The ice is nice and thick at the North Pole this Christmas Eve. Santa and his team will be able to use the sled without adding pontoons.
Neither global warming nor El Nino will stop The Jolly One from making his appointed rounds. Al Gore startled many observers at the recent United Nations climate conference in Copenhagen when he claimed there is a 75 percent chance that the Arctic sea ice will nearly disappear in summer within five to seven years. That projection is outside the mainstream of scientific opinion, which currently calls for such conditions to arrive around 2030, assuming computer models of the climate prove to be accurate. In the meantime, the polar ice pack is repeating the pattern of recent years, in which the dark autumn allows it to recover, in area if not in thickness, to something like its historic seasonal extent.
El Nino, which is marked by unusually warm sea surface temperatures in the central and eastern tropical Pacific Ocean, is not known to be much of a factor in Arctic weather. It has much more substantial impacts in tropical and temperate latitudes. The moderate El Nino that began early last summer is pretty typical of the breed.
As I noted here last June, El Nino frequently produces below-average hurricane activity in the North Atlantic. There were nine named tropical storms in the Atlantic this year, including three hurricanes, two of which became major hurricanes. When the season began, forecasters were calling for nine to 14 named storms, of which four to seven would become hurricanes, including one to three major cyclones. Reality came in at or just below the low end of the official predictions.
El Nino also often produces strange autumn and winter weather in the Lower 48 states, and we are seeing that, in abundance.
An active subtropical jet stream, typical of El Nino, is generating frequent storms along the Gulf coast. This helped produce Houston’s earliest snowfall on record on Dec. 4, as well as phenomenally wet weather in much of the Southeast. By mid-December, New Orleans had recorded more than 22 inches of rain for the month, more than doubling the previous record for the entire month. A foot of rain fell in just one evening last week in Hallandale, Fla., a few miles south of Fort Lauderdale. In Georgia, a friend reports that Santa is going to have to rent a boat to keep his date with her kids.
Meanwhile, Burlington, Vt., tied its record for the latest first snowfall of the season, on Dec. 7. Though October was cold in the Northeast, November was very warm — a pattern I have noticed in previous El Ni√±o years.
In winters with powerful El Ninos, cold air tends to get locked at high latitudes, producing mild weather in the North Central and Northeastern states. But when El Nino is more moderate, as is the case this year, the cold air can periodically break through. If the cold coincides with one of those strong southern storms, you can get a lot of snow — like the one to two feet that fell from Virginia to Massachusetts last weekend.
A cold wave that gripped western Europe this month, producing unusually heavy snows in England and France and knocking out trans-channel train service, is not unrelated to our weather, either. Simultaneous wintry weather on the U.S. East Coast and in western Europe is often tied to what meteorologists call the negative phase of the North Atlantic Oscillation, or NAO. Basically, a negative NAO is a period of weakening in the high-atmosphere westerly winds that are driven between a semi-permanent cyclone near Greenland and an opposing anticyclone over the Azores. The weaker winds permit polar air to move southward over the United States and Europe. At the same time, East Coast storms are blocked by other stagnant weather systems from moving out to sea, so they migrate up the coastline instead. That is what happened in last weekend’s nor’easter.
The NAO usually reverses after a week or two. When it does, mild air from the Pacific and Atlantic will flood across America and Europe, respectively, and the wintry weather will let up.
The NAO is a big weather driver every winter, not just in El Nino years. El Nino is simply adding some interesting quirks to the season.
This autumn reminded me of another El Nino season, the winter of 1972-73. I remember sitting in my classes at the Bronx High School of Science, watching snow fall in mid-October, which is highly unusual in New York City. A big Thanksgiving snowstorm buried the interior Northeast that year, though we only saw a thin coating near the coast. The rest of the winter brought a series of storms, but it was never quite cold enough to snow. The city recorded only 2.8 inches of snow that entire winter, which is its lightest snowfall season on record. In fact, Pensacola, Fla., had almost as much snow that year (1.9 inches) as Central Park.
So if you see snowflakes on the palmettos or bare grass in New England this winter, don’t assume global climate change is responsible. There has been strange weather as long as there has been weather.
Happy holidays and safe travels to all, no matter what mode of conveyance you choose.