![\"GOES-16](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2019\/04\/190420_goes16_waterVapor_Chicago_anim.gif\")
<\/a>GOES-16 Low-level (7.3 \u00b5m, left)<\/em> and Mid-level (6.9 \u00b5m, right)<\/em> Water Vapor images, with hourly plots of surface reports [click to play animation | MP4<\/strong><\/a>]<\/p><\/div>GOES-16 (GOES-East)<\/em> Low-level (7.3 \u00b5m<\/strong><\/a>) and Mid-level (6.9 \u00b5m<\/strong><\/a>) Water Vapor images (above)<\/strong><\/em> revealed a southwest-to-northeast oriented band of anomalously-dry air<\/strong><\/a> along the northwest periphery of a slow-moving low pressure center over the eastern US on 20 April 2019<\/strong><\/a>. The hourly dew point dropped to 10\u00baF at Chicago O’Hare<\/strong><\/a>, with a Relative Humidity value of 12% — a new record low value<\/strong><\/a> for Chicago. In addition, the dew point dropped to 6\u00baF at the Chicago Midway<\/strong><\/a> and Chicago Executive<\/strong><\/a> airports. With this dry air in place, note that the coastline of a portion of southern Lake Michigan could be seen in the 7.3 \u00b5m (and to a lesser extent, the 6.9 \u00b5m) Water Vapor images.<\/p>\n AWIPS examples of the GOES-16 Low-level and Mid-level Water Vapor imagery are shown below.<\/p>\n GOES-16 Low-level (7.3 \u00b5m)<\/em> and Mid-level (6.9 \u00b5m)<\/em> Water Vapor images [click to play animation | MP4<\/strong><\/a>]<\/p><\/div>A larger-scale view of the GOES-16 Low-level Water Vapor (7.3 \u00b5m) image at 1201 UTC (below)<\/strong><\/em> showed that the Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX) rawinsonde sites were located within the elongated zone of dry air.<\/p>\n GOES-16 Low-level Water Vapor (7.3 \u00b5m)<\/em> image at 1201 UTC, with plots of rawinsonde sites [click to enlarge]<\/p><\/div>Plots of GOES-16 Water Vapor weighting functions<\/strong><\/a> for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX) at 12 UTC (below) <\/strong><\/em>showed significant contributions from Band 10 (7.3 \u00b5m, violet)<\/em> radiation originating at the surface — this allowed the thermal signature of the outline of Lake Michigan to be easily seen in the 7.3 \u00b5m Water Vapor imagery. Although the contribution of Band 9 (6.9 \u00b5m, blue)<\/em> radiation originating near the surface was small, it was still enough to enable a brief and subtle coastal signature to be seen in the 6.9 \u00b5m images.<\/p>\n GOES-16 Water Vapor weighting functions for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX)\u00a0 at 12 UTC [click to enlarge]<\/p><\/div>Plots of Total Precipitable Water sounding climatology<\/strong><\/a> for Gaylord, Michigan (KAPX) and Lincoln, Illinois (KILX), with record minimum values for 20 April at 12 UTC highlighted within a red box (below)<\/strong><\/em> showed that the 0.10″ at KAPX and the 0.12″ at KILX set new records for that date\/time.<\/p>\n<\/a><\/a><\/a>