Archive for the ‘Winter weather’ Category

Halloween Blizzard of 1991

Thursday, October 29th, 2009

HallowLoop

The Halloween Blizzard of 1991 was an early-season storm that moved north from the Gulf of Mexico to the upper Great Lakes. Unseasonably cold air allowed the rich moisture-laden airmass to deposit a long band of snow from the Panhandle of Texas northeastward to western Lake Superior. Many early-season snow total records were broken, and single-storm records fell at Minneapolis (28.4″) and Duluth (36.9″) Typically storms from the Gulf of Mexico do not move due north; however, eastward motion of this system was blocked by a large nor’easter off the coast of New England (the so-called “Perfect Storm”).

In the visible loop above, notice the rapid melting of snow deposited by the system in west-central Texas, despite record cold (30 and 31 October 1991 are the only October days in Amarillo history that stayed below 30 all day) Snowcover in South Dakota (The Missouri River stands out) also speaks to the chill in the airmass on the cold side of the storm.

(Coming soon: Infrared and Water Vapor imagery of this storm)

Snow cover in Colorado, Kansas, and Nebraska

Friday, October 23rd, 2009
MODIS visible and 2.1 µm near-IR snow/ice channel images

MODIS visible and 2.1 µm near-IR snow/ice channel images

AWIPS images of the MODIS visible and 2.1 µm near-IR “snow/ice” channels (above) showed areas of snow cover across parts of eastern Colorado, far northwestern Kansas, and Nebraska on 23 October 2009. Snow is a strong absorber at the 2.1 µm wavelength, so it appears very dark on the snow/ice channel image.

The corresponding MODIS Land Surface Temperature product (below) revealed significantly colder LST values in the middle to upper 30s F (darker green colors) where the snow cover was deeper. There was a lack of surface reports in the exact areas of deeper snow cover, except for Limon in eastern Colorado (station identifier KLIC), which was reporting a surface air temperature of 39º F at the time.

MODIS Land Surface Temperature product + surface METAR data

MODIS Land Surface Temperature product + surface METAR data

Snowfall amounts from this particular storm (which moved through the region on 22 October) included 15 inches at Elizabeth, Colorado, 12 inches at Brady, Nebraska, and 4 inches at Saint Francis, Kansas. These locations are marked on a MODIS Red/Green/Blue (RGB) true color image from the SSEC MODIS Today site (below, displayed using Google Earth).

MODIS true color image (displayed using Google Earth)

MODIS true color image (displayed using Google Earth)