Enhanced-V storm top signature over Nebraska

May 13th, 2009 |
MODIS 11.0 µm IR image + storm reports + lightning data

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

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

Valley fog in the southern Appalachian Mountains

May 12th, 2009 |
1-km MODIS vs 4-km GOES-12 fog/stratus product

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.

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