GOES-11 + GOES-12 water vapor channel images

AWIPS images of the GOES-11 + GOES-12 water vapor channels (above) showed the large size of a major snowstorm that impacted much of the western US during the 10 October – 12 October 2008 time frame. This storm dropped as much as 48.8 inches of snow at Cole Creek, Montana and 29.7 inches at Lander, Wyoming (their greatest October snowfall on record), and Glasgow, Montana received 12.8 inches of snow on 12 October (their heaviest snowfall for any calendar day during the month of October). At Billings, Montana the snow depth of 9 inches on 13 October was the earliest date on record for a 9-inch snow depth.

AWIPS images of the MODIS visible channel and the 1.6 µm near-IR “snow/ice” channel (below) displayed the areal coverage of snow on the ground across much of Wyoming, eastern Montana, far northwestern South Dakota (including the higher elevations of the Black Hills) and western North Dakota, stretching northeastward into portions of Saskatchewan and Manitoba on 13 October. Snow cover exhibits a darker signal on snow/ice channel imagery (in contrast to supercooled water droplet clouds, which appear as lighter shades of gray).

MODIS visible and snow/ice channel images

An AWIPS image of the MODIS Land Surface Temperature (LST) product (below) showed the effect of the deep snow cover on surface temperatures across much of Wyoming and Montana on 13 October — LST values within the snow swath were only in the upper 20s to low 30s F (green colors), compared to the 60s and 70s F (orange colors) north of the deep snow cover. The daily maximum temperature on 13 October at Glasgow, Montana was only 37º F (which tied the record for coldest maximum temperature for that date), while the daily high temperature of 28º F at Wisdom, Montana was the earliest date for such a cold maximum temperature.

MODIS Land Surface Temperature product

A 250-meter resolution MODIS true color image (below, viewed using Google Earth) displayed the extent of the snow cover across parts of Wyoming and Montana. Note that there were a few snow-free patches located within the broad swath of snow cover (a result of the complex terrain across the region).

MODIS true color image (viewed using Google Earth)

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GOES-11, GOES-12, GOES-13 water vapor images

Strong southwesterly winds over the southern and central Rocky Mountains led to the development of mountain waves downwind of the higher terrain in Colorado and New Mexico on 10 October 2008. A distinct mountain wave signature was seen on 6.7 µm water vapor channel imagery from GOES-11 and 6.5 µm water vapor channel imagery from GOES-13 and GOES-12 (above). Note the improved appearance of the mountain waves on the 4-km resolution GOES-13 and GOES-12 imagery (compared to the 8-km resolution GOES-11 imagery). These mountain waves were also easier to identify and track using GOES-13, due to the more direct viewing angle of GOES-13 (positioned at 105º W longitude) and also the fact that GOES-13 was able to operate and supply imagery through the eclipse period (when the satellite was in the Earth’s shadow, and the solar panels could not supply power to the spacecraft).

AWIPS images of GOES-12 and MODIS water vapor channel data

AWIPS images of the GOES-12 and MODIS water vapor channel data (above) showed further improvement in mountain wave identification using 1-km resolution data from MODIS. Mountain waves on water vapor imagery have long been recognized as a signature of potential clear air turbulence, and there were indeed a few pilot reports of light to moderate turbulence over eastern Colorado and New Mexico (below).

AWIPS image of GOES-12 water vapor channel data + pilot reports

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GOES-13 visible images (Hurricane Norbert)

GOES-13 visible imagery (above) revealed the rather large eye of Hurricane Norbert on 08 October 2008 — Norbert was a Category 4 storm at that time, and the eye appeared to be about 30-35 nautical miles in diameter.  Hurricane Norbert underwent a period of rapid intensification during the pre-dawn hours on 08 October, which was clearly seen on a plot of the Advanced Dvorak Technique intensity estimate (below) from the CIMSS Tropical Cyclones site.

CIMSS Advanced Dvorak Technique

To illustrate the diversity of tropical cyclone spatial scales, it is interesting to compare the large eye of Hurricane Norbert (in the eastern Pacific Ocean) with the small cluster of deep convection around the core of Tropical Storm Marco (2 days earlier in the Gulf of Mexico) — Marco is not much larger than the eye of Norbert! The visible and IR images shown below are from the same satellite (GOES-13) at the same time of day (20:00 UTC), displayed with the same magnification (zoomed in to an effective 0.5 km resolution). According to the National Hurricane Center discussions, Tropical Storm Marco may have been one of the smallest tropical cyclones on record, with tropical storm force winds only extending about 10 nautical miles away from the center.

GOES-13 visible images (Hurricane Norbert and Tropical Storm Marco)

GOES-13 IR images (Hurricane Norbert and Tropical Storm Marco)

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AWIPS images of GOES and MODIS fog/stratus product

AWIPS images of the GOES-12 and MODIS fog/stratus product around 07:30 UTC or 3:30 AM local time   (above) told two very different stories regarding the formation of river valley fog across parts of the Northeast US on 07 October 2008. In general, there was a surprising amount of disagreement between to two images: the 4-km resolution GOES-12 fog/stratus product suggested that fog was forming over places like the Finger Lakes region of New York and the Lake Champlain region along the Vermont/New York border, while the 1-km resolution MODIS fog/stratus product indicated significant areas of river valley fog across parts of northern Pennsylvania into southern New York.

A closer view (below) helps to illustrate the problem of fog/stratus product verification — there was a lack of reporting stations in the actual areas where river valley fog was forming.

AWIPS images of GOES and MODIS fog/stratus product

A 1-km resolution NOAA-15 AVHRR fog/stratus product (below) from a few hours later (11:10 UTC or 7:10 AM local time) indicated that the fingers of river valley fog across northern Pennsylvania and southern New York had increased in the hours leading up to sunrise.

NOAA-15 fog/stratus product

Post-sunrise GOES-12 and GOES-13 visible images (below) revealed the widespread coverage of river valley fog across the Pennsylvania/New York border region, which dissipated rather quickly by 15:00 UTC or 11 AM local time.

GOES-12 and GOES-13 visible images

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