Convective snow squalls in the Upper Midwest

April 2nd, 2016

GOES-13 Visible (0.63 µm) images, with hourly surface weather symbols [click to play animation]

GOES-13 Visible (0.63 µm) images, with hourly surface weather symbols [click to play animation]

A vigorous clipper-type shortwave moved rapidly southeastward across the Upper Midwest on 02 April 2016; there were widespread convective elements associated with this system as seen in GOES-13 Visible (0.63 µm) images (above), which produced moderate to heavy snowfall at times (and even thundersnow) creating brief white-out conditions (time-lapse video from the AOSS rooftop camera in Madison, Wisconsin). A sequence of visible images from the polar-orbiting MODIS, VIIRS, and AVHRR instruments (below) provided another detailed view of these convective elements. This disturbance produced strong winds and accumulating snowfall; more information can also be found here from the NWS Chicago.

MODIS, VIIRS, and AVHRR visible images [click to enlarge]

MODIS, VIIRS, and AVHRR visible images [click to enlarge]

A pronounced warm/dry signature of middle-tropospheric subsidence (yellow color enhancement) was evident on GOES-13 Water Vapor (6.5 µm) images (below), which appeared to be along or just ahead of the areas of stronger wind gusts at the surface.

GOES-13 Water Vapor (6.5 µm) images with hourly wind gusts in knots [click to play animation]

GOES-13 Water Vapor (6.5 µm) images with hourly wind gusts in knots [click to play animation]

This area of middle-tropospheric subsidence was located along the leading edge of a strong (110-120 knot) 500 hPa jet, as indicated by the NAM40 model isotachs (below).

GOES-13 Water Vapor (6.5 µm) images with METAR surface reports, surface fronts, and NAM40 500 hPa wind isotachs [click to play animation]

GOES-13 Water Vapor (6.5 µm) images with METAR surface reports, surface fronts, and NAM40 500 hPa wind isotachs [click to play animation]

The convective elements were relatively shallow, with cloud-top infrared brightness temperatures only in the -20 to -30º C range (cyan to darker blue color enhancement) as seen in 4-km resolution GOES-13 Infrared Window (10.7 µm) images (below) and also in 1-km resolution MODIS, VIIRS, and AVHRR infrared images.

GOES-13 Infrared Window (10.7 µm) images, with hourly surface weather symbols [click to play animation]

GOES-13 Infrared Window (10.7 µm) images, with hourly surface weather symbols [click to play animation]

The 24-hour snowfall amounts ending at 12 UTC on 02 and 03 April are shown below, from the NOHRSC site. There was a narrow swath of snowfall in excess of 3 inches just north of the track of the surface low (surface analyses), from northeast Minnesota across Wisconsin to southwest Lower Michigan.

24-hour snowfall amounts (in inches) ending at 12 UTC on 02 and 03 April [click to enlarge]

24-hour snowfall amounts (in inches) ending at 12 UTC on 02 and 03 April [click to enlarge]

Large grass fire in Oklahoma and Kansas

March 23rd, 2016

GOES-13 Shortwave Infrared (3.9 µm) images, with surface reports [click to play animation]

GOES-13 Shortwave Infrared (3.9 µm) images, with surface reports [click to play animation]

A grass fire (now referred to as the “Anderson Creek fire”) was first reported in western Woods County, Oklahoma around 2245 UTC or 5:45 PM local time on 22 March 2016. “Hot spot” signatures (yellow to red to black pixels) on GOES-13 Shortwave Infrared (3.9 µm) images (above) showed that the fire proceeded to make a very fast run to the north during the overnight hours, crossing over the Kansas border into Comanche and Barber Counties. The fire eventually jumped Highway 160  — which runs west-to-east across the northern portion of those 2 counties (highways are plotted in violet) — forcing it to be closed for several hours. As of the afternoon of 23 March, the fire was reported to have burned at least 72,000 acres; on that evening, the mayor of Medicine Lodge, Kansas (station identifier KP28) called for a voluntary evacuation as the fire began to approach the edge of the town. Note that GOES-13 (GOES-East) had been placed into Rapid Scan Operations (RSO) mode specifically to monitor the extremely critical fire risk, and was providing images as frequently as every 5-7 minutes.

