CHICAGO (Reuters) - (The opinions expressed here are those of the author, a market analyst for Reuters.)
Abnormal dryness has accelerated in the United States over the last several weeks and the parched conditions could linger into the springtime.
Specifically, this could mean subpar moisture for the winter wheat crop and a drier start to the U.S. corn and soybean planting campaign for some areas, unless last year’s weather pattern is able to repeat.
According to the U.S. Drought Monitor, some 55 percent of the country was drier than normal as of Dec. 12, up from 48 percent in the prior week and 37 percent just three weeks earlier. (reut.rs/2o5m6Xl)
One year ago, the exact same portion of the United States exhibited unusual dryness. But it was deeper-seated last year as 30 percent of the country was considered to be in at least a moderate drought compared with 24 percent today.
However, this year’s dryness is focused more in the center of the country and particularly in the Plains, where wheat is grown in the winter and corn and soybeans are planted in the spring.
For some of the Plains states, the descent has been rapid. Only 18 percent of top-winter wheat grower Kansas was dry in mid-November, but today that portion is 99 percent.
Kansas’ neighbor to the north, Nebraska, which also produces winter wheat but is best-known for corn and soybeans, has dryness covering 83 percent of the state compared with 9 percent two weeks earlier.
Well-above average temperatures and virtually no rainfall over the past two months are responsible for this trend, along with stronger-than-usual winds that have also accelerated the dry-out. In the Northern Plains, there has been a distinct lack of snow cover, which is relied upon in the winter months to replenish soil moisture.
There are some precipitation chances in the longer-term forecast, but temperatures in the middle of the country are likely to remain above normal for the next few days under a generally dry pattern, so the drought conditions may intensify into next week.
Generally speaking, when the United States has a December drought, the dryness is still present in the spring, to some degree. (reut.rs/2o3RZ2p)
The exception to that was this past spring, when abundant March and April rainfall blanketed much of the country, eliminating most of the dryness that set in at the end of 2016.
In fact, the rainy spring of 2017 was so significant that for a stretch of eight weeks in May and June, the United States as a whole was as drought-free as ever in records dating back to January 2000. (reut.rs/2CjDZ7I)
Last spring, there were much fewer areas than usual with corn and soybean planting delays owing to dry conditions, though overly wet conditions also slowed many farmers’ progress.
One thing that the United States will have to contend with this year is La Niña, which occurs when the surface temperatures along the equatorial Pacific Ocean turn cooler than normal.
The U.S. Climate Prediction Center on Thursday bolstered earlier predictions for La Niña to sustain through Northern Hemispheric winter, unlike last year when the phenomenon faded earlier on.
Under a La Niña pattern, the entire southern half of the United States - including the winter wheat belt - is often drier than usual during the wintertime.
But there is not necessarily a distinct outcome for winter wheat yield based on La Niña. Winter wheat can usually handle dry winter conditions, so long as it receives a couple good shots of rain in the April time frame.
In Kansas, dry soil moisture conditions during December more often than not are linked to wheat yields below the long-term trend. (reut.rs/2ku2sPF)
However, the current drought in Kansas is not as deeply rooted as in some previous dry Decembers, meaning that just a little bit of precipitation in the coming weeks could prevent the state from descending too far into a drought.
Only 21 percent of the state is currently considered in a moderate drought as of Dec. 12. Historically, Kansas has extremely good chances of above-average wheat yields when that number remains below 30 percent during December.
Note: The latest GFS and EC weather model runs for the U.S. Plains on the Thomson Reuters Agriculture Weather Dashboard:
Editing by Matthew Lewis