GOES-12 10.7 µm IR window images

An unusually-large derecho event formed over Kansas during the pre-dawn hours on 08 May 2009, and then moved rapidly eastward across Missouri and Illinois during the morning hours. GOES-12 10.7 µm IR window images (above) showed the large areal coverage of cold cloud tops (which were as cold as -79º C in southeastern Kansas).

The impressive derecho left a long swath of storm reports (below), which included several tornadoes and wind gusts to 87 knots (100 mph) at 11:30 UTC in Kansas, 81 knots (93 mph) at 12:15 UTC in Missouri, and 92 knots (106 mph) at 18:25 UTC in Illinois. Hail as large as 2.75 inch in diameter was reported in Missouri at 14:34 UTC.

MODIS 11.0 IR window image + storm reports

As the storm matured toward mid-day, it began to display transverse banding on both the northern periphery and the  southern periphery of the cloud shield (below). This transverse banding is often a signature of high-altitude turbulence — and there were indeed a number of pilot reports of turbulence along the edges of the convective complex.

MODIS 6.7 µm water vapor image + pilot reports of turbulence

The storm was also a prolific producer of lightning: at one point, it was producing over 4000 cloud-to-ground strikes every 15 minutes (below).

GOES-12 IR image + cloud to ground lightning strikes

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MODIS 6.7 µm and GOES-12 6.5 µm "water vapor channel" images

AWIPS images of the 1-km resolution MODIS 6.5 µm and the 4-km resolution GOES-12 6.5 µm “water vapor channel” images (above) demonstrate the advantage of better spatial resolution for the detection of small-scale features such as the mountain waves that had formed over much of New Mexico and the adjacent states on 08 May 2009. A small amount of parallax shift is also evident on the GOES-12 image, with the features being displaced slightly to the northwest.

The presence of mountain waves implies the potential for turbulence (especially when the wave patterns interfere, as they do in this particular case) — however, very few aircraft were flying in the area at that hour, and there was only one pilot report of light turbulence at 36,000 feet near the Arizona/New Mexico border.

MODIS water vapor image + pilot reports

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GOES-12 visible images

GOES-12 visible channel images (above) showed advection fog that developed over Lake Michigan during the day on 07 May 2009. As pointed out on the US Air Quality (aka The Smog Blog) site,  this fog “fooled” the MODIS Aerosol Optical Depth (AOD) algorithm, causing a false signal of very high AOD over Lake Michigan. Also note the appearance of “shock waves” in the fog bank as it encountered obstructions to the southwesterly boundary layer flow in two areas: (1) along the western coastline of Lower Michigan (250-m resolution MODIS true color image), and (2)  some of the larger islands in the northern portion of Lake Michigan (250-m resolution MODIS true color image).

This fog formed as warm and relatively humid air (with dew points in the middle 50s F) moved across the cold waters of Lake Michigan. An AWIPS image of the MODIS Sea Surface Temperature (SST) product (below) indicated that that mid-lake SST values were still in the 37-39º F range — and  this was confirmed by the water temperature values of 37º F and 38º F reported by buoys 45002 and 45007, respectively.

MODIS Sea Surface Temperature product

The western portion of the advection fog feature was quite thin, so the fog edge was difficult to pick out on the MODIS 11.0 µm “IR window” imagery (below). However, the fog boundaries were quite apparent on the 3.7 µm “shortwave IR” imagery, due to the reflection of solar radiation off the top of the water droplet fog feature (which made the fog appear darker/warmer).

MODIS visible, 11.0 µm IR window, 3.7 µm shortwave IR images

The GOES sounder Cloud Top Height product (below) indicated that the tops of the fog feature over the southern half of Lake Michigan were generally around 2580 feet (darker brown color enhancement).

GOES-12 sounder Cloud Top Height product

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GOES-11 visible images

GOES-11 was placed into Super Rapid Scan Operations (SRSO) on 05 May 2009, as a test for support of the upcoming VORTEX2 field experiment. During SRSO, images are available at 1-minute intervals for short periods of time. The GOES-11 visible channel imagery (above) shows severe convection in southwestern Nebraska, which produced hail up to 1.25 inch in diameter (SPC storm reports).

SPC storm reports

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