Weather probably tops the list of the most talked-about subjects about which we can do absolutely nothing. We praise it, as in this past year when Southeastern farmers experienced near-perfect weather, and we curse it, as in all of the drought-plagued years that have come before.
We've made a science of predicting weather, or attempting to predict weather, and we can make all sorts of assumptions about past weather events. The crux, of course, is that we still can't do anything about it. Anything, that is, but talk about it.
The lure of weather talk was obvious at the recent Beltwide Cotton Conferences in San Antonio, as farmers and other attendees filled an auditorium to hear Brad Rippey of USDA give a presentation entitled, “What We Know about the Weather: Short- and Long-Term Weather Trends.”
In the last few decades, says Rippey, advances in high-performance computing and a better understanding of oceanic and atmospheric processes have allowed forecasters to make more accurate short- and long-term weather predictions.
By tracking jet-stream oscillations and quickly changing phenomena such as the North Atlantic Oscillation and the Pacific/North America pattern, short-term forecast models provide reasonable day-to-day accuracy out to approximately two weeks, he says. Long-term forecast models may even provide some accuracy several months in advance in certain situations, such as with the presence of El Nino or La Nina during the cold season.
In order to gain a better understanding of future (short- and long-term) conditions in the Cotton Belt, it's helpful, says Rippey, to look at the weather experienced by the South in 2003. From the Delta to the Southern Atlantic region, this past year featured generally cooler-than-normal weather.
For example, Mississippi marked its 29th coolest year since records began in 1895. In contrast, persistently warmer-than-normal weather was observed from the southern High Plains westward into California. In fact, Arizona noted its hottest year during the 109-year period of record keeping.
Plentiful precipitation accompanied the cool weather pattern in the Southeast — to the delight of farmers — highlighted by the wettest year on record in Virginia and North Carolina. However, drought was a major problem for dryland cotton on the southern High Plains, while water-supply issues remained in the headlines across the Southwest. New Mexico reported its fifth-driest year on record.
The U.S. Drought Monitor shows that in the Cotton Belt, areas from southern California to the southern High Plains are entrenched in long-term drought. Although rangelands, pastures and dryland crops continue to be adversely affected in the Southwestern drought area, an even greater concern is long-term water supplies. Meanwhile, a long-term wetness is affecting the Southeast. Again, nary a complaint can be heard from our farmers here.
A brief look at short-term forecast tools for the Cotton Belt includes the Pacific/North America pattern (PNA) and the North Atlantic Oscillation (NAO), says Rippey. Both of these phenomena have been locked into relatively persistent phases for more than a year and continue to influence weather patterns across the South.
In fact, these phases continue to work together to contribute to a cool, wet meteorological winter (December-February) weather pattern in the Southeast. The only surprise with the persistent and on-going patterns has been a westward shift in the area of expected dryness, leaving the Southeast saturated and the southern Plains parched.
Of course, predicting the weather beyond the next two to three months becomes a much trickier proposition. On its Web site, the National Weather Service's Climate Prediction Center publishes skill scores for its long-lead outlooks, says Rippey. Historically, the outlooks have only limited skill, he adds, but they are most reliable during the cold-season months, especially in the presence of a strong El Nino or La Nina signal.
Long-lead forecasting is in its infancy, says the meteorologist, in part because the effects of annual to decade-long climate variations are better understood than the processes that cause them. Still, he adds, the understanding of ocean-atmosphere interactions have improved greatly in recent decades, and more progress is expected in the near future.