Raymarine e7, User Reference

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13.10 Glossary of weather terms
Term Definition
Cold front The boundary between two different air masses where cold air pushes warm air out of the way and brings colder weather.
Cyclone A large area of low atmospheric pressure, characterized by inward spiralling winds. A “low” also called a “depression”. Also the name
used for a hurricane in the Indian Ocean and Western Pacific.
Depression
An area of low pressure. Also called a cyclone.
Dry line A region where there is a strong gradient in dew point temperatures. It is often found in a region where strong thunderstorms develop.
Forecast
Something that tells us what the weather is probably going to be like.
Front The boundary between two masses of air with different temperatures (i.e. a mass of cold air and a mass of warm air).
High Also known as an ’anticyclone’ an area of high atmospheric pressure with a system of winds rotating outwards. This usually means dry
weather. It is the opposite of a ’low’.
High Pressure A mass of air that presses down strongly on the surface of the Earth because it is being cooled and is therefore more dense.
Hurricane A violent, spiralling storm that forms over the Atlantic Ocean, with winds over 120 kph. Such storms usually have a lifespan of several days.
Also known as a typhoon or tropical cyclone. There are 5 levels of hurricane:
• Category 1 — Winds 7495 mph (6482 kt or 119153 km/hr). Storm surge generally 45 ft above normal. No real damage to building
structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some damage to poorly constructed signs. Also,
some coastal road flooding and minor pier damage.
• Category 2 — Winds 96110 mph (8395 kt or 154177 km/hr). Storm surge generally 68 feet above normal. Some roofing material, door,
and window damage of buildings. Considerable damage to shrubbery and trees with some trees blown down. Considerable dam age to
mobile homes, poorly constructed signs, and piers. Coastal and low lying escape routes flood 24 hours before arrival of the hurricane
centre Small craft in unprotected anchorages break moorings.
• Category 3 — Winds 111130 mph (96113 kt or 178209 km/hr). Storm surge generally 912 ft above normal. Some structural damage to
small residences and utility buildings with a minor amount of curtain wall failures. Damage to shrubbery and trees with foliage blown off
trees and large trees blown down. Mobile homes and poorly constructed signs are destroyed. Low lying escape routes are cut by rising
water 35 hours before arrival of the centre of the hurricane. Flooding near the coast destroys smaller structures with larger structures
damaged by battering from floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles (13
km) or more. Evacuation of low lying residences with several blocks of the shoreline may be required.
Using the weather application (North America only)
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