Ag Weather Forum

Summer La Nina Less Likely

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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Updated Pacific Ocean forecasts now show a neutral temperature trend during summer 2016, with cooling to La Nina levels holding off until end of summer-early fall. (IRI Graphic)

The latest run of Pacific Ocean temperature forecasts is notably milder for the summer weather pattern than we saw during April. The latest analysis by the International Research Institute on Climate and Society (IRI) has a 90 percent probability for the Pacific Ocean sea surface temperatures to be Neutral during the May/June/July time frame. The June/July/August period still features a probability for Neutral values at around 55 percent. Pacific cooling to La Nina levels does not go over 50 percent until the July/August/September period.

This latest forecast is a sharp departure from previous forecasts. As recently as two weeks ago, the early-May forecast production by IRI had the Neutral probability at only 55 percent for the May/June/July period, with La Nina chances at 55 percent in June/July/August (versus the 55 percent chance for Neutral now). The early-May IRI forecast production also had La Nina cooling probability jumping to 65 percent in the July/August/September period (versus 55 percent now), with 70 to 75 percent probability in August/September/October (compared with 58 percent now).

The bottom line is -- Pacific cooling to La Nina is deferred compared to previous forecasts.

The implications for U.S. crop weather are important. It now appears that the timing of hotter and drier conditions will also hold off until a time more on the order of mid-August rather than mid-June or mid-July. And, as noted in a previous blog item, whether such a development is long-lasting, or is a brief occurrence, is still to be determined.

NOAA is certainly not throwing in the towel on summer 2016 weather. The Climate Prediction Center has a call for normal to above-normal temperatures during the next three months, with precipitation varying from the climatology-focused "equal chances" in the Midwest to "above normal" in the central, western and southern Plains. That's a summer weather pattern which maybe does not bring ideal, new-record type production, but still puts crops in position to meet trendline yields.

There's one other feature that the weather maps are also showing these days, which has been spotted by my colleague Mike Palmerino, and it's this: Hot high pressure is not a feature on the upper-air weather maps until you get to central and southern Mexico. Back in 1983 (which has been cited in the conversation about what's happening for this summer), there was a building hot-weather high pressure ridge at this time of the spring already occurring in the southwestern U.S. That high expanded and ballooned into the Midwest during the mid to late summer time frame. That is certainly not happening right now; in fact, the Desert Southwest has temperatures that, while mild, in the low 80s Fahrenheit, do not show extreme heat. Nor is such a feature in the forecast for next week, either.

Conditions may change, of course. But, the indications heading into late May are for a large part looking quite favorable for the U.S. crop weather pattern this summer.

Bryce
Twitter @BAndersonDTN

(BA/AG)

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