Lulled to Sleep (April 3, 2013)

As we wind down out of another high amplitude winter, many of the climate forcing signals are now neutral or too weak to have an impact on the daily sensible weather.  Before examining current conditions, let’s remind ourselves where we have been and why.  This past winter, and in fact the seasons before it, were dominated by extremely “blocky” flow, as the ocean basins of both the Pacific and Atlantic are in long term states that have a tendency to support such patterns.  Superimpose on this pattern a “La Nina” like state of the tropical pacific, and we had a pattern that produced the drought in the US Midwest last summer and periods of dryness in Argentina this past growing season.  Make no mistake about it, these events are not unrelated, but are a manifestation of the current climate regime.  The winter continued to see a strong blocking pattern, which is why mother nature has been reluctant to loosen old man winter’s grip.   You may also have taken notice of late freezes/cold spells across many different regions of the globe….from Argentine soy in March, the US wheat/early corn in the plains and deep south, to the current cold wave across Europe impacting winter wheat yields.  Again, these are not unrelated.   They are the state of the current climate system.  Whereas we had decades of mostly zonal flow that resulted in few major crop problems from 1985-2005, we now will have a period of “blocking” flow.   Crop disruptions will revert to their long term mean, growing seasons will be at risk for slow starts and abrupt ends.  Some of the most devastating freezes in US growing areas occurred in the 1970/80’s.  It is not new, just the old adage the what is old is new again.

As regards the current state of the climate, we remain in the background state of predisposition to blocking patterns.   However, the transitions from winter to springs are almost always like a staggering drunk, first this way, then that way, and so on until the final destination is reached.  In our case, that final destination will be the established pattern that will dominate the summer weather in 2013.  As of now, the short to medium term climate forcings that interact with the background climate state, are very weak or non-existent.  The tropical Pacific is hovering around the neutral state, flirting at times with La Nina (more blocking/less rainfall) and El Nino (less blocking/more rainfall).  The Madden-Julian Oscillation (MJO), which cavorts around the globe and enhances/suppresses convective responses, plays a meaningful role in predicting weather in the 2-4 week time frame.  However, right now the MJO is too weak to lend any guidance.   As is the tropical pacific.  Thus, the atmosphere is a bit more chaotic and a bit less unpredictable.  Rains can fall in just about any place, as no “locking” or “blocking” mechanisms are in place.   From this, we are at risk of being lulled to sleep.  The March-May period is notoriously unreliable in the tropical Pacific, and the MJO will not stay weak forever.

The good news is we can plant US crops more/less on time, though decidedly behind last year’s record pace.  However, the prospects for the summer remain wide open, and we have only the background state to rely on, one that is pre-disposed to blocking patterns.  This is not a forecast of another crop problem, just a reminder that on climate scales, weeks and a month or two are not meaningful changes.  The evolution of these parameters between now and end of June will determine crop fates not just in the US but globally.   This pattern has taught us since 2010 to be respectful.   That is what I currently am doing…..

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