Morphed Total Precipitable Water imagery (from this site) for the 24 hours ending at 0100 UTC on 19 February 2019, above, shows two Tropical disturbances spinning on either side of the Equator. Cyclone Oma in the Southern Hemisphere was northwest of New Caledonia in the Coral Sea. A second disturbance over the north Pacific, albeit very close to the Equator, was near Pohnpei and will pass near Chuuk later this week. Interests in Micronesia should pay attention to this area of disturbed weather.

Himawari-8 Clean Window imagery (10.41 µm) (courtesy JMA), below, shows the better organization of Oma in contrast to the more disorganized nature of the tropical wave over Pohnpei.

Refer to the CIMSS Tropical Webpage (Link) for more information on Oma. The National Weather Service on Guam is issuing statements on the tropical system in Micronesia. (From 0245 UTC on 19 February 2019, for example) (Update: This is now Tropical Depression 02W; a projected path as of 1200 UTC on 19 February is here. The current forecast has this storm achieving typhoon status late Wednesday).

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The 250-hPa jet streak currently over the CONUS contains wind speeds approaching 200 kt (230 mph) and is assoc. w/ standardized anomalies >3? spanning from Texas to Michigan. I suspect this jet streak is also helping cross-country flights arrive early on the East Coast! ? ? pic.twitter.com/z7474e6bXk

— Alicia M Bentley (@AliciaMBentley) February 17, 2019

An unusually strong jet streak was located over the Lower 48 states on 17 February 2019. GOES-16 (GOES-East) Upper-level Water Vapor (6.2 µm) images with plots of 6.2 µm Derived Motion Winds (above) showed numerous tracked targets along and south of the jet axis — within the jet streak exit region over the Mid-Atlantic states, some velocity values were as high as 181 knots (below).

A plot of rawinsonde data from Lincoln, Illinois at 00 UTC (below) showed wind speeds as high as 190 knots at a pressure of 231 hPa. The 250 hPa wind speed of 184.7 knots set both a daily and an all-time record speed for that pressure level (the old all-time record was 175 knots for a sounding on 10 Dec at 00 UTC).

GOES-16 Air Mass RGB images from the AOS site (below) provided a classic portrayal of the green hues of warm/moist tropical air south of and the orange/red hues of cold/dry polar air north of this strong jet stream.

===== 18 February Update =====

The large southward dip of the polar jet stream — evident in the GOES-16 Air Mass RGB images from the previous day — brought cold air into the Desert Southwest, resulting in snowfall at lower-elevation locations such as Las Vegas, Nevada. GOES-17 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice (1.61 µm) images (above) revealed snow on the ground in the Las Vegas area — much of which quickly melted with increased surface heating after sunrise. Snow cover is a good absorber of radiation at the 1.61 µm wavelength, so it appeared as darker shades of gray on the Snow/Ice images; the distribution of the heavier snowfall amounts (which naturally melted more slowly) was influenced by the topography of the area. This snowfall forced the closure of Interstate 15 from Las Vegas to the Nevada/California border for several hours due to icy pavement and multiple traffic accidents.

The snow cover was apparent in Visible imagery from 4 GOES (below) — GOES-17 (GOES-West), GOES-15 (the backup GOES-West), GOES-16 (GOES-East) and GOES-13 (the backup GOES-East, which had been brought out of storage for annual maintenance activities).

? Lots of chatter this morning about the snow in #Vegas! Here’s a look at some of the observed totals, with most of the accumulations favoring the southern and western edges of town. #VegasWeather ? pic.twitter.com/oo6UHwJUix

— NWS Las Vegas (@NWSVegas) February 18, 2019

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GOES-16 “Red” Visible (0.64 µm) images (above) revealed a cloud-free notch over northeastern Indiana during the early morning hours on 16 February 2019. The corresponding GOES-16 Cloud Top Phase product (below) indicated that the cloud layer across that region was composed of supercooled water cloud droplets. The point source of this cloud notch feature was the Steel Dynamics industrial site southeast of Columbia City — emissions from this location contained particles that acted as efficient ice condensation nuclei, causing the supercooled droplets to glaciate and fall from the cloud as snow. The cloud notch initially passed over Huntington (located about 15 miles to the south), and the Northern Indiana NWS office received a report of ice crystals or fine snow and hazy sunshine when the clearing moved over that location. The automated ASOS sensor at the Huntington airport did not report any snow, but the visibility briefly dropped to 7 miles with a lowering of cloud height just after 14 UTC.

