We had an interesting day of weather. It started out with a severe thunderstorm watch issued at 8:55am for a severe line of storms moving ENE at 40 mph. The main line of storms started to move more easterly and passed through Whiteside, Lee, Ogle and DeKalb County. This massive storm complex was also producing torrential rainfall with totals nearing 3 inches in some places. With the main part of the squall line passing just to our south, most of us thought we were in the clear and soon the rain would quiet down as well. However, after the rain ended, strong-gusty winds picked up behind the heavy rainfall. Here is what happened. What we experienced was a wake low. A wake low is an area of low-pressure that sometimes forms behind a squall line that has stratiform rain behind the main line of storms. However, there can also be a pocket of high pressure that forms because of the rain-cooled air. With these two pressures close to each other, it can cause strong-gusty winds behind the main storm complex. Rockford Lutheran School experienced these gusty winds. The wind was clocked at 46 mph by the the automated observation system at Rockford International Airport.
This post was written by Cyndi Kahlbaum on May 29, 2011