GOES-13 10.7 µm IR channel images + severe weather reports (click image to play animation)

A major outbreak of severe thunderstorms along a strong cold frontal boundary swept eastward across much of the southeastern US on 22 January – 23 January 2012, producing widespread damaging winds, large hail, and tornadoes (SPC storm reports). Two tornadoes produced EF-3 damage in Alabama. AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data with overlays of severe weather reports (above; click image to play animation) showed the cold cloud top IR brightness temperatures of -60 to -70 C (red to black color enhancement) associated with some of the strongest storms. For more information, see summaries from the National Weather Service forecast offices at Litttle Rock AR, Jackson MS, and Birmingham AL.

POES AVHRR 12.0 µm and MODIS 11.0 µm IR images

A sequence of 1-km resolution POES AVHRR 12.0 µm IR and MODIS 11.0 µm IR images (above) displayed greater detail in the storm top thermal structures, with a number of  -70 to -80 C (black to light gray color enhancement) IR brightness temperature values seen on the higher resolution imagery.

Of particular interest was what appeared to be some sort of “cloud trench” oriented from north to south across Tennessee around 08:00 UTC, which exhibited significantly warmer MODIS 11.0 µm IR brightness temperatures and a warmer/drier signal on the corresponding MODIS 6.7 µm water vapor image (below). This feature was also apparent on a few of the 4-km resolution GOES-13 IR images around that time. The etiology of this satellite signature is unclear at this time.

MODIS 11.0 µm IR channel and 6.7 µm water vapor channel images

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GOES-15 0.63 µm visible channel images (click image to play animation)

A large outbreak of blowing dust developed in the wake of a cold frontal passage across parts of New Mexico, Texas, and Oklahoma on 22 January 2012. At Lubbock, Texas winds gusted to 60 mph, and surface visibility was reduced to 0.5 mile. The strongest wind gust was 77 mph, farther to the north in the Texas panhandle region (NWS Lubbock summary). Early in the day, the consolidation of numerous smaller blowing dust plumes into a single large blowing dust “cloud” could be seen on 1-km resolution GOES-15 (GOES-West) 0.63 µm visible channel images (above; click image to play animation).

Later in the day, due to a more favorable forward scattering angle, the areal extent of the airborne blowing dust could be better seen on 1-km resolution 0.63 µm visible channel images from the GOES-13 (GOES-East) satellite (below; click image to play animation). The leading edge of the primary large dust plume began to move northeastward over Oklahoma, while a number of smaller dust plumes could be seen moving southeastward across the Oklahoma and Texas panhandle regions behind a secondary cold front. Note that the GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes.

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

A 250-meter resolution MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below, viewed using Google Earth) displayed even greater detail in the structure of the blowig dust plume at 20:02 UTC.

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

There was also a bit of smoke mixed in with the blowing dust, due to a few small wildfires that were burning across the region. Three small wildfire “hot spots” (dark black to yellow pixels) could be seen on an AWIPS image of 1-km resolution MODIS 3.7 µm shortwave IR data at 20:00 UTC (below).

MODIS 3.7 µm shortwave IR image

Over southern Oklahoma at 21:23 UTC a pilot reported that at an altitude of 9000 feet the flight level visibility was zero due to blowing dust (below).

GOES-13 0.63 µm visible channel image + Aircraft pilot report

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GOES-13 10.7 µm IR images + surface frontal analysis (click image to play animation)

AWIPS images of 4-km resolution GOES-13 10.7 µm IR data (above; click image to play animation) showed a variety of cloud features across the central and southern US between 07:01 UTC and 09:30 UTC on 19 January 2012. In particular, note (1) the darker gray (warmer) low clouds streaming northward from the Gulf of Mexico into Texas, signalling a northward return flow of low-level moisture (Total Precipitable Water values of 15-25 mm); (2) a large lighter gray (colder) banner cloud extending downwind of the Rocky Mountains, due to northwesterly flow aloft interacting with the high terrain; and  (3) a long lighter gray (colder) cloud band exhibiting some transverse banding, associated with a strong 165-knot core jet stream flowing southeastward from Nebraska to Tennessee.

Below are corresponding examples of 1-km resolution IR images from polar-orbiting satellites from the 08:22 to 08:43 UTC time period. The oldest “legacy” instrument is the AVHRR, carried on the constellation of NOAA POES satellites. A newer instrument is the MODIS, carried on the NASA Aqua and Terra satellites. The most recently-launched satellite is the NASA NPP, which carries the VIIRS instrument.

POES AVHRR 12.0 µm IR image

Aqua MODIS 11.0 µm IR image

NPP VIIRS M15 10.763 µm IR image

NPP VIIRS 10.763 µm IR image (viewed using Google Earth)

Images such as these from polar-orbiting satellites are available less frequently that those from GOES, but they offer a more detailed view of cloud features due to improved spatial resolution. The more modern instruments such as MODIS and VIIRS also contain many more channels (or spectral bands) than are available from the current generation of GOES satellites. These additional bands allow the creation of a variety of quantitative satellite products.

For example, if we focus our attention on the low cloud features in Texas, using MODIS data we can be more descriptive in terms of the Cloud Type (water), Fog Depth (as deep as 1300 feet), and Probability of Marginal Visual Flight Rules MVFR (as high as 70-80%) or Probability of Instrument Flight Rules IFR (as high as 50-60%).

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

A strong cold front moved southward across the south-central US on 17 January 2012, dropping temperatures as much as 20 degrees F in 1-2 hours with wind gusts of 30-40 knots. The cold air behind the front (lighter gray enhancement) was clearly evident on AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (above; click image to play animation).

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

As the cold front moved southward, a lee-side cold frontal gravity wave was seen along its leading edge on 4-km resolution GOES-13 6.5 µm water vapor channel images (above; click image to play animation). Note the very complex wave structure that was displayed on a 1-km resolution MODIS 6.7 µm water vapor channel image at 08:34 UTC (below). In addition, the MODIS water vapor image showed great detail in the mountain waves across parts of New Mexico and far southwestern Texas, as strong westerly flow was interacting with the terrain in that region.

MODIS 6.7 µm water vapor channel image + Surface frontal analysis

Jayton, Texas NOAA Wind Profiler time series

As the cold front passed the Jayton, Texas NOAA wind profiler site (station identifier JTNT2) after about 12 UTC, the transition to a northeasterly flow of cold air was evident (above). Even though the depth of the cold air was not more than about 1.5 km, the lee-side cold frontal gravity wave was able to be seen on the water vapor imagery due to the fact that the cold, dry air mass shifted the peak of the GOES-13 water vapor weighting function down to within the 700-500 hPa pressure level — much lower than the height of the water vapor weighting function of the US Standard Atmosphere air mass (below).

Amarillo, Texas water vapor weighting function vs US Standard Atmosphere water vapor weighting function

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