Kevin Myatt is The Roanoke Times' weather columnist.

kevin.myatt
@roanoke.com
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Weather with Kevin Myatt

Recent columns

• We got graupel, but not on official record
• Moisture could get caught up in cold blast
• Forecast for Weather Journal: Partly print, with frequent Internet
• Column archive

Read the Weather Journal blog

• Sprinkles or flurries possible Tuesday, but maybe something bigger for the weekend?
• For now, it looks like a quiet, mostly mild week ahead for SW Virginia
• Coldest morning of winter so far likely across much of Southwest Virginia; Tuesday precipitation looking doubtful
• Weather Journal blog

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Weather is a study in contrasts.

Friday's Roanoke Times included an Associated Press article about how worldwide ocean temperatures in July were the warmest they have been in 130 years of record-keeping.

It also included a column of mine that briefly noted the coolest July on record, dating to 1895, in six states just to our north and northwest, something I delved into in greater detail on Aug. 12.

The National Oceanic and Atmospheric Administration's latest monthly climate statement vividly illustrates air-temperature contrasts around the world that were present in July. It noted temperatures in July of 4 to 7 degrees Fahrenheit above normal in Europe, northern Africa and western North America, while at the same time temperatures were 4 to 7 degrees below normal over the eastern United States, central Canada and southern South America.

Air masses, rather than spread out evenly with moderate temperatures, tend to lump together in pockets of extreme warmth and cold. The various jet streams that drive storms around the world thread around these pockets of heat and cold like belts around pulleys.

Warm oceans can heat air temperatures in certain regions, but they can also provide more energy for large storm systems, and not just those of a tropical nature.

Boundaries between cool air temperatures over land and warm areas over the ocean are ripe for the development of large low pressure systems that can spread wide swaths of heavy rain and/or snow. That's something to keep in mind as we move toward fall and winter.