Hot summer after a cold winter
Joe D’Aleo, ICECAP
Washington DC and many cities of the east and south had a warm to record warm summer (while parts of the west had a cold to record cold) with the average for the nation the 4th warmest on record. For Washington, it broke many of the records set in 1980 and 1988. It tied with the number of 90F days set in 1988 and fell just 12 days short of the number of 90F days for the year (a few additional still possible) set in 1980.
A hot summer is very typical when a strong La Nina follows a strong El Nino winter (1999, 1988, 1966) or when record strong arctic blocking in winter fades (1977). This past winter we saw a record for negative Arctic Oscillation (AO) beating out 1976/77 and 1965/66
The summer was 2.2F above normal for the nation, ranking it as fourth warmest. See map:
That matches how much last winter the US averaged below normal (2.2F). Last winter was coldest in the south and southeast (in a few spots, coldest ever). Colder to the south of DC but recall DC and surroundings had a record seasonal snowfall.
Besides 1980, 1988, other hot summers included 1881, where this record from “Andy” out of the Naval Observatory shows an amazing summer following a very cold January/winter. He writes:
I am attaching a rather rare document, Washington DC weather records for the year 1881 taken at the Naval Observatory.
I have highlighted an incredible late summer, early autumn heat wave that got started on August 20th and did not really end until October 4th. There has never been anything remotely approaching the intensity and duration of this heat wave for so late in the year in modern times.
An unbelievable temperature of 108.5 was recorded on the very late date of September 7th! Also the average September average high temperature of 90.8 dwarfs anything you can find in recent years. One could argue that the site or thermometer might reflect a warm bias. Examining the data, June was actually quite cool and July was about average. And back then, no one was pushing an agenda!
The summer this year was characterized by hot days with high humidities and thus very warm nights. Nighttime lows were especially above the normal. Ironically many of the same areas with warmth this summer had very cool summers the last two years with a record/near record cold July in 2009.
That was consistent with a summer after a La Nina winter, one with low solar and high latitude volcanic activity. Last summer and last winter we were told that was weather not climate. This makes any claims that a hot summer this year is indicative of a warming world disingenuous. With La Nina coming on, look for a cool summer again next year. With a negative PDO look for colder years ahead. This will accelerate when the Atlantic cools. The active hurricane season will remove some of the heat built up in the Atlantic by the El Nino suppressed activity last year and reduced winds (mixing) and increased sunshine with a suppressed jet stream, weakened suppressed subtropical high pressure due to record blocking this past winter.