   Climate and Weather Prediction - January 13, 1999 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County The New Year will bring above average rainfall with storms coming about every two weeks, no late frosts, no early spring frosts, and lower than average summer temperatures. I suppose everybody will be pleased with that forecast and, by the way, does anyone want to make an offer on the 89A bridge. I'm sorry to say that my long-term forecast is not based on science but on pure optimism. The weather is the subject of uncountable daily conversations. The local phenomenon we call weather can be defined as the daily atmospheric conditions with respect to temperature, precipitation, humidity, wind and barometric pressure. Although talking it about is easy, it is much more difficult to predict with any accuracy. However, computer simulations, radar, satellite imagery, etc. have greatly increased our ability to predict the weather. Conversely, climate refers to prevailing weather conditions in a given area over time. Our knowledge of a climate becomes increasingly accurate with as more years of data are collected. Often, reliable weather data has been collected for a relatively short time (20-30 years) so that monthly and yearly averages do not reflect true long-term trends. Even 100 years is a short time span when one is trying identify a reliable average rainfall or daily maximum/minimum temperature. In 1998, we received adequate winter precipitation, a nicely spaced monsoon season, and some fall precipitation as well. Tuzigoot National Monument and Sedona Ranger Station have been recording weather data since 1977 and 1948 respectively. In 1998, Tuzigoot received 13.23 inches of precipitation compared to Sedona's 24.23 inches. Tuzigoot's yearly average precipitation is 13.67 inches (21 years) and Sedona's is 18.35 inches (50 years). Storm patterns, topography, elevation, and to a smaller extent, the fickle nature of monsoons accounts for the almost twofold difference in rainfall between these sites last year. El Nino conditions were also present in 1998. This usually increases our winter precipitation. The 1998 average monthly temperatures for these two sites were very similar to their long-term averages. What about the weather predictions for 1999? Most meteorologists predict a La Nina weather pattern to begin this year. La Nina is characterized by below normal surface water temperatures in the equatorial Pacific Ocean. Past La Nina events have led to above average winter temperatures and below average precipitation in the southwestern United States. La Nina events can last as long as two years. The National Oceanic and Atmospheric Administration has been researching and modeling El Nino and La Nina behavior. If the pattern continues, it does not bode well for local farmers and ranchers. Let=s hope this La Nina will be short-lived. I recently picked up a copy of Harris' Farmer's Almanac. It amazes me how it can forecast the weather a year in advance. The December 1998 forecast for the southwest was "near normal temperatures and slightly above normal precipitation" and "abundant mountain snowfall". Well, anyone can be off occasionally. The January 1999 forecast reads "a good chance for precipitation, locally heavy, January 2-5, 10-11, 16-29 and 28-31". Oh well, the recipe section of the Almanac looks great. Understanding weather patterns takes some study and I am not an expert, but the Internet is a good place to start learning. For those that use computers, the Verde Watershed Association website has several links to weather forecasts and climate data at verde.org. John Parsons at the Verde Natural Resources Conservation District is responsible for this excellent site. The University of Arizona Cooperative Extension has publications and information on climate and local growing seasons. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@kachina.net and be sure to include your address and phone number. |