1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) showed thunderstorms that produced tornadoes, large hail and damaging winds (SPC storm reports) in the Dallas/Fort Worth, Texas area after sunset on 20 October 2019. One of the tornadoes produced EF-3 damage in North Dallas.

In a larger-scale view of GOES-16 Infrared images (below), other thunderstorms were seen that produced a variety of severe weather in other parts of Texas, Louisiana, Oklahoma, Arkansas and Missouri — including winds of 82 mph in Oklahoma and 80 mph in Arkansas. The rapidly-pulsing behavior of overshooting tops was well captured by the 1-minute imagery.

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1-minute Mesoscale Domain Sector GOES-17 (GOES-West)  “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed thunderstorms that developed along a fast-moving cold front, producing a swath of damaging winds (SPC storm reports) across southern Idaho on 19 October 2019.

5-minute GOES-17 Mid-level Water Vapor (6.9 µm) images (below) displayed signatures of a jet stream and shortwave trough that were moving across the region that day.

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An animation sequence of GOES-17 (GOES-West) Mid-level Water Vapor (6.9 µm) images with surface reports, then contours of PV1.5 pressure, followed by Air Mass Red-Green-Blue (RGB) images (above) showed the remnants of Typhoon Hagibis in the southern Bering Sea on 14 October 2019. During this time period, the extratropical cyclone was analyzed as a Hurricane Force low (surface analyses) —  winds gusted to 62 knots at Adak (PADK) and 60 knots at Shemya (PASY). The PV1.5 surface represents the “dynamic tropopause”, which model fields depicted as  descending as low as the 700 hPa pressure level. Due to the markedly-lower tropopause around and west of the low center, those areas appeared as deeper hues of red/orange on the Air Mass RGB images (influenced by the higher concentrations of ozone-rich stratospheric air within the atmospheric column). The striping seen early in the animation was caused by GOES-17s ABI Loop Heat Pipe issue.

In rawinsonde data from St. Paul Island (PASN), the objectively-decoded tropopause descended from 226 hPa (11 km) at 12 UTC on 14 October to 336 hPa (8.1 km) at 00 UTC on 15 October (below).

On the following day, a toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) images at 2319 UTC on 15 October and 0100 UTC on 16 October (below) showed the remnants of Hagibis briefly making landfall southeast of Anadyr, Russia (UHMA) as a Gale Force low. Winds at Anadyr gusted to 54 knots shortly after the low moved inland.

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With the approach of an anomalously-deep 500 hPa low, an early-season winter storm produced very heavy snowfall and blizzard conditions across the Northern Plains — particularly in central/eastern North Dakota and southern Manitoba — during the 10 October – 12 October 2019 period. GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the long duration of precipitation across that region. Text listings of snowfall totals and wind gusts are available from WPC, NWS Bismarck and NWS Grand Forks (more complete storm summaries: NWS Bismarck | NWS Grand Forks). The highest storm total snowfall amount in far southern Manitoba was 32 inches south of Morten (which reported a snow depth of 30 inches on the morning of 12 October), with 30 inches in central North Dakota at Harvey.

GOES-16 “Red” Visible (0.64 µm) images (below) displayed the storm during the daylight hours on 10/11/12 October.

On 11 October, GOES-16 Visible images with an overlay of GLM Flash Extent Density (below) revealed intermittent clusters of lightning activity over northwestern Minnesota, northeastern North Dakota and southern Manitoba — while no surface stations explicitly reported a thunderstorm, NWS Grand Forks received calls from the public about thundersnow. The texture of cloud tops in the Visible imagery also supported the presence of embedded convective elements, which likely enhanced snowfall rates as they pivoted across that area. An animation of GOES-16 Visible imagery with plots of GLM Groups and surface weather type is available here.

Note that this lightning-producing convection was occurring near the leading edge of the cyclone’s mid-tropospheric dry slot, as seen in GOES-16 Water Vapor imagery (below).

One important aspect of this storm was the formation of a TROugh of Warm air ALoft or TROWAL (SHyMet | Martin, 1998) as the surface low began to enter its occluded phase on 11 October — contours of Equivalent Potential Temperature along the 295 K isentropic surface (below) helped to diagnose the axis of the TROWAL as it curved cyclonically from southwestern Ontario to southern Manitoba and then southward over North Dakota.

A similar animation with contours of 295 K specific humidity (below) also displayed the orientation of a west-to-east cross section B-B’ (green) across northern Northern Minnesota and northern Minnesota.

The Line B-B’ cross section at 16 UTC (with and without contours of Equivalent Potential Temperature) is shown below. Note the deep column of upward vertical velocity (highlighted by color shading of Omega) centered over Langdon, North Dakota — the moist TROWAL airstream can be seen sloping isentropically upward and westward behind the 3 g/kg Specific Humidity contour, as it approached the region of upward vertical motion. Langdon received 27 inches of snowfall; the prolonged southward passage of the TROWAL over North Dakota likely contributed to this accumulation.

As the storm was gradually winding down on 12 October, its circulation exhibited a very broad middle-tropospheric signature on GOES-16 Water Vapor imagery (below).

Here are your 3 day storm total snowfall reports across central ND. #NDWX pic.twitter.com/UA5JvAAgd0

— NWS Bismarck (@NWSBismarck) October 12, 2019

Event Review for Oct 10-12th. Preliminary, still in progress. https://t.co/473C9RB6Qr pic.twitter.com/HT5t374Tzl

— NWS Grand Forks (@NWSGrandForks) October 13, 2019

===== 17 October Update =====

After the area had already experienced its wettest Fall season on record, additional rainfall and snowmelt from this winter storm exacerbated ongoing flooding problems. A comparison of 250-meter resolution Aqua MODIS True Color and False Color Red-Green-Blue (RGB) images (source) centered over northeastern North Dakota (above) revealed flooding along the Red River (which flows northward along the North Dakota / Minnesota border) — water appears as darker shades of blue in the False Color image.

A Suomi NPP VIIRS Flood Product depicting floodwater fractions in the Red River Valley north of Grand Forks ND (as visualized using RealEarth) is shown below.

===== 18 October Update =====

On 18 October — 1 week after the height of the historic blizzard — GOES-16 Day Cloud Phase Distinction RGB images showed significant snow cover (brighter shades of green) remaining in parts of northeastern North Dakota and southern Manitoba that received the highest storm total snowfall accumulations (for example, 32″ south of Morden MB, 29″ at Vang ND, 28″ at Olga ND and 27″ at Langdon ND). The site south of Morden MB reported a residual snow depth of 10 inches that morning.

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