I'm working a model of one of the fastest ocean oscillations, the North Atlantic Oscillation (NAO). The NAO can show up to 2 strong cycles per year in comparison to ENSO, which has El Nino peaks every 2 to 7 years

It appears that the model for NAO is not as sensitive to annual or semi-annual impulses like all the other behaviors (ENSO, QBO, PDO, AMO, IOP) require for modeling. So instead of an impulse, it appears to more directly correspond to monthly tidal variations.

![](https://imagizer.imageshack.com/img923/8181/xjA7Ww.png)

This is promising. The time-series is dense enough that cross-validation may work well here.

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*New/Edited follows*

This is a cross-validation, trying to overfit an interval from 1980 to 2000 and observing how the out-of-band intervals respond -- quite stable.

![fit](https://imagizer.imageshack.com/img922/1354/NppJ53.png)

The non-impulsed lunisolar tidal forcing is identical for ENSO and NAO, which removes many degrees of freedom from the fitting process.

![forcing](https://imagizer.imageshack.com/img923/1213/gPGBfx.png)

The LTE modulation for NAO is quite strong, approximately that of used in PDO in the prior comment #309. Perhaps this is expected as both NAO and PDO are northern/higher latitude behaviors

![mod](https://imagizer.imageshack.com/img923/1534/aGC6Y4.png)