What a scorcher we had yesterday! In fact, it was the hottest day in 13 years! Among the sizzling high temperatures recorded in West Michigan: 97 in Grand Rapids, tying the daily record set way back in 1931, 98 in Kalamazoo, tying the daily record set in 1971, and 100 in Coldwater, marking the first time since July, 1999, that West Michigan has a seen triple digit air temperature.
The max temps marked the 11th time this summer we've had a 90 day. If the forecast for the next few days proves accurate, we'll add a few more days to that number, giving us more 90 days than we recorded in each of the last five summers; and we still have July and August to go! The latest 6 to 10 day outlook from the Climate Prediction Center (see graphic) suggests more hot, dry weather is on the way.
The average number of 90 days, taken from the last ten years, is eleven. As is usually the case with statistics, and specifically those involving weather, the "average" is deceptive. Several extremes work together to equal the number we call average. For example, in four of the last ten summers, we had five or fewer 90 days. In three of the ten, we had many more: the summer of 2007 had 14, summer 2002 had 19, and the summer of 2005 had an amazing 27 (see bar chart). We're actually a little ahead of the pace set in 2005. At the end of June, 2005, we had marked eleven 90 days. By the end of this month, that number will be about twelve or thirteen.
So, are we in for more of the same? Will the next couple of months also be hot and dry? The "usual suspects" that typically tip us off to what Mother Nature has planned for our weather months in advance give mixed signals. For example, when coming out of a La Nina (which ended last April), summer in West Michigan is more often than not cooler than average. However, that is contradicted by climatology which shows that our summers are typically warmer than average when following a warmer than average winter and spring.
The Arctic Oscillation, another important factor to consider when trying to project future weather conditions, is in a positive phase, which usually means warmer than average temperatures in our part of the Continent. Considering the conflicting signals, I think the best predictive tool to use when making a forecast for the rest of the summer is persistence -- that is to say that what has been happening will likely continue. In other words, there isn't any compelling reason to believe that we'll have a large-scale weather pattern change in the near future. Therefore, it is reasonable to expect that we'll continue to see warmer than average temperatures with below average precipitation. As always, stay tuned!