Meteorology is perhaps one of the most despised professions in the eye of the general public. Certainly it can not be worse than a lawyer or a mechanic, but to the uneducated person, a meteorologists job should be easy. After all, “how hard is it to look at a map and figure out where the rain is going?” Not so much…
The weather as a whole is very difficult to predict, mother nature is not so easily anticipated. There’s a vast amount of variables that go into the creation of a snowfall/ice/sleet/rain forecast in the winter. Models which are used for forecast prediction can have problems anticipating low level moisture, upper level temperatures, where the freezing line is, the list goes on. Models tend to put out snowfall forecasts which do not take these other factors into account. The result is amounts need to be adjusted higher or lower depending on the other variables included, some of these the model detects on its runs, but does not implement in the snowfall forecasts. Dry slots moving into storms can also zap a storm of its moisture, causing an abrupt and unexpected decrease to snowfall totals and even the death of a winter storm.
Another factor involved in winter forecasting is track. Unlike summer systems which typically move in a general direction across a generic swath of the country (give or take in the northern or southern tier of states), winter storms tend to move in a different motion. With different components being involved in the actual system, it can result in a wider area seeing precipitation, but fewer areas or greater areas receiving snow vs. rain. A ten mile discrepancy in track of a storm can be the difference between a location picking up 8″, or picking up 2″.
Why use models?
Well, models have always been used to a certain degree. Whether it’s by hand, or whether it’s by a computer model, data is collected and then output in a model that helps forecasters generate an appropriate forecast for the area. But there are some terms that people don’t understand when reading a forecast. First, models. There are many models that can be used to forecast weather including, but not limited to the: GFS, GEM, EURO, ECMWF, UKMET, and NAM/ER.
The GFS is the Global Forecasting System.
The GEM is the Global Environmental Multiscale Model.
The EURO is the European Forecast Model.
The ECMWF is the European Centre for Medium-Range Weather Forecasting Model.
The UKMET is the United Kingdom Meteorology Forecast Model.
The NAM (sometimes NAMER) is the North American Model.
These are all forecast models which use data to output various outcomes on a potential winter storm. Sometimes they are similar, sometimes they are not. Consistency from run to run increases forecast confidence, but confidence can never be one-hundred percent. Models which are similar to each other can have the wrong solution, but they can also be accurate. The model is useless without a forecaster behind the computer analyzing the data that the model is presenting. Thus, a forecaster never usually makes a forecast copied from a model. The chances of the model having a total grasp on a situation have indeed increased over the years, but still remain low.
So what else would have to go into a forecast in the winter? Gut instinct, or what the meteorologist has seen before. If the person analyzing the data sees one thing, but knows the conditions a time before yielded a different result, he or she may be tempted to modify their forecast accordingly. Say for example if a model shows a storm dropping 4-7″ of snow across the upper Mississippi Valley, but the last two storms which exhibited the same characteristics only dropped 2-4″. The result would most likely be a snowfall forecast of 1-3″ with isolated amounts up to 4″.
One model is also not a go to for weather during a certain season. One might be better at tracking certain things, but that does not mean that all credibility should be placed into it, and the others should be dismissed.
Winter forecasting is hard. It’s never going to be a perfect science. Regardless of what your local television or newspaper weatherman says, all meteorologists look at these models and have to make their own assessment on them. If they don’t, they’re ripping their forecast off of someone else. So don’t get agitated at your television weatherman, instead…realize the challenges that go into forecasts, understand the science involved, and chill out. The fact is, if things are life threatening, you will get the information you need regardless of whether or not you pay attention to the television or not.
And as always, do yourself a favor and purchase a NOAA All Hazards Radio. If you need a forecast solution that is blended. Weather that talks to you that has good accuracy, 24 hours a day, year round.