Strong jet stream over the Lower 48 states

February 17th, 2019 |

GOES-16 Upper-level Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to play animation | MP4]

GOES-16 Upper-level Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to play animation | MP4]

An unusually strong jet stream 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 Derived Motion Winds (above) showed numerous tracked targets along and south of the jet stream axis — within the jet streak exit region over the Mid-Atlantic states, some velocity values were as high as 181 knots (below).

GOES-16 Upper-level Water Vapor (6.2 µm) image, with plots of Derived Motion Winds at 0002 UTC [click to enlarge]

GOES-16 Upper-level Water Vapor (6.2 µm) image, with plots of Derived Motion Winds at 0002 UTC [click to enlarge]

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.

Plot of 00 UTC rawinsonde data from Lincoln, Illinois [click to enlarge]

Plot of 00 UTC rawinsonde data from Lincoln, Illinois [click to enlarge]

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.

GOES-16 Air Mass RGB images [click to play animation | MP4]

GOES-16 Air Mass RGB images [click to play animation | MP4]

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

GOES-17 "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice (1.61 µm) images [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice (1.61 µm) images [click to play animation | MP4]

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).

Visible images from GOES-17, GOES-15, GOES-15 and GOES-13 [click to play animation | MP4]

Visible images from GOES-17, GOES-15, GOES-15 and GOES-13 [click to play animation | MP4]



Erosion of supercooled cloud layers downwind of industrial sites

February 16th, 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]

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.

GOES-16 Cloud Top Phase product [click to play animation | MP4]

GOES-16 Cloud Top Phase product [click to play animation | MP4]

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.

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]

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.

Terra MODIS True Color and False Color RGB images [click to enlarge]

Terra MODIS True Color and False Color RGB images at 1610 UTC [click to enlarge]

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 nucle — causing the supercooled cloud water droplets to become smaller, which made them more reflective and exhibit a brighter white appearance in the RGB images.

Terra MODIS True Color and False Color RGB images [click to enlarge]

Terra MODIS True Color and False Color RGB images [click to enlarge]

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 report — 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.

GOES-16 "Red" Visible (0.64 µm, left), Near-Infrared "Snow/Ice" (1.61 µm, center) and Near-Infrared "Cloud Particle Size" (2.24 µm, right) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, left), Near-Infrared “Snow/Ice” (1.61 µm, center) and Near-Infrared “Cloud Particle Size” (2.24 µm, right) images [click to play animation | MP4]

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.

GOES-16 Near-Infrared "Snow/Ice" (1.61 µm, left) and Near-Infrared "Cloud Particle Size" (2.24 µm, center) and Shortwave Infrared (3.9 µm, right) images [click to play animation | MP4]

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm, left), and Near-Infrared “Cloud Particle Size” (2.24 µm, center) and Shortwave Infrared (3.9 µm, right) images [click to play animation | MP4]

GOES-17 Data Fusion: An example, and where to find the data

February 15th, 2019 |

GOES-17 Water Vapor Imagery. 6.19 µm (top row), 6.95 µm (middle row), 7.34 µm (bottom row); Left Columm:  Imagery from the ABI; Right Column:  Data Fusion Imagery created using the GOES-17 ABI Band 13 (10.3 µm) Imagery. Animation from 0902 UTC – 1727 UTC. Data Fusion imagery is not computed for the first or last images. Click to play mp4 animation.

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.

GOES-17 (red) and GOES-16 (blue) brightness temperatures for an small domain midway between the two sub-satellite points. The GOES-17 6.19 Image at 1552 UTC is also shown (Click to enlarge).

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.

Moisture Streaming towards Southern California

February 14th, 2019 |

Morphed Microwave Total Precipitable Water, 1800 UTC 13 February to 1700 UTC 14 February 2019 (Click to enlarge)

A potent Atmospheric River is affecting the California Coast on 14 February 2019. The morphed microwave imagery, above (from this site), shows rich moisture from deep in the tropics moving onto the southern California and northwest Mexican coasts.  The animation below shows the Layered Precipitable water — also a product derived from microwave imagery — for the same time period, but at 3-hour time steps (from this site).  An interesting feature is that the 850-700 hPa moisture layer is not as continuous back to the tropics as the other 3 layers.

Advected Layer Precipitable Water, 18z 13 February to 18z 14 February 2019 (Click to enlarge)

You can also infer a large influx of moisture from the low-level water vapor imagery, as shown in the short animation below from GOES-17, from 1617 UTC (just as Loop Heat Pipe issues that cause missing data were ramping down) to 1857 UTC. One might also infer a long-duration event from this animation!

GOES-17 ABI Band 10 Infrared 7.3 µm Imagery (Low-Level Water Vapor Band) from 1617 UTC to 1857 UTC on 14 February 2019 (Click to animate)

The GOES-R All-Sky Total Precipitable Water product (from this site) is as yet produced only from GOES-16 data (The Loop Heat Pipe problems have a strong impact on all Baseline products, including Legacy Profiles that are used to create Total Precipitable Water, which impact is still under investigation). The western Pacific is on the limb of this product, but it does capture the deep moisture moving towards southern California.

GOES-16 All-Sky Total Precipitable Water, 1400 UTC on 14 February 2019 (Click to enlarge)

Much of the San Diego National Weather Service Forecast Office County Warning Area is under Flood and/or Wind Warnings! See the Screen Capture below from 1121 AM Pacific Standard Time.

Warnings (as of 11:21 AM PDT on 14 February 2019) over the San Diego County Warning Area (Click to enlarge)