By Drew Lerner
Bridge Global Weather Services
KANSAS CITY (B)--The latest set of long-range weather forecast maps released by the U.S. National Weather Service Dec. 16 suggested La Nina conditions would last through winter and into the heart of spring which is no different from the mid-November forecast. Little change in the winter and spring outlooks was also noted, but Bridge Global Weather Services continues to see a drier and warmer than usual summer for portions of the U.S. corn, soybean belt.
A warmer-than-usual winter continued to be the loudest message coming from the latest NWS long range forecast maps covering the next 15 months. A moderately strong La Nina episode remains well under way and all computer forecast models suggest the phenomenon will last through winter with many predicting it will linger into mid-spring. If the forecasts are correct U.S. residents in the central and southern states should see a continuation of mild to warm temperatures this winter. None of the nation is expected to be noticeably colder than usual, but normal temperatures may affect a large part of the Pacific Northwest and northern Plains.
Winter precipitation will be above average in the eastern Midwest--similar to that of the past few weeks--and above average across the northern states.
Both the temperature and precipitation patterns predicted come from highly correlated weather anomalies associated
with previous La Nina years. Therefore, the odds are quite high that the forecast will verify.
High correlations with La Nina in the spring season dictates dryness that was once anchored over the southwestern U.S. during winter will expand northeast across the heart of the hard red winter wheat producing region adding risk to a crop that went into dormancy in less than ideal condition. Persistent, below-average, precipitation in the Plains could easily lead to crop moisture stress in winter wheat areas and reduce production potentials. Weather in April and May will go a long way in determining yield potentials for next summer's crops, but that is when La Nina is expected to weaken and correlations with weather anomalies begin to fade.
Once La Nina weakens and begins to fade away forecasts from the NWS become less confident and picking a specific anomalous weather pattern for the summer becomes harder to achieve.
at all in the NWS forecast.
Bridge Global Weather Services continues to note the parallels to the middle 1960s. Weather patterns for the past couple of years have closely followed those of the middle 1960s and that has occurred despite an El Nino event in 1997 and La Nina conditions this past summer. La Nina and El Nino patterns do not correlate well with anomalous U.S. summer weather patterns and there have been nearly as many dry years as wet years. For this reason, GWS feels to accurately predict summer weather you must step back and look at the dominating weather pattern and assume that those patterns will return once La Nina or El Nino back away from their winter and early spring dominance.
As the spring La Nina pattern fades, GWS is anticipating a return to the middle 1960s weather pattern. That pattern was one of low precipitation and warm temperatures. No extremely hot and dry weather occurred for weeks or months on end that seriously hurt production potentials in the middle 1960s due to well-timed rain events. Actual rain amounts were often light, however. This coming year may be similar, but the influence of La Nina will play an important role in determining summer weather.
dryness and warmth. Combining the lingering effect of La Nina with the middle 1960s weather pattern reinforces the drier and warmer weather outlook which has GWS waving a few caution flags for farmers deciding what their crop will consist of this next growing season.
Dryness is already expected to be an issue in the Great Plains and western corn belt this late winter and early spring because of La Nina's bias for below-average precipitation. La Nina will have to break down quickly in the spring to allow a boost in rainfall to take place in the Plains and western corn belt prior to the corn and soybean planting season. Some moisture improvement is predicted and spring seeding progress is likely to advance swiftly. However, subsoil moisture is not likely to be fully replenished while spring rainfall is abundant and that will set the stage for faster drying and crop moisture stress as seasonal drying begins in June and July. That will likely be the seed of potential problems for the summer growing season, especially in Kansas, Nebraska, southern Iowa, Illinois and Missouri.
Low subsoil moisture and a bias for dry soil in the Plains could lead to a blocking weather pattern in the spring or early summer that could potentially exacerbate the dryness situation.
Meanwhile, the eastern U.S. corn and soybean belt will likely see abundant to excessive spring soil moisture because of La Nina. The wet conditions could lead to delayed planting, but once fieldwork takes place crops in the eastern Midwest should get along well in the late spring and early summer.
Some of the heat and dryness in the Plains and western Midwest could expand into the eastern Midwest during the heart of summer inducing a few weeks of potential moisture stress, but the situation should not get out of hand.
La Nina's continued weakening during the summer should increase the opportunity for a wet finish to the summer, GWS says. That wet finish may save soybeans from severe crop moisture stress and a significant decrease in yield, but corn will not likely be so lucky, especially in the western corn belt where the potential for lower yields may be greater than usual.