MJO-La Niña relationship

[Macrocane]

Recently we have been discussing if MJO is important or not during La Niña season I have been researching this afternoon about that and have found some interesting papers and articles (some of them are very technical :S), the most important excerpts:

-There is evidence that the interannual variability of the MJO is partly linked to the ENSO cycle. Strong MJO activity is often observed during weak La Niña years or during ENSO-neutral years, while weak or absent MJO activity is typically associated with strong El Niño episodes.

-Figure 3 illustrates MJO activity for three different September through June time periods via time longitude plots of velocity potential (a measure of the divergence of air in the upper atmosphere). The first figure shows regular but generally weak to moderate MJO activity during 1989-1990 while during 1996-1997 there are periods of strong MJO episodes but with less regularity. The final panel shows virtually no MJO activity as little eastward propagation is evident with the most dominant variability being the interannual ENSO (El Nino) signal.

http://www.cpc.noaa.gov/products/precip/CWlink/MJO/MJO_summary.pdf

-It has been observed, that during a positive phase of ENSO (La Niña), the frequency of the of the MJO tend to be higher. As an example, during La Niña event in 1982-1983, the period of oscillation observed was of 26-days, instead of the 40-60 days period. With the same line of thought, MJO in the Pacific appears to be weak after the peak and during a cold event. This suggest that the interannual variability of the MJO might be driven more by the atmospheric internal dynamics than surface conditions

http://www.rsmas.miami.edu/personal/mulate-medrano/docs/fall2008/MPO-511/MJO-presentation.pdf

-Overall, the MJO tends to be most active during ENSO neutral years, and is often absent during moderate-to-strong El Niño and La Niña events. The MJO activity during late 2007 and early 2008, which occurred during La Niña conditions, is unusual but not unprecedented.

http://www.cpc.noaa.gov/products/precip/CWlink/MJO/MJO_1page_factsheet.pdf

-A comparison of MJO patterns between El Niño and La Niña events leads to a conclusion that MJO propagates farther eastward along the equator during El Niño years, showing a tendency to decay from the date line.

(I don't have a link to this article)

So after reading I undesrtand that:
-MJO signal is weaker during la Niña seasons that means less convective activity associated to it but it propagates faster (26 days instead of 40-60).
- There are more MJO "waves" during La Niña seasons but as it was previously said, they are weaker than in Neutral years and they do not reach as east as in Neutral or El Niño.

Opinions and more info is well received.

[cycloneye]

Great information there. I have heard that in La Nina years,the MJO that normally moves from west to east tends to stick around the basin that has more energy or warmer waters, however is weaker. And that may be the case this year.

[MGC]

For several seasons I tracked when a tropical cyclone formed and the corresponding phase of the MJO. I found that there was a slight positive correlation of tropical cyclone formation and a positive MJO. It worked out to like 55% formed in the wet phase and 45% formed during the dry phase. So, I don't place that much emphasis on the phase of the MJO. The big factors for me are upper level winds and SAL outbreaks.......MGC

[KWT]

Well the La Nina is now pretty much into the moderate range and once you get into that zone the MJO tends to become very stagnant, as we also saw back in 1998.

Thats why I thought earlier in the summer we could nsomewhat be saved by a stronger La nina from a mental season number wise.

[weatherwindow]

could the increased frequency/speed of translation by related to the presence of the anamalous westerly winds noted in the pacific in most el nino events?

[djones65]

MGC, What were the years you kept track of the MJO versus tropical cyclone formations? I would like to look back at some of that data. It sounds fascinating to me. Can you please let us know how recent you were able to keep track of such info? Thanks in advance!

[MGC]

I think I used 2006-8. It would be nice to see the numbers since the AMO went warm in 1995......MGC

[KWT]

All I'll say is this years MJO is thus far a stronger version of 1998, this year at least has seen some attempt at moving into different phases and even though its not exactly a key factor this year it all helps. Still very close to 1998 in many ways right now.