Forecasting a Hot? Summer

Forecasting for a season is perhaps the most difficult, and as the public knows, most unreliable product put out by any group be it those, for example, from NOAA or people putting together The Old Farmers Almanac. If farmers, power companies, construction companies, those doing a lot of outdoor work, and even health professionals had a good heads up on weather and temperature trends over the course of  the next three months literally billions of dollars could be saved, and perhaps some lives as well. Unfortunately, model reliability and long range forecast skill sets are not up to par with public expectations when it comes to seasonal outlooks. Weather forecasts for the next week have gotten remarkably better over the last decade, and there has been improvement in long range outlooks, but current crystal ball methods we have for forecasting seasons leave much to be desired. Knowing the limitations of seasonal forecasting, in this post I will  attempt to make a broad forecast for the summer of 2017 in the United States keeping in mind potential dangerous temperature trends due to carbon pollution. By no means am I a skilled seasonal forecaster, but I will give this my best shot knowing that there is a need by the public craving to know what is in store this summer.😊

Right off the bat due to carbon pollution and the current associated global temperature the chances for any one location in the United States having below average temperatures this summer are slim. The following is the forecast for the lower forty eight states from NOAA:

Quoting from Climate Central: This map shows the odds of well above average temperature during summer of 2017. Well above average means “in the upper third of the 1981-2010 climate record.”  White shows areas with equal chances for any of the possible climate outcomes (cool, warm, or normal). Darker red colors mean higher chances (greater confidence). NOAA map, based on data from the Climate Prediction Center.

Notice that no area has a better than average chance of seeing below average temperatures. It’s no wonder looking at “the streak” as I like to call it, of more daily high maximum record temperatures than daily low minimum records, currently at 29, on a monthly basis:

Obviously, the higher the ratio of DHMX to DLMN records the higher averages are unless, for a quirky reason, a bunch of records get set in a relatively localized area across the U.S. This chart also includes the average rankings of the lower 48 states…1 would be the coldest month since 1895 and 123 the highest. One can see that ratios and rankings have lined up, statistically, well since the beginning of 2014. The streak runs from DEC 2014 to APR 2017, so far. MAY 2017 might be the 30th consecutive month… will have a post on MAY 2017 soon.

Boldly highlighted are eight months of ratios higher than 10 to 1. Any month with a greater than 10 to 1 has ended up very anomalously warm or hot with unusual weather in the U.S. If such a ratio occurs during a summer month, such as in JUN 2015, deadly heat can result. Are we due for a “deadly” month this summer looking at record trends? Perhaps, but at least there are some negative factors in favor of the “cold team”.

The first would be that surrounding North American sea surface temperatures have fallen some since this time last year:

A year ago the planet’s average temperature was slightly warmer coming off a near record strong El Nino. North America was surrounded by above average SST’s, which is not the case now. Thermodynamically, a land mass should be warmer more often than not if it is surrounded by above average temperature waters.

The second negative factor would be a persistent vortex at mid-levels of the atmosphere called the Hudson Bay low. Usually this low is centered near Hudson Bay, hence the name, but can dig southward through the eastern U.S. even during the warm months. This feature is actually an extension of the dreaded polar vortex, which brought colder than average conditions to the U.S. in 2013 and 2014, but has not had as much of an impact since the beginning of “the streak”. Cool weather systems rotating around this feature can bring below average temperatures to the eastern two thirds of the U.S. Should the feature persist this year, most people in the East won’t have to worry about a prolonged heat wave. In my thirty plus years as a meteorologist I have noticed that when we see strong systems digging through and south of the Great Lakes in May, summers in the East are not that torrid. One such system is bringing storms and refreshing weather to the South as of this post:

A third negative factor would be the lack of a large area enduring drought in May. In my experience dry springs in the Midwest and South usually lead to dry, hot summers. In meteorology dry ground is deemed one of many feedback mechanisms in the water cycle. “Pop up”, cooling storms are more prevalent during the summer over wet ground. We have all heard of horror stories from areas in and around rain forests when trees are chopped down leading to drought. The same thing happens here, although to a lesser extent, when land is dry during the spring. Looks like we are entering summer when ground is wet across most of the country, though. Historically, this map shows the smallest U.S. drought area in decades:

And finally, the U.S. is “way overdue” for at least one relative cool month of more DRLMN than DRLMX. However, there may come a time in the not so distant future because of global warming when “the streak” won’t just be a long period in between cool months, but a permanent, unwelcome guest.

So what is the bottom line summer 2017 forecast from the “Climate Guy” for some to snicker at if there is a bust when September rolls around? I’ll state that it will be above average, but not make the top ten rankings since 1895. Due to negative factors we might even have the streak broken should it not end in May. I also doubt that we will see an awful 10 to 1 or more ratio month of DRHMX to DRLMN.

I hope everyone has a safe summer. Even if conditions are below average for a month or two across portions of the U.S. there is likely to be periods of scorching weather. Be sure to hydrate and take precautions when maxes get above 85 degrees.

The Climate Guy


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