Chapter 9 Weather Forecasting

The least accurate forecast method of predicting the weather two days into the future during changeable weather conditions is usually the:

persistence forecasting

Why is knowledge of local effects so important to weather forecasters?

It provides additional guidance with which to make an accurate forecast.

The least accurate forecast method of predicting the weather two days into the future during changeable weather conditions is usually the:

persistence forecasting

Why is knowledge of local effects so important to weather forecasters?

It provides additional guidance with which to make an accurate forecast.

A probability forecast that calls for a "40 percent chance of rain" means that

there is a 40 percent chance that any random place in the forecast area will receive measurable rain

The general area where a severe thunderstorm is likely to form can often be predicted

up to 3 days in advance

A weather watch would probably be issued for which of the following conditions?

there is a chance for tornadoes tomorrow

Which forecasting method assumes that weather systems will move in the same direction and at the same speed as they have been moving?

steady state (like going steady)

A weather forecast for the immediate future that employs the trend method is called

nowcasting

A halo around the sun or moon often indicates

the approach of a warm front

Why are surface and upper-air weather data plotted on maps?

To determine the areal extent of weather systems, and to correlate them to features observed from radar and satellite imagery.

The _____ is a chart that shows how one or more weather variables has changed at a station over a given period of time.

meteogram

A prog is:

(like prognosis)

Final forecast chart representing atmosphere at specified future time.

A forecast of an extended period of dry weather would be made for a region beneath

An upper level ridge.

(ridge = high pressure, good weather stable weather, dry air)

The forecasting of weather by a computer is known as

numerical weather prediction

Why must short-term changes in the barometric pressure be used with caution?

Pressure undergoes a cycle of rises and falls every 12 hours or so.

The inherently chaotic behavior of the atmosphere _____ computer model errors.

increases

Why should a meteorologist check past and present weather observations before making a forecast for a specific location?

All of the above.

What type of forecast is based on the climate of a particular region?

climatological forecast

Which of the following statements is false?

Model output statistics (MOS) are always accurate.

The National Weather Service communication system in use today is known as _____.

AWIPS

(Advanced Weather Interactive Processing System)

Predicting the weather by weather types employs which forecasting method?

Analogue

The steps used by forecasters to steer their attention from large scales to smaller scales and from short time frames to longer periods is called _____.

forecast funnel

A weather warning indicates that:

Hazardous weather is either imminent or occurring with in forecast area.

While trend forecasting (extrapolation) works fairly well in the short term, why does it become less useful for longer forecast periods?

Weather systems do not often remain at constant speeds or development rates.

An overview of how temperatures and precipitation patterns may compare with normal conditions

seasonal outlooks

By examining a surface map, the movement of a surface low pressure area can be predicted based upon the

all of these

watch

A storm watch indicates that a storm poses a threat to an area (often within several days) and residents of the watch area should be prepared.

warning

A storm warning given when it is likely that a storm will strike an area within 24 hours.

AWIPS

Acronym for Advanced Weather Interactive Processing System. New computerized system that integrates and processes data received at a weather forecasting office from NEXRAD, ASOS, and analysis and guidance products prepared by NMC

meteogram

A chart that shows how one or more weather variables have changed at a station over a given period of time or how the variables are likely to change with time

soundings

An upper-air observation, such as a radiosonde observation. A vertical profile of an atmospheric variable such as temperature or winds.

analysis

The drawing and interpretation of the patterns of various weather elements on a surface or upper-air chart

numerical weather prediction (NWP)

Forecasting the weather based upon the solutions of mathematical equations by high-speed computers.

atmospheric models

Simulation of the atmosphere's behavior by mathematical equations or by physical models.

prognostic chart (prog)

A chart showing expected or forecasted conditions, such as pressure patterns, frontal positions, contour height patterns, and so on.

chaos

Th e property describing a system that exhibits erratic behavior in that very small changes in the initial state of the system rapidly lead to large and apparently unpredictable changes sometime in the future.

ensemble forecasting

a forecasting technique that entails running several forecast models each beginning with slightly diff erent weather information. Th e forecaster's level of confidence is based on how well the models agree (or disagree) at the end of some specified time.

persistence forecast

A forecast that the future weather condition will be the same as the present condition

steady-state (trend forecasting)

A weather prediction based on the past movement of surface weather systems. It assumes that the systems will move in the same direction and at approximately the same speed as they have been moving.

analogue method

forecast made by comparison of past large-scale synoptic weather patterns that resemble a given (usually current) situation in its essential characteristics.

statistical forecasts

A forecast based on a mathematical/ statistical examination of data that represents the past observed behavior of the forecasted weather element

probability forecast

A forecast of the probability of occurrence of one or more of a mutually exclusive set of weather conditions.

weather types

Certain weather patterns categorized into similar groups. Used as an aid in weather prediction.

climatological forecast

A weather forecast, usually a month or more in the future, which is based on the climate of a region rather than upon current weather conditions.

