It was a warm day in Fort Collins on September 28, 2011, with temperatures in the high 80s, but a dry cold front is moving down upon the foothills bringing 25 mph gusts of wind. The winds will continue through Thursday with temperatures hovering around 67 degrees for a high, then the cold front will leave and temperatures will move back into the 80s for the week’s end. A few, typical afternoon thunderstorms can be expected in the mountains this weekend, as well, so if your plans include a trip to Estes Park, pack an umbrella.
Do weather forecasts often use words such as “typical?” Perhaps not in Fort Collins or other cities situated in the foothills of the Rocky Mountains, but the persistence method, or assuming that the weather will remain unchanged from one day to the next as “typical” weather is one method of weather forecasting. The persistence method is used in places where the weather generally stays the same from day to day, such as southern California, or Texas in the summertime, where temperatures are generally around 100 degrees each day.
However, in the Colorado foothills it’s probably wiser to use the trends method to predict the weather. The trends method involves studying the speed and direction of the movement of cold fronts, high pressure centers, low pressure centers, cloudy areas, and precipitation, then predicting where these features will be in the near future. The trends method, for instance, would be an easy way to predict that Fort Collins will have a dry cold front with 25 mph winds tomorrow if the winds were tracked in advance and traveled from the same direction for a long period of time because the trends method works well if a weather system is moving at the same speed in the same direction for an average amount of time and uses simple mathematics to make the final prediction.
Another method, which does not seem to be working well this year with the unpredictable weather we’ve seen is the climatology method. The climatology method averages weather statistics accumulated over many years. Considering the historic drought in Texas, the flooding in the Midwest, and the haboobs, or massive dust storms, in Arizona, it’s been a strange year for weather and averages from past seasons might be unreliable for forecasting.
Here’s a method that might work for the weekend weather prediction–the analog method! The analog method is a little more complicated than the persistence method, but also works on the assumption that the weather will behave the same way it has in the past. For instance, today was very warm, but a cold front is approaching. The cold front is bringing 25 mph winds along with it and in the past, these winds pushed the cold front out of the area and the warm weather quickly returned. Although tomorrow’s high in Fort Collins will be around 67 with the arrival of the cold front, Friday’s high temperature is expected to be 76 as the cold front moves out of the area, then Saturday’s high temperature will be 83, and Sunday will be 81. In this particular situation, the analog method might work!
Can we be certain that the temperatures will rise this weekend? Of course not. Weather prediction is not an exact science, which is why meteorologists now use computers for Numerical Weather Prediction (NWP). Data fed into supercomputers produce predictions that factor in atmospheric variables, such as temperature, pressure, wind speed, and precipitation, the fancy word for rain.
The NWP method is also flawed, though, because nothing is precise when it comes to weather, particularly in and around mountainous areas, so mistakes will happen. The forecast will call for rain, and the sun will shine, or you may leave for your weekend picnic and spend a few hours sitting in the car, waiting out a thunderstorm.
Considering all of the above methods for weather prediction, the NWP method is the most reliable in spite of its flaws. However, for backyard forecasters, the trends and analogue methods work best, and if the daily weather is recorded in a journal, these methods can provide years of fun for the entire family as you learn about weather together!