Greenburgh Public Library Blog

Why Is Weather So Hard To Predict?

Why is the weather is so hard to predict? With the ever changing and advancing world of technology why can't we see into the future and predict the weather perfectly? Isn’t it just about reading numbers and looking at observations? In this post we will explore what actually goes into making a weather forecast and why it is so hard to predict!

In meteorology there are two types of forecasts: short term and long term. Both of these methods look at billions of daily observations from geostationary and polar orbiting satellites, weather balloons and ground stations. Short term forecasts usually range from 0-36 hours out. This is why when there is severe weather predicted, be it snow, rain or winds, we generally don’t know the specifics until 3 days before. Here’s a bit of advice: if you are hearing snow totals any sooner than three days before, be prepared for them to shift either direction! In short term forecasting forecasters look at temperature, clouds, precipitation, wind and pressure to generate their forecast.

The other forecast meteorologists look at is a long term forecast. Long term ranges from 8 to 14 days and usually includes monthly and seasonal outlooks. These forecasts are generated by looking at the same factors as the short term forecast but also include ground and sea temperatures, ocean currents, sea ice and atmospheric pollution. As a result of all these factors, long term forecasts are more of a probability game rather than an exact forecast. 

Even though there are two forecasting methods, the weather is not always perfect and can change hour to hour. What is known as the “Butterfly Effect” can very well affect the weather. Small changes in weather in one place can affect other places. Remember Winter Storm Juno in January 2015? It was predicted that Westchester would see a blizzard with anywhere from 18 to 30 inches of snow. Schools closed, states of emergencies were issued but, in reality, we only ended up getting about 6 to 12 inches of snow at the high point. What went wrong? Well, nothing technically went wrong. Unfortunately, most of the time meteorologists can have their best theories, but until the weather starts they won’t truly know the outcome. In this case, the heaviest bands of snow and strongest winds ended up moving more east than expected, causing the “epicenter” to shift more towards Long Island.  According to the Weather Channel, “The tremendous computing power of today’s forecast models allows us to predict these interactions with astonishing skill days in advance – a huge advance in a short time...But the complexity of the atmosphere is still greater than our ability to fully comprehend, measure, analyze and predict its behavior.”

If you're an amateur "meteorologist" like me, I hope you've enjoyed my tips on weather this season. If you'd like to learn more about weather and how it effects us, here are some extra resources you may enjoy:

We Are the Weather: Saving the Planet Begins at Breakfast by Jonathan Safran Foer
​Field Guide to The Weather: Learn to Identify Clouds and Storms, Forecast the Weather, and Stay Safe by Ryan Henning 
Weather 101: From Doppler Radar and Long-Range Forecasts to the Polar Vortex and Climate Change, Everything You Need to Know About The Study of Weather by Kathleen Sears
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