Lack of soil moisture exacerbates heat waves
By Summit Voice
SUMMIT COUNTY — The summer of 2012 is on pace to become the third-hottest on record since 1950, and could surge into first or second place, according to recent analysis by AccuWeather, Inc.
The private forecasting company is scrutinizing hourly and daily temperatures in 59 key cities to calculate the number of cooling-degree days, which is one way to measure summer heat across the country.
“The summer of 2012 is on pace to finish third hottest on the list of 62 summers since 1950, but is still in the running for number two or one on the list,” said Steven Root, a consulting meteorologist with AccuWeather partner WeatherBank, Inc.
Based on the way Root calculates temperatures, 2011 is the hottest summer on record, followed by 1951, during an early 1950s North American drought. The coolest summer during the period was 1965.
The 60-year average for cooling degree days is 51,923, according to Root’s calculations. NOAA’s 30-year average is 53,933 CDDs. In the past 10 years, the average CDDs is 56,134.
“This tells you that the summers are trending hotter in the most recent decades and years for the U.S. and southern Canada as a whole,” Root said.
In the U.S. as a whole, seven out of the last 10 summers have been hotter than the 62-year average. This compared to the 1960s and 1970s, when seven out of 10 summers were cooler than the NOAA’s recent 30-year average.
The AccuWeather forecasters didn’t discuss global warming, but other climate and weather experts have been suggesting there is a link between the overall trend of increasing global temperatures and the record summer temperatures in recent years.
According AccuWeather, the 1980s and 1990s, again in the U.S. as a whole, the number summers were about a 50-50 split being warmer or cooler than the NOAA 30-year average.
Last summer, heat got a later start, compared to this summer. Root expects the period through Sept. 15 to fall a bit behind last year’s pace and it is for that reason that this summer will probably fall a bit short of last year in terms of total CDDs.
“It will still be close and another big, broad surge of extreme heat can push the summer over the top in terms of CDDs,” Root said.
“We expect more surges of heat to build out of the Plains and into the East in the coming weeks,: said AccuWeather.com’s long-range forecaster Paul Pastelok.
“While cooler and potentially wetter conditions are projected to expand in the West, the most extreme warmth, relative to normal, could be forced out of the Plains and take root in the Great Lakes and Northeast, during September and October,” Pastelok added.
Root and Pastelok agreed that dry soil conditions and existing extreme warmth could continue to skew averages through the remainder of the summer.
Soil moisture takes energy away from the sun, so that less of the sun’s energy is available to heat the ground and the air nearest the ground.
In the 15 years Root has been making seasonal weather projections, he has run into some problems in the most recent years, due to more extremes in temperature (hot and cold) than during the prior years.
“In the recent five years, I have had to manually override the data due to the high number and magnitude of temperature extremes, compared to prior decades,” Root said.
Root chose 1950 as the starting point since this is when a high number of the reporting stations throughout the U.S. and southern Canada began recording hourly temperature data.
“Even with this starting point we had to create a few virtual weather stations for the first few years, based on knowledge of weather in the missing locations, relative to surrounding actual stations,” Root said.