New Year, New Weather Pattern. Still Driven By El Nino and the Hot Oceans.

JETPATTERN

The weather pattern is finally changing. We’ve seen 5-6 weeks of extreme warmth in the Eastern U.S., floods and tornadoes in the south, and in the West, cold and snow. The new year will be different, but it will still be a rather mild and wet El Nino pattern, just not as warm as it has been in Eastern North America. The polar jet will dip down closer to New England, and the strong ridge over the Southeast will weaken, while warmer air moves into Western Canada and Alaska. This “omega block” in the west means the pattern will likely lock in for sometime.

The short of it is this: We will still see a wet and stormy pattern for the South and the East, but it will not bring the record warmth we saw in December. The weakening ridge in the East also will allow the polar jet to provide some cold Arctic air at times in the Northeast U.S. so some winter snows are probable. FYI: The Polar jet forms on the boundary between the Arctic air, and less cold but chilly air to the south. A strong sub-tropical jet stream is almost always associated with a strong El Nino.

The long-range pressure pattern called the NAO in the Atlantic is also indicating the likelihood of colder air in the East, as it is forecast to go into a negative phase in early January. It has been strongly positive for weeks and a negative phase usually brings colder air to the Eastern U.S.

gfs_nao_bias

This is a summary of several long-range model runs and you can see some are more strongly negative with the NAO than others. The wider circles is an average.

 

 
One thing to remember is that the oceans world-wide are the warmest on record and this means a lot more water vapor than usually is evaporating into the atmosphere from them. More serious flooding is likely a good bet, and perhaps in places that have so far escaped.