GOES-12 10.7 µm IR images

A west-to-east oriented stationary front was draped across the Upper Midwest and Great Lakes states on 19 May 2009. AWIPS images of the GOES-12 10.7 µm IR window channel (above) showed that there was a general lack of cloudiness in the vicinity of the frontal boundary, which allowed the thermal contrast on either side of the front to be seen (with the warmer air and darker gray land surfaces located south of the front). However, the IR imagery also seemed to indicate that the far eastern portion of the front was beginning to  sag southward, as seen by the of  surge colder IR brightness temperatures (lighter gray shades) along the northeastern Wisconsin shoreline of Lake Michigan.

A closer view of the northern portion of Lake Michigan using GOES-12 visible channel images (below) showed that there was a patch of lake stratus propagating quickly southwestward along the western shoreline of the lake, presumably along and just behind the leading edge of the advancing frontal boundary. Air temperatures at buoy 45002 dropped to 39º F as northeasterly winds increased behind the front.

GOES-12 visible images

AWIPS images of the MODIS 250-meter resolution “true color” image and the corresponding 1-km resolution MODIS 11.0 µm IR window image (below) revealed both the leading edge of the colder air (the transition from warmer red and yellow colors to the colder green colors) inland across the northeastern counties of Wisconsin, as well as a wave/undular bore signature on the waters of Lake Michigan.

MODIS true color image + MODIS 11.0 µm IR image

Consecutive image of the MODIS Land Surface Temperature (LST) product (below) also showed the southward progression of the colder air. In addition, note the appearance of the slightly warmer (lighter green color enhancement) southwest-to-northeast oriented tornado damage swath located farther inland — this damage swath was from the  07 June 2007 tornado event.

MODIS Land Surface Temperature (LST) images

Consecutive  250-meter resolution MODIS true color images (below) indicated that the wave/undular bore signature over the waters of Lake Michigan continued to propagate southward during this time, marking the leading edge of the advancing lake-enhanced cold frontal segment.

250-meter resolution MODIS true color images

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GOES-11 SRSO visible images

The GOES-11 satellite was once again placed into Super Rapid Scan Operations (SRSO) on 13 May 2009, providing images as frequently as every 1 minute during portions of the late afternoon and early evening hours. The GOES-11 visible channel imagery (above; also available as a QuickTime animation) shows the explosive development of severe convection along a dryline in Oklahoma, Kansas, and Missouri. According to the SPC Storm Reports, this line of storms produced several tornadoes, hail up to 2.75 inch in diameter, and wind gusts to 80 mph.

GOES-11 10.7 µm IR imagery (below; also available as a QuickTime animation) revealed that the cloud top temperatures quickly cooled to values of -60º to -70º C (red to black colors) as these thunderstorms developed and intensified.

GOES-11 10.7 µm IR images

The plot of the coldest GOES-11 IR brightness temperatures (below) for the initial (and largest)  storm that formed in eastern Kansas  shows that the minimum cloud top temperatures cooled to within a few degrees of the -64º C tropopause temperature (taken from the Topeka, Kansas rawinsonde report) after around 22:00 UTC. It is interesting to note that there was a slight cloud top temperature warming seen at 22:45 UTC — which is about 7 minutes prior to the first reported tornado from that particular storm. If this type of “pre-tornado cloud top temperature warming” signal is something that frequently occurs, then having access to satellite imagery at a high temporal resolution will be critical to utilizing any possible predictive value of such a signal.

Plot of GOES-11 10.7 µm IR brightness temperatures

A comparison of the 4-km resolution GOES-11 10.7 µm and the 1-km resolution NOAA-15 10.8 µm IR images (below) demonstrates the value of higher spatial resolution: a clear “enhanced-v” signature was seen on the NOAA-15 image, while no such signature was obvious on the GOES-11 image. Note that the minimum cloud top brightness temperature in the overshooting top region was 15º C colder on the NOAA-15 IR image. Also, due to the large satellite viewing angle from the GOES-11 satellite (the satellite zenith angle for Topeka, Kansas is 61 degrees), a significant parallax shift was apparent with this particular storm — the overshooting top region was displaced farther to the northeast of Emporia, Kansas (KEMP) on the GOES-11 IR image.

GOES-11 10.7 µm and NOAA-15 10.8 µm IR images

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MODIS 11.0 µm IR image + storm reports + cloud-to-ground lightning data

A well-defined “enhanced-v” storm top signature was seen on MODIS 11.0 µm IR window image (above) over Nebraska around 08:09 UTC (3:09 am local time) on 13 May 2009. The magnitude of the cold/warm cloud top temperature couplet was rather large (-72º C to -50º C) for this particular enhanced-v feature. Also note the presence of a  cloud-top packet of gravity waves, which could be seen propagating westward away from region of the enhanced-v signature. Hail as large as 1.0 inch in diameter was being reported, and there were a large number of both negative and positive cloud-to-ground lightning strikes in the enhanced-v region around the time of the MODIS IR image.

A comparison of the 1-km resolution MODIS 11.0 µm IR image and the corresponding 4-km resolution GOES-12 10.7 µm IR image (below) shows the advantage of better spatial resolution for displaying cloud top temperature structure. Also note the slight parallax error on the GOES-12 image, with the features being shifted several miles to the northwest (due to the large satellite viewing angle of the geostationary satellite).

MODIS 11.0 µm IR image + GOES-12 10.7 µm IR image

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1-km MODIS vs 4-km GOES-12 fog/stratus product

AWIPS images of the 1-km resolution MODIS fog/stratus product and the 4-km resolution GOES-12 fog/stratus product (above) demonstrate the advantage of higher spatial resolution for the detection of widespread small-scale fingers of valley fog that had formed during the overnight hours over much of the southern Appalachian Mountains states on 12 May 2009. This region had received heavy precipitation during the preceding week which led to major flooding — as a result the soil moisture was quite high, enhancing the potential for radiation fog formation.

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