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

GOES-17 (GOES-West) “Red” Visible (0.64 µm) images (above) showed the motion of pack ice away from the southwest coast of Alaska on 20 November 2021. Strong offshore winds (gusting in excess of 30 knots at times) were causing the ice motion away from the coast into the Bering Sea — although some landfast ice was also evident.

During the subsequent nighttime hours, a sequence of 3 Suomi-NPP VIIRS Day/Night Band (0.7 µm) images (below) allowed sea ice motion to be monitored during the long night, when GOES-17 Visible imagery was not available — providing that there is ample illumination from the Moon, which there was in this case (since it was in the Waning Gibbous phase, at 99% of Full).

Suomi-NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

This ice growth was being promoted by colder than normal Sea Surface Temperatures in that portion of the Bering Sea — along with the offshore flow of very cold air that had been in place across much of Alaska during the previous days. In fact, Interior Alaska recorded its first -40ºF/-40ºC temperatures of the winter season on this day.

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NOAA-20 Day Night Band imagery from early morning (from the VIIRS Today website at CIMSS) on 19 November 2021 shows the impact of the total lunar eclipse on Day Night Band imagery. A lunar eclipse will always occur during a Full Moon; ample lunar illumination off the east coast accompanied that descending NOAA-20 pass between about 0635 and 0640 UTC (as shown in this orbital path image from this website) — just as the lunar eclipse was starting. By the time NOAA-20 overflew the central US (0815 to 0825 UTC), near totality was occurring. The overflight on the west coast (0955 to 1005 UTC) occurred as the eclipse was starting to wane, so a bit more lunar illumination was available.

A similar Day Night Band image from Suomi-NPP (also from the VIIRS Today website) is below, and it shows similar differences in swath illumination. The west coast overpass by Suomi-NPP occurred around 1050 UTC; by then the eclipse had ended. Suomi NPP Day Night Band imagery is also available at the NASA Worldview site.

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Cold temperatures over the Great Lakes (the Green Bay 850-mb sounding temperatures, for example, were -11.9º C at 0000 UTC and -8.1º C at 1200 UTC) on 18-19 November 2021 generated extensive cloud cover and occasional snow showers. The nighttime microphysics RGB, above, showed extensive stratiform clouds downwind of Lake Michigan. The GOES-16 Cloud Top Phase product at this time (here) uniformly showed water droplets over lower Michigan.

Skies over eastern Lake Michigan were clear enough at 0811 UTC to allow some lake-surface temperature computations using NOAA-20 VIIRS channels and the ACSPO algorithm. Diagnosed lake-surface temperatures are in the low 50s (º Fahrenheit; the colorbar range is 40º to 55º F).

NUCAPS Sounding Availability points are also shown in the image above, and three points near/over western Lake Michigan — near Escanaba MI, east of Sheboygan WI, and near Racine, WI — are shown below.

NUCAPS profiles on this day over western Lake Michigan were uniformly warmer than 2-hour forecast NAM Nest profiles from the 0600 UTC model run. The image below compares (via Sharppy, using the NUCAPS in the Cloud methodology outlined here) model (red and green lines) and NUCAPS (purple lines) near Escanaba. NUCAPS shows warmer low-level temperatures (and also cooler mid/upper-tropospheric temperatures). Comparisons for the NUCAPS point east of Sheboygan and NAM Nest values at Sheboygan, and the NUCAPS point near Racine and the NAM Nest values at Milwaukee (note that for those two linked plots, the colors are flipped: NUCAPS Temperature and Dewpoint are red and green, respectively, and NAM Nest values are purple) are similar: NUCAPS values in the lowest part of the atmosphere are warmer than the NAM Nest. How might that affect the downwind production of lake-effect clouds and precipitation?

NUCAPS profiles give a model-independent estimate of temperature and dewpoint in the atmosphere. They are available about halfway (in time) between routine upper-air soundings in the lower 48 states of the USA. ‘NUCAPS Sounding Availability’ can be found under the ‘Satellite > S-NPP and NOAA-20’ menu.

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In-flight turbulence affected Hawaiian Air Flight 51 (JFK to HNL) late in the afternoon on 17 November 2021 (Click here for the flight path from the flightaware website. A screen-capture of the flight levels, below (cropped from the FlightAware website), shows turbulence occurring between 0141 and 0145 UTC on 18 November as the plane was flying at FL400 near 22.5º N, 154º W. That places the storm in the middle of MOG values exceeding 50% in a convective storm to the northeast of Hawaii, a storm in which other planes were also experiencing turbulence, as shown in the animation above (taken from the CIMSS Turbulence website). Here is the image for 0150 UTC, right after the turbulence affected the aircraft.

One passenger suffered a minor head injury during this event, and declined treatment. (Link). Training on this product is available at this site (direct link to recording is here).

GOES-17 ABI Imagery (and level 2 Products), below, show persistent vigorous convection developing in a region with Lifted Indices around -2. Level 2 Cloud Top Height, at bottom, (the colorbar has been modified from default values to 35000-45000 feet), show persistent development of cloud tops exceeding 40000 feet, the cruising level of HAL51!

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