Preliminary SOI - December '06

(Updated below)

The SOI is a 30-day moving average and with one day to go before the end of the month the index comes in near -4.9. After flirting with zero during the last few days of November and into the middle of December...by month/s end the SOI had been in steady decline.




+ENSO Lives...but for how long?

More evidence that +ENSO is holding its own is found in outgoing long wave radiation (OLR) anomalies. Decreased OLR caused by increased cloudiness produced by deep...moist convection is typical during +ENSO events. EEBE, increasing OLR (decreasing cloudiness) would suggest the current +ENSO is fading...but the data for December do not suggest that is happening.

Red areas depict cloudy areas where OLR is below climo.


December - Week 1


December - Week #2


December - Week #3


December - Week #4



Working against the current state are 1) the trade winds that have returned to near normal 2) cooling sub-sfc water...and 3) the continued steady decline in region 3.4 SSTAs. Weekly US and AU SSTA data cover different 7-day periods. The US lags AU by ~4 days.


Weekly anomalies through 12/24
US 1.4 1.3 1.2
Au 1.3 1.2 1.1

A steady decline...indeed.



Waters are still warm and producing plenty-o-convection...for now. The trade winds appear to be working against an eastward propagation of the warmer SST near 180°. It/s only a matter of time before the fuel in region 3.4 is exhausted and it/s over.

Update: End-of-month SOI was -2.4.