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Stratus clouds affecting surface temperatures in Alaska

By Scott Bachmeier •

A comparison of GOES-17 (GOES-West) Nighttime Microphysics RGB and “Clean” Infrared Window (10.35 µm) images (above) showed the formation and motion of patchy stratus clouds (RGB shades of yellow) over Interior Alaska on 17 December 2019.  Note how the clouds are difficult to detect and track on the 10.35 µm images, since the... Read More

GOES-17 Nighttime Microphysics RGB and

GOES-17 Nighttime Microphysics RGB and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

A comparison of GOES-17 (GOES-West) Nighttime Microphysics RGB and “Clean” Infrared Window (10.35 µm) images (above) showed the formation and motion of patchy stratus clouds (RGB shades of yellow) over Interior Alaska on 17 December 2019.  Note how the clouds are difficult to detect and track on the 10.35 µm images, since the temperatures of cold land surfaces and stratus cloud tops were similar. Since these high latitudes receive little to no sufficient solar illumination to allow useful visible imagery during the winter season, the RGB product can be a helpful tool for monitoring the evolution of such low clouds.

Plots of surface data from Bettles (PABT) and Fort Yukon (PFYU) (below) showed that the stratus cloud deck — with bases in the 6,000-10,000 feet range — had an impact on surface air temperature trends, with warming occurring as radiational cooling was slowed and/or reversed as the clouds moved overhead. Temperatures continued to rise at Bettles as the cloud coverage remained broken to overcast, while the temperature briefly dropped again at Fort Yukon as the cloud coverage thinned to scattered.

Plot of surface data from Bettles, Alaska [click to enlarge]

Plot of surface data from Bettles, Alaska (PABT) [click to enlarge]

Plot of surface data from Fort Yukon, Alaska [click to enlarge]

Plot of surface data from Fort Yukon, Alaska (PFYU) [click to enlarge]

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Severe weather across the Deep South

By Scott Bachmeier •

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed thunderstorms that produced a variety of severe weather (SPC Storm Reports) across the Deep South on 16 December 2019. Numerous overshooting tops could be seen with these storms.GOES-16 “Clean” Infrared Window (10.35 µm) images (below) indicated that many of the overshooting tops exhibited brightness temperatures... Read More

GOES-16

GOES-16 “Red” Visible (0.64 µm), with 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 (above) showed thunderstorms that produced a variety of severe weather (SPC Storm Reports) across the Deep South on 16 December 2019. Numerous overshooting tops could be seen with these storms.

GOES-16 “Clean” Infrared Window (10.35 µm) images (below) indicated that many of the overshooting tops exhibited brightness temperatures as cold as -70ºC (darker black pixels) — which closely corresponded to the Most Unstable air parcel Maximum Parcel Level (MU MPL) calculated from 21 UTC rawinsonde data from Jackson, Mississippi.

GOES-16 "Clean" Infrared Window (10.35 um), with SPC Storm Reports plotted in cyan [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm), with SPC Storm Reports plotted in cyan [click to play animation | MP4]

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Moderate to Severe Turbulence over the High Plains

By Scott Bachmeier •

As a strong 170-knot jet streak (Satellite Liaison Blog) flowed southeastward over the High Plains on 13 December 2019, GOES-16 (GOES-East) Mid-level (6.9 µm) Water Vapor images (above) showed numerous pilot reports of moderate to severe turbulence at altitudes of 26,000-50,000 feet. The Turbulence SIGMETs were issued due to strong speed shear along the poleward... Read More

GOES-16 Mid-level (6.9 µm) Water Vapor images, with plots of Pilot Reports of turbulence (cyan and red), Turbulence SIGMETS (red boxes) and RAP40 model isotachs of maximum wind (yellow) [click to play animation | MP4]

GOES-16 Mid-level (6.9 µm) Water Vapor images, with plots of Pilot Reports of turbulence (cyan and red), Turbulence SIGMETS (red boxes) and RAP40 model isotachs of maximum wind (yellow) [click to play animation | MP4]

As a strong 170-knot jet streak (Satellite Liaison Blog) flowed southeastward over the High Plains on 13 December 2019, GOES-16 (GOES-East) Mid-level (6.9 µm) Water Vapor images (above) showed numerous pilot reports of moderate to severe turbulence at altitudes of 26,000-50,000 feet. The Turbulence SIGMETs were issued due to strong speed shear along the poleward (northeast) edge of the jet streak — this speed shear was evident by the closely-spaced isotachs of maximum wind speed from the RAP40 model.

