NORFOLK -- Winter doesn't officially start for more than a month, but Hampton Roads has already had a taste of cold temperatures.
Is it a sign of things to come?
The National Weather Service says the upcoming winter for the mid-Atlantic states is, well, hard to predict right now. It could be colder or warmer than usual and it could be wetter or drier than usual. There could be snow or there might not be.
Some of the uncertainty comes from waters in the tropical Pacific that started warming earlier this year, but now the warming’s stalled.
There are plenty of other weather situations far from Hampton Roads that could impact us.
Recent studies suggest a link between Siberian snow cover in autumn and the amount of cold air outbreaks in the eastern US. This year's more widespread Siberian snow, in theory, will strengthen the high pressure over northern Asia, reinforcing an upper air pattern which steers frigid air southward from the Arctic all season.
Looking back at Fall 2011, there was less Siberian snow cover so the polar jetstream stayed north for the most part. That gave Hampton Roads a relatively mild winter season.
Another pattern to watch is the North Atlantic Oscillation, a periodic variation in the strengths and positions of a low system around Iceland and a high at the Azores. In a negative phase, cold air builds up over Canada and moves south, creating a colder and drier winter. That’s what helped steer Sandy along the east coast and into the northeast U.S. and brought another nor'easter a week after Sandy hit.
Right now, the North Atlantic Oscillation is trending more positive, which draws developing storms east across the Atlantic Ocean.
By early December, expect a negative pattern again, so the eastern United States would tend to be colder with more chances for snow. Snow? Kids love it; drivers hate it.
The bottom line? The annual winter forecast calls for a colder season than last year, which is actually closer to normal for Hampton Roads. And there’s a good chance for at least one significant snowstorm.
To highlight the importance of being winter-ready, the National Weather Service and the Va. Dept. of Emergency Management have set aside Dec. 2-8 as Winter Preparedness Week.