DIY North Atlantic Oscillation

DIY NAO from reanalysis MSLP data

I thought I would try and add some extra functionality to my MSLP reanalysis application to allow me create my own DIY North Atlantic Oscillation series. It’s the simplest of approaches to NAO that I could find, to calculate it I subtract a grid point at the 37.5N 40W close to the Azores with a grid point in central Iceland at 65N 20W. I’ve also added extra locations such as Lisbon and London to mimic other varieties of the NAO or westerly index if I like. The graph above shows my DIY NAO of pressure differences between the Azores and Iceland, I’ve overlaid that with the five named storms that starts in November 2019, compare this with graph below which show the pukah NAO values. You can see the stormy January- February period clearly enough along with the anticyclonic spell at the end of March. The NAO since mid April has been oscillating around zero, reflecting the run of meridional weather that we’ve been experiencing of late, with the flow either coming from the north or the south.

Hurrell NAO Index data courtesy of NCAR/UCAR

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