Weather Terms:  

The following are common weather terms and explanations that are used by weather monitoring stations. You can scroll down to view the simple explanations of our monitoring sensors and common questions or click on one of these links to get a more detailed description of weather terminology.  

What's measured by the weather station on our roof ?
The meters on our graphs report the current weather from the outside sensors mounted on the roof. They are processed thru the Oregon Scientific Weather Station control panel and sent directly to one of our Pentium computers. Here, all the information is collected and processed into a graphic data file by the WeatherView32 software.  The data is then uploaded automatically to the Sarah's WeatherView web site for you to view.  Our information is also collected and sent to several other monitoring stations all across the country.

Wind speed and direction
Winds are referred to by the direction from which they blow. A north wind is one which blows from the north. I The word "anemometer" may be familiar to you. It is used to describe an instrument which measures wind speed. It comes to us by way of the Greek word for wind, "anemos." Anemone (the windflower), animal and animate also come to English by way of "anemos" and its Latin word cousin "animus" which alternately means vital force, soul, spirit and yes, ol' man breath!

Relative humidity
Relative humidity is a percentage of moisture in the air as compared to the maximum amount of moisture the air can hold. This maximum varies with temperature-warm air can hold more moisture than cool air.

Temperature
Temperatures on the North Carolina coast tend not to be as hot or as cold as temperatures in Western North Carolina. This is because water heats and cools more slowly than land.

Wind chill/heat index
The combination of temperature, humidity and wind speed can make the air feel hotter or cooler than the actual temperature. Wind makes us feel cooler. High humidity makes a hot day feel hotter.

Dew point
Dew point is the temperature at which air becomes saturated, or unable to hold additional moisture. Warm air can hold more water vapor than cool air. When the temperature drops during the night, the air can't hold as much moisture, and dew forms.

Barometer
Barometric pressure is a measure of the weight of the air pressing down on us. Cold, dry air weighs more than warm, moist air. Watching how the pressure changes over time tells more than the pressure alone. Rising pressure usually indicates that a high pressure system is approaching, typically bringing clearing skies. Falling pressure usually means a low pressure system is approaching, often bringing clouds and precipitation. Rapid changes in pressure warn of strong winds.

Rainfall
The average rainfall measured in inches. 

World Weather
On a global scale, weather is the movement of heat, water and electrical charges from one place to another. Sunlight provides the energy to drive the system. The sun's heat evaporates billions of tons of water from the surface of the oceans. This water vapor forms clouds. The sun shines more directly on the equator and tropics than on the poles, causing major differences in temperature. These temperature differences drive the winds. The movement of all this water vapor and air helps create imbalances in electrical charges in the air and on the ground. More than a million bolts of lightning each day bring the electrical charges into balance.

Doppler Radar
Radar systems gather information by bouncing radio waves off of objects. Weather forecasters examine rainfall and other weather events using a special kind of radar called Doppler radar. A high-powered antenna rotates and sends out pulses of radio waves. The pulses bounce off the falling rain and return to the radar source. By measuring the time between pulses and the amount of time it takes these radio echoes to come back, the radar system can calculate the distance and direction of the rain. Doppler radar also measures changes in the radio waves, which indicate wind speed and direction. A computer combines the radar information with a map, so we can tell where rain is falling. Special software lets the system focus in on small areas, allowing forecasters to examine weather in towns and even neighborhoods.

The Doppler Effect
The Doppler effect is a physical phenomenon named after Austrian physicist Christian Doppler. You may have experienced the Doppler effect if you've listened to the sound of a fast-moving object, such as a car or train, as it passes you. The pitch of the sound is higher as the object making the sound comes toward you. The pitch drops as the object passes you and moves away. The Doppler effect occurs because the sound waves are squeezed together as the object moves toward you, then stretched farther apart as the object moves away.This effect doesn't just happen with sound waves. Light and radio waves also show the Doppler effect. Doppler radar systems use this principle to tell whether rain is moving closer or going farther away.

What exactly is high pressure? What about low pressure?
High pressure is an area of sinking air. As it sinks, the air warms and tends to evaporate moisture, and that's why we often associate clearing skies with high pressure. Low pressure is an area of rising air that cools, causing the water vapor to condense into cloud droplets, raindrops or snowflakes.

What's the difference between "rain" and "rain showers" in the forecast?
Meteorologists forecast "rain" when they expect the wide, flat stratus clouds that produce rainfall over large areas. When puffy cumulus clouds are expected, meteorologists forecast "rain showers" because these clouds may cause rainfall over your house, while your neighbor across the street might remain dry.