38 Weather Forecasting Terms You Need to Know [Glossary]

The How It’s Made series has revealed how the weather experts create an accurate, reliable weather forecast. It explores everything from Weather Observations,Meteorological Expertise, and everything in between. It’s shown the essential factors that turn a forecast from good to great.

To wrap up the series here is our essential glossary of weather forecasting terms.

 

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There are so many unique terms used in modern weather forecasting that it can feel like the weather experts have their own language. To help you get to grips with the terminology, we’ve curated together 38 weather forecasting terms that you need to know.

 

So, from ensemble forecasting to spatial resolution, here are definitions you need in one, handy blog post. 

 

Bathymetry

This is is the underwater depth of a lake or ocean, usually referenced against Lowest Astronomical Tide (LAT) or Mean Sea Level (MSL), also known as seafloor elevation.

 

Climate Forecast / CF Convention

Designed to promote the processing and sharing of files created with the NetCDF API, these conventions enable users of data from different sources to decide which quantities are comparable.

 

Decluttering

This is a cleaning process that removes false signals or ‘clutter’ from raw data, thus improving its accuracy. Our own algorithm can detect and remove false signals from real radar echoes.

 

Derived or converted data

Raw data manipulated so that it can provide better insight, for instance, the amount of fresh snow or the probability of thunder.

 

Downscaling

Weather model data used for forecasting is usually available on a coarse grid and doesn’t always resolve local weather within those grid lines. With downscaling, you can combine geospatial data with data from the coarse grid to create a location specific forecast.

 

ECMWF

Stands for the European Centre for Medium-range Weather Forecasting, that operates a high quality global weather model (including the ocean).

 

Ensemble forecasting

Minor changes in the atmosphere can have a dramatic effect on forecasts. Ensemble forecasting is when a weather model is run several times in parallel with small changes to the initial conditions each time, resulting in an ensemble or set of forecasts.

 

ENS plume

This refers to the fifty slightly perturbed runs of ECMWF atmospheric weather model’s high resolution forecast. The data is used to provide a distribution of possible values per weather element, also known as plume forecast. Wider plumes indicate more uncertain weather.

 

Forecast window/depth

This is the length of a forecast. For instance, a 10-day forecast window means a forecast up to ten days ahead.

 

Funneling

When air flow need to squeeze through smaller openings. This speeds winds up and is otherwise known as the Venturi Effect.

 

Gap filling

See interpolation.

 

Grid

Refers to the collection of points in two or three dimensions with attributes describing the static environment (such as depth, elevation, land mask, and vegetation). Weather models deliver forecasts also on a grid, in that case a grid “point” refers to an (rectangular) area rather than just a point.

 

Governing equations

Describe how the values of unknown variables within a model change when one or more of the known variables changes. For instance, conservation of mass, energy, momentum (Navier-Stokes equations).

 

Harmonic components

The gravitational pull of the sun and the moon influences the tide on earth. The daily, seasonal and yearly orbits of sun and moon all are responsible for a component of the tide. Via  superposition of a series of cosines the final effect on local water elevation and resulting tidal currents can be computed.

 

Hindcast

This is a model study that predicts values for a time in the past. Used mainly to compare model data with measurements to assess model behavior.

 

“On-the-spot”

It’s possible to make weather forecasts hyperlocal by zooming in on expected conditions at precise locations and point in time.

 

Interpolation

Sometimes referred to as ‘gap filling’, this is the process of filling in the unknown data between two known values. A wide range of algorithms, depending on the weather parameter involved, is applied by expert meteorologists. Interpolation is also the process to estimate the model weather forecast at a location or time step in between model grid points.

 

Metocean

A combination of the words ‘meteorology’ and ‘oceanography’. Refers to data which originates from either field.

 

MeteoBase

This is the final, edited version of MOS forecasts (see MOS).

 

Model

A set of governing physical or statistical equations to calculate a weather forecast.

 

MOS

Stands for ‘Model Output Statistics’ and describes the post-processing technique that reduces systematic errors in raw weather model data.

 

MOS station

Typically a location for which there is observation data available. It can also be a location with no observation data available, but which is downscaled.

 

Multi-model forecasting

Describes the process of using several weather models to generate a (usually more accurate) weather forecast.

 

NCAR

National Centre of Atmospheric Research, Boulder, Colorado.

 

NCEP

National Centre of Environmental Prediction, a subsidiary of NOAA located in Washington D.C.

 

NOAA

National Oceanographic and Atmospheric Administration, Silver Sprint, Maryland.

 

Nowcasting

This describes the forecasting of weather for the short term (typically from 2-6 hours). It is especially useful for predicting of small scale events such as individual showers and thunderstorms.

 

Ocean circulation

Refers to the global current in the ocean basins that are caused by differences in temperature, salinity, and wind shear.

 

Orography

Another name for the topographic relief of mountains. Can also include hills and most elevated terrains.

 

Residual current

This is the average ocean current over one tidal cycle or one day or one year. See ocean circulation.

 

Spatial resolution

The granularity or density of geographic grids that are being used to track atmospheric conditions. Smaller grids offer higher spatial resolution and more accurate results but they are computational more expensive

 

SWAN

Stands for ‘Simulating Waves Nearshore’, and is a third-generation wave model that computes random, short-crested, wind-generated waves in coastal regions and inland waters.

 

Temporal resolution

Refers to the timespan between measurements or the timespan between numerical forecast forecast output. More frequent measurements result in higher temporal resolutions.

 

Verification

Undertaken on demand, this is the analysis of forecast against observation data for specific sites, periods and elements.

 

Verification database

The archive that contains raw data for the ECMWF model, MOS, observations, maritime and road data, and more.

 

WRF

Stands for ‘Weather Research and Forecasting’ and refers to the model developed by the National Centre of Atmospheric Research (NCAR).

 

Weather code

A number that classifies the weather conditions. For instance, fog patches or shower with hail. They help define the weather icons we typically see on TV forecasts.

 

Wx

A morse code word for ‘weather’ (.-- -..-).

 

Have we missed something? If you spot any gaps in our glossary of terms for weather forecasting, just let us know!

 

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