El Nino Over...For now

[Guest Fred Bear]

Looks like the drought may slowly be breaking folks. Thank God too. The farmers have been doing it very tough and I have been unlucky to experience the effects first hand. Here is some info via the Bureau of Meteorology:

 

ENSO Wrap-Up

 

A regular commentary on the El Nino-Southern Oscillation

 

Contents

 

* Current status.

 

* El Niño - what it is and what it isn't.

 

* El Niño education.

 

* How El Niño affects Australia.

 

* Some useful links.

 

CURRENT STATUS as at 7 March 2007

 

Next update expected by 28th March 2007 (three weeks after this update).

 

| Summary | In Brief | Details |

 

Summary: Pacific Ocean continues to cool

 

The eastern equatorial Pacific Ocean has continued to cool rapidly following the demise of the El Niño event. While current conditions are neutral, the cooling has increased the likelihood of, though not guaranteed, a switch to La Niña conditions over the coming months. The Trade Winds have mostly been close to or somewhat stronger than normal since December, the SOI has been neutral for three of the past four months and is now close to zero and cloudiness has shifted to the western Pacific. There would now appear to be little chance of a return to El Niño conditions in 2007, with a continuation of neutral, or a switch to La Niña conditions, the more likely scenarios.

 

What does this mean for Australia? Firstly, whilst a rapid cooling of the Pacific at the end of the El Niño would normally be associated with a return to more normal, or in some cases above normal rainfall patterns, it is unlikely such rain will be enough to make up for the long-term drought through eastern and southern Australia. This particularly applies to water supplies, which in some instances require several years of healthy rainfalls to recover to a satisfactory level. Nonetheless, we continue to be cautiously optimistic that there will be a general easing of dry conditions in drought-affected areas over the next one to two seasons.

 

A La Niña in 2007?

 

The chance of a La Niña developing in 2007 is thought to be higher than the long-term average (which is about one in five or 20%) because (a) they have a tendency to follow an El Niño; (b) the El Niño has decayed somewhat earlier than normal thereby giving time for a La Niña to begin developing during the critical March to June period; and © a large pool of cold sub-surface water remains in the central to eastern tropical Pacific Ocean and is starting to affect surface temperatures in the region. La Niña events are generally associated with wetter than normal conditions across much of the eastern half of the country from about autumn. Computer models generally indicate further cooling in the Pacific Ocean.

 

Map showing recent winds and temperatures in the tropical Pacific. Click on the map for a larger version. From NOAA/PMEL/TAO website.

 

From the NOAA/PMEL/TAO website.

 

In Brief

 

* Equatorial Pacific SSTs have further cooled and anomalies are below zero in the eastern equatorial Pacific.

 

* Negative subsurface anomalies have strengthened and reached the surface in the eastern Pacific.

 

* The SOI has a current (5th March) 30-day value of zero.

 

* Trade Winds have generally been close to or somewhat stronger than average in the western Pacific during February.

 

* Cloudiness near the date-line has recently been close to or slightly below average.

 

* Most computer models predict further cooling of the Pacific during the first half of 2007.

 

Graph of 30-day Southern Oscillation Index values from 2003.

 

This graph is updated automatically each day. The data are available here.

 

Details

 

During February the equatorial Pacific showed strong cooling, with the values of the NINO3 and NINO3.4 indices averaging close to zero for the month and the NINO4 index below its El Niño threshold. The timing of the cooling in the equatorial Pacific is somewhat early but still consistent with past El Niño events.

 

The current weekly NINO indices have all decreased since their peak in late November to early December, and are now negative in the eastern equatorial Pacific, close to zero in the eastern to central equatorial Pacific and below levels typical of an El Niño event elsewhere. Compared with two weeks ago, the 7-day SST anomaly map shows a further strengthening of the cool anomaly pattern in the eastern equatorial Pacific, with anomalies less than -2.0°C in a small area.

