As if the general strike in Venezuela and the crisis in Iraq weren't enough, America's energy consumers have a fresh threat to worry about - an all-out invasion from the north country.

It looks as if the Arctic air that began pouring into the country late last week could lock the eastern half of the nation into its most severe and prolonged cold spell in seven years. The frigid temperatures are likely to persist through the month, said Joe Bastardi, the long-range forecasting guru at Accu-Weather Inc.

Expect more blizzard footage from Buffalo, a frigid siege in New England and a deep chill all the way into the Southeast.

And expect to pay a whole lot more to heat your house this winter than last year.

Crude-oil prices slipped a bit last week, but don't be fooled.

The Energy Department's Energy Information Administration estimates that for a variety of reasons, the average U.S. household will end up spending 43 percent more on heating oil than it did in the last heating season - which was a mild one - and 34 percent more for natural gas.

And that forecast was based on an assumption of normal temperatures! If it gets truly cold for a long period, you'll end up paying even more.

"It could really generate some high spot increases," said Dave Costello, an energy-administration economist.

Where have you gone, El Niño?

If this winter has proved anything, it's that El Niño isn't everything. El Niño, that periodic warming of surface waters in the equatorial Pacific, is still out there brewing away. It is expected to continue cooking along moderately through March. So far, however, it has been playing a tepid second or third banana to overpowering forces in the North Pacific and the North Atlantic.

One of the extraordinary features of the winter so far has been the consistency of the North Atlantic Oscillation. Unlike its close cousin, the Arctic Oscillation, which affects weather across the Northern Hemisphere, the NAO primarily affects Western Europe and the northeastern United States.

The NAO is monitored by an index that measures pressure differences between Greenland and the Azores. When the pressures in Greenland are higher than they are in the Azores, the index is said to be negative, and cold air tends to ooze out of the frozen northlands and into the Northeast. With few exceptions, the index has been consistently negative since October.

That's a big reason the government's forecast of a mild winter in the Northeast isn't panning out so far. For now, NAO forecasts are good only for about a week in advance and aren't much use in seasonal outlooks.

"NAO is something we can't forecast, and it certainly plays a much larger role in the Northeast than El Niño," said Mike Halpert, a climate center meteorologist.

His colleague, Vernon Kousky, the center's El Niño expert, said that the NAO is working in tandem with a pattern in the North Pacific. A strong area of lower pressure, or lighter air, has taken hold in the Gulf of Alaska. In response, a strong area of higher pressure has formed to the south, along the U.S. and Canadian west coasts.

Air blows clockwise around centers of high pressure, so areas to the east experience north and northwest winds, and it is those winds that are delivering cold air into the eastern United States.

A strong El Niño, such as the one in 1997-98, can dominate weather across the nation, but when it is weaker, such as this one, it becomes only one of the factors governing the winter.

"It allows the natural variability in the higher latitudes to take shape," said Kousky. "The higher latitudes are bigger players."

Meteorologists simply lack the case studies to know how any given El Niño will interact with those other players.

"We don't have enough El Niño events with the different flavors of El Niño," said Kousky.

This particular winter has been nothing like recent El Niño-influenced winters. In fact, more snow (11.5 inches) has fallen already at Philadelphia International Airport than in the last two El Niño winters combined (10.6). And the real snow season is just starting.

It is also worth noting that we just had the snowiest December since 1966.

These developments ultimately will come home to you via your fuel bills.

Oil consumption was more than 6 percent higher in December 2002 than in December 2001, according to the Energy Department. The data are preliminary, but that would be a record increase.

So get out the sweaters and blankets. And the checkbook.