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Weather Wise

published: April 3rd 2020
by: Brian Bledsoe

One thing I continue to watch for is how the Pacific Ocean keeps changing. This is important, because it has been in a relative warm phase for the past five or so years. When it starts to cool off, the potential for a La Niña episode increases, which can cause drought issues for the Western/Southern Plains. 
January 1st, 2020 Sea Surface Temperature Anomalies

    Notice how much “orange” and “yellow” existed across the Pacific basin? That was indicative of a fairly warm state...even suggesting hybrid/modoki El Niño. However, in the past few months, some big changes have taken place. See below...
March 30th, 2020 Sea Surface Temperature Anomalies

    Notice the “tongue” of blue that is trying to develop off the west coast of South America and the larger blue area that has developed off the west coast of North America? That “blue” represents ocean temperatures that are cooler than average. When you compare the two maps, the development off the west coast of North America is pretty significant. That suggests that the overall phase of the Pacific Decadal Oscillation has recently shifted to a colder phase. That evidence is shown below, in a graph that charts the recent short term phases of the PDO since 2015:

    Until recently, the PDO has either favored a warm phase, ala 2015 through most of 2017, or a neutral phase. Lately, the PDO has dipped significantly and has certainly caught my attention. This is a trend that if continued, will no doubt lead to a La Niña episode...and one that could be potentially significant.  Some computer models have been hinting at that kind of development. One in particular, is the NMME model...check out the sea surface temperature anomaly forecast from it:
NMME Sea Surface Temperature Anomaly Forecast:
May, June, July

July, August, September

    See the blue shading extend off the west coast of South America? That would certainly be a rather robust La Niña by later this summer. Is this overkill? Perhaps, but other models are leaning this way too...even the EURO model. The graphic below shows the main Niño region continuing to cool down (trend below the zero line) for the rest of the year. 

    While we are technically in the “spring predictability barrier” time of year, most models are showing the Pacific continuing to cool off. While I can’t be certain that type of trend will continue, it is something I am sounding the alarm on, and watching closely. If that trend continues, I would expect regional drought to become a more significant issue in the coming months. Especially, during the back half of the year and possibly into 2021.