Rainfall continues to be relatively sparse for most of southern New England, and as we enter a very warm to hot period over the next 4-6 days, the lack of rainfall will become more evident. If you are planting anything this time of year, including a new lawn, be sure you are watering it properly. Plants which went into the ground in spring could still benefit from a good soaking this weekend.
The map below shows the percentage of average rainfall that has fallen over the past 30 days. I really like this map, because it gives a good idea of how above- or below-average the rainfall has been. Of course, looking at a 30-day period in time also means the rain could have fallen at the beginning of the period, and thus it can still be dry even if you are in an above-average area. What you should notice is how much of southern New England has not seen average rainfall the past 30 days. The only area with significant rainfall is over northern Franklin County and parts of the Berkshires, but this rain fell nearly 2 weeks ago.
The rest of the holiday weekend looks fabulous, with warm and sunny conditions and tolerable levels of humidity. In spite of the summer pattern, there are major signs of fall. September 5 is somewhat significant both meteorologically and astronomically. This is because today begins the 30 days of the most rapid declines of the year in both temperature and daylight. During this period, the nights will quickly start to outweigh the days, and temperatures will lose about 10 degrees from their average.
The loss of daylight is predictable to the second, but the loss of temperature isn’t that simple, especially this September. As El Nino continues to gain strength, the changes it creates will likely bring more warmth to the northern latitudes this fall, including this month.
El Nino Grows
We are presently in the middle of a strengthening El Nino, and this has somewhat predictable consequences for weather patterns across the globe. This year’s El Nino is in the top two on record for this point in an El Nino’s development. There can still be major surprises, even in these strong El Nino years, but they do stack the odds on certain sides of the meteorological deck. Think of an El Nino year as pushing certain meteorological levers towards colder, wetter, warmer, or drier depending on the region of the globe.
Nearly all of the long range models agree the rest of the month will be warmer than average for a large swath of North America. This is typical for El Nino years, and doesn’t mean the entire winter will be warm just because September is. Also, with the average temperature falling a full 10 degrees, a day that is 10 degrees above average in the first week of the month is not nearly as warm as a day like that 4 weeks later.
The map below is courtesy of WeatherBell Analytics.
One of the models I review shows the northern tier staying quite warm through September. Remember, even within a very warm month, there could be a cold snap for a day or two. However, based on current trends, an early frost is not likely this year for any of you.
First Part Of Winter
Let’s take a look at one of the forecasts for the upcoming winter through January (we will consider this the first half of winter). Across the south, it’s forecast to be cooler than average, and across the north, it will be a warmer one. This is a classic El Nino pattern, and this map is from the National Weather Service. It doesn’t mean this is going to be exactly what happens. As a matter of fact, I circled the area I am most concerned could end up colder and snowier than average— it runs from roughly the southern part of New England, including Cape Cod down through the mid-Atlantic area and back to the Ohio Valley.
I must stress that even a year which ends up with above-average snowfall and below-average precipitation overall won’t necessarily be like the previous winter for those areas. I strongly believe this winter will be significantly milder and less snowy when compared to the previous one.
The other area of notable interest this winter looks to be the Pacific Northwest. There a significantly milder and drier winter overall is likely. Many forecasters from both the public and private sectors are in agreement that this part of the country could have the most significant warmth for the winter season.