Prognostic chart
Encyclopedia
Prognostic charts are maps which display what the weather is expected to be like at a future time; in other words, a forecast map. Within the United States
, manual prognostic charts generated by the National Centers for Environmental Prediction
have special symbols which require interpretation. Those generated by atmospheric models
as output from numerical weather prediction
can have a variety of information on them, such as temperature
, wind
, precipitation
, automated weather front
s, or derived atmospheric fields such as vorticity, stability indices, or frontogenesis
. Errors with prognostic charts can be determined either via absolute error, or by considering persistence and absolute error combined.
indicate the positions of high and low pressure areas, as well as frontal zones, up to five days into the future. Surface wind direction and speed is also forecast on this type of chart. Wave prognostic charts show the expected sea state at some future time. Low-level prognostic charts used by aviator
s show the forecast between the Earth's surface and 24000 feet (7,315.2 m) above sea level
over the next two days. They show areas where visual flight rules
are in effect, instrument flight rules
are in effect, the height of the freezing level, the location of weather features, and areas of moderate to severe turbulence. Prognostic charts can be made of isentropic surfaces (along a certain potential temperature surface determined in degrees Kelvin
) in regards to moisture advection
, mean temperatures at the surface, mean sea level pressures, and precipitation either for a single day or multiple days. For purposes of severe weather
, prognostic charts can be issued to depict current weather watches, convective outlooks for thunderstorm
s multiple days into the future, and fire weather
outlooks.
s, turbulence
, weather fronts, rain
and snow
areas, precipitation type and coverage indicators, as well as centers of high and low pressure. Within the United States, these type of maps are generated by the Hydrometeorological Prediction Center
, the Storm Prediction Center
, the Ocean Prediction Center
, and the National Hurricane Center
. The Aviation Weather Center resends these maps, as well as generates specialized maps for aviation.
Atmospheric models are computer programs that produce meteorological information for future times at given locations and altitudes. Within any modern model is a set of equations, known as the primitive equations
, used to predict the future state of the atmosphere. These equations—along with the ideal gas law
—are used to evolve the density
, pressure
, and potential temperature scalar field
s and the velocity
vector field
of the atmosphere through time. Additional transport equations for pollutants and other aerosol
s are included in some primitive-equation mesoscale models as well. These equations are initialized from the analysis data and rates of change are determined. These rates of change predict the state of the atmosphere a short time into the future; the time increment for this prediction is called a time step. This time stepping is repeated until the solution reaches the desired forecast time. Time steps for global models are on the order of tens of minutes, while time steps for regional models are between one and four minutes. The global models are run at varying times into the future. The UKMET Unified Model
is run six days into the future, the European Centre for Medium-Range Weather Forecasts
model is run out to 10 days into the future, while the Global Forecast System
model run by the Environmental Modeling Center
is run 16 days into the future. The visual output produced by a model solution is known as a prognostic chart, or prog.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, manual prognostic charts generated by the National Centers for Environmental Prediction
National Centers for Environmental Prediction
The United States National Centers for Environmental Prediction delivers national and global weather, water, climate and space weather guidance, forecasts, warnings and analyses to its Partners and External User Communities...
have special symbols which require interpretation. Those generated by atmospheric models
Atmospheric models
Static atmospheric models describe how the ideal gas properties of an atmosphere change, primarily as a function of altitude....
as output from numerical weather prediction
Numerical weather prediction
Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic...
can have a variety of information on them, such as temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
, precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
, automated weather front
Weather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
s, or derived atmospheric fields such as vorticity, stability indices, or frontogenesis
Frontogenesis
Frontogenesis, in meteorology, refers to the formation or strengthening of an atmospheric front. During frontogenesis, the temperature gradient tightens and as a result the thermal wind becomes imbalanced. To maintain balance, the geostrophic wind aloft and below adjust, such that regions of...
. Errors with prognostic charts can be determined either via absolute error, or by considering persistence and absolute error combined.
Definition
The forecast map showing the state of the atmosphere at a future time is called a prognostic chart. Prognostic charts generated by computer models are sometimes referred to as machine-made forecasts.Variety
Surface weather prognostic charts for marinersSailor
A sailor, mariner, or seaman is a person who navigates water-borne vessels or assists in their operation, maintenance, or service. The term can apply to professional mariners, military personnel, and recreational sailors as well as a plethora of other uses...
indicate the positions of high and low pressure areas, as well as frontal zones, up to five days into the future. Surface wind direction and speed is also forecast on this type of chart. Wave prognostic charts show the expected sea state at some future time. Low-level prognostic charts used by aviator
Aviator
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...
s show the forecast between the Earth's surface and 24000 feet (7,315.2 m) above sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
over the next two days. They show areas where visual flight rules
Visual flight rules
Visual flight rules are a set of regulations which allow a pilot to operate an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minimums, as specified in the rules of the...
are in effect, instrument flight rules
Instrument flight rules
Instrument flight rules are one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other are visual flight rules ....
are in effect, the height of the freezing level, the location of weather features, and areas of moderate to severe turbulence. Prognostic charts can be made of isentropic surfaces (along a certain potential temperature surface determined in degrees Kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
) in regards to moisture advection
Moisture advection
Moisture advection is the horizontal transport of water vapor by the wind. Measurement and knowledge of atmospheric water vapor, or "moisture", is crucial in the prediction of all weather elements, especially clouds, fog, temperature, humidity thermal comfort indices and...
