Weather Forecasting 2009 Predicting the weather People have

Weather Forecasting 2009

Predicting the weather • People have needed to predict the weather since the dawn of time. • Hunting, farming, and all outdoor work depends on the weather. • Folklore grew around the observations people made. A ring around the sun or moon, means that rain will come real soon. Red sky at night, sailor's delight; red sky in the morning, sailor's take warning.

Modern Forecasting • Relies on: • Observation using various instruments • Computer models • Previous trends and patterns in the weather. • Can be accurate up to five days in the future.

Trends and Patterns • Meteorologists: Scientists that study the causes of weather and try to predict it. • They use data collected over the past 100 or more years to make their predictions. • So when they say “There is a 40% chance of rain today, ” they mean that in the past, when the conditions were similar, it rained 40% of the time.

Weather Instruments • A thermometer measures temperature. A barometer measures air pressure. A rain gauge measures precipitation. An anemometer measures wind speed. • Weather vanes find wind direction. • A psychrometer measures relative humidity.

Weather Technology • New technologies have made short range (2 to 5 days or so) forecasting fairly reliable. • They are now working on long range predictions. • Changes in technology are making this possible: • Satellites and computers.

Computer Models • Computers can take millions of pieces of data and process this information to make predictions. • Predictions are only as good as the computer model.

Weather Radar • Uses Doppler radar to track moving storms and precipitation. • NEXRAD is the new generation Doppler radar that tracks wind and precipitation. • This allows tornadoes to be accurately tracked.

Weather Balloons • Weather balloons carry equipment up to 30 kms high • A radiosonde attached to a weather balloon measures weather high in the atmosphere. • This equipment records data and sends it to weather stations

Weather Satellites • A lot of data comes from satellites • They take pictures of the earth from outer space. • They can also collect data on temperature, cloud height, and moisture. • Then the satellites send their data to weather stations

Weather Maps • There are many different kinds of weather maps. • Data from local weather stations from all over the country is collected to create national weather maps.

Temperature Map • Shows the current temperatures.

Radar Maps • Shows precipitation.

National Wind Map • Shows wind speed and direction.

Infrared Satellite • Shows cloud top temperature.

Fronts

Visible Satellite • Shows picture from space.

Precipitation • Shows precipitation in inches.

Humidity • Shows the relative humidity.

Isobars • Show areas of equal pressure. • Inner most circles will be the low or high pressure areas.

Isotherms • Lines show areas of equal temperature. • Isotherm maps show where temperatures are relatively high and low, and also where temperature changes are gradual or dramatic over a distance.

NWSChapter and 16 Maps Weather Maps • The National Weather Service produces weather maps based on information gathered from about 1, 000 weather stations across the United States.

Weather Map Symbols • These are the symbols you would see on a weather map. • The arrows or bumps point in the direction the front is moving.