Tuesday, February 11, 2014

El Nino Won't Come Quick Enough To Break the California Drought

Some basic climatology.
The Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal oscillation are two of the major quasi-periodic Sea Surface Temperature anomaly patterns. Here are the tables of monthly values for the AMO and the PDO.

The El Nino-Southern Oscillation (ENSO) is distinct from the PDO but the PDO cool phase appears to correlate with a 2:1 La Nina/El Nino ratio whereas the warm phase correlates with twice as many El Nino's. Here is the current Oceanic Nino Index.

The PDO entered its cool phase in 2007, 30 years after it entered its warm phase in 1977. The oscillations are called quasi-periodic because the length of the phase can vary by a fairly large percentage, especially in the case of the AMO.

Even though the phases last decades, the anomaly can go in the opposite direction for months at a time.
A click on the PDO table shows that the negative anomaly starting in September 2007 lasted for 23 consecutive months, one of the longest consecutive strings in the record.

Here are the current Sea Surface Temperature anomalies via Unisys Weather:

Current Sea Surface Temperature Anomaly Plot

We have a couple dozen posts on El Nino on the blog, usually in connection with grain crops.

When talking about this, remember the distinction between El Nino 'conditions', which is a positive anomaly of .5 degree or greater in the Nino 3.4 zone of the Pacific and an El Nino, which is the same anomaly but recorded in three rolling three-month periods i.e. five consecutive months. By the time of an official El Nino call the bulk of the move is usually behind you.

We have had one (weak) 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.

Be that as it may, should Cali get relief Australia would get hit so you are trading cheap almonds for expensive wheat. Here are the latest forecasts (new ones next week) from IRI and Columbia University's Earth Institute:

The model plumes seem to be saying El Nino conditions rather than a full blown El Nino and the probability charts seem to indicate no real chance of anything developing before the June/July/August rolling three month period.

More to come.