing a closure of that section of highway between Memphis and Childress (station identifier KCDS). McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (below; click image to play animation) showed that an optically thick band of blowing dust was moving through the region between Memphis and Childress around the time of the accident.

GOES-13 0.63 µm visible channel images (click image to play animation)

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