2. WEATHER The term weather describes the state of the air at a particular place and time – whether it is warm or cold, wet or dry, and how cloudy or windy it is.

3. AIR MASS Air masses form above parts of the Earth that have similar characteristics, such as an ocean, or a large forest. In order for an air mass to take form, the air must remain above that location for at least a couple of days, before moving on. In order for this to happen there needs to be a high pressure system in the area.

4. FRONTS Weather fronts are formed as the leading edge of two air masses approach each other. The warmer air will always slide over the top of the cooler air and usually brings some sort of precipitation.

5. COLD FRONT A cold front is defined as the transition zone where a cold air mass is replacing a warmer air mass. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it. When a cold front passes through, temperatures can drop more than 15 degrees within the first hour.

6. WARM FRONT A warm air front is the place where a warm air mass replaces a cool air mass. We already know that warm air overrides cold air. This is because the air masses have different temperatures and densities. Warmer tropical air is forced over the cooler polar air. This forms a bulge on the front - called a warm front. If a warm front passed overhead when you were standing outside, you would feel the air warming up.air mass

7. HUMIDITY Humidity is a term for the amount of water vapor in air.water vaporair Relative humidity is the amount of moisture in the air compared to what the air can "hold" at that temperature. When the air can't "hold" all the moisture, then it condenses as dew.

8. HURRICANE A hurricane or typhoon (sometimes simply referred to as a tropical cyclone, as opposed to a depression or storm) is a system with sustained winds of at least 33 meters per second (64 kn) or 74 miles per hour (119 km/h). 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 contained in the moist air.storm systemlow-pressurethunderstormsaircondensationwater vapor

9. ISOBARS A line drawn on a weather map connecting points of equal pressure is called an "isobar“, and they are given in millibars.pressuremillibars

10. LAND BREEZE a coastal breeze blowing at night from land to sea, caused by the difference in the rate of cooling of their respective surfaces.

11. SEA BREEZE a wind from the sea that develops over land near coasts. It is formed by increasing temperature differences between the land and water which create a pressure minimum over the land due to its relative warmth and forces higher pressure, cooler air from the sea to move inland.wind

12. SNOWFLAKE Individual snowflakes are nearly unique in structure.

13. WIND air in natural motion, as that moving horizontally at any velocity along the earth's surface: A gentle wind blew through the valley.