 

Subsurface data for February shows that warmer than average conditions in the top 150 m of the Pacific between the date-line and 120°W have all but disappeared in the eastern Pacific. Cool subsurface anomalies are now established in the eastern Pacific, replacing the former warm anomalies in the region. The cool subsurface anomalies have strengthened since January, and are now affecting surface temperatures. A continuation of this process is likely to result in further cooling of both the Pacific surface and subsurface i.e. increasing the chances of a switch to cool ENSO conditions.

 

The TOGA-TAO subsurface data for the 5 days ending 4th March shows a similar picture to the February anomalies. The cool subsurface anomalies have caused negative anomalies to develop at the surface in the eastern equatorial Pacific. Warm anomalies, present in the eastern equatorial Pacific since around May last year, have now disappeared. The MJO-associated westerly wind burst in mid-January caused some weak warming in the subsurface in the region of the date-line which persisted into February. However, this remains fairly weak and has not shown any signs of eastward propagation.

 

An archive of past SST and sub-surface temperature charts is available.

 

The Southern Oscillation Index (SOI) was in a negative phase from May to October but neutral conditions returned in November and December with values of -1 and -3 respectively (see SOI graph, SOI table). Reflecting an increase in Pacific cloudiness and a temporary reduction in the Trade Winds, the SOI in January fell to -7, but rose to a February value of -3. The SOI has since risen further with an approximate 30-day (5th March) value of zero.

 

During cool/warm ENSO episodes, there is a sustained strengthening/weakening of the Trade Winds across much of the tropical Pacific but a return to near-average values as the ENSO event decays. This is what occurred with the 2006-07 event, with the Trade Winds being weakest in October prior to a return to average or above average values from late November, with a brief temporary weakening occurring in January in association with an MJO passage. The TAO/TRITON map (small image above), for the five days ending 4th March, shows near-normal Trade Winds in the eastern Pacific and slightly stronger Trade Winds in the central to western Pacific.

 

Cloudiness near the date-line in the central to west Pacific is another important indicator of warm/cool ENSO conditions, as it normally increases/decreases during these episodes. Cloudiness around the equatorial date-line was generally above normal (i.e., OLR below average) since the start of August, in keeping with the developing phase of the El Niño event. From mid-December to early January cloudiness was close to average, or somewhat below, in line with the easing of other ENSO indicators. After a sharp increase in cloudiness in mid-late January, February has seen a return to near-average to slightly below average conditions.

 

In the latest survey of a dozen international computer models, two of the eleven models surveyed predict cool conditions, consistent with a La Niña event, developing by July 2007, and persisting until October 2007. The remainder of the models show neutral conditions, with the majority on the cool side of neutral. This survey includes the POAMA model, run daily at the Bureau of Meteorology, which, typical of many other forecast models, shows a decline in warm conditions to cool neutral conditions over the next few months.

 

THE NEXT UPDATE OF THE DETAILED SECTION ABOVE IS EXPECTED BY 28TH MARCH

 

The other links section below can be used to keep track of important developments across the Pacific Basin.

 

What is El Niño?

 

Although originally named for a local warming of the ocean near the coast of Peru in South America, "El Niño" now refers to a sustained warming over a large part of the central and eastern tropical Pacific Ocean. Combined with this warming are changes in the atmosphere that affect weather patterns across much of the Pacific Basin, including Australia. These altered weather patterns often help promote further warming of the ocean because of the changes they cause in ocean currents.

 

Map showing departures from average ocean surface temperatures at the height of the 1997/98 El Niño.

 

Map showing departures from average ocean surface temperatures

 

in November 1997 at the height of the 1997/98 El Niño.

 

El Niño events occur about every four to seven years and typically last for around 12 to 18 months. They are a natural part of the climate system and have been affecting the Pacific Basin for thousands of years.

 

Each El Niño event is unique in terms in terms of its strength (as measured by numbers such as the Southern Oscillation Index or changes in ocean temperature), as well as its impact in terms of altered rainfall patterns. Furthermore, El Niño events have a life-cycle during which the impacts vary, both in terms of spatial extent and timing.

