30 December 2015
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. We’ve had an omega block in the Western U.S. and East Pacific for some time now, but it’s shifting eastward, and this will bring changes.
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’s forecast to go into a negative phase in early January. The NAO has been strongly positive for weeks, and a negative phase usually brings colder air to the Eastern U.S. The interaction between this colder air, and the strong El Nino induced subtropical jet, may very well bring some very stormy weather to the Mid-Atlantic and the New England states.
One thing to remember. 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. This bizarre weather has been the result of both El Nino and the warming climate.
All in all, from what I am seeing on the weather charts as we leave 2015, is strong indications that January may well be one to remember.