BELLRINGER

EXPLAIN IN COMPLETE SENTENCES

WHAT ARE PRINCIPLES OF RADAR WORK

Weather Analysis and Weather Analysis and ForecastingForecasting

Dr. R. B. SchultzDr. R. B. Schultz

Weather Information AgenciesWeather Information Agencies• In the United States, the governmental agency responsible

for gathering and disseminating weather related information is the National Weather ServiceNational Weather Service (NWS).

• Perhaps the most important services provided by the the NWS are forecasts and warnings of hazardous weather including:– thunderstorms, – flooding, – hurricanes, – tornadoes, – winter weather, – and extreme heat.

• The process of providing weather forecasts and warnings throughout the United States occurs in three stages.

Stages of Weather Forecasts and Warnings

• First, data is collected and analyzed on a global scale.

• Second, a variety of techniques are used to establish the future state of the atmosphere; a process called weather forecastingweather forecasting.

• Finally, forecasts are disseminated to the public, mainly through the private sector.

Forecasting and Analysis• The task of determining the future state of the

atmosphere is called weather forecastingweather forecasting. • Weather analysis,Weather analysis, assessing the current

atmospheric conditions involves:– collecting, – transmitting, – and compiling millions of pieces of observational data.

• On a global scale, the World Meteorological World Meteorological OrganizationOrganization is responsible for gathering, plotting, and distributing weather data.

• Once collected, the information is distributed to three National Meteorological CentersNational Meteorological Centers near Washington, D.C., Moscow, and Melbourne, Australia.

Weather Maps• Normally, the large body of weather data once

collected is displayed on a synopticsynoptic (observations made at the same time) weather map.

• A weather map shows the status of the atmosphere and includes data on:• temperature, • humidity, • pressure, and • airflow.

• In addition to surface maps, twice-daily upper air charts which depict the pressure field are drawn at various millibar levels.

Weather Forecasting Approaches

• The approaches used in modern weather forecasting include:– traditional synoptic weather forecastingsynoptic weather forecasting, – numerical weather predictionnumerical weather prediction, – statistical methodsstatistical methods, and – various short-range forecasting techniquesshort-range forecasting techniques.

•Synoptic weather forecasting, the preeminent method for making weather predictions until the late 1950s, involves the analysis of synoptic (summary) weather charts, employing several empirical rules.

•This is the first way weather predictions were made.

Synoptic Weather Forecasting

Numerical Weather Prediction

• Numerical weather prediction, used extensively in modern weather forecasting, is based on the fact that the gases of the atmosphere obey many known physical principles.

• Ideally, these physical laws can be used to predict the future state of the atmosphere, using the current conditions.

• This really should be called “Chemical Weather Prediction” since it uses a great deal of chemistry.

• Numerical weather prediction uses a number of highly refined computer models that attempt to mimic the behavior of the atmosphere.

Numerical Weather Prediction (cont.)

Statistical Methods

• Statistical methods, using past weather data to predict future events, are often used in conjunction with numerical weather predictions.

• One statistical approach, the analog methodanalog method, examines past weather records to find ones that come close to duplicating current conditions.

• The Farmers’ Almanac uses statistical methods to predict future events. Usually correct 40-50% of the time.

Short-Range Forecasting

• The simplest short-range forecasting techniques, called persistence forecastspersistence forecasts, predict that the future weather will be the same as the present conditions.

• Another technique, often called nowcastingnowcasting, uses radar and geostationary satellites to quickly forecast severe weather events, such as thunderstorms, tornadoes, hail storms, and microbursts.

Long-Range Forecasting

• Long range weather forecastingLong range weather forecasting is an area that relies heavily on statistical averages obtained from past weather events, also referred to as climatic climatic datadata. .

• Weekly, monthly, and seasonal weather outlooks prepared by the National Weather Service are not weather forecasts in the usual sense.

• They indicate only whether the region will experience near-normal precipitation and temperatures or not.

Forecasting Skill• Weather forecasting relies on the skill of the

forecaster.

• Very short-rangeVery short-range (0 to 12 hours) forecasts have demonstrated considerable skill, especially for predicting the formation and movement of large weather systems.

• Short-rangeShort-range forecasts (12 to 72 hours) of maximum and minimum temperatures and wind speeds are quite accurate. Furthermore, predicting precipitation amounts is much better than forecasts made only two decades ago.

• Medium-rangeMedium-range forecasts (3-7 days into the future) have shown significant improvement in the last 20 years. However, the predictability of the day-to-day weather for periods beyond 7 days is usually small.

Technical Advances• Many technical advances have been made to

improve forecast accuracy.

• Automated Surface Observing SystemsAutomated Surface Observing Systems (ASOS) are now being used in places currently outside the observational network.

• Interactive microcomputer systems make it possible for forecasters to display, manipulate, and rapidly digest the great quantity and variety of available data.

• Advanced radar networks such as NEXRADNEXRAD (Next Generation Weather Radar) in association with Doppler radar, aid in the detecting and tracking of small-scale weather phenomena, such as tornadoes and thunderstorms.

Weather Satellites

• Weather forecasting relies heavily on information provided by both polarpolar and geostationary weather geostationary weather satellitessatellites. .

• Their primary importance is to help to fill gaps in observational data, especially over the oceans.

• Weather satellites can generate several types of images, including:

– visible,

– infrared, and

– water vapor images.

• Currently, infrared images (images obtained from radiation emitted rather than reflected by an object) from satellites help determine regions of possible precipitation within a cyclone.

• Future satellites will be able directly or indirectly to detect wind speeds, humidity, and temperatures at various heights.

Weather Satellites (cont.)

Weather Satellite

Observations and Forecasting

• For many years meteorologists have been aware of a strong correlation between cyclonic disturbances at the surface and the seasonal fluctuations in the wavy flow of the westerlies aloft.

• Frequently, when upper-air flow produces large-amplitude waves and a general north-to-south flow, cold air moves southward and cyclonic activity dominates the weather.

• On the other hand, when the flow is nearly west-to-east, mild temperatures and few cyclonic disturbances are experienced south of the jet stream.

• Although the effects of the upper-level flow on weather are well documented, the somewhat unpredictable manner of the flow aloft keeps long range weather forecasting beyond the forecaster's reach.

Jet Stream Patterns

Key Terminology

National Weather Service Forecasting

Analysis World Meteorological Org. (WMO)

National Meteorological Ctr. Synoptic Forecasting

Numerical Weather Prediction Statistical Methods

Short-Range Forecasting Analog Method

Persistence Forecasting Nowcasting

Long-range Weather Forecasting Climatic Data

Automated Service Observing System (ASOS)

NEXRAD (Next Generation Weather Radar)

Polar Satellite Geostationary Satellite

ACTIVITY

Discuss in a group and write a report about principles of behavior in severe weather. Present your report to class. Distribution of work: person 1 – what are dangers of severe weather?, 2 – what are physicaldamages of severe weather?, 3 – what is the timeline of severe weather?,4 - how can we practically implement these principles.Distribution for groups:Group I – hurricane; II – tornado; III – heavy snowstorm;V – heavy rain and wind; VI – dangerous thunderstorm; VII – heavy hail; VIII – freezing after heavy snow and rain with high wind

EXIT QUIZ

What is the weather system content?

2. Describe imaging in the weather system

3. Why do we need several radar sources in the weather system?

4. What are these sources?

5. What is the future of the weather system?