A major winter storm produced widespread blizzard conditions in North Dakota and northwestern Minnesota (as well as far northern South Dakota) as low pressure deepened (3-hourly surface analyses) while moving from South Dakota across Minnesota (and eventually over Ontario and western Quebec) during the 05 December – 08 December 2016 period. Storm total snowfall amounts included 16.0 inches in Montana, 19.0 inches in North Dakota and 13.9 inches in Minnesota; peak wind gusts were as high as 63 knots (72 mph) in South Dakota, 56 knots (64 mph) in North Dakota and 37 knots (43 mph) in Minnesota (KBIS PNS | KFGF PNS | WPC storm summary). In North Dakota, nearly the entire portion of both Interstates 94 and 29 were closed. The large size of the storm could be seen on GOES-13 (GOES-East) Water Vapor (6.5 µm) images (above).

A closer view using GOES-13 Water Vapor imagery with overlays of hourly reports of surface winds and wind gusts (below) showed that wind speeds remained strong enough to create travel-restricting blowing snow over eastern North Dakota and western Minnesota even into the early hours of 08 December (due to the continuing strong pressure gradient between the large low in Canada and the arctic high that was moving into Montana and Wyoming.

In the wake of the storm on 09 December, a southeastward flow of cold arctic air (with surface air temperatures in the 0 to -15º F range) over the still-unfrozen water of Lake Sakakawea (which exhibited MODIS Sea Surface Temperature values as warm as 37.9º F) caused lake effect cloud bands to form and extend downwind of the lake — these cloud bands were very evident in a comparison of 250-meter resolution Aqua MODIS true-color and false-color Red/Green/Blue (RGB) images from the MODIS Today site (below). In the false-color image, snow/ice appears as shades of cyan, in contrast to supercooled water droplet clouds which appear as shades of white. The 1.6 µm snow/ice band used to create the MODIS false-color image will also be available with the ABI instrument on the GOES-R series (beginning with GOES-16).

With a fresh, deep snow cover and cold arctic air in place, strong nocturnal radiational cooling allowed North Dakota to experience its first -30º F low temperatures of the season on the morning of 10 December. Aqua MODIS Land Surface Temperature values at 0939 UTC or 3:39 am local time (below) were as cold as -39º F (darker violet color enhancement) near the sites that reported the -30º F low temperatures.

View only this post Read Less

December 6, 2016 marked the 50th anniversary of the launch of ATS-1 on 06 December 1966. ATS-1 was the first meteorological satellite to be placed into a geostationary orbit — an example of one of the first ATS-1 visible images is seen below, and early ATS images.  More information is available from SSEC and NOAA/NESDIS.

View only this post Read Less

6-hour interval GOES-15 (GOES-West) Water Vapor (6.5 µm) images with overlays of GFS model 500 hPa geopotential height (above) showed middle to upper tropospheric moisture that was being drawn northwestward toward Hawai’i by the circulation of a closed low centered southwest of the state during the 01-02 December 2016 period.

A closer view using 15-minute interval GOES-15 Water Vapor images (below) showed 2 distinct pulses of moisture moving across the eastern portion of the island chain. Due to the prolonged flow of moisture and the variable terrain, Flood Warnings and Winter Storm Warnings were issued for the Big Island of Hawai’i (as shown using RealEarth).

Hourly images of the MIMIC Total Precipitable Water (TPW) product (below) showed the large plume of moisture, which had its roots within the Intertropical Convergence Zone (ITCZ). Maximum TPW values in the vicinity of Hawai’i were in the 50-55 mm (2.0-2.2 inch) range. 24-hour rainfall amounts were as high as 6.27 inches on the island of Hawai’i and 3.67 inches on the island of Kauai.

===== 03 December Update =====

GOES-15 Visible (0.63 µm) images (below) provided glimpses of the snow-covered peaks of Mauna Kea and Mauna Loa (circled in red) on the Big Island of Hawai’i early in the day on 03 December.

View only this post Read Less

Wildfires had been burning in the Great Smoky Mountains for a few weeks (see previous blog posts) as extreme to exceptional drought persisted over the region. However, on 28 November 2016 weather conditions became conducive to extreme fire behavior — and this allowed the Chimney Tops 2 Fire south of Gatlinburg, Tennessee to race rapidly northward (fire perimeter map), driven by strong southerly winds gusting to at least 30-40 knots (as were recorded in Knoxville KTYS, located about 25 miles northwest of Gatlinburg). Widespread evacuations were necessary, and at least 13 fatalities were reported.  4-km resolution GOES-13 Shortwave Infrared (3.9 µm) images (above) showed the development of a fire “hot spot” (the cluster of pixels at the center of the images exhibiting a black to yellow color enhancement) during the day, before clouds moved overhead to mask the fire hot spot signature. The warmest infrared brightness temperature seen during this time period was 326.8 K (brighter yellow pixels) on the 1700 UTC image.

Even though cloud cover was increasing, a detailed view of the fire hot spot was provided by an AWIPS II image of 375-meter resolution Suomi NPP VIIRS Shortwave Infrared (3.74 µm) data at 1815 UTC on 28 November (below). An AWIPS I version of this image is available here. Due to the cloudiness, no discernible hot spot appeared on the lower-resolution 1815 UTC GOES-13 Shortwave Infrared image.

Props to NWS meteorologist Carl Jones for spotting this somewhat unexpected result: the glow of the fire was evident on the following nighttime Suomi NPP VIIRS Day/Night Band (0.7 µm) image, even though there was a thick layer of clouds over the fire itself:

#Gatlinburg fire shines brightly despite clouds on VIIRS DNB overnight pass. @TravelGburg @NASANPP @CIMSS_Satellite @UWSSEC @UWCIMSS #tnwx pic.twitter.com/8CiIdL8Rrg

— Carl Jones (@northflwx) November 29, 2016

An AWIPS II image comparison of VIIRS Infrared Window (11.45 µm), Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) data at 0816 UTC on 29 November is shown below. Cloud-top Infrared Window brightness temperatures were in the -40 to -55º C range over the fire region (such air temperatures were foundd within the 9.5-10.5 km altitude range on the Nashville sounding when the cloud band was over central Tennessee at 00 UTC). While no fire hot spot signature was evident on the Shortwave Infrared image (due to masking by the clouds), the very distinct bright glow of the fire (which appeared rather large in size, due to scattering of light by the water and ice particles present in the various cloud layers) was seen on the Day/Night Band image. AWIPS I versions of these images are available here.

Additional information is available on the Wildfire Today site (post 1 | post 2 | post 3 | post 4 | post 5).

View only this post Read Less