Over southeastern Colorado, one aircraft encountered Severe Turbulence at an altitude of 36,000 feet at 1637 UTC, while another reported Moderate to Severe Turbulence at 37,000 feet at 1645 UTC (due to a mountain wave, which caused fluctuation in airspeed of +/- 20 knots) (below).

GOES-16 Water Vapor (6.9 µm) image with a pilot report of severe turbulence at 36,000 feet [click to enlarge]

GOES-16 Water Vapor (6.9 µm) image with a pilot report of severe turbulence at 36,000 feet [click to enlarge]

GOES-16 Water Vapor (6.9 µm) image with a pilot report of moderate to severe turbulence at 37,000 feet [click to enlarge]

GOES-16 Water Vapor (6.9 µm) image with a pilot report of moderate to severe turbulence at 37,000 feet [click to enlarge]

 

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Cold air over the Upper Midwest

By Scott Bachmeier •

GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) showed pockets of cold surface brightness temperatures — darker blue represented the -30 to -35ºC (-22 to -31ºF) range — over parts of North Dakota during the 4 hours leading up to sunrise on 10 December 2019. As of 12 UTC, the coldest locations... Read More

GOES-16

GOES-16 “Clean” Infrared Window (10.35 µm) images, with select minimum temperatures as of 12 UTC [click to play animation | MP4]

GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) showed pockets of cold surface brightness temperatures — darker blue represented the -30 to -35ºC (-22 to -31ºF) range — over parts of North Dakota during the 4 hours leading up to sunrise on 10 December 2019. As of 12 UTC, the coldest locations in the US (including Alaska) were Rugby and Watford City, North Dakota with -22ºF; however, Grand Forks International Airport later dropped to -25ºF at 1245 UTC.

With the cold and dry arctic air mass in place across the Upper Midwest, GOES-16 Low-level (7.3 µm) and Mid-level (6.9 µm) Water Vapor imagery (below) was able to sense the thermal contrast between cold, snow-covered land surfaces and the still-unfrozen reservoirs along the Missouri River in North Dakota and South Dakota.

GOES-16 Low-level (7.3 µm) and Mid-level (6.9 µm) images, with rawinsonde sites indicated in yellow [click to play animation | MP4]

GOES-16 Low-level (7.3 µm) and Mid-level (6.9 µm) images, with rawinsonde sites indicated in yellow [click to play animation | MP4]

GOES-16 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Aberdeen, SD (below) showed the downward shift of the peak pressures for all 3 spectral bands — with some contributions of radiation originating from the surface indicated for both the 7.3 µm and 6.9 µm bands.

GOES-16 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Aberdeen, SD [click to enlarge]

GOES-16 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Aberdeen, SD [click to enlarge]

According to the climatology of Precipitable Water for Aberdeen SD (below), the 12 UTC value of 0.06 inch tied the record minimum value for that date/time. The 12 UTC sounding at Bismarck ND failed at a pressure level near 400 hPa — but the PW value of 0.05 inch calculated from that data would be slightly less than the record minimum value of 0.06 inch for that date/time.

Climatology of Precipitable Water for Aberdeen, SD [click to enlarge]

Climatology of Precipitable Water for Aberdeen, SD [click to enlarge]

On a NOAA-20 VIIRS Visible (0.64 µm) image with plots of available NUCAPS sounding locations (below), soundings northeast of Bismarck KBIS and southeast of Aberdeen KABR are denoted by 1 and 2, respectively.

NOAA-20 VIIRS Visible (0.64 µm) image, with plots of available NUCAPS sounding locations [click to enlarge]

NOAA-20 VIIRS Visible (0.64 µm) image, with plots of available NUCAPS sounding locations [click to enlarge]

Plots of the NOAA-20 NUCAPS sounding profiles northeast of Bismarck KBIS and southeast of Aberdeen KABR around 19 UTC are shown below. Precipitable Water values calculated for these two soundings remained quite low, at 0.03 inch and 0.04 inch.

NOAA-20 NUCAPS sounding profile northeast of Bismarck (Point 1) [click to enlarge]

NOAA-20 NUCAPS sounding profile northeast of Bismarck KBIS (Point 1) [click to enlarge]

NOAA-20 NUCAPS sounding profile southeast of Aberdeen KABR (Point 2) [click to enlarge]

NOAA-20 NUCAPS sounding profile southeast of Aberdeen KABR (Point 2) [click to enlarge]

GOES-16

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

Examples of “river effect” cloud plumes — produced by cold air flowing across deep, relatively warm water in some of the Missouri River reservoirs — were evident in GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images over North Dakota (above) and South Dakota (below).

GOES-16 "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

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