2009-01-25 00:05:46.000 – Mike Carmon,  Observer

Model Output Statistics (MOS). Can you decode?

The science of meteorology has many facets to it: observing, broadcasting, forecasting, researching, etc. At some point, most meteorologists will come into contact with all of these. Each discipline has its own pros and cons, but personally, I’d have to say forecasting is one area that can be the most frustrating.

Weather forecasting has been practiced since 650BC, when the Babylonians tried to analyze the skies, study the clouds, and predict the weather. The first hard, extensive record of an attempt to understand and predict the atmosphere was a text called Meteorologica by Aristotle, and is in fact where the name of the science, meteorology, is derived from. Techniques for forecasting have evolved through the years, and everything from astrology to dice have been used in an attempt to understand the complicated motions of the atmosphere.

The most important breakthrough came in the 20th century, when Lewis Fry Richardson proposed a technique that is still used today-numerical weather prediction (NWP). This is a technique in which theoretical equations that govern the behavior of the atmosphere are used to “calculate” the weather days in advance. Although the idea was groundbreaking and is still utilized to this day, at the time, computer power and speed were no where near the magnitude needed to generate forecasts in an expedient manner.

As computer power has enhanced over the last half of the 20th century, weather forecasting has become much easier and accurate. However, I’m sure that at some time in your life, you have prepared yourself for a rainy day due to what you’ve heard on a morning forecast, dragging out your umbrella or canceling your outdoor plans, only to see the sun break through the clouds later that day. Or, the weatherman said the rain was going to hold out, and wouldn’t you know it, the clouds gather and skies open up, unleashing a deluge and spoiling your game. So, why does this happen with all of the computer power we possess today? The fact is, NWP is based on the idealized atmosphere. The hard truth is the atmosphere rarely acts in an ideal manner. But, it is the best approximation we have. It is nearly impossible to account for every subtle or unexpected atmospheric occurrence that affects the weather.

In spite of all that, forecasts in general have improved tremendously from what they were even ten years ago. But the fact remains that the atmosphere is always changing, and probably will never be completely understood. That is the most frustrating part of forecasting-especially on Mt. Washington. If there was ever a location that exemplifies how fleeting the weather is, it is our mountain. That is why forecasted winds of 60-80 mph suddenly approach 100 mph without warning, and the summits forecasted to be in the fog all day suddenly emerge for an hour or two. We can only watch from the inside, humbly, and be reminded that even though we (and meteorologists in general) can be nearly spot on with our forecasts much of the time, there is always a monkey wrench waiting in the wings.


Mike Carmon,  Observer

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