Intense derecho event

May 8th, 2009 |
GOES-12 10.7 µm IR window images

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

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

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

GOES-12 IR image + cloud to ground lightning strikes

Mountain waves

May 8th, 2009 |
MODIS 6.7 µm and GOES-12 6.5 µm water vapor channel images

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 watr vapor image + pilot reports

MODIS water vapor image + pilot reports