Cloud-Top Cooling Rate

May 30th, 2012 |
GOES Sounder DPI Lifted Index 1600 UTC on May 30 2012

GOES Sounder DPI Lifted Index 1600 UTC on May 30 2012

Satellite descriptors of the atmosphere over the central High Plains on May 30th suggested an atmosphere ripe for convection. For example, the GOES Sounder DPI Lifted Index showed an axis of instability from central Oklahoma to northwest Kansas, with widespread values (yellows, reds, purples) at or below -4. (The unstable area overlaps nicely with the slight risk for the day diagnosed for the day by the Storm Prediction Center). The NearCasting product (below, and available on-line here) suggests that convective instability will persist over southern Nebraska and extend southward into Oklahoma for most of the day.

GOES-13 NearCast product (click image to play animation)

GOES-13 NearCast product (click image to play animation)

GOES-13 Visible Imagery and UW Cloud-Top Cooling Rate

GOES-13 Visible Imagery and UW Cloud-Top Cooling Rate (click image to play animation)

Given this type of environment, what can cloud-top cooling rate tell you? The Cloud-Top Cooling Rate is a satellite-based product that diagnoses how quickly the growing convective towers are cooling with time, and strong cooling means rapid vertical convective growth. The strongest cooling is where the strongest convective growth is occurring, and that cooling is well-correlated with the subsequent development of NEXRAD signatures (MESH, maximum VIL, reflectivity at -10 C, etc.) The loop above shows GOES-13 visible imagery with the cloud-top cooling rate superimposed. (Real-time imagery of the cloud-top cooling rate product is available here) The The cloud-top cooling rate product highlights a persistently and quickly growing convective feature near McCook, Nebraska before and shortly after 1700 UTC. By 1800 UTC, that feature is a severe thunderstorm warned for high winds and hail.

The UW Cloud-Top Cooling Rate product is being evaluated at the Hazardous Weather Testbed taking place this month. At the HWT Blog, there are many examples of using the product in concert with knowledge of the synoptic and mesoscale conditions to anticipate strong thunderstorm development.

SPC storm reports show that the system with the strong Cloud-Top Cooling Rate subsequently produced 1-inch hail near Holdrege.

Whitewater-Baldy Fire: the largest on record in New Mexico

May 30th, 2012 |
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)

On 30 May 2012, the Whitewater-Baldy Fire complex was declared to be the largest fire on record for the state of New Mexico, having burned over 170,000 acres. On the previous day (29 May), GOES-13 0.63 µm visible channel images (above; click image to play animation) showed a vary large column of smoke that was drifting eastward across New Mexico into Texas.

A sequence of daily (early afternoon) 250-meter resolution MODIS true color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below; click image to play animation) displayed the variability in smoke plume size and direction as the fire continued to grow after 15 May. Much of the thicker smoke was confined to higher altitudes, but some smoke did settle into the boundary layer and create air quality problems downwind of the fire complex.

Daily MODIS true color Red/Green/Blue (RGB) images (click image to play animation)

Daily MODIS true color Red/Green/Blue (RGB) images (click image to play animation)

A night-time AWIPS comparison of Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band (DNB) images (below) revealed the ring of “hot spots” (red to yellow to black pixels on the shortwave IR image) and the glow of the active fires (bright white on the DNB image) around the periphery of the large fire complex. The lights of the surrounding cities and towns could also be seen on the DNB image.

Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

===== 01 June Update =====

A relatively thin veil of smoke on 01 June 2012 (as seen on the 250-meter resolution MODIS true-color image) allowed the size of the Whitewater-Baldy fire burn scar to be revealed on the corresponding MODIS false-color Red/Green/Blue (RGB) image (below).

MODIS true-color and false-color Red/Green/Blue (RGB) images

MODIS true-color and false-color Red/Green/Blue (RGB) images