Dear Tom, 

You recently mentioned the improved technology and use of computer models as factor in the improvement in the accuracy of weather forecasts. There are so many computer models, how do you know which one to use?

Thanks, Tom Rowan, Park Ridge

Dear Tom,

Meteorologists have access to a plethora of computer models, often yielding widely divergent outputs. With a winter storm bearing down on Chicago, the same-storm computer guidance often varies from just rain or a few inches or snow to more than one foot. So much information is available to the forecaster, the guidance can often be a confusing and contradicting information overload. Experience teaches a forecaster which models are more reliable in different weather situations. One favorable tool is to ensemble the output data, giving the forecaster a consensus outcome, which frequently turns out to be the best solution.