A nighttime comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 0823 UTC or 3:23 AM local time (below) showed the hot spots and the bright glow of the large and very hot fire.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images {click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images {click to enlarge]

A sequence of Shortwave Infrared images from POES AVHRR, Terra/Aqua MODIS, and Suomi NPP VIIRS (below) provided higher-resolution snapshots of the rapid northward progression of the fire during the overnight hours (aided by strong southerly winds), followed by an east/northeastward expansion during the subsequent daylight hours (driven by a switch to strong southwesterly winds after the passage of a dryline).

POES AVHRR (3.7 µm), Terra/Aqua MODIS (3.7 µm), and Suomi NPP VIIRS (3.74 µm) Shortwave Infrared images [click to enlarge]

POES AVHRR (3.7 µm), Terra/Aqua MODIS (3.7 µm), and Suomi NPP VIIRS (3.74 µm) Shortwave Infrared images [click to enlarge]

GOES-13 Visible (0.63 µm) images (below) revealed a large increase in smoke produced by the fire during the day on 23 March. This smoke was drawn cyclonically northeastward then northward around the circulation of a storm system that was deepening over western Kansas. Afternoon wind gusts were as high as 61 mph in Newton, Kansas. Downstream of the fire source region, smoke reduced the surface visibility to 4 miles at Hutchinson, Kansas (station identifier KHUT) at 21 UTC or 4 PM local time, and Wichita (station identifier KICT) reported a visibility of 1.75 miles at 00 UTC or 7 PM local time; ash falling from the smoke aloft caused the surface air quality in Wichita to briefly deteriorate to unhealthy levels.

GOES-13 Visible (0.63 µm) images, with surface reports [click to play animation]

GOES-13 Visible (0.63 µm) images, with surface reports [click to play animation]

In the early afternoon at 1748 UTC or 12:48 PM local time, a pilot report near the northern flank of the fire (below) indicated that the tops of the smoke towers were already rising to altitudes of 8000 to 11000 feet above ground level.

GOES-13 Visible (0.63 µm) image, with surface reports and a pilot report of smoke altitude [click to enlarge]

GOES-13 Visible (0.63 µm) image, with surface reports and a pilot report of smoke altitude [click to enlarge]

It is of interest to note that a similar (albeit smaller) grass fire spread rapidly northward from Oklahoma into Kansas, one county to the west and about one month earlier: the Buffalo fire. That event had the benefit of Super Rapid Scan Operations of GOES-14, which provided imagery at 1-minute intervals. The ABI instrument on the GOES-R satellite will be capable of providing 1-minute images over 2 pre-defined mesoscale sectors.

===== 24 March Update =====

Anderson Creek Fire perimeter map [click to enlarge]

Anderson Creek Fire perimeter map [click to enlarge]

A map of the Anderson Creek Fire perimeter (above) was issued by the Oklahoma Forestry Services at 1642 UTC or 11:42 AM local time. At that time, an estimated 397,420 acres (621 square miles) had been burned — which makes it the largest wildfire on record for the state of Kansas.

A comparison of Suomi NPP VIIRS true-color and false-color Red/Green/Blue (RGB) images from the SSEC RealEarth site (below) showed the extent of the burn scar, with smoke plumes drifting south-southeastward from 2 small areas of fires that were still actively burning at 2106 UTC or 4:06 PM local time. As discussed above, it can be seen that the fire crossed (and forced the closure of) US Highway 160 between Coldwater and Medicine lodge, and came very close to the town of Medicine Lodge.

Suomi NPP VIIRS true-color and false-color images [click to enlarge]

Suomi NPP VIIRS true-color and false-color images [click to enlarge]

===== 25 March Update =====

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

With ample illumination from the Moon (in the Waning Gibbous phase, at 98% of Full), the contrast between the dark Anderson Creek fire burn scar and the lighter surrounding grassland was very apparent on a Suomi NPP VIIRS Day/Night Band (0.7 µm) image at 0742 UTC or 2:42 AM local time. This example demonstrates the “visible image at night” capability of the VIIRS Day/Night Band.

