winteroutlook2004-05c.jpg courtesy of NOAAThe NOAA Climate Prediction Center released its winter weather outlook yesterday. It can be said with a great deal of certainty that the outlook for New York and the rest of the northeast is for equal chances of above, below, or near normal temperatures and precipitation from December through February.

Huh?

At first glance our winter outlook seems pretty silly. Take a look at the outlook for the country as a whole, and the conditions behind the outlook, and it begins to make much more sense. If you were to shut off the Sun, our atmosphere's energy would dissipate within a few weeks. The oceans, however, have enough energy to do their thing for years to come. That means if you want to predict how the atmosphere will behave more than a few weeks into the future you have to look to the oceans because there is no information in the atmosphere upon which to base a forecast. In the oceans, specifically the equatorial central Pacific, a weak-to-moderate El Niño is likely to form and stay around through the winter. An El Niño of this expected magnitude pushes the jet stream northward in the Northwest, bringing them warmer, drier conditions, and southward in the Southeast, bringing them colder, wetter weather. New York is stuck on the cusp of the jet stream changes, hence our wishy-washy forecast.

But, wait, there's more! The jet stream over the eastern U.S. is also affected by the North Atlantic Oscillation (NAO). The NAO is like a giant see-saw of atmospheric mass between the tropics and poles over the Atlantic Ocean. Our winter weather greatly depends on how that mass is distributed. Unfortunately, we can't predict the NAO more than a couple of weeks in advance, so we're still left with a wishy-washy winter outlook.

Want to know more about El Niño, the North Atlantic Oscillation and how they affect our weather? This Saturday is Open House for Columbia University's Lamont-Doherty Earth Observatory. There will be exhibits, talks, demonstrations, and hands-on science covering the breadth of research done at the Observatory. The Observatory is located in Palisades, NY so you'll have to drive, bicycle, or take a bus to get up there. Gothamist usually works at the Open House but we are unable to be there this year because part of our head is missing. Don't let our absence stop you!