Testing of GOES-16 and GOES-17 Mode 6 scan strategy

February 19th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play animation]

Both GOES-16 (GOES-East) and GOES-17 (GOES-West) were placed into the Mode 6 scan strategy for a 3-day period of testing beginning at 1500 UTC on 19  February 2019 — which provides Full Disk images every 10 minutes (instead of every 15 minutes for the more common Mode 3 scan strategy). Further details on GOES-R series scan modes are available here and here. GOES-16 Full Disk “Red” Visible (0.64 µm) images are shown above, with Mid-level Water Vapor (6.9 µm) images below.

GOES-16 Mid-level Water Vapor (6.9 µm) images [click to play animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images [click to play animation]

One of the more striking features over the North Atlantic Ocean was a rapidly-intensifying Hurricane Force low — an animation that cycles through GOES-16 Visible and Water Vapor images of this system is displayed below.

GOES-16 "Red" Visible (0.64 µm) and Mid-level Water Vapor (6.9 µm) images [click to play animation]

GOES-16 “Red” Visible (0.64 µm) and Mid-level Water Vapor (6.9 µm) images [click to play animation]

Full Disk animations of GOES-17 Visible and Water Vapor images are shown below.

GOES-17 "Red" Visible (0.64 µm) images [click to play animation]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation]

GOES-17 Mid-level Water Vapor (6.9 µm) images [click to play animation]

GOES-17 Mid-level Water Vapor (6.9 µm) images [click to play animation]

The more frequent 10-minute images allowed a short-lived signature of orographic waves within a transient dry slot immediately downwind (northeast) of Atka (PAAK) in the Aleutian Islands of Alaska  (below) — such a signature often indicates a high potential of turbulence. There were also areas of transverse banding seen with the jet stream cirrus just southeast of Atka (another satellite signature of turbulence).

GOES-17 Low-level (7.3 µm) and Mid-level (6.9 µm) Water Vapor images [click to play animation]

GOES-17 Low-level (7.3 µm, left) and Mid-level (6.9 µm, right) Water Vapor images [click to play animation]

Tropical Disturbances in both Hemispheres

February 19th, 2019 |

Morphed Total Precipitable Water for the 24 hours ending 0100 UTC on 19 February 2019 (Click to enlarge)

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.

Himawari-8 AHI Clean Window (10.41 µm) Infrared Imagery, 1400 UTC 18 February – 0230 UTC 19 February 2019 (Click to play animated gif)

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).

Strong jet streak 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 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).

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. 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).

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]