On Monday, temperatures reached into the 70s, many degrees above average for the date. The warm weather brought my thoughts back to the summer and reminded me that our drought is very much still in play.
We’ve seen some much-needed rain in the past few weeks, but unfortunately, it’s done little to move the drought needle in most of New England. The image below shows that, in spite of the rain, most areas are running 1 to 2 inches below average since late September.
Rainfall continues to be sparse this fall.
Drought in New England isn’t common. Typically, the fluctuation in precipitation doesn’t have nearly as large a range as snowfall. There are fewer than 10 years since 1872 in which the total precipitation has been more than 10 inches below the long-term average of just over 41 inches of rainfall. This year, Portland has had just over 25 inches of rainfall, 10 inches below where we would typically be by now.
To understand the drought, it’s worth widening the time period and looking at rainfall over the past three years. The map below shows just how far behind the area is with regard to precipitation. Notice that during this period some areas are 16 to 20 inches below average. This is as if it didn’t rain for four or five months.
Drought conditions are worse for southern New England, but still bad in extreme southern and western Maine.
The past couple of springs have set the stage to make the drought worse. Notice the image below showing just how far below average rain was during the spring of 2015. The lack of rain combined with the strong sunshine dried out the ground rapidly after the snow melted.
The spring of 2015 was also dry and set the stage for the current drought.
Speaking of snow, the big snows two years ago didn’t help the situation. The snow that winter was very light and contained less water than would typically occur. There just wasn’t a lot of moisture in the snow so when it melted the ground didn’t absorb very much. It’s one of the reasons why there was little or no flooding after the big snows of 2015.
The next chart illustrates how low precipitation has been since meteorological spring and then summer began. Much of the region saw around half the normal rainfall during these periods.
Dry weather since spring 2016 has prolonged the drought.
The main reason for the dry weather is a continued persistent ridge in the Atlantic. While this is a typical pattern for the core of summer, it’s more unusual for it to last for so long. Before you make a leap to this being part of climate change, remember that New England has seen droughts before and this is likely just part of a large cyclical pattern which will eventually swing back to a wetter period in the coming 12 to 24 months.
High pressure off the Eastern Seaboard has kept the region from receiving typical rainfall.
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