La Nina And The Rest Of 2011

[damianslaw]

To those more knowledgeable than myself, when is the current La Nina expected to peak? Has it peaked already? Is it expected to weaken dramatically or slowly and when is likely?

Are we then likely to see a neutral phase of the ENSO? or revert to another El Nino?

Do we want to see a rapid weakening of La Nina if we are to see a nice mild spring and warm summer??

Lots of questions.. any answers most welcome

[Guest]

I wish

[Alex]

I believe it's forecast to start dropping but it's unlikely to get to a neutral state until the autumn more like a weak one during the summer. So chances are in my book that august may be nice but I'm worried about the first part of summer.

[knocker]

Latest from the Australian Bureau of Meteorology issued today.

Australia continues to feel the effects of one of the strongest La Niña's on record. During La Niña events, tropical cyclone numbers are typically higher than normal during the November to April period, while summer daytime temperatures are often below average, particuarly in areas experiencing excess rainfall.

Climate indicators of ENSO continue to indicate a strong, mature La Niña, although there are clear signs the event has passed its peak. Pacific Ocean temperatures have increased, especially below the surface, while atmospheric indicators such as the Southern Oscillation Index (SOI), trade winds and cloud patterns have eased from their peaks reached about a month ago.

These observations are consistent with long-range forecast models surveyed by the Bureau which show the Pacific gradually warming during the southern autumn. Given that March to June is the ENSO transition period, there is a spread among the model predictions for the middle of 2011. The most likely outcome is for a return to neutral conditions, but there is a chance of La Niña persisting for the rest of the year.

The influence of the Indian Ocean Dipole (IOD) on Australian rainfall is limited during the months from December through to April.

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

[Gavin P]

We're at the spring predictability barrier right now, which mean no model is really able to get a handle on where ENSO goes next. It will almost certainly weaken over the next few months, but remain an influence up to summer. Beyond that we could get a double dip La Nina with a second peak occuring through autumn and winter 11/12 (I think this is the most likely scenario, personally) We could keep weak La Nina conditions going through autumn and winter 11/12, we could go to neutral ENSO conditions or even have an El Nino.

[knocker]

We're at the spring predictability barrier right now, which mean no model is really able to get a handle on where ENSO goes next. It will almost certainly weaken over the next few months, but remain an influence up to summer. Beyond that we could get a double dip La Nina with a second peak occuring through autumn and winter 11/12 (I think this is the most likely scenario, personally) We could keep weak La Nina conditions going through autumn and winter 11/12, we could go to neutral ENSO conditions or even have an El Nino.

Given that no model is really able to get a handle on where ENSO goes next I'm quite interested on what you base your statement "Beyond that we could get a double dip La Nina with a second peak occuring through autumn and winter 11/12 (I think this is the most likely scenario, personally)?

[Gavin P]

Just a hunch. We had double La Nina peaks in 98-99 and 99-00 and again in 74-75 and 75-76 and again 54-55 and 55-56, so its something that happens quite regularly.

Edited February 2, 2011 by Gavin P

[damianslaw]

Just a hunch. We had double La Nina peaks in 98-99 and 99-00 and again in 74-75 and 75-76 and again 54-55 and 55-56, so its something that happens quite regularly.

Mmm mixed thoughts about such prospects happening if those yearly analogues are anything to compare the likely conditions we will experience.

99-00 brought a very poor winter for snow and cold, though the summer of 99 saw some very warm sunny summery weather at times, winter 75-76 was another poor one for snow and cold but came on the back of an excellent summer and winter 55-56 saw the very cold Feb, don't know what the summer delivered I don't think it was particularly special.

So potentially good for the summer but likely poor for most of next winter.in terms of snow and cold. However, none of the above years saw the exceptional cold start to winter we had at the end of last year - so perhaps not worth bothering comparing with these years..

[Snowyowl9]

2008 was the last la nina and we had a much colder snowier latter half of March and first half of april.

1999-2000 gave more heavy snow in april.

Was 1989 a la nina too another winter came in april.

[Weather-history]

2008 was the last la nina and we had a much colder snowier latter half of March and first half of april.

1999-2000 gave more heavy snow in april.

Was 1989 a la nina too another winter came in april.

Posted this a fortnight ago

Looking back at past La Nina's and cold spells in the spring if anything

1903-04: cold March

1906-07: -

1908-09: cold March

1916-17: was a severe winter which extended well into April

1920-21: -

1924-25: cold March after mild winter

1928-29: cold April after severe winter

1931-32: cold February-April period

1938-39: -

1942-43: unusual snow event in May in north

1949-50: notable late season snow event in south

1954-55: cold extended into March, late season snow event in May

1955-56: cold April

1964-65: very wintry first half to March

1970-71: Cold March

1973-74: -

1974-75: wintry spells in the spring

1975-76: cold March

1988-89: cold April

1995-96: cold spells in the spring

1998-99: notable wintry spell in April

1999-00: first half of April was cold

2000-01: wintry spells in March and April

2005-06: wintry March until last week

2007-08: wintry spells in late March and early April

2010-11: ?

[Snowyowl9]

Thanks very much for those very informative stats as ever MR Data.

I`m going to book these dates down this time.

I didn`t know 2005-06 was one,nor 95-96 come to that.

[summer blizzard]

La Nina peaked in September as the second strongest La Nina on record. It then weakened before strengthening again during January (probably why we lost the sustained cold).