A Likely Possible Answer to the Recent Unusual Weather, page 1

I done a bit of research and the most likely cause of the extreme weather in the USA and elsewhere, is in my opinion due to the influence of the ENSO, or the El Nino Southern Oscillation (or El Nino as commonly known).

So what is El Nino?

El Niño-Southern Oscillation (ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon

What is Southern Oscillation Index?

The atmospheric signature, the Southern Oscillation (SO) reflects the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin, Australia

Despite being mostly confined (but not exclusively) to the Pacific ocean, El Nino and La Nina, can influence weather patterns around the globe. Most ENSO activity takes place in Australia and South America, however, the North American continent also experiences fluctuations.

Typically, in an El Nino period, the northern parts of the USA experience warmer winters, while the southern parts recieve wet and cooler conditions (particulary from the mid to east regions). See image below for more detail

In a La Nina period, the northern parts of the USA recieve cold conditions, and the north west coast experiences more precipitation (as we have recently seen in Washington state). The north eastern and central states also experience a wetter period. The southern states recieve warmer than normal temperatures, which can also be accompanied by lower than average rainfall. See image below for more detail

On the other side of the Pacific, in tropical Australia (where I live), we recieve wetter weather. So far this year, we have had above average and earlier than normal rainfall, which has been very apparent in the state of Queensland.

El Nino also affects the location and the direction of the jetstream, which can greatly affect temperature and rainfall patterns.

During El Nino events, the jetstream brings in moist air from the pacific to the southern states resulting in normal rainfall and cooler upper air for the south east region.

During La Nina events, the jetstream is enhanced in the polar areas, and brings heavier rainfall to the northeast and cooler than normal temperatures. There is also a variable jetstream further south, pushed north by the trade winds, which results in heavier rainfall and cooler weather in the pacific northwest. The southern states then become drier and warmer as the cooler, wetter conditions are restricted to the north.

From an external source:

For the contiguous United States, potential impacts include above average precipitation in the Northern Rockies, Northern California, and in southern and eastern regions of the Pacific Northwest. Below-average precipitation is expected across the southern tier, particularly in the southwestern and southeastern states.

These are the latest model outlooks for ENSO (most done in November or late October 2008)from the various meteorological departments for December 2008 to March 2009

Australia Met Bureau- Neutral
ECMFW- Neutral
UK Met Office- Cool (La Nina)
NCEP- Cool (La Nina)
GMAO/NASA- Neutral
JMA Japan- Neutral

As you can see there are indications towards a La Nina type period

This is the summary from my work of our latest ENSO outlook

ENSO conditions across the equatorial Pacific Ocean have now been neutral for several months, but some indices are more indicative of a cool ENSO phase. All sea surface temperature indices are neutral but there has been some cooling across the central tropical Pacific. Trade winds are now stronger than normal across the entire tropical Pacific, particularly in the western half of the basin and the SOI has been strongly positive since August, with the 30-day average at +17 on 29 November. There is now cooler-than-average water in the subsurface from the dateline to the South American coast. Our ENSO Wrap-up has more details.

Again, as you can see, the ENSO is leaning towards cooler temperatures, relating to a La Nina period.

Considering that El Nino events have occured recently (see below extract0, a La Nina pattern will seem like a very different weather pattern from the norm. But in fact, it is a normal weather pattern that we havent seen for a lengthy period for a long time

Recent El Niños have occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998, 2002-2003, 2004-2005 and 2006-2007

La Niña also formed in 1995, and in 1999-2000. The last La Niña was a minor one, and occurred 2000-2001.

So considering the above quote, the last major La Nina, was almost an entire decade ago. (Darwin Met Office, where I work, recorded our largest ever annual rainfall total 1999). So of course the current increase in rainfall and temperature fluctuations across the USA will seem strange.

So that concludes, it. In my own opinion, there is nothing amiss with the earths weather pattern, its normal, just a different period of weather patterns

www.bom.gov.au...

en.wikipedia.org...

www.elnino.noaa.gov...







[edit on 27/12/2008 by OzWeatherman]

reply to post by mungodave

---

Thanks for that

It didnt really occur to me until I read the unusual weather thread where people were describing the unseasonal weather conditions they were experiencing. So I put 2 and 2 together and its seems the likely cause.

Of course micro climates will have a big effect on certain places, but overall I think these effects are strongly influenced by the La Nina weather pattern

reply to post by OzWeatherman

---

Well, I have little doubt that global climate change is a real phenomena. The globe heats and cools in (regular?) cycles. Whether or not the current warming trend is a natural cycle or is substantially due to man's activity is the question we have yet to fully answer. Again, I don't doubt that mankind is having some sort of an impact. It seems rather naive to me to think that cause and effect relationships halt when talking about mankind's changes to atmospheric composition - however minor they may or may not be. After all, proliferation of single-celled organisms had enough of an impact on Earth's atmosphere at one time to change it dramatically and cause an ecological disaster - substantially changing the land, air, and the life which would soon occupy them dramatically.

That took several million years though, iirc, and insofar as our current trend in climate change - again, I don't doubt that it's happening. I just don't know to what degree that we're pushing it along, nor do I think the data is there to justify the doomsday scenarios.

As far as my friend is concerned, she's not very science minded. I doubt she's even understand the concept, and would continue to rely on news-bites and headlines to inform her. Again, to a degree, she seems to think the Earth is "alive" in a sense... a sort of Gaia... and that we're pissing it off. This is a concept that I wholly reject and until we'd be able to get past that - there's no point in arguing data.

[edit on 28-12-2008 by Lasheic]

Originally posted by Lasheic
reply to post by OzWeatherman

---

Well, I have little doubt that global climate change is a real phenomena. The globe heats and cools in (regular?) cycles.

I totally agree. Its all part of the natural balance of the earth. For example, high pressure moves into areas of low pressure, low pressure moves into areas of high pressure. Thats the areason why you cant have two hurricanes or cyclones sitting right next to each other. And the same is true for temperature. What heats, cools and vice versa

Again, I don't doubt that mankind is having some sort of an impact. It seems rather naive to me to think that cause and effect relationships halt when talking about mankind's changes to atmospheric composition - however minor they may or may not be.

Thats true again. Regardless of wether global warming is a myth, reducing harmful gases in the atmopshere will be nothing but beneficial

That took several million years though, iirc, and insofar as our current trend in climate change - again, I don't doubt that it's happening. I just don't know to what degree that we're pushing it along, nor do I think the data is there to justify the doomsday scenarios.

Agree agree agree

Thats what Ive thought for a while. ATS'ers do tend to blow things out of propoertion here too, despite having no background in the science.

As far as my friend is concerned, she's not very science minded. I doubt she's even understand the concept, and would continue to rely on news-bites and headlines to inform her. Again, to a degree, she seems to think the Earth is "alive" in a sense... a sort of Gaia... and that we're pissing it off. This is a concept that I wholly reject and until we'd be able to get past that - there's no point in arguing data.

Well thats ok, lol

I cant say thats the way I think. Im very science minded and work in the area of weather, so knowing how the mechanisms work to influence the patterns is crucial, as is analysing climatic data

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