Record May snowfall in Duluth, Minnesota

May 9th, 2019 |


GOES-16 “Red” Visible (0.64 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the cloudiness associated with a midlatitude cyclone (surface analyses) that moved across the Upper Midwest on 08 May09 May 2019.  The system produced accumulating snowfall from extreme eastern South Dakota to central/northeastern Minnesota, northwestern Wisconsin and Upper Michigan — storm total accumulations were as high as 10.6 inches at Duluth, Minnesota (observations), 10.4 inches at Poplar, Wisconsin, 5.0 inches at Atlantic Mine, Michigan and 3.0 inches at Astoria, South Dakota (NOHRSC maps of snowfall/snowdepth). Note that the NW-SE oriented band of snowfall straddling the South Dakota/Minnesota border may have been enhanced by upslope flow as northeasterly surface winds encountered rising terrain of the Coteau des Prairies.

GOES-16 Mid-level Water Vapor (6.9 µm) images (below) showed the formation of a SW-NE oriented deformation zone across Minnesota — forcing for ascent was further aided by a stretched lobe of 500 hPa vorticity and 310 K potential vorticity that moved northeastward across the region during this period, along with a favorably-coupled 250 hPa jet streak configuration. Cloud features within the deformation zone across eastern South Dakota into southern/central Minnesota had an appearance resembling convective elements/bands in both the Visible and Water Vapor imagery.

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to play animation | MP4]

Although lightning was not widespread — and thunder was not explicitly reported in any first-order station observations — there were isolated small clusters of GOES-16 GLM Groups detected, first over northeastern, then central and finally over southwestern Minnesota between 2256 and 0036 UTC (below), indicating the presence of thundersnow.

GOES-16 “Red” Visible (0.64 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of surface weather type (yellow) and GLM Groups (red) [click to enlarge]




Through occasional breaks in the clouds later in the day on 09 May, GOES-16 Day Cloud Phase Distinction Red-Green-Blue (RGB) images (below) revealed the stationary signature of fresh snow cover (darker green) across central to northeastern Minnesota and far northwestern Wisconsin (glaciating cloud tops also appear as shades of green).

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

===== 10 May Update =====

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 Visible images (above) showed two swaths of snow cover remaining across northeastern Minnesota (where reported snow depths were 1-2 inches) and northwestern Wisconsin (where reported snow depths were 4-5 inches) on the morning of 10 May.

Comparisons of GOES-16 Land Surface Temperature (LST) and Visible images at 1401 UTC and 1501 UTC (below) indicated that LST values were as much as 10ºF colder within the areas of snow cover (brighter shades of cyan) compared to adjacent bare ground.

GOES-16 Land Surface Temperature and “Red” Visible (0.64 µm) images at 1401 UTC [click to enlarge]

GOES-16 Land Surface Temperature and “Red” Visible (0.64 µm) images at 1501 UTC [click to enlarge]

Severe weather outbreak across eastern Texas and the Deep South

April 13th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

An outbreak of severe weather began in eastern Texas on the morning of 13 April 2019, where thunderstorms produced hail up to 3.0 inches in diameter, tornadoes and damaging winds (SPC storm reports). 1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (above) showed the clusters of thunderstorms that developed as a surface low and associated frontal boundaries moved eastward (surface analyses). The corresponding GOES-16 “Clean” Infrared Window (10.3 µm) images (below) revealed numerous overshooting tops with infrared brightness temperatures as cold as -70 to -75ºC. In addition, the storm producing 3.0-inch hail and damaging winds at 1428 UTC exhibited an Above-Anvil Cirrus Plume (Visible/Infrared toggle).

GOES-16 "Clean" Infrared Window (10.3 µm) images, with SPC storm reports plotted in purple [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in purple [click to play MP4 animation]

A comparison of Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images at 1650 UTC is shown below.

Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Later in the day, the thunderstorms continued to produce a variety of severe weather as they moved eastward across Louisiana and Mississippi, as shown by GOES-16 Visible and Infrared images (below).

GOES-16 "Red" Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 "Clean" Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

After sunset, the thunderstorms continued to move eastward, spreading more serve weather across Mississippi into Alabama and far southern Tennessee (below).

GOES-16 "Clean" Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (below) provided additional views of the storms as they were moving across Mississippi and Alabama. Several bright lightning streaks were evident on the Day/Night Band images. Note: the NOAA-20 image (downloaded and processed from the Direct Broadcast ground station at CIMSS) is incorrectly labeled as Suomi NPP.

VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]

VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 at 0645 UTC and Suomi NPP at 0734 UTC [click to enlarge]

On a NOAA-20 VIIRS Day/Night Band (0.7 µm) image at 0825 UTC (below), an impressively-long (~400 mile) dark “post-saturation recovery streak” extended southeastward from where the detector sensed an area of very intense/bright lightning activity northeast of Mobile, Alabama.