, mean temperatures at the surface, mean sea level pressures, and precipitation either for a single day or multiple days. For purposes of severe weather
Severe weather
Severe weather phenomena are weather conditions that are hazardous to human life and property.- Examples Include :Severe weather can occur under a variety of situations, but three characteristics are generally needed: a temperature or moisture boundary, moisture, and , instability in the...
, prognostic charts can be issued to depict current weather watches, convective outlooks for thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s multiple days into the future, and fire weather
Wildfire modeling
In computational science, wildfire modeling is concerned with numerical simulation of wildland fires in order to understand and predict fire behavior. Wildfire modeling can ultimately aid wildland fire suppression, namely increase safety of firefighters and the public, reduce risk, and minimize...
outlooks.
Manual
Manual prognostic charts have special symbols which require a legend or previous knowledge which depict tropical cycloneTropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
s, turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
, weather fronts, rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
and snow
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
areas, precipitation type and coverage indicators, as well as centers of high and low pressure. Within the United States, these type of maps are generated by the Hydrometeorological Prediction Center
Hydrometeorological Prediction Center
The Hydrometeorological Prediction Center is one of nine service centers under the umbrella of the National Centers for Environmental Prediction , a part of the National Weather Service, which in turn is part of the National Oceanic and Atmospheric Administration of the U.S. government...
, the Storm Prediction Center
Storm Prediction Center
The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
, the Ocean Prediction Center
Ocean Prediction Center
The Ocean Prediction Center , established in 1995, is one of the National Centers for Environmental Prediction’s original six service centers. Until January 12, 2003, the name of the organization was the Marine Prediction Center. Its origins are traced back to the sinking of the RMS Titanic in...
, and the National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
. The Aviation Weather Center resends these maps, as well as generates specialized maps for aviation.
Automated
Primitive equations
The primitive equations are a set of nonlinear differential equations that are used to approximate global atmospheric flow and are used in most atmospheric models...
, used to predict the future state of the atmosphere. These equations—along with the ideal gas law
Ideal gas law
The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law...
—are used to evolve the density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
, pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
, and potential temperature scalar field
Scalar field
In mathematics and physics, a scalar field associates a scalar value to every point in a space. The scalar may either be a mathematical number, or a physical quantity. Scalar fields are required to be coordinate-independent, meaning that any two observers using the same units will agree on the...
s and the velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
vector field
Vector field
In vector calculus, a vector field is an assignmentof a vector to each point in a subset of Euclidean space. A vector field in the plane for instance can be visualized as an arrow, with a given magnitude and direction, attached to each point in the plane...
of the atmosphere through time. Additional transport equations for pollutants and other aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
s are included in some primitive-equation mesoscale models as well. These equations are initialized from the analysis data and rates of change are determined. These rates of change predict the state of the atmosphere a short time into the future; the time increment for this prediction is called a time step. This time stepping is repeated until the solution reaches the desired forecast time. Time steps for global models are on the order of tens of minutes, while time steps for regional models are between one and four minutes. The global models are run at varying times into the future. The UKMET Unified Model
Unified Model
The Unified Model is a Numerical Weather Prediction and climate modeling software suite originally developed by the United Kingdom Met Office, and now both used and further developed by many weather-forecasting agencies around the world...
is run six days into the future, the European Centre for Medium-Range Weather Forecasts
European Centre for Medium-Range Weather Forecasts
The European Centre for Medium-Range Weather Forecasts is an independent intergovernmental organisation supported by 19 European Member States and 15 Co-operating States...
model is run out to 10 days into the future, while the Global Forecast System
Global Forecast System
The Global Forecast System is a global numerical weather prediction computer model run by NOAA. This mathematical model is run four times a day and produces forecasts up to 16 days in advance, but with decreasing spatial and temporal resolution over time...
model run by the Environmental Modeling Center
Environmental Modeling Center
The Environmental Modeling Center , improves numerical weather, marine and climate predictions at the National Centers for Environmental Prediction , through a broad program of research in data assimilation and modeling...
is run 16 days into the future. The visual output produced by a model solution is known as a prognostic chart, or prog.