Sometimes, according to weather forecasts, it is paradoxically difficult to understand what the weather will be like. Should you dress warmer? Do I need to bring an umbrella? But in reality, it doesn't get any easier for meteorologists – predicting the weather is quite difficult even with the help of modern technology. Portal popsci.com explainHow is the probability of precipitation determined and how to interpret this percentage.
Precipitation is any amount of water that falls to the Earth's surface as part of the natural water cycle. Precipitation comes in many forms, including rain, snow, ice and hail, and is predicted using satellite data and mathematical formulas.
To understand what a chance of rain means, you need to understand what it doesn't mean. So, if the weather forecast predicts a 30% chance, this does not mean that 30% of the area will experience rain. It also does not indicate rain intensity: 30% would not be light rain and 100% would not be heavy rain.
Meteorologists use a variety of forecast models, some global and some more regional. Using satellite information and formulas, they track weather fronts and predict where rainfall may occur. If you see a 30% chance of rain in your weather app, that means meteorologists ran 10 weather simulations using a particular model and 3/10 times there was rain.
Precipitation probability also does not predict how long the rain will last, how much water will fall, or how hard it will fall. For example, the forecast may say there is a 100% chance of rain, but it could take the form of a light shower that lasts all day or a strong storm that clears in 15 minutes.
There are other nuances. Normally, any precipitation initially exists as snow because the atmosphere is much colder than the planet's surface. Absolute clouds are always cold – no matter how high or low they are in the sky. But changes in temperature can be calculated, allowing meteorologists to predict sleet, freezing rain and snow.
Snow showers occur when snowflakes partially melt as they fall through a thin layer of warm air. Melting snow freezes as it passes through a layer of cold air just above the surface and eventually falls to the ground as frozen raindrops.
But freezing rain does not fall in the form of ice crystals. It also starts as snow, but as it passes through a layer of warm air, the snowflake completely melts and changes from a solid to a liquid. The water droplet then expands and freezes if there is a pocket of cold air in its path or the ground temperature falls below zero. As a result, they form a thin layer of ice, which is dangerous for both drivers and pedestrians.
Yes, it is difficult for meteorologists to predict weather phenomena related to ice. Due to the complex interaction between warm air, cold air and different atmospheric layers, the forecast can change at any time.
As a rule, the most accurate forecast is the one that predicts the weather in the near future – unfortunately, 10-day or weekly forecasts are not always correct. There is no ideal time frame here: meteorologists can only predict temperature patterns in advance with a high degree of confidence.
