A68a Update

December 3rd, 2020 |

A very large iceberg broke off the Larsen-C Ice Shelf on the Antarctic Peninsula in July 2017 (recall this CIMSS Satellite Blog post) or this more recent post. While NOAA’s GOES-16 ABI visible sensors may not be ideal, they can monitor the iceberg’s location if the cloud cover is not too thick, as shown in the “natural color” animation. A similar loop, in the animated gif format. These composite images include information from ABI “blue” and “red” visible bands, along with the near-infrared “vegetation” band. A sample still image from November 21, 2020. More information can be found in the quick guide.

A GOES-16 natural color animation, at 15:30 UTC each day. The first day is November 4 , while the last day is December 2, 2020.

Thanks to a recent tweet by Simon Proud, showing a GOES-16 animation of A68a:

The geo2grid software was used to generate these loops.

Lake Erie surrounded by snow

December 2nd, 2020 |

NOAA-20 VIIRS True-Color image, 1752 UTC on 2 December 2020 (Click to enlarge)

NOAA-20’s early afternoon pass over Lake Erie on 2 December 2020 produced a stunner of an image.  Snow surrounds the open lake, a result of the first widespread storm of the season over the eastern Great Lakes.

This image was created using Polar2Grid and Direct Broadcast data at the UW-Madison CIMSS.  The direct link is here.  Images from other passes from NOAA-20 are in this directory, and from Suomi-NPP are here.

Daily VIIRS True-Color images from NOAA-20 for the Great Lakes

December 1st, 2020 |

Daily true-color images from NOAA-20 VIIRS over Lake Erie, 1-30 November 2020 (Click to animate)

CIMSS provides sectorized VIIRS true-color imagery for each of the five Great Lakes, and for the entire Great Lakes basin at the Direct Broadcast ftp site (ftp://ftp.ssec.wisc.edu/pub/eosdb/j01/viirs/ and ftp://ftp.ssec.wisc.edu/pub/eosdb/npp/viirs for NOAA-20 and Suomi-NPP, respectively). The imagery above shows NOAA-20 images saved from that site and merged together to make an animation (except for 12, 13, 14 November. Mea Culpa) over Lake Erie. Click here to view the animation as an mp4. (Additional animations for the other Great Lakes have also been created:  Lake Ontario in animated gif / mp4) Lake Huron in animated gif / mp4 ; Lake Michigan in animated gif / mp4; Lake Superior in animated gif ; mp4)

The daily views allow a user to view slow changes in the Lake’s circulation — when skies are clear. Such was the case on 8, 9 and 10 November, shown below. A slow anticyclonic motion in the widest part of central Lake Erie is apparent.

NOAA-20 VIIRS true-color imagery over Lake Erie on 8, 9, and 10 November 2020 (Click to enlarge)

Comparing NUCAPS temperature values to forecast fields

November 29th, 2020 |

Gridded NUCAPS estimates of 850-mb Temperature, 1851 UTC on 30 November 2020 (Click to enlarge)

Late November is a time when cold outbreaks can pass over relatively warm Great Lakes waters (click here for recent observations) and produce lake-effect snow. Gridded NUCAPS observations derived from NOAA-20 CrIS and ATMS data, above, shows a large area with temperatures colder than -12ºC over northwest Ontario and northern Minnesota, just upwind of the Great Lakes;  Lake Superior’s surface temperature at the time was around 5ºC —  a temperature difference that support lake-effect precipitation.  How well do the NUCAPS observations compare to model predictions of the environment?

Forecasts from the 1200 UTC run of the NAM, below, valid at 1800 UTC, and from the 1500 UTC run of the Rapid Refresh, valid at 1900 UTC, show -12ºC in bright magenta.  (Model analyses taken from this website)  NUCAPS analyses suggest the cold air is moving south faster than anticipated by the model.


6-h forecast of 850-mb Temperature, valid 1800 UTC on 29 November 2020 (Click to enlarge)

4-hour forecast of 850-mb temperature from the Rapid Refresh, valid 1900 UTC on 29 November 2020 (Click to enlarge)

This site can be used to view gridded NUCAPS fields outside of AWIPS.  The 850-mb analysis from the pass is shown below.  It’s important to recall that Gridded NUCAPS fields include data from all retrieved profiles — including profiles for which the infrared retrieval failed (usually in locations with thick clouds, and those from which the infrared and microwave retrievals both failed (usually in locations with rain). This mapping for the temperature gridding below shows where infrared retrievals failed (yellow) and where infrared and microwave retrievals both failed (red).

850-mb Temperature fields, 1849 UTC on 29 November 2020 (Click to enlarge)

The ‘yellow’ points north and west of the Great Lakes were associated with clouds that are apparent in this VIIRS True Color image, taken from the UW-Madison Direct Broadcast ftp site (Link). The clouds were associated with a departing low pressure system (link).

NOAA-20 VIIRS True-Color imagery, 1850 UTC on 29 November 2020 (Click to enlarge)