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Land breeze convergence cloud band in Lake Michigan

By Scott Bachmeier •

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface and buoy reports [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a narrow cloud band that had developed in Lake Michigan in response to land breeze induced convergence on the morning of 23 September 2018. With inland temperatures cooling overnight into the 30s and 40s F (the coldest in both Wisconsin and Michigan was 29ªF) and lake water temperatures of 64ºF (at the North Michigan buoy 45002) to 69ºF (at the South Michigan buoy 45007), a well-defined nocturnal land breeze was established along the western and eastern shorelines of the lake.

Nighttime VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC (below) showed that the cloud band had not yet formed at those times.

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

The Terra and Aqua MODIS Sea Surface Temperature product (below) confirmed that mid-lake water temperatures were generally in the middle to upper 60s F (green to light yellow enhancement) across the entire length of Lake Michigan.

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

An examination of the MODIS SST product with overlays of RTMA surface winds (below) showed that there was no clear signature in the model wind field of enhanced convergence either before or after the mid-lake cloud band had formed.

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

However, an overpass of the Metop-A satellite at 1559 UTC provided ASCAT surface scatterometer winds that did a better job than the RTMA at highlighting the mid-lake convergence that was helping to sustain the cloud band (below). This example underscores the value that satellite-derived winds can have over even high resolution models.

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]

Categories: Aqua, GOES-16, Metop, MODIS, NOAA-20, Satellite winds, Suomi NPP, Terra, VIIRS