Very cold surface air temperatures occurred in northeastern Montana and northwestern North Dakota on the morning of 08 February 2019 — with official lows of -50ºF near Antelope and Four Buttes in Montana and -47ºF at Bottineau in North Dakota (and according to MesoWest, -49ºF was registered at a Department of Transportation site west of Crosby in far northwestern North Dakota). GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) revealed surface brightness temperatures across those areas were as cold as -47ºC (-53ºF).

A sequence of VIIRS Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 (below) showed similar surface brightness temperatures, with some pixels as cold as -48ºC (-54ºF). The color enhancement applied to the VIIRS images is the same as that used on the GOES-16 images above, with the red colors beginning at the -40ºC breakpoint (violets begin at -50ºC). While there is not a direct correspondence between satellite-sensed surface infrared brightness temperatures and air temperatures measured in an above-ground instrument shelter, with improving satellite spatial resolution the difference is often within 1-3ºC (or 2-5ºF).

Highs & lows from across the area today. The cold spots this morning were the stations 13 mi. NNW of Four Buttes & 2 mi. WSW of Antelope, both checking in at -50!

The "warm" spots this afternoon were 16 mi. NNE of Mosby at 15, & 5 mi. west of Landusky at 14. #mtwx #cold #brrr pic.twitter.com/UCPScKGS7b

— NWS Glasgow (@NWSGlasgow) February 9, 2019

The all-time record low minimum for any @NDAWNmesonet set at Hofflund this morning was a -47.3?F (-44.0?C) reading looking at the raw data, so there was no rounding down to get to -47?. #impressive

— Daryl Ritchison (@DarylRitchison) February 8, 2019

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* GOES-17 images shown here are preliminary and non-operational *

Transient pockets of cloud-top waves were evident on GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) north of Hawai’i on 06 February 2019. Some of the waves were located along the tops of convective cloud features, while others appeared to be randomly distributed.

Plots of rawinsonde data from Lihue, Hawai’i (below) showed that winds within the middle to upper troposphere had a general westerly component — so these mesoscale cloud-top wave features were oriented perpendicular to the flow.

There was only 1 pilot report of turbulence within the broad region exhibiting these waves, occurring at 2304 UTC at an altitude of 33,000 feet — and this appeared to coincide with a discrete wave packet that was propagating eastward (below).

While the more robust wave packets could also be seen in GOES-17 “Clean” Infrared Window (10.3 µm) images (below), their complete areal coverage was more obvious in the Water Vapor imagery — particularly where the wave features were more subtle.

Aviation advisories for Significant Weather (SIGWX) had been issued for that region (below), which included a Moderate risk for Clear Air Turbulence (CAT) from 28,000-39,000 feet and the possibility of isolated/embedded Cumulonimbus (CB) clouds with tops to 38,000 feet, along with a west-northwest high-level jet stream from 290º at 90 knots. The pilot report of turbulence at 33,000 feet included winds from 261º at 81 knots.

The cloud-top waves were also seen in a sequence of VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP, viewed using RealEarth (below).

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One of my favorite things to watch are upper-level +PV anomalies moving offshore the east coast & sparking surface cyclogenesis.

We had a classic example last night, where a pre-existing baroclinic zone (thanks to the Gulf Stream) rapidly evolved into a striking occluded low. pic.twitter.com/74ylYWj5z8

— Philippe Papin (@pppapin) February 4, 2019

The approach of an upper-tropospheric Potential Vorticity (PV) anomaly induced rapid cyclogenesis just off the US East Coast on 04 February 2019, with the surface low rapidly occluding (surface analyses). The eastward-propagating PV Anomaly was apparent on GOES-16 (GOES-East) Air Mass RGB images from the AOS site (below) as darker shades of orange — transitioning to shades of red as the tropopause descended to lower altitudes bringing more ozone-rich air from the stratosphere into the atmospheric column.

A sequence of Infrared Window images from Terra MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) (below) showed the cyclone at various stages of development. The surface low passed over  the Cape Lookout, North Carolina buoy as it was intensifying, with winds gusting to 44 knots around 12 UTC (winds/pressure | peak wind gusts).

A similar sequence of Visible images from Terra MODIS (0.65 µm) and NOAA-20/Suomi NPP VIIRS (0.64 µm) (below) showed the cyclone during daylight hours.

===== 05 February Update =====

After the primary center of circulation began to weaken, a pair of residual lower-tropospheric vortices (surface analyses) was seen to persist on GOES-16 “Clean” Infrared Window (10.3 µm) images (above), rotating around each other in a binary interaction known as the Fujiwhara effect. The two vortices were also evident in NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0620 UTC (below) — in spite of the lack of illumination from a New Moon, airglow alone was sufficient to provide an impressive “visible image at night” with the Day/Night Band. (note: the NOAA-20 VIIRS images are incorrectly labeled as Suomi NPP)

During the early morning hours, an undular bore was evident on GOES-16 “Red” Visible (0.64 µm) images (below), moving toward the westernmost vortex. As the bore began to move over warmer waters of the Gulf Stream, it slowly dissipated.

Although not particularly intense, this slow-moving midlatitude cyclone was able to draw an appreciable amount of moisture northward from the tropics/subtropics as shown by the MIMIC Total Precipitable Water product (below).

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The Korean Meteorological Administration (KMA) has released its first true-color image created with data from the AMI sensor on the GEOKOMPSAT-2A (GK2A) satellite that was launched in late 2018.   This first image from GK2A is experimental and preliminary, just like the initial images from Himawari-8,  -9, GOES-16 and GOES-17 were preliminary:  all newly-launched satellites go through a check-out period during which radiometric and geometric calibration work is ongoing.  That is what is happening with the  GK2A satellite now.  Despite the preliminary nature of the GK2A imagery, however, it can be paired with Himawari-8 imagery to create stereoscopic views of the Earth — in true color!   To view the image pair in three dimensions, cross your eyes until three circles appear, and focus on the circle in the middle;  it should appear then as a sphere.

(Image pair courtesy Bodo Zeschke, Australian Bureau of Meteorology ;  Himawari image courtesy JMA ; GK2A image courtesy KMA and Dr. Hyesook Park. GEOKOMPSAT-2A is also known as Chollian-2a)

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