National Environmental Satellite, Data and Information Service (NESDIS)



How Bits and Bytes of Data Become a Forecast

Monday, September 9, 2019

Every day in America, millions of people wake up with the same question on their minds, “What’s the weather today?” The US Department of Commerce found that the majority of Americans check the weather forecast 3.8 times per day, equating to 301 billion forecasts consumed per year! These days, we take accurate forecasts — available multiple days in advance — for granted. 


This information wasn’t always as readily available as it is today. It takes a lot of smart science, technological infrastructure, and computing power to get the right data and information to generate a forecast. And the value of that information is profound. It helps people answer a wide variety of questions, from “What will I wear today?” to “When should I harvest my crops,” “When should I ship my product” or “When should I evacuate to avoid the storm?”

Step 1: Data Collection

NOAA has constellations of Earth-observing satellites that monitor the atmosphere, temperature and surface of the Earth 24/7/365.  As each satellite flies by the satellite receiving ground station, it transmits data it has collected to the satellite receivers on the ground. Partner agencies, both here and abroad, also share their satellite data with us. NOAA scientists create mathematical algorithms that interpret these bits and bytes of data into meaningful, useful information.

In addition to the satellite data collected at these receiving stations, NOAA data are also collected from ocean buoys, weather balloons, stream gauges, aircraft and doppler radar. For example, the National Weather Service’s Nexrad (Next Generation Radar) is a network of 159 Doppler radar stations that scans weather data in two million locations. NOAA operates multiple servers and supercomputers to combine this vast and constant data supply.

Step 2: Modeling 

NOAA’s supercomputers are one of the most powerful weather-predicting systems in the world. Currently, the combined processing power of these supercomputers is 5.78 petaflops, which is more than 10,000 times faster than the average desktop computer. The supercomputers are housed in two primary centers, in Reston, Virginia, and Orlando, Florida. Each location features two rows of computers working in tandem, each 40 feet long. 

These computers run sophisticated numerical models (computer programs) of the atmosphere, oceans, and land variables that produce both imagery and text information that National Weather Service forecasters use to create reliable forecast predictions. 

All weather models work on the same basic principles, solving for a large number of complex equations for various locations at both the surface, and different heights (layers) of the atmosphere. These equations solve for many parameters such as temperature, dew point, wind speed, in addition to many others. Once all these calculations have been completed for a given time step, the solutions can be put together to form a picture, or map, of what the future state of the atmosphere looks like based on the model’s calculations. This new set of variables is then input back into the model and repeated many times over, giving us a range of forecasts valid from a few hours to many months into the future!

Step 3: Getting the Forecast to You

NOAA’s substantial observing infrastructure provides foundational data and information for forecasters both here and around the world. This data and information get to you in a number of ways. 

For example:

Meteorologists on TV take this information and will use it to explain the weather in their broadcast area. Many are highly skilled and have a lot of experience with the local climate and conditions.

Companies specializing in forecasting use the data to create forecasts tailored to specific sectors, such as agriculture or real estate.

Insurance companies use the information to understand the impacts of major disasters, including the costs of rebuilding damaged infrastructure.

Retailers use this information to understand when to ship their goods.

Emergency managers use the information to help determine where to pre-position resources in advance of a storm.

The value of NOAA data is estimated to reach tens of billions of dollars, and the savings in life and property realized by improved hurricane and other severe weather forecasts is critical to the American people. And of course, every day, we all rely on knowing “what’s the weather going to be today.”