Summer of July 2011 was a year for the record books with exceptional heat and 12 record breaking temperatures. However, 2012 has already smashed these records!

With more than 155 all-time high temperatures recorded in just the first 15 days of July, National Oceanic and Atmospheric Administration (NOAA) calls it the warmest summer since record-keeping began in 1880. The exceptionally hot summer has resulted in drought in the agricultural heartland of the country sending prices of grains skyward.

The current heat wave is the fourth to hit the nation this year. According to a recent report, the 2012 drought is the biggest seen in over 50 years, covering more area than the historic drought of 1936 during the Dust Bowl years.

The Pressure Is On…

The United States is experiencing an unusually warm summer, because of a persistent ‘high pressure’ system hanging over a large part of the country. Also called a heat ridge or dome, it is a lump of high-level, slow-moving high pressure air that is blocking cooling winds, leaving everything inside the dome sweltering.

Heat domes occur every year when high pressure builds in summer as the land heats more quickly than the ocean. Most move along within a few days, but sometimes a combination of factors keeps the hot air in place for a long time.

This dome initially began in the western mountains and has been slowly shifting eastward to the Midwest and Southeast of the US along with the Jet stream. The Jet Stream is the way wind moves across the entire planet (see notes for more). The temperatures are being fed further by baking temperatures of the inland, causing moisture to evaporate into humidity and creating a steaming hot ‘pressure cooker’ like feel.

Is relief in sight?

Normally the jet stream helps move the different pressure systems along breaking one weather system down with another. (See notes to learn more about air pressure). However this summer, the jet stream has been far too north of the US, not helping move the colder air front to the lower reaches of the continental US.

Of course rain bearing low pressure winds are making their way into continental US from the southeast and the southwest. But meteorologists believe that the relief for this air movement will be short lived. It appears that the heat dome may not completely dislodge itself for the remainder of the summer leaving the country reeling with above-average temperatures throught the central and eastern part of the country.

The early heat waves of the summer and the higher spring time temperatures in  both spring and winter could possible be a sign of change in climatic patterns. Could this be the clearest signs yet of global warming? The debate is on.