CIMSS Satellite Blog

GOES-16 Low-level (7.3 µm, left) and Mid-level (6.9 µm, right) Water Vapor images [click to play animation | MP4]

GOES-16 (GOES-East) Low-level (7.3 µm) and Mid-level (6.9 µm) Water Vapor images (above) revealed a southwest-to-northeast oriented band of anomalously-dry air along the northwest periphery of a slow-moving low pressure center over the eastern US on 20 April 2019. The hourly dew point dropped to 10ºF at Chicago O’Hare and to 6ºF at Chicago Midway and Chicago Executive airports. With the 10ºF dew point, the Relative Humidity was 12% — a new record low value for Chicago. Note that the coastline of part of the southern portion of Lake Michigan could be seen on the Low-level and Mid-level Water Vapor images.

AWIPS examples of the GOES-16 Low-level and Mid-level Water Vapor imagery are shown below.

GOES-16 Low-level (7.3 µm) and Mid-level (6.9 µm) Water Vapor images [click to play animation | MP4]

A larger-scale view of GOES-16 Low-level Water Vapor (7.3 µm) image at 1201 UTC (below) showed that the Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX) rawinsonde sites were located within the elongated zone of dry air.

GOES-16 Low-level Water Vapor (7.3 µm) image at 1201 UTC, with plots of rawinsonde sites [click to enlarge]

Plots of GOES-16 Water Vapor weighting functions for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX) at 12 UTC (below) each showed significant contributions of Band 10 (7.3 µm, violet) radiation originating at the surface — this allowed the thermal signature of the outline of Lake Michigan to be easily seen in the 7.3 µm Water Vapor imagery. The contribution of Band 9 (6.9 µm, blue) was small near the surface, but still enough to allow a brief and subtle coastal signature on the 6.9 µm images.

GOES-16 Water Vapor weighting functions for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX)  at 12 UTC [click to enlarge]

Plots of Total Precipitable Water sounding climatology for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX), with record minimum values for 20 April at 12 UTC highlighted within a red box (below) showed that the 0.10″ at KAPX and the 0.12″ at KILX set new records for that date/time.

Plots of Total Precipitable Water sounding climatology for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX), with record minimum values for 20 April at 12 UTC highlighted within a red box [click to enlarge]

from CIMSS Satellite Blog http://cimss.ssec.wisc.edu/goes/blog/archives/33001