 

More information from the Bureau's Climate Variability and El Niño brochure

 

El Niño - What it isn't

 

El Niño is not a freak of climate, it's not a rogue weather phenomenon, and it isn't in any way abnormal. Furthermore it is not a scourge, and as far as Australia is concerned, it shouldn't be thought of as a synonym for drought, although it's often linked to reduced rainfall in eastern and northern Australia. Finally, and unfortunately, it's not regularly periodic so that predicting an event with more than about six to nine months warning is extremely difficult.

 

Thunderstorm approaching Bargara Beach, Bundaberg, Queensland. Picture: CASSANDRA PRINCE, from the Bureau of Meteorology 2001 Calendar

 

Thunderstorm approaching Bargara Beach, Bundaberg, Queensland.

 

Picture: CASSANDRA PRINCE, from the Bureau of Meteorology 2001 Calendar

 

What has happened in Australia during previous El Niño events?

 

More often than not, El Niño events result in reduced rainfall across parts of eastern and northern Australia, particularly during winter, spring and early summer. However, the precise nature (where and when) of the impact differs quite markedly from one event to another, even with similar changes and patterns in the Pacific Ocean. The progress of some events was punctuated by timely rains that made a significant difference to the season.

 

For example, the 1982/83 and 1997/98 events were both very strong as measured by changes in the Pacific, yet their impacts in Australia were completely different. Eastern and southern Australia was gripped by severe drought in 1982/83, but in 1997 average to above average falls were common in May, and a dry spell over winter was broken by widespread and heavy rains in September. Severe drought can sometimes result from a relatively weak event, as occurred in 2002/03.

 

Furthermore, changes in the Indian Ocean can enhance the general tendency for reduced rainfall in eastern Australia, or mask it by contributing to timely falls.

 

* Composite or average rainfall decile patterns in previous El Niño and La Niña events.

 

* Detailed analysis of the impact of 24 El Niño events in Australia.

 

Other Useful Links

 

The Weekly Tropical Climate Note issued by the Darwin office of the Bureau of Meteorology discusses the main features of the tropical atmosphere and ocean, including the intra-seasonal oscillation or 30-60 day wave which is thought to sometimes impact on the development of El Niño events.

 

The Bureau of Meteorology Research Centre (BMRC) has recently developed maps of Out-going Longwave Radiation (OLR), a useful El Niño monitoring tool. Negative anomalies show areas which, in general, have been cloudier (and potentially wetter) than normal.

 

The TAO / TRITON data display page is excellent for creating your own plots of numerous variables that are relevant to El Niño.

 

Note however that information coming from other countries is likely to describe timing and impacts relevant to those countries, which will not be the same as those in Australia.

 

 

[Ultralights]

i remember reading recently, that following studies of Ice cores from the mountains of south America, it has been found that El Nino and el nina events can last up to 160 Yrs!! and the 5 yrs we have had it it relatively short!

 

could you imageine the mess we would be in if this one lasted another 150 yrs!!

 

some things that have me thinking, being an Australian, in an Aussie climate, is why are we growing Rice in the Hay plains region??? why arnt all the rice fields up north, where the rain is!! on the coastal tropics regions??

 

and as for meat! why are we farming beef cattle? when we should be farming Kangaroos for their leaner, lower fat and a hell of a lot more tasty meats!! Kangaroo farms wont require acres of hay and other grains to feed them....

 

and countless paddocks on the east coast are empty, why arnt these paddock leased on good terms to farmers struggling? in Asia there isn't a square foot of land that isn't utalised for a crop, yet here on the coast many paddocks have just 1 or 2 cows or nothing but grass.

 

 

[slartibartfast]

Did it signal the end of a drought for you Chris?

 

 

[Yenn]

Don't believe it! Our wet season has been a total failure, both my dams are just about dry and we cannot expect rain now in enough quantity to run off.

 

As for Asians farming our paddocks I think they would find it very dry.

 

The cattle dug a track right across the airstrip going to water, but we have managed to repair the worst of it. Maybe I should take up religion and pray for rain.