On Sunday, July 29, 2018 at 12:18:26 PM UTC-4, Jim wrote:
I have spent a few days on Google looking for a description of what "N" means on Constant Pressure Charts.

The best I have found is that "N" identifies an area of little or no vorticity. Is this right?

I think X means an area of positive Vorticity advection and the letter N means negative Vorticity advection.

see https://www.weather.gov/source/zhu/Z...vorticity.html .