Mesoscale Convective Vortex moving across Missouri and Illinois

August 8th, 2013
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

 

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the well-defined signature of a Mesoscale Convective Vortex (MCV) moving northeastward across Missouri and Illinois during the day on 08 August 2013.

A comparison of 1-km resolution MODIS 0.65 µm visible channel data at 16:16 and 19:35 UTC (below) showed that the MCV was approaching a frontal boundary over southern Illinois.

MODIS 0.64 µm visible channel images

MODIS 0.64 µm visible channel images1-km resolution Suomi NPP VIIRS

1-km resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 19:05 UTC (below) indicated that the clouds associated with the MCV were generally low-level clouds, exhibiting IR brightness temperatures in the +5 to +10º C range (lighter cyan color enhancement).

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

A comparison of 1-km resolution POES AVHRR 0.86 µm visible channel with the corresponding CLAVR-x Cloud Top Temperature (CTT), Cloud Top Height (CTH), and Cloud Type products (below) indicated the following characteristics of the MCV cloud signature over far southwestern Illinois at 19:44 UTC: CTT values in the -5 to -8 C range (light blue enhancement), CTH values in the 5-6 km range (orange to yellow enhancement), and a Cloud Type consisting of supercooled water droplets (green enhancement).

POES AVHRR visible channel, Cloud Top Temperature, Cloud Top Height, and Cloud Type products

POES AVHRR visible channel, Cloud Top Temperature, Cloud Top Height, and Cloud Type products

 

GOES-13 Sounder DPI estimates of Total Precipitable Water (Click for animation)

GOES-13 Sounder DPI estimates of Total Precipitable Water (Click for animation)

Mesoscale Convective Complexes are most likely to persist in regions of abundant moisture and low shear. GOES Sounder data can give an indication of moisture in regions where clouds do not obscure the view. Clouds were abundant as the MCV formed in this case, but the animation of Total Precipitation Water (above) shows an atmosphere rich in moisture. Sounder estimate of Lifted Index, below, indicate instability. (Both animations stop at 1400 UTC, just as the MCV was seen emerging from the convective complex over southwest Missouri). The ‘blended’ Percent of Normal Total Precipitable Water product, here, shows values exceeding 100% of normal over the mid-Mississippi River Valley.

GOES-13 Sounder DPI estimates of Lifted Index (Click for animation)

GOES-13 Sounder DPI estimates of Lifted Index (Click for animation)

Strong storm in the Gulf of Alaska

August 6th, 2013
GOES-15 6.5 µm water vapor channel images (click image to play animation)

GOES-15 6.5 µm water vapor channel images (click image to play animation)

McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed the complex pattern of intensification of a storm over the western Gulf of Alaska on 06 August 2013. According to the NOAA NWS Ocean Prediction Center, this was the first cyclone to produce storm-force winds (greater than 47 knots) over the North Pacific Ocean since 21 June 2013.

AWIPS images of 1-km resolution Suomi NPP VIIRS 11.45 µm IR channel and 0.64 µm visible channel data with an overlay of the corresponding surface analysis (below) showed the cloud features associated with the storm system at 23:14 UTC.

Suomi NPP VIIRS 11.45 µm IR and 0.64 µm visible images (with surface analysis)

Suomi NPP VIIRS 11.45 µm IR and 0.64 µm visible images (with surface analysis)

Severe thunderstorms in northwestern Kansas

August 5th, 2013
GOES-13 0.63 µm visible channel images with overshooting top detection icons (click image to play animation)

GOES-13 0.63 µm visible channel images with overshooting top detection icons (click image to play animation)

 

AWIPS images of 1-km resolution GOES-13 0.63 µm visible channel images with automated overshooting top detection icons (above; click image to play animation) showed the development of a large mesoscale convective system across northwestern Kansas during the afternoon hours on 05 August 2013. Note that the surface air temperature at Goodland, Kansas (KGLD) dropped from 91º F at 19 UTC to 69º F at 20 UTC (with southeasterly winds gusting to 34 knots).

4-km resolution GOES-13 10.7 µm IR channel images with automated overshooting top detection icons (below; click image to play animation) revealed the formation of a very broad and well-defined “enhanced-V” storm top signature, with cloud-top IR brightness temperatures becoming as cold as -80º C at 23:15 UTC. Overshooting top detection began after 19:45 UTC, once GOES-13 cloud-top IR brightness temperatures became -71º C or colder.

GOES-13 10.7 µm IR channel images with overshooting top detection icons (click image to play animation)

GOES-13 10.7 µm IR channel images with overshooting top detection icons (click image to play animation)

During the early stages of convective development, GOES-13 10.7 µm IR images combined with 15-minute cloud top cooling rates (below) showed the development of significant cloud top cooling rates along the Colorado/Kansas border area at 18:15 UTC (prior to the formation of weak, brief landspout tornadoes just northeast of Goodland, Kansas during the 18:28-18:40 UTC period) — a maximum cloud top cooling rate of 35.3º C in 15 minutes was detected at 18:45 UTC.

GOES-13 10.7 µm IR channel images with Cloud Top Cooling Rates

GOES-13 10.7 µm IR channel images with Cloud Top Cooling Rates

A comparison of 1-km resolution Soumi NPP VIIRS 11.45 µm IR channel and 4.-km resolution GOES-13 10.7 µm images (below) demonstrated the ability of higher spatial resolution VIIRS data to detect much colder IR brightness temperatures associated with the more vigorous overshooting tops (-82º C on VIIRS, vs -71º C on GOES). In addition, a northwestward GOES image parallax shift was seen, due to to the large viewing angle of the GOES-13 satellite positioned at 75º W longitude. Shortly after the time of these images, this storm produced hail of 1.0 inch in diameter at 20:11, 20:21, and 20:54 UTC (SPC storm reports)

Suomi NPP VIIRS 11.45 µm IR and GOES-13 10.7 µm IR images

Suomi NPP VIIRS 11.45 µm IR and GOES-13 10.7 µm IR images

Comparisons of 1-km resolution POES AVHRR Cloud Top Temperature and Cloud Top Height products at 20:21 UTC (above) and 21:16 UTC (below) showed that the coldest cloud top temperatures (-85º C and -87º C, respectively) were seen in regions where the maximum cloud top height values were generally around 15 km. It is likely that the most vigorous overshooting tops associated with the coldest cloud top temperature values were as much as 2-3 km higher than this mean 15 km thunderstorm anvil cloud top height. Conversely, cloud top height values were around 13 km in the “warm wake” region immediately downwind of the coldest overshooting tops.

Saharan Air Layer outbreak over the Atlantic Ocean

August 2nd, 2013
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) revealed the hazy signature of a dust-laden Saharan Air Layer (SAL) that was propagating westward across the North Atlantic Ocean during the 01 August – 02 August 2013 period. The full disk satellite perspective helped to emphasize how large the areal coverage of this particualr SAL outbreak was. A closer view of the leading edge of the SAL feature is available here.

The SAL moved over Puerto Rico during the day on 02 August, as seen by the transition to a very warm and dry signature just above the 850 hPa pressure level in consecutive rawinsonde data profiles (below) from San Juan (TJSJ).

The Meteosat-10 Saharan Air Layer product (below; click image to play animation) showed the strong westward push of the SAL during the 31 July – 02 August time period.

Meteosat-10 Saharan Air Layer (SAL) product (click image to play animation)

Meteosat-10 Saharan Air Layer (SAL) product (click image to play animation)