nowcast forecast

Short-term weather forecasts varying from minutes up to a few hours.

short-range forecasts

Generally used to describe a weather forecast that extends from about 6 hours to a few days into the future.

medium-range forecasts

Generally used to describe a weather forecast that extends from about 3 to 8.5 days into the future

long-range forecasts

Generally used to describe a weather forecast that extends beyond about 8.5 days into the future

AWIPS (Advanced Weather Interactive Processing System)

New computerized system that integrates and processes data received at a weather forecasting office from NEXRAD, ASOS, and analysis and guidance products prepared by NMC.

meteogram

A chart that shows how one or more weather variables has changed at a station over a given period of time or how the variables are likely to change with time.

soundings

An upper-air observation, such as a radiosonde observation. A vertical profile of an atmospheric variable such as temperature or winds.

analysis

The drawing and interpretation of the patterns of various weather elements on a surface or upper-air chart.

numerical weather prediction

Forecasting the weather based upon the solutions of mathematical equations by high-speed computers.

atmospheric models

Simulation of the atmosphere's behavior by mathematical equations or by physical models.

prognostic chart (prog)

A chart showing expected or forecasted conditions, such as pressure patterns, frontal positions, contour height patterns, and so on.

chaos

The property describing a system that exhibits erratic behavior in that very small changes in the initial state of the system rapidly lead to large and apparently unpredictable changes sometime in the future.

ensemble forecasting

A forecasting technique that entails running several forecast models each beginning with slightly different weather information. The forecaster's level of confidence is based on how well the models agree (or disagree) at the end of some specified time.

persistence forecast

A forecast that the future weather condition will be the same as the present condition.

steady-state (trend) forecast

A weather prediction based on the past movement of surface weather systems. It assumes that the systems will move in the same direction and at approximately the same speed as they have been moving. Also called trend forecasting.

analog method

A forecast made by comparison of past large-scale synoptic weather patterns that resemble a given (usually current) situation in its essential characteristics.

statistical forecasts

A forecast based on a mathematical/statistical examination of data that represents the past observed behavior of the forecasted weather element.

probability forecast

A forecast of the probability of occurrence of one or more of a mutually exclusive set of weather conditions.

weather types

Certain weather patterns categorized into similar groups. Used as an aid in weather prediction.

climatological forecast

A weather forecast, usually a month or more in the future, which is based upon the climate of a region rather than upon current weather conditions.

nowcast

Short-term weather forecasts varying from minutes up to a few hours.

watch

A forecast indicating that atmospheric conditions are favorable for hazardous weather to occur over a particular region during a specified time period.

warning

A forecast indicating that hazardous weather is either imminent or actually occurring within the specified forecast area.

short-range forecasts

Generally used to describe a weather forecast that extends from about 6 hours to a few days into the future.

medium-range forecast

Generally used to describe a weather forecast that extends from about 3 to 8.5 days into the future.

long-range forecast

Generally used to describe a weather forecast that extends beyond about 8.5 days into the future.

seasonal outlooks

Outlooks that extend over three-month periods ranging out to a year or more, typically showing the odds that precipitation and temperature will be above or below average.

forecast funnel

A sequence of steps used by forecasters to analyze current and projected conditions, moving from larger to smaller scales during the process.

What is the function of the National Center for Environmental Prediction?

determine data requirements, optimum data processing techniques, and suitable presentation methods for predictions and products distributed to users of climatic, hydrologic, meteorological, space weather, and oceanographic information.

List at least four tools a weather forecaster might use when making a short-range forecast.

Meteogram, soundings, satellite information, wind profiles.

In what ways have high-speed computers assisted the meteorologist in making weather forecasts?

Computers (AWIPS) processes info from Doppler radar, satellites, and the ASOS to create progs and ensembles.

How are computer-generated weather forecasts prepared?

Analysis is the final chart after a meteorologist has interpreted the weather patterns and corrected any errors. A prog is the final chart made by a computer with surface and upper air charts and a variety of forecast charts.

What are some of the problems associated with computer-model forecasts?

Computer models idealize the atmosphere and make certain assumptions about it. Most models also don't have global coverage, so errors happen at the boundaries of their regions.

Describe four methods of forecasting the weather and give an example for each one.

- persistence forecast: what will happen today will happen tomorrow: good in dry, stable conditions
- steady forecast- forecast a front to continue to move the same speed and direction- good for 1-2 days
- analog forecast: compare features on a weather chart that are occurring now to patterns from the past
- statistical forecasting: uses equations and stats to forecast and learns from its mistakes (MOS)
- climatological forecast: forecast based on the climate of an area

How does pattern recognition aid a forecaster in making a prediction?

They will be able to look at a prog and recognize that they have seen the weather situation before, so they can use it as a guide for current/future weather.

How can ensemble forecasts improve medium-range forecasts?

They are made by running several simulations of a single model each with slightly different conditions. Meteorologists can use them to find what they all have in common.