How dry will U.S. get this summer?

by Drew Lerner
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US weather outlook map
Source: World Weather, Inc.
 
There are certainly plenty of reasons why forecasters have predicted 2016 to be a problem year for U.S. grain and oilseed production, but is it really going to be as bad as implied by some? World Weather, Inc. decided to look at the weather patterns one more time, but with the intention of finding a reason why this year’s drought scenario might not pan out.

 

What we found was interesting, but not necessarily a game changer if you have been following our forecasts since last autumn. If you are looking for severe drought that mimics 2012 or 1983….you may want to look again.

First, as a reminder, it is important to recall that La Niña is not a weather pattern, but is a phenomenon that removes moisture from the middle latitudes in both the Northern and Southern Hemisphere. As moisture is withdrawn from the atmosphere there is a tendency for the air to become drier. That drier tendency results in faster heating and cooling. Therefore, when La Niña is present and has been around for a while, there is a much higher potential for wilder swings in temperature extremes over land masses in both hemispheres. However, La Niña removes the moisture without directly impacting weather patterns. Often, whatever weather patterns are prevailing during La Niña will usually continue, but with decreasing moisture and the potential for wider temperature swings.

That is why all La Niña events do not perform the same and that is why some areas can actually benefit from a La Niña event while others suffer. If the prevailing weather pattern over a particular area in the world is wetter biased, La Niña will help to reduce some of the moisture to support better production potentials without so much excessive moisture. However, La Niña becomes a real problem when the prevailing weather pattern is dry and warm, because as it removes atmospheric moisture the already dry areas become drier and that helps temperatures swing more widely with faster daytime heating and quicker nighttime cooling.

Europe rainy and cool

Europe is in the midst of a wet and cool weather bias and producers there are hoping La Niña will kick in soon to leave some hope that it will not be rainy and cold all summer. That is the forecast for Europe. Many areas in central and southern Europe are expected to trend wetter and cooler frequently during the summer. La Niña offers some hope that it might not be so wet and that there may be some warmer air to contend with, but only after La Niña has prevailed for a while.

The situation in the United States is different. The central and southern Plains are moving quickly into a dry and warm weather pattern that has repeated multiple times in the past. La Niña has not yet evolved enough to have much influence on the pattern, but over a period of several weeks the potential for the U.S. Plains to become hotter and drier is high because that is what La Niña tends to do. It will remove moisture from the atmosphere and the drier air will lead to faster warming each day and greater heat stress along with less rainfall. But the longer La Niña takes to fully deploy, the less likely it is to significantly influence the Northern Hemisphere’s growing season.

Some drought forecasters have suggested that below average rainfall will impact the northern U.S. Plains and parts of Canada’s Prairies this summer, but that is not in the prevailing pattern for 2016. More timely rainfall is, however, and adding La Niña does not necessarily create drought in these areas. Allowing periods of rain to move across the northern Plains and southern Canada then offers precipitation potentials to the northern and eastern Midwest while the hot, dry pattern prevails in the central and southern Plains, west-central and southwestern Corn Belt and Delta. That is why our official forecast has never been hot and dry for the Canadian Prairies or the northern U.S. Plains.

Today, there is still no La Niña. There are hints of La Niña coming, but ocean temperatures are well mixed in the equatorial Pacific Ocean, meaning the influence of La Niña on the world’s weather has yet to begin. The central United States is in a developing dryness pattern which has little to do with La Niña and much more to do with the prevailing weather pattern. Today’s prevailing weather pattern is mimicking 1980, and in that year (a neutral ENSO year) dryness and heat were a problem in the central and southern Plains, Delta and southeastern states and not across the heart of the U.S. Midwest, northern Plains or Canada. In fact, the pattern actually promotes a seasonable bias in temperatures and precipitation in the higher latitudes.

The implication here is that with La Niña still not in place, other prevailing patterns may take precedent and dominate the weather this summer. As noted above, the prevailing pattern will be a mix of 1980 and 1998 and the odds are high that the west-central U.S. Corn Belt, central and southern Plains and the lower Mississippi River Basin will struggle with dryness during a large part of the summer. Production cuts are expected in each of these areas. It should be noted that neither 1980 nor 1998 were serious drought years and production of corn and soybeans was not far off from trend line yields. This year could still be different because of the eventual influence of La Niña.

Meanwhile, weather conditions across the northern and eastern Midwest will be favorable for supporting good summer crop development and yield potentials. As a result, some of the lost production from Nebraska and Iowa to the Mississippi Delta area and Texas will be countered by good yields in other areas. The debate over how much loss will occur will be settled by watching weather in July. The deeper dryness and heat get into the Midwest, the lower summer yields are likely to fall.

Officially, the area mentioned above will suffer the greatest declines in production. Confidence is high that the weather anomalies will be drier and warmer than usual, but how significant that becomes will be determined by how quickly La Niña kicks in and how significant high latitudinal cooling becomes in late July and August. The greater cooling that occurs in western Canada, the greater rainfall is likely to be in the northern and eastern Midwest. The strength of high pressure aloft over the central and southern Plains will also have much to say about rainfall distributions.

Keep an eye on late July

July is expected to be the most stressful month of the summer and thankfully for some producers the month of June was a favorable weather month, leaving crops and soil conditions mostly good with the exception of some southwestern crop areas where dryness is already a problem. The last days of June and the first half of July may be the driest period for the heart of the Midwest and the central and southern Plains while temperatures will be warmest in the Midwest during the middle to latter part of July. The central and southern Plains will be warmest in July.

Two things must happen in late July to put the brakes on declining crop and field conditions. First, there needs to be cold air pooling in western Canada and the U.S. Pacific Northwest, and second, there needs to be good amount of moisture from the southwest monsoon flowing from Mexico into Montana and North Dakota. If these two features are present with some significance, then relief is likely to impact the Midwest in a timely manner during late July and August to save production. If, however, the moisture influx is weak and/or cool air is limited in Canada and the northwestern U.S., then the odds become greater that dryness will become a more serious event.

Still, U.S. production is not expected to be as seriously cut as in the more serious drought years of 1983, 1988 and 2012, and there is potential that corn will yield close to trend yields while soybeans slip a little below the trend yield.

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