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Shear vorticies over the western US

By Scott Bachmeier •

GOES-16 (GOES-East) Upper-level Water Vapor (6.2 µm) and Air Mass Red-Green-Blue (RGB) images (above) displayed a series of shear vortices migrating southwestward over the western US on 09 November 2020. The “dynamic tropopause” — taken to be the pressure of the PV1.5 surface — descended to the 500-600 hPa level within the largest and... Read More

GOES-16 Upper-level Water Vapor (6.2 µm) and Air Mass RGB images [click to play animation | MP4]

GOES-16 Upper-level Water Vapor (6.2 µm) and Air Mass RGB images [click to play animation | MP4]

GOES-16 (GOES-East) Upper-level Water Vapor (6.2 µm) and Air Mass Red-Green-Blue (RGB) images (above) displayed a series of shear vortices migrating southwestward over the western US on 09 November 2020. The “dynamic tropopause” — taken to be the pressure of the PV1.5 surface — descended to the 500-600 hPa level within the largest and most well-defined vortex that was moving over Montana and Idaho. These features displayed hues of red to orange in the Air Mass RGB images (for example, at 2101 UTC), indicative of the dry and ozone-rich stratospheric air within the vortices. Aircraft reports of turbulence are sometimes seen in the general vicinity of these shear vortices, as the local tropopause is deformed (such as on 07 June 2017); in this case, there were only two instances of turbulence reported (at 1545 UTC and 0200 UTC).

GOES-16 Upper-level Water Vapor (6.2 µm) image at 2101 UTC, with contours of PV1.5 pressure (red) and the orientation of cross section I-I' (cyan) [click to enlarge]

GOES-16 Upper-level Water Vapor (6.2 µm) image at 2101 UTC, with contours of PV1.5 pressure (red) and the orientation of cross section line I-I’ (cyan) [click to enlarge]

The GOES-16 Water Vapor image at 2101 UTC (above) showed the northwest-to-southeast oriented cross section line I-I’ — and RAP40 model fields along that line (below) revealed the descent of stratospheric air (characterized by low values specific humidity along with high values of potential vorticity) within the shear vortex when it was located near the Idaho/Montana border.

Cross section of RAP40 model Potential Vorticity (color image + red contours), Specific Humidity (green contours) and wind barbs (cyan) [click to enlarge]

Cross section of RAP40 model Potential Vorticity (color image + red contours), Specific Humidity (green contours) and Wind (cyan) [click to enlarge]

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Tropical Storm Eta enters the Florida Straits

By Scott Bachmeier •

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images (above) showed Tropical Storm Eta as it began to move across the Florida Straits after 15 UTC on 08 November 2020. Deep convection began to develop across far southern Florida around 02 UTC on 09 November, just north of Eta’s broad circulation center — and... Read More

GOES-16

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images (above) showed Tropical Storm Eta as it began to move across the Florida Straits after 15 UTC on 08 November 2020. Deep convection began to develop across far southern Florida around 02 UTC on 09 November, just north of Eta’s broad circulation center — and the tropical storm made landfall in the Florida Keys at 0400 UTC. The strongest wind gusts were found to the north/northeast of the storm.

Sea Surface Temperature and Ocean Heat Content [click to enlarge]

Sea Surface Temperature and Ocean Heat Content [click to enlarge]

Maps of Sea Surface Temperature and Ocean Heat Content from the CIMSS Tropical Cyclones site (above) indicated that Eta was moving over warm water (SST around 28ºC, and a pocket of modest OHC) north of Cuba. GOES-16 Longwave Infrared (11.2 µm) images, with contours of 02 UTC deep-layer wind shear (below) showed that the hurricane was moving through an environment of moderate southwesterly shear, which limited intensification.

GOES-16 Longwave Infrared (11.2 µm) images, with contours of 19 UTC deep-layer wind shear [click to enlarge]

GOES-16 Longwave Infrared (11.2 µm) images, with contours of 19 UTC deep-layer wind shear [click to enlarge]

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Individual Great Lake true-color sectors available at the CIMSS Direct Broadcast site

By Scott Lindstrom •

The CIMSS Direct Broadcast site is now routinely creating True-Color imagery over 6 different domains: The Great Lakes, and each of the 5 individual lakes: Superior, Huron, Michigan, Erie, Ontario (Click on each image to see the domain). File name examples are shown here. Suomi NPP and NOAA-20 are in similar orbits,... Read More

VIIRS True Color Imagery from Suomi-NPP (1729 UTC) and NOAA-20 (1818 UTC) on 4 November 2020  over the pre-defined Great Lakes domain (click to enlarge)

The CIMSS Direct Broadcast site is now routinely creating True-Color imagery over 6 different domains: The Great Lakes, and each of the 5 individual lakes: Superior, Huron, Michigan, Erie, Ontario (Click on each image to see the domain). File name examples are shown here. Suomi NPP and NOAA-20 are in similar orbits, about 50 minutes apart, so it’s common to be able to create an animation, as shown below with Lake Erie. Note that the colors in the toggle below, and in the Basin-wide toggle above, can show differences because of view angles. In particular, the slanted view angle over Lakes Michigan and Superior in the 1729 UTC Suomi-NPP image in the toggle above allows for the true-color imagery to show a thin layer of smoke over portions the those lakes.

VIIRS True Color Imagery from Suomi-NPP (1729 UTC) and NOAA-20 (1818 UTC) on 4 November 2020  over the pre-defined Lake Erie domain (click to enlarge)

If NOAA-20 or Suomi-NPP only samples part of the lake, then a partial image is created, as shown below from NOAA-20 pass viewing Lake Ontario at 1639 UTC on 4 November. (NOAA-20 viewed the entirety of Lake Ontario at 1818 UTC).

VIIRS True Color Imagery from NOAA-20 (1639 UTC) on 4 November 2020 over the pre-defined Lake Ontario domain (click to enlarge)

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Melting of lake effect snow cover in Pennsylvania

By Scott Bachmeier •

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a narrow northwest-to-southeast oriented swath of snow cover across far northwestern Pennsylvania on 04 November 2020. With full sunshine and strong southerly winds helping air temperatures warm into the 60s F, this narrow band of snow cover melted by the end of the day.... Read More

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 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a narrow northwest-to-southeast oriented swath of snow cover across far northwestern Pennsylvania on 04 November 2020. With full sunshine and strong southerly winds helping air temperatures warm into the 60s F, this narrow band of snow cover melted by the end of the day. This lake effect snowfall event occurred late in the day on 01 November; lake surface water temperatures across interior Lake Erie (below) were as warm as the middle 50s F (brighter green color enhancement).

NOAA-20 VIIRS Sea Surface Temperature product [click to enlarge]

NOAA-20 VIIRS Sea Surface Temperature product [click to enlarge]

The lake effect snow cover was more apparent in GOES-16 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) — a 2-day animation covering the daytime hours on 03-04 November showed how quickly much of this snow cover melted on 03 November, with a narrow swath (where 6-12 inches of snowfall occurred) persisting into 04 November. In addition, a thin ribbon of fog in parts of the Allegheny River valley was apparent right after sunrise on 04 November, which quickly dissipated with the onset of daytime heating. The melting remains of the band are also apparent on 4 November in this toggle of VIIRS True Color imagery (from this blog post)

GOES-16 True Color images [click to play animation | MP4]

GOES-16 True Color images [click to play animation | MP4]



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