Associations Between ENSO and AO in Winter

A moderately warm ENSO event seems to be a lock this winter. The multi-variate ENSO Index (MEI) is bullish as are a majority of numerical and statistical ENSO forecast models...even though the Southern Oscillation (data) hasn/t made up its mind.

Conventional wisdom suggests this scenario favors a split-flow regime with an active...moisture-laden sub-tropical jet (STJ) and opportune phasing with the polar jet (PJ) and producing strong cyclogenesis along the eastern seaboard. Add arctic HIGH pressure over eastern Canada and it/s snow-time.

The graphic below was extracted from NCEP/Climate Prediction Center/s ATLAS No. 8 - Relationships Between El Niño-Southern Oscillation and the Arctic Oscillation: A Climate-Weather Link

It shows composite fields for 500 mb geo-potential height...surface temperarture...and precipitation during +ENSO and three phases (positive...neutral...and negative) of the Arctic Oscillation (AO).

Best-case for snow crows during warm ENSO is a negative AO (bottom row of charts).

Otherwise...the mid-level long-wave trof axis is suppressed to the south...(neutral AO) or there/s no trof at all (+AO) and temperatures are above normal with the best moisture contained across the Deep South and the Mississippi and Tennessee River valleys.