NOAA-20 VIIRS Day/Night Band (0.7 µm) image at 0825 UTC [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) image at 0825 UTC [click to enlarge]

Large hail in Texas

April 6th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with GLM Groups plotted in cyan and SPC storm reports plotted in red [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images with plots of GLM Groups (above) showed a large and electrically-active Mesoscale Convective System (MCS) which produced hail up to 4.5 inches in diameter (SPC storm reports) in eastern Texas on 06 Aprill 2019. These severe thunderstorms intensified generally along and north of a quasi-stationary frontal boundary (surface analyses).

The corresponding GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed that cloud-top infrared brightness temperatures associated with the strongest overshooting tops were around -70ºC (dark black enhancement). Earlier that afternoon, a higher spatial resolution Suomi NPP VIIRS Infrared Window (11.45 µm) image at 1950 UTC showed brightness temperatures as cold as -77ºC just northeast of where 2.0-inch diameter hail was reported at Marquez — located approximately midway between station identifiers KLHB and KPSN — at 2015 UTC. Assuming the 00 UTC Lake Charles sounding was representative of the air mass these storms were developing in, the -77ºC temperature would be at an altitude over 1 km higher than the Most Unstable parcel’s Equilibrium Level.

GOES-16 "Clean" Infrared Window (10.3 µm) images, with GLM Groups plotted in beige and SPC storm reports plotted in cyan [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with GLM Groups plotted in beige and SPC storm reports plotted in cyan [click to play animation | MP4]

With better cloud-top shadow contrast, GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images (below) were helpful to locate the presence of Above-Anvil Cirrus Plume (AACP) features with the 2 strongest cells — and a comparison with 10.3 µm Infrared images indicated slightly warmer brightness temperatures with these AACPs (for example, at 2244 UTC and  0005 UTC).

GOES-16 Near-Infrared "Snow/Ice" (1.61 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

GOES-16 All Sky Total Precipitable Water (TPW) and Convective Available Potential Energy (CAPE) products (below) showed the areal coverage and trends in moisture and instability across the region on that day.

GOES-16 All Sky Total Precipitable Water (TPW) images [click to play animation]

GOES-16 All Sky Total Precipitable Water (TPW) product [click to play animation]

 

GOES-16 All Sky Convective Available Potential Energy (CAPE) product [click to play animation]

GOES-16 All Sky Convective Available Potential Energy (CAPE) product [click to play animation]

Hurricane Force low off the US East Coast

April 2nd, 2019 |

GOES-16 "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a cluster of deep convection just to the north of the center of a rapidly-intensifying midlatitude cyclone (surface analyses) off the coast of North Carolina on 02 April 2019. In addition, convection was later seen developing along the north-south cloud band marking the leading edge of the cyclone’s cold front. The rapid deepening of this hurricane force low easily met the criteria of a bomb cyclone — its central pressure dropped 20 hPa in just 12 hours (from 1004 hPa at 18 UTC on 02 April to 984 hPa at 06 UTC on 03 April).

The primary convective cluster began to exhibit a large amount of lightning after 1830 UTC, as seen in plots of GOES-16 GLM Groups (below). To the east of this intensifying convection, one ship report at 18 UTC included winds from the east at 50 knots — in addition, a moderate to heavy shower of hail was being reported and their surface visibility was restricted to 1.25 miles (18 UTC surface analysis).

GOES-16 "Red" Visible (0.64 µm) images, with GLM Groups and surface wind gusts plotted in red [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with GLM Groups and surface wind gusts plotted in red [click to play animation | MP4

There were several factors pointing to the development of a sting jet with this storm, as discussed here and here. GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below) revealed distinct areas of warming/drying (darker shades of yellow to orange) that possibly highlighted rapidly-descending air associated with a sting jet (for example, on the 1946 UTC images).

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

After 23 UTC, GOES-16 “Clean” Infrared Window (10.3 µm) images (below) portrayed the formation of a large eye-like feature indicative of a warm seclusion (00 UTC surface analysis). Lightning activity remained very high during that time.

GOES-16 "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play animation | MP4]


A comparison between 1-km resolution Terra MODIS Infrared Window (11.0 µm) imagery at 0237 UTC with an Aqua MODIS Sea Surface Temperature product at 1755 UTC on the following afternoon (below) showed that the storm intensified and formed the large eye-like feature over the northern portion of the axis of warmest Gulf Stream water (where SST values were in the 70-76ºF range).

Terra and Aqua MODIS Infrared Window (11.0 µm) images from 0237 UTC and 0649 UTC, along with the Aqua MODIS Sea Surface Temperature product at 1755 UTC [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image at 0237 UTC, along with the 1755 UTC Aqua MODIS Sea Surface Temperature product [click to enlarge]

With a nighttime overpass of the NOAA-20 satellite at 0651 UTC, the eye-like feature was apparent in VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (below). Although the Moon was in the Waning Crescent phase (at only 8% of Full), that illumination with the aid of airglow was sufficient to provide a useful “visible image at night” using the Day/Night Band; a streak of bright pixels was due to intense lightning activity within a line of thunderstorms just ahead of the cold front. Note: the NOAA-20 images are incorrectly labeled as Suomi NPP.

NOAA-20 VIIRS Infrared Window (11.45 µµ) and Day/Night Band (0.7 µm) images [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images, with an overlay of the 06 UTC surface analysis [click to enlarge]