Is anyone besides the Australian Weather Service predicting that the current La Nina may have peaked?

La Nina is one half of the El Nino Southern Oscillation (ENSO), the other half being El Nino. El Nino episodes are somewhat easier to predict than La Nina ones as they tend to follow a slightly more regular pattern.

The present La Nina comes on the back of the strongest El Nino since 1998 and quickly manifested itself into a strong episode. The strength of ENSO episodes is measured on the Oceanic Nino Index (ONI), values greater than plus one indicate strong El Nino conditions and values less than minus one are strong La Nina’s. The latest ONI is minus 1.4, this is only marginally lower than last months value and could give the impression that the episode is peaking.

However, La Nina’s often have an extended peak period and it’s not uncommon for there to be an easing of conditions followed by a second onset.

The most recent comparable event began in 1997 and saw the establishment of the strongest El Nino on record. Just as has happened recently, this rapidly gave way to La Nina conditions; values then were very similar to the present values. After a few months they too had reached minus 1.4, conditions began to slowly ease for the next six months but then returned and peaked at minus 1.6 after a further six months. In all, that episode lasted from July 1998 to June 2000.

Another very similar event began in 1972 with a La Nino episode very similar to the one we had recently, this also rapidly gave way to La Nina conditions with very similar values to those witnessed recently. This episode also had two distinct troughs to it, the first being an ONI of minus 2.1 after 8 months and the second being minus 1.7 after 32 months.

For comparison purposes the last 10 ONI values are…

1.7 / 1.5 / 1.2 / 0.8 / 0.3 / -0.2 / -0.6 / -1.0 / -1.3 / -1.4

This compares to the same stage of the ENSO phase in 1972 with values of…

2.0 / 2.1 / 1.8 / 1.2 / 0.5 / -0.1 / -0.6 / -0.9 / -1.1 / -1.3

Which was then followed by…

-1.4 / -1.7 / -2.0 / -2.1 / -1.9 / -1.7 / -1.3 / -1.1 / -0.9 / -0.8 -0.6 / -0.5 / -0.5 / -0.7 / -0.9 / -0.7 / -0.6 / -0.6 / -0.7 / -0.8 / -0.9 / -1.1 / -1.2 / -1.3 / -1.5 / -1.6 / -1.7 / -1.7 / -1.6 / -1.2 / -0.8 / -0.6 / -0.5

It doesn’t always follow that there will be a protracted La Nina, there have been occasions when conditions have quickly returned to a neutral phase. At the moment it could go either way – either over in a few months or dragging on for ages.

Personally, I suspect that the peak is now or soon, conditions will lessen over the next three or four months but remain in a moderately strong phase (less than –0.5) before returning to neutral values (between –0.2 and +0.2) some time around next June.

Here are some model forecasts…

http://www.bom.gov.au/climate/coupled_model/poama....

http://gmao.gsfc.nasa.gov/cgi-bin/products/climate...

http://www.cpc.ncep.noaa.gov/products/analysis_mon...

http://www.ecmwf.int/products/forecasts/d/charts/s...

http://www.metoffice.gov.uk/science/specialist/sea...

http://ddb.kishou.go.jp/climate/ElNino/elmonout.ht...

Probably not

I'm not.