Someone looks at the 300 hour GFS (forecast for almost 2 weeks out) and posts all over social media that their area is going to get hit with feet of snow. A local radio station in the Twin Cities was talking about this very storm dumping 2 feet of snow on Minneapolis– bringing about the worry of our next ‘snowpocalypse’ or ‘snowmageddon’.
While calm conditions and a steady pattern can be easier to forecast, it’s a different story when talking about storms. Upper-atmospheric winds play a major role, but small local geography or temperature differences can change the path or amount of precipitation from one town to the next.
And with snow ratios ranging from 4 to 1 all the way up to almost 30 to 1, even knowing the water equivalent exact totals remain tricky. For example, Meteorologist Joel Barnes keeps record of which storm tracks bring drastically different snowfall totals to the Front Range of Colorado.
A weather forecast can pretty reliably tell you whether you’ll need an umbrella tomorrow. Meteorologists use computer programs called weather models to make forecasts.
NOAA, the National Oceanic and Atmospheric Administration, operates three types of environmental satellites that monitor Earth’s weather : This information helps forecasters understand how quickly a storm, such as a hurricane, is growing and moving.
It provides space weather alerts and forecasts while also monitoring the amounts of solar energy absorbed by Earth every day. These satellites use instruments to measure energy, called radiation, emitted by the Earth and atmosphere.
These measurements can also help forecasters predict seasonal weather patterns, such as El Niño and La Niña. Polar orbiting satellites collect essential information for the models that forecast severe weather like hurricanes, tornadoes and blizzards days in advance.
The information they collect is also needed to assess environmental hazards such as droughts, forest fires, poor air quality, and harmful coastal waters. Modern weather predictions are a combination of computer-based models and human experience.
As a rule of thumb, the closer a weather forecast is in time, the more accurate it is. Long-term predictions have a larger margin of error because there are more unknown variables.
Past, current, or predicted temperature values displayed in a weather report may not always represent the warmest or coldest temperature for a location on a particular day. Weather is defined as the state of the atmosphere with respect to heat or cold, wetness or dryness, calm or storm, clearness, or cloudiness.
It includes temperature, pressure, humidity, clouds, wind, precipitation, and fog. While weather relates to mostly temperature and precipitation on a day-to-day basis, climate is the term for average atmospheric conditions over longer periods of time.
Forecasts change as details become clearer when any weather event approaches, and this is certainly the case with snowstorms. Atmospheric changes, timing and temperatures can make big differences in snowfall amounts.
Forecast details become clearer and more certain as a storm gets closer due to additional and more accurate information. For systems that track from the Pacific Ocean across the Lower 48, the data available before a storm reaches the West Coast is limited.
But once it moves into the West, additional data about the system in ingested into models improve the forecast. For instance, it can be tough to determine how much sleet and freezing rain, if any, may impact snowfall totals.
The track of a storm is influenced by the jet stream, or upper-level winds, so changes not just at the surface but aloft can make a difference. Changes in the upper-level pattern even at a great distance from where impacts from a particular event are expected can play a role in how a storm evolves.
The graphics below show an example of how a relatively small change in the track of an area of low pressure can make a big difference for Northeast. Examples of two possible scenarios where small shifts in track and amount of cold air available can result in different impacts.
Warmer water temperature near the coast can also sometimes play a role in whether snow or rain falls. The setup for freezing rain is similar to sleet except the warm layer is closer to the ground.
As a result, raindrops do not have time to refreeze into ice pellets and freezes when it makes contact with objects and the ground. Whenever we decide to go outside our front door, we typically check the forecast for the day.
The answer to this timeless question of how weather forecasting works has its roots in observational data, mathematical modeling, and computation. Various sources, such as weather stations, satellites, sea buoys, commercial airliners and ships gather data from all around the world.
The supercomputers at the National Oceanic and Atmospheric Administration (NOAA), for example, can complete 2.8 quadrillion calculations (yes, you read that correctly. Supercomputers are programmed to use mathematical models based on past weather patterns and the geography of that particular region.
Mathematical models are in the form of equations that describe key processes regulating weather, such as Earth’s rotation, wind speed, and direction, precipitation, evaporation, etc. When these data points are fed from various measuring instruments and sensors to the supercomputers, they run a set of complicated equations, depending on how it’s being modeled by the meteorologist, and generates a forecast.
The green lines indicate jet streams, which are near the core of maximum winds. Meteorologists closely focus on observational data points when coming up with a weather forecast.
This will result in a higher amount of humidity, which increases the chances of rain, hail, or snow. The variation in temperature between these two regions also has notable effects, leading to regular rainfall/snowfall, or in some cases, thunderstorms/tornadoes.
Thus, on any given day, if the temperature and dew point are close, it leads to a higher amount of water vapor. The US, being a large and populous country dealing with wide fluctuations in weather conditions across the vast landmass, probably needs multiple agencies specializing in different niches for a more accurate forecast.
Over the years, the techniques used in weather forecasting have improved by leaps and bounds. According to the National Oceanic and Atmospheric Administration (NOAA), five-day forecast predictions by weather agencies now has a 90% accuracy.
Meteorologists admit that weather forecasting still isn’t an exact science. Due to advances in research and the usage of artificial intelligence, weather forecasting is improving significantly.