July 15, 2010
Is Pollen Forecasting Accurate?
If you suffer from environmental allergies, you may find yourself paying more attention to your local news reports in the spring or fall. In fact, the daily pollen count might make a difference in whether you’ll have a good day or a bad one. As allergists, we believe pollen forecasting will become more common. But how accurate is it?
In truth, pollen forecasting is a very complex topic. Take ragweed and other fall weeds, for example. If you were to take a five-year history of ragweed pollen, you could generate a graph of each season that shows the average start date, peak date and end date.
Pollen levels can vary day-by-day due to daily weather events, such as rain and fluctuating temperatures. For example, rain and cooler weather will reduce or stop the release of pollen. So, once the pollen season has started, you can make a general prediction of the next day based on the pollen graph and the weather forecast of the current day.
However, these predictions are only as reliable as the weather forecast. In addition, this model does not take into account such factors as wind speed and relative humidity. Also, a summer with a lot of rain and more sunny days will allow for good growth and will increase pollen levels.
Spring pollen reduction is much more complex because flowering plants release pollen in response to temperatures staying above a certain threshold. Therefore, there is more variation in the springtime pollen counts than in the ragweed counts.
Forecasts may be used to predict which direction the pollen is going. This is particularly applicable in large metropolitan areas surrounded by rural or suburban regions. As an example, pollen may be carried into the city on prevailing winds.
So what’s the practical take on pollen counts? When we hear on the news that the pollen count is very high, it really means that the count the day before was high. Therefore, you really cannot rely on the pollen count for predicting the current day with accuracy.