Undular bore over Texas

March 18th, 2016

GOES-15 Visible (0.63 µm) images with surface plots [click to play animation]

GOES-15 Visible (0.63 µm) images with surface plots [click to play animation]

GOES-15 (GOES-West) Visible (0.63 µm) images (above) showed the wave clouds associated with an undular bore moving southeastward across Texas during the day on 18 March 2016. The leading undular bore (and packet of solitary waves behind it) were propagating ahead of the advancing cold front (reference).

A nighttime Suomi NPP VIIRS Day/Night Band image at 0814 UTC or 3:14 am local time (below) showed the early stage of bore wave cloud formation over the Texas Panhandle. Due to ample illumination from the Moon (in the Waxing Gibbous phase, at 78%  of Full), this example illustrated the “visible image at night” capability of the Day/Night Band.

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

CLAVR-x POES AVHRR Cloud Top Temperature and Cloud Top Height products (below) indicated values of around +6º C and 2 km, respectively, for the undular bore wave cloud features ahead of the cold front at 1714 UTC.

POES AVHRR Cloud Top Temperature and Cloud Height products [click to enlarge]

POES AVHRR Cloud Top Temperature and Cloud Height products [click to enlarge]

The 2 km cloud top height was consistent with the depth of the stable layers seen above the surface seen in rawinsonde data profiles at Midland (KMAF) and Forth Worth (KFWD), 2 locations which were ahead of the cold frontal boundary at 1200 UTC.

Midland (KMAF) and Fort Worth (KFWD) rawinsonde data profiles at 1200 UTC [click to enlarge]

Midland (KMAF) and Fort Worth (KFWD) rawinsonde data profiles at 1200 UTC [click to enlarge]

Rapidly intensifying mid-latitude cyclone off the US East Coast

March 5th, 2016

GOES-13 Water Vapor (6.5 µm) images [click to play MP4 animation]

GOES-13 Water Vapor (6.5 µm) images [click to play MP4 animation]

An area of low pressure rapidly intensified off the US East Coast during the 04 March05 March 2016 period (surface analyses). GOES-13 (GOES-East) Water Vapor (6.5 µm) images (above; also available as a large 57 Mbyte animated gif) showed classic signatures of the various stages of strong mid-latitude cyclone development — most notably the formation of a well-defined comma head and dry slot. Even though the storm was well offshore, impacts near and along the coast included snowfall amounts as high as 6.7 inches at Princess Anne, Maryland, 5.0 inches at Montross, Virginia, and 2.6 inches at Topsfield, Massachusetts; winds gusted to 55 mph at Jennettes Pier, North Carolina and 53 mph at Nantucket, Massachusetts. In Newfoundland, Gander received 17.3 inches of snow, and winds gusted to 77 mph at Cape Pine.

Aqua MODIS Water Vapor (6.7 µm), Infrared (11.0 µm), and Visible (0.65 µm) images [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm), Infrared (11.0 µm), and Visible (0.65 um) images [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm), and Visible (0.65 µm) images at 1737 UTC (above) and Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1722 UTC (below) showed the storm around the time the Ocean Prediction Center indicated that it began producing hurricane force winds (18 UTC analysis).

Suomi NPP VIIRS Visible (0.64 µm) and Infrared (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared (11.45 µm) images [click to enlarge]

A sequence of POES AVHRR Infrared (12.0 µm) images at 1852, 2205, and 0100 UTC along with Metop ASCAT surface scatterometer winds (below) showed the storm as it continued to intensify. Even though AWIPS labeled the ASCAT winds with a time stamp of 0228 UTC, cursor sampling found winds as strong as 57 knots south of the storm center and 59 knots north of the storm center at 0155-0156 UTC.

POES AVHRR Infrared (12.0 µm) images at 1852, 2205, and 0100 UTC, with Metop ASCAT winds at 0155 UTC [click to enlarge]

POES AVHRR Infrared (12.0 µm) images at 1852, 2205, and 0100 UTC, with Metop ASCAT winds at 0155 UTC [click to enlarge]

The Ocean Prediction Center posted an animation of Geocolor images of the storm on Twitter: