Astronomical summer ended today at 4:44 p.m. E.D.T. However, if you’ve been monitoring the weather, you had clues this transition to autumn was underway weeks ago.
One hint was the dearth of tropical storm activity in the Atlantic Ocean basin. Thanks to many factors, including a larger than average African dust field and stronger westerly winds at high altitudes across the tropical Atlantic, even warm sea surface temperatures couldn’t make the hurricane/tropical storm season kick into gear.
Another hint was the rather limited heat wave activity. While parts of the Desert Southwest and Southern Plains baked in high temperatures, much of the rest of the Nation didn’t. For example, even with an end of August hot spell across the northern Plains, the area still reported near to slightly below average temperatures for the month (Fig. 1), according to NOAA’s National Climatic Data Center.
For the Nation as a whole, meteorological summer (which typically starts about 3 weeks before astronomical summer, hence the months of June, July and August) was warmer (by 1.2 degrees F) than the twentieth century average.
August temperatures were 1.0 degree F above the 20th century average, making August 2013 the 28th warmest such month on record for the contiguous U.S, given some 130 years of data.
September has already seen well below average temperature readings from the northern Plains across the Great Lakes into New England. Minneapolis, MN and Boston, MA are among cities that have already reported morning lows into the middle 40’s. Albany, NY has seen its readings dip into the upper 30’s. Frost warnings have pock-marked the meteorological landscape, even before astronomical summer came to an end.
Significant storminess has arrived in the Aleutian Islands and southern Alaska. This pattern also allowed storminess to sneak southward along the U.S. and Canadian West Coasts. Forecasts for the next week bring a major winter type storm ashore in western Canada. Rainfall in Seattle, WA this month is already at 60 percent above September average.
Finally, arctic sea has started to reform after a summer minimum. This year’s sea ice loss was substantially less than last years, thanks to more cloudiness and colder air masses that affected the region.
© 2013 H. Michael Mogil