Pattern makers

How the jet stream affected our weather last week

Last week, parts of Alaska were warmer than Boston. To understand this, it's worth looking at the two jet stream patterns you may see this time of year:

West to east
A zonal flow jet stream pattern is when air flows on latitudinal lines from west to east, typically resulting in colder air going to the north and warmer air to the south. In this scenario, Boston is colder than, say, Washington D.C., which then is colder than Florida.
The meridional jet stream pattern is an amplified pattern with more temperature extremes and storminess. It brings cold air over places where the jet stream dips and warmer temperatures over areas where the jet stream is bulged northward.
This week
The pattern we experienced was more like the meridional jet stream, as there is a dip in the jet stream and cold temperatures over the eastern half of the nation, warmer in the West. This is why parts of Alaska were warmer than Boston.

SOURCE: AccuWeather

Patrick Garvin/Globe Staff