A “pneumonia front” pushed through Chicago Tuesday evening, with plummeting temperatures, a wind shift and wind gusts to 30-40 mph. The pic. above is from 10 am – bright and clear – nice blue water.
The term “pneumonia front” is attributed to Milwaukee NWS meteorologist Rheinhart Harms, who also coined the term “Alberta Clipper”. A pneumonia front is a sharp cold front that moves north to south down Lake Michigan. It is most common in spring when the land is warm and the lake water is very cold. Fronts like this have been known to drop the temperature 30 degrees in half an hour in Chicago. It also produces a shart wind shift to NNE and the wind can gust to 40 mph. Here’s what happened yesterday evening:
At 8 pm, Waukegan (north of Chicago) had a temp. of 59° and a variable wind at just 6 pm. One hour later, the temperature was 43° and they had a northeast wind at 23 mph gusting to 37 mph. At 9 pm (same time), the temperature at the Chicago Water Intake (Harrison-Dever Crib) was 62.4° with a west wind at 14 mph. At 10 pm, the temp. was 41.7° (a drop of 20.7° in an hour), and the wind was north at 26 mph with a peak gust of 38 mph. O’Hare Airport was 59° at 9 pm with a west wind at 6 mph. At 10 pm they were 44° with a north wind at 24 mph, gusting to 36 mph. At 10 pm, the wind at Midway Airport was NE at 28 mph with a gust to 38 mph. Not too far south, Joliet was 60° with a west wind at 6 mph.
Earlier in the evening the front went thru Milwaukee. At the shore, the temp. dropped from 61.9° t 6 pm to 41.7° at 7 pm. At the Milwaukee Airport, the temp. dropped from 64° at 5 pm to 48° at 7 pm and the wind shifted from WNW to NNE.
At Michigan City, Indiana – the temp. at 9 pm was 56° with a WSW wind and a humidity of 40%. At 10 pm, the temp. was down to 43.5°, the humidity rose to 75% and the wind was north gusting to 38 mph.
On the Michigan shore, the front was more subtle…the prevailing wind was coming off the cold lake to start with…the South Haven Beach never got to 50° all day. At 9 pm, at the S. Haven beach, the temp. was 45.5° and the wind was NW at 5 mph. At 10 pm, the temp. had dropped to 42.3° and the wind was north at 17 mph. At the Muskegon Beach, the wind shifted from south to north, but the temp. only dropped 2° in an hour, because it was cold to start with…the high temp. at the Muskegon Beach was 45.7°.
This pic. is at the Muskegon Beach the morning of April 8 (2019). I think what we have here is a subtle fog bow. It’s mostly a faint white, but you may be able to make out a smidgen of color.