It’s not often that the entire state of Wisconsin is “cloud-free” — but the MODIS “color balanced” Red/Green/Blue (RGB) image (above; courtesy of Sam Batzli, SSEC / WisconsinView Project) shows a beautiful example of Wisconsin and adjacent areas on 05 October 2010. Note that we used quotation marks around the term “cloud free”: there was in fact a small smoke plume seen drifting northward from a fire that was burning in the far northwestern part of the state. Otherwise, the vast diversity of vegetation across the region was quite evident by their differences in appearance on the image — from the golden orange hues of Autumn tree leaf colors in northern Wisconsin and the Upper Peninsula of Michigan, to the tan-colored fields of harvested corn across parts of southern Wisconsin, northern Illinois, northeastern Iowa, and southeastern Minnesota.

Also of interest are the bright cyan-colored areas of water over far southern Lake Michigan and also over far northern Lake Superior — these were signatures of  algae blooms. MODIS Sea Surface Temperature values on this day ranged from the upper 40s F in western Lake Superior to the middle 60s F in southern Lake Michigan (below).

Back to the smoke plume seen in the MODIS image above: a comparison of AWIPS images of the 4-km resolution GOES-13 3.9 µm shortwave IR and the corresponding 1-km resolution MODIS 3.7 µm shortwave IR images (below) demonstrated the importance of spatial resolution for determining the exact location of small-scale features such as actively burning fires. The fire “hot spot” was significantly hotter on the MODIS image (48.5º C, orange color enhancement) than on the GOES-13 image (28.5º C, darker gray color enhancement).

===== 07 OCTOBER UPDATE =====

Yet another cloud-free day over Wisconsin two days later on 07 October, allowing a nice comparison of the changing Autumn tree colors (below).

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Multiple rounds of severe thunderstorms moved northward across southern Arizona on 05 October 2010, producing hail as large as 2.5 inches in diameter, wind gusts as high as 75 mph, and rainfall in excess of 2 inches at some locations (SPC Storm Reports). According to NWS Phoenix, the 2.5 inch diameter hail was some of the largest hail ever reported in Arizona.

A 3-panel comparison of Visible channel images from GOES-11, GOES-15, and GOES-13 (above) showed the large clusters of convection, some of which moved through the Phoenix area (station identifier PHX). After 18:30 UTC, the GOES-11 satellite was placed into Rapid Scan Operations (RSO) mode, allowing images as frequently as every 5-7 minutes (in contrast to the standard operational 15-minute image interval on GOES-15 and GOES-13).

A comparison of GOES-11 Visible (0.65 µm) and Infrared Window (10.7 µm) images is shown below.

MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images (below) showed a closer view of the storms at 21:01 UTC or 3:01 pm local time. MODIS cloud-top infrared brightness temperatures were as cold as -61ºC (darker red color enhancement). Cloud-to-ground lightning strikes, severe reports of hail and wind, and surface METAR reports are also overlaid on the MODIS images.

The POES AVHRR Cloud Top Temperature (CTT) product (below) displayed a minimum CTT value of -63ºC just southeast of Chandler/Williams Air Force Base (station identifier KIWA) at 21:28 UTC or 3:28 pm local time.

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The series of three 250-meter resolution MODIS true color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed the changes in color of the Fall foliage across parts of the Upper Peninsula of Michigan, far northern Wisconsin, and the Arrowhead of northeastern Minnesota on 4 different days: 19 September, 26 September, and 03 October 2010. These Red/Green/Blue images are created using MODIS Bands 01/04/03.

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The first lake-effect snow flurries of the season were observed in the Upper Peninsula of Michigan at Gwinn, Sawyer Airport (station identifier KSAW) on 02 October 2010. An AWIPS image of MODIS 11.0 µm IR channel data (above) showed a few disorganized cloud bands over Lake Superior, with the coldest cloud top IR brightness temperature values of -13.5º C over the KSAW area.

Looking at the buoy data and the ASCAT winds over Lake Superior (below), the wind speeds over the water were not particularly strong — but the winds at KSAW gusted as high as 36 mph during the day. The could be attributed in part to terrain interaction, as the surface winds encountered a rather abrupt change in topography immediately inland across the Upper Peninsula of Miichigan (where the elevations quickly rise to 1000-1800 feet).

The AVHRR Sea Surface Temperature (SST) product from late in the day on 01 October (below) indicated that SST values across much of the central and eastern part of Lake Superior were in the middle to upper 50s F (around 12 to 15º C). With 850 hPa air temperatures of 0º C to -5º C, the “Delta-T” values were not of sufficient magnitude for the formation of well-defined lake-effect snow bands.

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