Friday, July 31, 2009

El Nino in a Cold PDO – Are they Different?

In Wednesday's post "El Nino May Ease Worst Texas Drought, Cut Florida Storm Risk" I made passing reference to the difference:

...The last paragraph on California is iffy. We haven't had an El Nino since the Pacific Decadal Oscillation went into it's cool phase in September 2007 so all of the satellite and other high tech data was gathered during the 31 year PDO warm phase, entered in July 1976. We know about ENSO cold/PDO warm but you have to go back to 1947 for the start of last PDO cool phase, i.e. pre-satellite.

There is some reason to suspect that California and the southwest will have a weather pattern different from what our short term memories consider a typical El Nino.
Today, lo and behold, this showed up in the emails. From Intellicast:

Warming is taking place again this year in the eastern tropical Pacific.

Recently the SOI spiked 5 STD negative indicative of that trend towards El Nino.

Last year the warming peaked below threshold El Nino levels in July and returned to La Nina by winter.

This year there appears to be enough subsurface warmth to take it further.

But the PDO remains cold with some slight rebound. El Ninos tend to be briefer and weaker during cold (negative) PDO eras, which is where we have been it appears most of the time since 1998.

Note the positive PDO is a basin wide El Nino like pattern with more emphasis on cold northwest, the negative a basin wide La Nina like pattern with more northwest basin warmth.

MUCH MUCH MORE chart porn and analysis:
...The ENSO and PDO seem to reinforce each other and track well together. We should expect PDO to bounce some but if the Pacific is really in the cold mode, the El Nino should be brief and at most moderate like they were from the 1950s through the 1970s and again in the middle 2000s. La Nina should return if not by/during winter during 2010.