Wednesday, October 24, 2012

Australian Bureau of Meteorology puzzled by El Nino fizzling out

(WeeklyTimesNow) The Bureau of Meteorology's latest wrap up on the El Nino Southern Oscillation says ENSO continues to show neutral values.

National Climate Centre climatologist Catherine Ganter says this is unusual behaviour for El Nino at this time of year. Says Ganter:
"It is a bit strange. The fact that El Nino has retreated so late is unusual."
Ms Ganter says since winter and spring the atmospheric indicators had remained neutral, but now the ocean indicators were tending more towards neutral.
"At this time of year El Nino tends to be locking in and consolidating rather than retreating. However, the dry weather system could not be rule out completely.

At this stage the climate models say sea surface temperature remains in the Pacific’s late retreat to neutral considered unusual Indicators of the El Niño Southern Oscillation (ENSO) continue to show neutral values. Temperatures in the tropical Pacific Ocean generally remain near average, after being close to El Niño thresholds in late winter. Atmospheric indicators such as the Southern Oscillation Index (SOI) and tropical cloud patterns have persisted at neutral levels through much of the southern winter and spring.

The retreat from El Niño thresholds over the past several weeks is considered highly unusual, as September–October is typically the time when developing El Niño (or La Niña) events consolidate and mature. While some chance of El Niño remains, climate models surveyed by the Bureau of Meteorology suggest sea surface temperatures in the tropical Pacific Ocean are likely to be warmer than average, but stay within the neutral range for the rest of 2012 and early 2013.

This year has seen a positive Indian Ocean Dipole (IOD) event, which partly explains the unusually dry conditions experienced over much of Australia in recent months. Outlooks from the Bureau’s climate model indicate the IOD is likely to return to neutral values over the next month. A positive IOD is typically associated with decreased winter and spring rainfall over parts of southern, central and northern Australia, but declines in both value and influence with the onset of the Australian monsoon at the start of summer.

Forecasters surprised by El Nino turnaround

(ABC News)The bureau's manager of climate prediction services, Dr Andrew Watkins, has changed the forecast.

"Come September, all of a sudden, the temperature started to cool down, the trade winds started to become a little bit enhanced, and the cloud patterns and other indicators like that headed away from El Nino," he said.

"So this is what we're looking at as climatologists, giving us the heads up about what may happen over the next few months, and indeed what we're seeing now is a backing off from those El Nino thresholds."
Dr Watkins says they are not sure why there has been a cooling down.
"It actually is quite a unique situation if we end up not going into an El Nino event," he said.

"It'll sort of be the biggest turnaround that we've actually seen in our records going back to about 1950, so quite unprecedented."
Warming in the Pacific Ocean as recently as August pointed to another El Nino weather event, but the forecasters witnessed a huge turnaround.

While it is good news, they say they have never seen conditions change so quickly.

"When we go and look at our records of ocean temperatures in the tropical Pacific, we really haven't reached the level that we reached, say, in early September, and then turned around away from El Nino," Dr Watkins said.
"Every time we've got that close to an El Nino, it's actually settled in and indeed September, October is the normal time things bed down with these events.

"We actually haven't seen a turnaround quite like that."

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