Winter '09 / '10 - SOI - October

-14.7 and falling!

October registers a rather robust value compared to historical values for the month (data) and a sharp decline from September (+3.9).  Last month's SOI is almost two standard deviations (2STD = -19.5) below the period of record normal. 

The Southern Oscillation index (SOI) has been oscillating about 0 since early spring...in contrast to Multivariate ENSO Index (MEI) which has been bullish on +ENSO during the same period.

With the addition of October's SOI...the 'Top-5' analog years (using a least-squares and coefficient of determination method) are...

1 - 2001 (also top-ranked analog year for NHEMI snow cover and 4th for NOAM snow cover)

2 - 1984 (also 5th rank for NOAM snow cover)

3 - 1999 (also 3rd rank for NOAM snow cover and 5th rank for NAO)

4 - 1963

5 - 1967

SOI turned positive during the '01 / '02 winter.  Not a good match given the widespread expectation for a moderate +ENSO event.

1984 would be a slightly better analog.  QBO was east...as will be the case this winter; however...MEI indicated -ENSO conditions.

1999 was a moderate -ENSO winter.

1963 has a good association with MEI...which was moderate +ENSO.  QBO was west and  PDO negative.

1967 was not quite a moderate -ENSO winter.

Not a lot of corroborating support for choosing SOI as a leading indicator for the upcoming winter.