Farther to the east, GOES-16 Visible images (below) showed prominent industrial plumes coming from the Detroit, Michigan and Cleveland, Ohio areas — with smaller plumes originating from points southeast of Lorain and southwest of Canton in Ohio. Light snow was intermittently reported at 2 sites south of Detroit as the industrial plume passed overhead. As with the previous case over Indiana, these industrial plumes were occurring within a supercooled water droplet cloud layer.

250-meter resolution Terra MODIS True Color and False Color Red-Green-Blue (RGB) images from the MODIS Today site (below) provided a more detailed view of the industrial plumes coming from the Detroit and Cleveland areas. The darker cyan color appearing within the cloud gaps was a signature of glaciated cloud material that was descending from the supercooled cloud layer, falling as snow. Since there was no snow on the ground reported that morning at Detroit in Michigan or at Cleveland and Akron in Ohio, we can be confident that the dark cyan was not a signature of surface snow cover being viewed through gaps in the cloud deck.

In a larger-scale view of Terra MODIS True Color and False Color RGB images from RealEarth (below), note the presence of another industrial plume with its point source south of Sarnia, Ontario — in contrast to the other industrial plumes, the emissions from that source contained particles which acted as cloud condensation nuclei — causing the supercooled cloud water droplets to become smaller, which made them more reflective and exhibit a brighter white appearance in the RGB images.

Looking at the Ontario plume using GOES-16 Visible, Near-Infrared “Snow/Ice” (1.61 µm) and Near-Infrared “Cloud Particle Size” (2.24 µm) imagery (below), higher reflectivity of the smaller supercooled water droplets within the industrial plume is most apparent in the Near-Infrared images. This plume passed over Chatham, Ontario (CYCK), where light snow was reported — though it’s unclear whether this snow was simply ongoing synoptic system and/or lake effect snow, or if there was some minor plume enhancement aiding the snowfall.

The Ontario industrial plume also exhibited a warmer signature on GOES-16 Shortwave Infrared (3.9 µm) images (below), since smaller supercooled water droplets are more efficient reflectors of incoming solar radiation.

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The GOES-17 Loop Heat Pipe issue means that certain infrared bands lose data integrity at certain times, times that vary over the course of the year. Late February is a time of year when the impacts on data are very noticeable (This figure — from this blog post — shows other times of the year when the issue is most noticeable).  The Data Fusion process that uses GOES-17 ABI Band 13 imagery (relatively unaffected by the LHP issues) can create approximations of the missing imagery.  This allows for qualitative views of those missing bands.

The animation above (click here for an animated gif) shows GOES-17 Water Vapor Channels on the left (6.19 µm, 6.95 µm and 7.34 µm) and GOES-17 Data Fusion images on the right. At the beginning of the animation (0902 UTC), Data Fusion is not implemented; it uses information at 0902 to create subsequent imagery, however. In the first few frames of the animation, the impact of the LHP warming are not apparent. By 1007 UTC, however, the GOES-17 Water Vapor Bands are becoming noticeably warmer than the Data Fusion imagery. (An initial signal that LHP issues are starting is a general warming in the imagery). Data dropouts start at 1102 UTC, first at 7.34 µm, then at 6.95 µm and finally at 6.19 µm. By 1202 UTC, data integrity is lost completely, but Data Fusion maintains a signal that allows a user to qualitatively track features in the image. Shortly after 1500 UTC, data starts to reappear, initially mostly at 6.19 µm, then 6.95 µm and finally at 7.34 µm. By 1632 UTC, the PACUS (Pacific/CONUS) image shows data, but it is cooler than the Fused data (Note the cooler cloud top temperatures in all three water vapor bands).

Warmth going into LHP Data Drop-outs and coolness coming out of LHP Data Drop-outs have been documented in this directory tree that compares GOES17 and GOES16 imagery in a region in between the two satellites (a region with similar view angles). The figure below (from here, accessible from this website) shows that GOES-17 brightness temperatures (in red) are warmer than GOES-16 (in blue) before data loss, and cooler than GOES-16 immediately subsequent to data loss.

Fusion Data (in the form of netCDF files written comforming to mission standards; the netCDF files are readable by SIFT and McIDAS-V, for example) are available via ADDE from the SSEC Data Center. Send an email here for more information. Imagery is also available at the SSEC Data Center via the geo browser.

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