General interpretation « CIMSS Satellite Blog

Using NUCAPS to nowcast convective development

August 27th, 2019 | Scott Lindstrom

GOES-16 Visible Imagery (0.64 µm) at 1721 UTC on 27 August 2019. A swath of NOAA-20 NUCAPS soundings from 1718 UTC is also shown, and individual profiles from the Upper Peninsula of Michigan southeastward to southwest Lower Michigan are plotted. (Click to enlarge)

The animation above shows the 1721 UTC GOES-16 Visible (0.64 µm) image along with NUCAPS profile locations from a NOAA-20 overpass. Convection is approaching from the west, from central Wisconsin. NUCAPS soundings can give a good estimate for how far south that convective line might develop, and a north-south series of profiles is shown in the imagery above. Note in particular how soundings show increasing mid-level stability; a strong inversion between becomes apparent between the NUCAPS Sounding just south of Door County on the western short of Lake Michigan and over eastern Lake Michigan on the Michigan shoreline. This thermodynamic snapshot would argue that convection should not develop much farther south than central Lake Michigan! the 1926 UTC Visible image, below, toggled with radar, confirms this forecast.

GOES-16 Visible Imagery (0.64 µm) at 1926 UTC on 27 August 2019 — toggled with Base Reflectivity at 1924 UTC (Click to enlarge)

NUCAPS from one satellite will periodically, north of about 40 N, supply profiles on two consecutive passes. That happened on 27 August over Lake Michigan as might be expected given that the 1718 UTC pass had its westernmost swath over Lake Michigan. The animation below shows the swath from 1901 UTC. The strengthening inversion as you move south over Lake Michigan is apparent at 1901 UTC as well.

GOES-16 Visible Imagery (0.64 µm) at 1906 UTC on 27 August 2019. A swath of NOAA-20 NUCAPS soundings from 1901 UTC is also shown, and individual profiles over Lake Michigan Michigan are plotted. (Click to enlarge)

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Ship tracks in the East Pacific, and eddy circulations near the California coast

April 24th, 2019 | Scott Bachmeier

GOES-17 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-17 (GOES-West) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed a number of ship condensation trails (or “ship tracks”) over the East Pacific Ocean on 24 April 2019. Aerosols from the exhaust of ships cause a “cloud seeding effect”, which results in a higher concentration of smaller cloud droplets compared to the surrounding unperturbed clouds. These smaller cloud droplets are more effective reflectors of sunlight, leading to a warmer (darker red) 3.9 µm signature.

GOES-17 Visible images (below) revealed a few eddy circulations within the marine boundary layer stratocumulus off the coast of southern California, along with other interesting Channel Island cloud interactions — some of the eddy circulations exhibited a small cloud-free center. Surface winds were light and variable over the Channel Islands (surface analyses), with a thermal low situated well inland over the Desert Southwest (the national high temperature on 24 April was 106ºF at Death Valley, California).

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

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Stereoscopic views in the Visible and Near-Infrared

February 20th, 2019 | Scott Lindstrom

GOES-16 (left) and GOES-17 (right) Visible Imagery (0.64 µm) from 1422 UTC to 2257 UTC on 20 February 2019 (Click to play mp4 animation)

Stereoscopic views of Visible Imagery (from GOES-16 and GOES-17, above) allow for visualization of three dimensions, as shown in the mp4 animation above (click here for an animated gif of the same scene). The imagery captures multiple cloud layers over the western United States (a map will show up in the animation) as a potent system moved eastward.

GOES-R includes four channels in the near-visible including the Cirrus Channel at 1.37 µm. The Cirrus Channel is useful here because the water vapor absorption of 1.37 µm energy means that any near-surface signal is absorbed, so mostly high-level clouds are present (low clouds become visible in the cirrus channel in very dry atmospheres). The animation below (the animated gif is here) is a stereoscopic view created with 1.37 µm imagery and the structure of the high clouds is more apparent.

GOES-16 (left) and GOES-17 (right) Band 4 Near-Infrared Imagery (1.37 µm) from 1422 UTC to 2257 UTC on 20 February 2019 (Click to play mp4 animation)

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Stereoscopic views of a small storm over the North Pacific Ocean

January 16th, 2019 | Scott Lindstrom

Himawari-8 AHI and GOES-17 ABI Band 13 (10.41 µm and 10.35 µm, respectively) at 0400 UTC on 16 January 2019 (Click to enlarge)

GOES-17 Data in this post are preliminary and non-operational.

The toggle above shows clean window imagery from the Advanced Himawari Imager (Band 13, 10.41 µm) on Himawari-8 (data courtesy JMA) and clean window imagery from the Advanced Baseline Imager (ABI, Band 13, 10.3 µm) on GOES-17 (GOES-17 data are non-operational). There is a small developing storm between the Hawai’ian Islands and Alaska that is resolved by both satellites. The storm is in between the two satellites and therefore ideal for stereoscopic views created from Visible 0.64 µm imagery (Band 3 for AHI, Band 2 for GOES-17). That is shown below. Thirty-minute timesteps are used because GOES-17 scans a full disk every 15 minutes (in Mode 3 that is currently operational; Mode 6, if used, scans a Full Disk every 10 minutes; and Mode 4, continuous Full Disk, the highest data rate for the GOES-R series, scans a Full Disk every 5 minutes). Himawari scans a Full Disk every 10 minutes. The three-dimensional representation facilitates the identification of warm conveyor belts associated with this developing storm. (This link shows the same animation but with the imagery flipped so it can be viewed in Google Daydream).

GOES-17 non-operational Visible (0.64 µm) imagery (left) and Himawari-8 Visible (0.64 µm) imagery (right), every half-hour from 2000 UTC on 15 January to 0400 UTC on 16 January (Click to animate)

Thanks to Mary Ellen Craddock, Northrop-Grumman, for the reminder that stereo imagery is possible with GOES-17 and Himawari. (It should be even better with Himawari-8 and South Korea’s GEOKOMPSAT-2A!)

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