Large storm system over the western/central US

April 17th, 2016

GOES-14 Water Vapor (6.5 µm) images [click to play MP4 animation]

GOES-14 Water Vapor (6.5 µm) images [click to play MP4 animation]

GOES-14 Water Vapor (6.5 µm) images (above; also available as a large 85 Mbyte animated GIF) showed the development of a large upper-level closed low centered over the western US during the 15 April17 April 2016 period. This large storm system was responsible for a wide variety of weather, ranging from heavy snow and high winds in the Rocky Mountains to heavy rainfall and severe weather from eastern Colorado to Texas (SPC storm reports: 15 April | 16 April | 17 April).

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]

Strong storm over the Upper Midwest and western Great Lakes

March 16th, 2016

GOES-13 Water Vapor (6.5 µm) images, with surface analyses [click to play animation]

GOES-13 Water Vapor (6.5 µm) images, with surface analyses [click to play animation]

A strong storm rapidly deepened as it moved northeastward across the Upper Midwest and western Great Lakes on 16 March 2016. GOES-13 Water Vapor (6.5 µm) images (above) showed the evolution of the system as the cloud shield expanded and became more elongated in a west-to-east orientation. On the previous day, this storm produced widespread hail and tornadoes from far eastern Iowa into northern and central Illinois (SPC storm reports).

A closer view of GOES-13 Visible (0.63 µm) images with METAR surface reports (below) revealed the strong winds caused by the tight pressure gradient — a peak wind gust of 61 mph was recorded at Waukesha in southeastern Wisconsin, with multiple power outages across the region caused by wind-related tree damage. Heavy rain (as much as 2-3 inches) produced some minor river flooding in various parts of Wisconsin; across northern Wisconsin, northeastern Minnesota, and the Upper Peninsula of Michigan the rain changed to snow, with as much as 18.5 inches accumulating at Redridge, Michigan, 13.0 inches at Lutsen, Minnesota, and 8.0 inches at Poplar and Sand Bay, Wisconsin. The weight of the wet snow was causing tree limbs to fall, with additional power outages being reported.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

With the strong winds associated with this storm, there were also scattered pilot reports of moderate turbulence across the region, including 2 reports of severe turbulence over southern Wisconsin as seen below.

GOES-13 Water Vapor (6.5 µm) image, with pilot report of severe turbulence [click to enlarge]

GOES-13 Water Vapor (6.5 µm) image, with METAR surface reports and a pilot report of severe turbulence [click to enlarge]

GOES-13 Water Vapor image, with pilot report of severe turbulence [click to enlarge]

GOES-13 Water Vapor image, with METAR surface reports and a pilot report of severe turbulence [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: