Tag Archives: SOI

2009 SOI so far refuses tango with El Nino

The large climate groups including NOAA in the USA, are predicting an El Nino event in 2009.

The Australian Bureau of Meteorology (BoM) said on 8 July “Leading climate models indicate that warming of the Pacific will continue for the next few seasons, with very little chance of the current development stalling or reversing.”

It is is noteworthy that the Southern Oscillation Index (SOI) which should be trending towards negative monthly values for an El Nino – still shows a positive 30 day average value of 8.38 as of the 18th July 09. SOI information.

The BoM discuss effects of the “classical” or “canonical” ENSO events since 1900 and I have plotted the month by month SOI numbers showing development of those El Nino events – adding in 2002 and 2006. We can compare 2009 with the series of strong El Nino’s and it is clear that the SOI in 2009 is too positive for us to be expecting a “canonical” El Nino.

2009 SOI compared strong El Nino years

I have put in a nominal 0 value for July but note that as I write the 30 day average at 18th July is 8.56.

So it looks unlikely we will see a “canonical” El Nino start in 2009. But hey !!, we might see a weaker event.

Interesting too that the TAO SST map for the El Nino regions for the 17th July seems to show the anomaly weaker than the BoM inset shows re the 8th.

NOAA TAO SST anomalies

The BoM say their next comment is on 22nd July – it will be interesting to examine the nuances in what they say – in the light of hard data.