Editor’s Note: We want to thank Drew Lerner, Doane’s weather consultant and President of World Weather Inc., for allowing us to share this version of a special report he sent to commercial clients last week regarding early frost risks.
Worry over the potential for early frost and freeze conditions in North America has started to rise significantly in the commodity trade this week and rightly so. With crops planted late and maturing late, there is potential for notable crop production cuts in a seasonably normal frost and freeze event, let alone one that is earlier than usual. It caught my attention as a meteorologist big-time when the low at Bismarck, ND sank to 39 degrees on July 26!
Weather patterns this summer have not allowed the Northern Hemisphere to warm up normally and reports from the arctic suggest ice accumulations are way ahead of recent years. A recent report from the polar region shows the number of above freezing days this summer was reduced by nearly half. These issues, along with the ten-day, 30-day and 18-year cycles all add merit to the mid-July CFS model prediction for a couple “threat periods” for early season frost and freezes in September. (But I must caution the CFS model “track record” for accurate temperature forecasts six weeks in advance is not very good.)
Other early warning signs: Low temperatures Aug. 14th in portions of Wisconsin and Minnesota slipped to the middle 30s, the day after similar lows occurred as far west as northeastern North Dakota. This cool period also followed some patchy soft frost reported in a few Saskatchewan, Canada locations a few days before that. It had been roughly three weeks since the last bout of unusually cold nighttime lows (18 to 19 days to be precise). Normally, when unusually cool weather patterns occur in late summer, observing the rhythm in which the cold bouts occur can sometimes be the best indicator of when the next bout of cold will arrive. If that is true in this case, the first days in September will need to be closely monitored for the next bout of coolness in Canada’s Prairies and/or the northern U.S. Plains.
The 18- to 19-day interval between cold shots is also close to the second occurrence of the 10-day cycle, which fits well in the general timing of weather events in the atmosphere. But again, I must caution that predicting the first frost and freeze event of the year is one of the greatest challenges put to a meteorologist and/or climatologist since it requires predicting temperatures within two to three degrees of accuracy 6 to 8 weeks ahead. And the difference between a damaging frost or freeze event and one of only minor consequence to yields is often determined by a degree or two in temperature. But with that said, there are a number of issues that need to be discussed in this report that reinforce prospects of early season frost and freezes.