|Detailed NAO 12z GFS forecast from today (Nov. 1)|
|Latest NAO Ensembles|
The first official cold outbreak of the winter may be coming sooner rather than later as the ensembles that forecast for the NAO appear to be aiming for a negative trend later this month.
First off, many of you are probably wondering what the NAO is.
The NAO, in a nutshell, is the pressure differences between a semi-permanent low pressure system over Iceland and a semi-permanent high pressure system over the Azores. The higher the difference: the NAO goes positive. The weaker the difference: the NAO goes negative and can persuade cool areas of air to be inserted into the US. The latest 12z GFS shows a massive low pressure system giving way to brutal air from Canada about 312 hours out. Since that is in the long range GFS time frame, it will be changing.
First off, here's what this massive low and following cold look like from the Atlantic frame.
NOT VALIDATE AT THE SURFACE. They do provide forecasters with a general idea on if a region will be cold at the surface.