30th August BoM ENSO Update - Increasing risk of an El Niño

[P.K.]

CURRENT STATUS as at 30th August 2006
Next update expected by 13th September 2006 (two weeks after this update).

| Summary | In Brief | Details |

Summary: Increasing risk of an El Niño

After several months of mixed signals, a much more consistent pattern of key ENSO indicators has emerged during August. A further drop in the Southern Oscillation Index (SOI), warming over much of the tropical Pacific and a marked decrease in the strength of the Trade Winds, are all indicative of the incipient phase of an El Niño event.

Below average rainfall during late autumn and winter across Australia's southern half, especially in the southeast and southwest, is also consistent with the early stages of an El Niño event. Furthermore, even if El Niño thresholds are not reached, a warming Pacific and a low SOI bias the climate towards drier and warmer than average conditions across eastern and northern Australia for the remainder of 2006. These conditions are reflected in the spring outlooks for rainfall and temperature.

However, to qualify as an El Niño event, the central to eastern Pacific ocean needs to warm by a further 0.5°C over the next two to four months, accompanied by a continued weakening of the Trade Winds and above average central Pacific cloudiness. While most computer models indicate continued warming in the Pacific, forecast values generally do not rise above El Niño thresholds during 2006. However, most of the models have not factored in the developments that have taken place during August. A sustained warming beginning in August is unusual, in that ENSO events typically begin to evolve between March and June.

http://www.bom.gov.au/climate/enso/

[Jim Hughes]

BTW congrats on the NHC link here for your recon stuff.

[P.K.]

I get the impression you are thinking "I told you so" to the BoM.

[marcane_1973]

That tells me what I predicted earlier in the month of August. This will be a below average season with not many Hurricanes at all.

[Jim Hughes]

I get the impression you are thinking "I told you so" to the BoM.

I wouldn't stoop to that level P. K.

[AussieMark]

In Brief

* During August, the changes in all key ENSO indicators are consistent with an incipient El Niño.
* Equatorial Pacific SSTs have warmed in August, with those in the west being close to their El Niño thresholds.
* Subsurface temperatures have also increased. A Kelvin Wave of very much increased temperatures is in the eastern Pacific, propagating towards the South American coast.
* The SOI has fallen to a current (27th August) 30-day value of −16.
* The Trade Winds have been much weaker than average in the second half of August, and were reversed for a time to the west of the date-line.
* Cloudiness near the dateline along the equator has been a little above average so far in August. In general, cloudiness has been increasing in this area since late May.
* Most computer models predict further warming but with temperatures remaining in the neutral range during the southern spring and summer. However, they haven't yet factored in the significant developments of August.