May begins Monday, if you can believe it. It’s the last month of meteorological spring (March, April, May) and the doorstep to summer.
Interestingly, we’ve seen a consistent pattern in our monthly weather over the past year. The past 10 months have all been drier than normal (which is why we continue to be in a drought, even though we’ve seen rain recently), and 11 months have been warmer than normal.
So far, April has been a close call on precipitation given the past week of rain. But if we fall short this weekend, then it’ll be 11 dry months in a row, too.
Not surprisingly, our warmest May on record was set just two years ago, but our coolest May periods on record were way back at the turn of the previous century. Given the way Earth is warming, it’s nearly impossible to get a record cold month anymore. We also haven’t set any overall May precipitation records since about the middle of the last century.
We don’t expect to trigger any all-time records this year, but here is our latest thinking:
Temperatures should run one to two degrees warmer than the 30-year average of 66 degrees.
Rain should end up being higher than average for the first time since May of last year. Look for something between 4 and 4.5 inches.
Warm and wet start. Next week should average warmer than normal with 80s on May 1, followed by more comfortable but warm-leaning 70s the rest of the week. A very active, stormy pattern across the Eastern U.S. is favoring a wetter-than-normal first half of the month, offering a solid head start this time. The end of April finally turned toward the wetter side, and it seems like that trend continues into May.
Developing El Niño. While various long-range guidance suggests this new incoming El Niño event in the tropical Pacific is much weaker than the Godzilla episode of two years ago, it is developing at one of the fastest rates we have ever seen. As a result, the atmosphere is already showing signs of responding to it with an associated elevated global wind situation. What that means for you and me is a very active jet stream pattern that should prevent big heat from dominating, but also generate an active storm track over the United States. Our warmth may come more from low temperatures than highs. No 90-degree weather is forecast for the first two weeks of May at this point.
Models. The National Weather Service’s long-range CFS (Climate Forecast System) weather model is showing a nationally cooler-than-normal pattern for the first time in a long time. Nationally, we have experienced about 26 months in a row of warmer-than-normal conditions, so this CFS outlook is a real break from persistence, although the main cooler impacts are expected for the Midwest and South, with the East Coast closer to normal or just slightly warmer. Precipitation is shown to be on the wet side. These maps are an average of the past 40 model runs.
National Weather Service. This was released last week and does not incorporate all the new CFS model runs of the past week. We suspect that their final update, to be released April 30, should be considerably cooler overall, especially the nation’s midsection: