High Surf Terminology, High Island Surf Cam, Ocean Rip Currents, Ocean Safety Sign

Select the first letter of the word from the list below to jump to an appropriate section of the glossary:
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Advisory:

A textual or verbal message issued when hazardous weather or hydrologic conditions exist, are imminent, or are likely to occur. Advisories are issued for conditions that may cause major inconvenience and could lead to situations that threaten life or property.

Atmospheric Pressure:

The weight of the atmosphere, in force per unit area.

B

Beaufort Wind Scale:

A scale classifying wind strength in terms of observable effects over sea and land.

Building:

Intensification of high pressure systems (applied to a ridge or high pressure center).

C

Central pressure:

The atmospheric pressure at the center of a high or low: the highest pressure of a high; the lowest pressure of a low.

Circulation:

In the greater sense, an organized movement of air.

Coastal Flooding:

Coastal inundation caused by a rise in sea level due to such phenomena as seismic sea waves, high surf, storm surge, or prolonged strong onshore flow of wind and/or high astronomical tides.

Combined Seas:

The combined height of swell and wind-driven waves generally referred to as "seas."

Cyclone:

An area of low pressure associated with inclement weather. Cyclonic winds blow in a counter-clockwise direction in the Northern Hemisphere and in a clockwise direction in the Southern Hemisphere.

Cyclonic circulation:

The movement of air around a low pressure center, counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere.

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D

Deepening:

A decrease in central pressure of a cyclone. Deepening is usually accompanied by an increase in wind speeds and by worsening weather.

E

El Nino:

A major warming of the equatorial waters in the Pacific Ocean. El Nino events occur every 3 to 7 years, and are characterized by shifts in "normal" weather patterns. El Nino has been linked to colder, wetter winters in parts of the U.S., drier hotter summers in South America and Europe, and drought in Africa. El Nino has caused reduced numbers of fish in South American coastal waters, and dry winters in Hawaii.

Extratropical Cyclone:

A term used to describe a cyclonic storm that forms outside the tropics, along a front in middle and high latitudes, or a tropical cyclone that has moved outside of tropical regions.

F

The distance that the wind travels over open water in which waves are generated. The length of the fetch area is measured in the direction of the wind.

Flood:

The condition that occurs when water overflows the artificial or natural boundaries of a stream, river, or other body of water. Also issued for the ponding of water at or near where rain is falling or has fallen. The term may also be used to alert the public of non-life-threatening flooding of small streams, streets, storm drains, and low-lying urban areas. It may also be used if small streams in rural areas reach or exceed their banks.

Frequency:

The number of waves occurring within a particular time interval.

Front:

The boundary between two air masses. If cold air is advancing on warm air, the front is called a cold front; if warm air is advancing on cold air, the front is designated a warm front.

G

Gale:

Wind speeds from 39-54 miles per hour (34-47 knots).

Gale Warning:

A textual and/or verbal bulletin issued when winds of 39 to 54 miles an hour (34-47 knots) are expected.

Gust:

A brief, sudden increase in wind speed, generally of a duration less than 20 seconds with a fluctuation greater than 10 mph (9 knots).

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H

High Pressure:

An atmospheric condition characterized by air descending, compressing and warming. High pressure generally inhibits the formation of clouds, meaning fair weather.

High Surf Advisory:

A National Weather Service Bulletin advising hazardous wave conditions which could cause injury, death, or property damage to individuals or facilities in coastal areas. Advisories specify affected shorelines and a range of anticipated wave heights.

High Wind Warning:

A National Weather Service Bulletin issued when sustained winds of 40 mph (35 knots) or greater are occurring or expected to persist for an hour or longer or if winds of 58 mph (50 knots) or greater are expected for any duration.

High Wind Watch:

A National Weather Service Bulletin issued when conditions are favorable for the development of high winds over all of or part of the forecast area but the occurrence is still uncertain. A High Wind Watch includes the area affected, the reason for the watch and the potential impact of the winds.

I

Indian Ocean:

Ocean area extending from the east coast of Africa to the East Indies and Australia.

Isobar:

On a weather map, a line connecting points of equal pressure.

J

Jet Stream:

A meandering and relatively narrow belt of strong winds (speeds of 50 knots or more) embedded in the normal wind flow aloft, generally found at high altitudes.

K

Knot:

A unit of speed equal to one nautical mile (or about 1.15 statute miles) per hour.

Kona:

A stormy, rain bearing wind from the southwest or south-southwest in Hawaii. It blows about five times a year on the southwest slopes, which are in the lee of the prevailing northeast trade winds (kona is the Polynesian word meaning "leeward").

Kona Storm:

A migratory low found at the surface and/or aloft, and accompanied in the Hawaiian area by widespread heavy rain and southerly winds.

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L

La Nina:

A condition where the central and eastern tropical Pacific Ocean turns cooler than normal.

Leeward:

Often used in reference to islands, as the protected side of an island, facing away from the direction that the wind generally blows. In Hawaii, those areas somewhat protected from the trade winds and windward showers. Typically the drier sides of the islands.

Low Pressure:

An atmospheric condition characterized by air rising, expanding and cooling. Low pressure encourages cloud formation and precipitation, and is associated with stormy weather.

Low Tide:

The lowest water level reached during a tide cycle.

M

Marine Forecast:

A forecast, for a specified oceanic and/or coastal area, of weather elements of particular interest to maritime transportation. These elements include wind, visibility, the general state of the weather, and storm warnings.

Millibar:

A unit of atmospheric pressure, normal surface pressure is approximately 1013 millibars (29.92 inches of mercury).

MPH:

Miles per hour.

N

Nautical Mile:

A unit of length used in sea and air navigation equivalent to 1.15 statute miles or 1,852 meters. Also called a sea mile.

O

Oceanography:

The exploration and scientific study of the ocean and its phenomena.

Offshore waters:

That portion of oceans, gulfs, and seas beyond coastal waters extending to a specified distance from the coastline, to a specified depth contour, or covering an area defined by specific latitude and longitude points.

P

Pacific High:

The semi-permanent subtropical high, centered normally at 30 degrees to 40 degrees North and 140 to 150 degrees West.

Pressure:

The forces exerted by the interaction of the atmosphere and gravity. A measure of the weight of the air, in meteorology usually measured with a barometer. Also known as atmospheric pressure.

Prevailing Wind:

The wind direction most frequently observed.

Primary swell direction:

The prevailing direction of swell propagation.

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Q

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R

Rip Current:

A narrow, powerful current of water that runs perpendicular to the beach, typically extending 200 to 2,500 feet (61 to 762 meters) in length, and less than 30 feet (9 meters) wide.

Rogue Wave:

An unpredictable, abnormally large wave that occurs on a seemingly random basis in the oceans.

S

Significant wave height:

The average height (trough to crest) of the 1/3rd highest waves. An experienced observer will most frequently report the highest 1/3rd of the waves observed.

Small Craft:

Generally a vessel under 65 feet (17 meters) in length. When a tropical cyclone threatens a coastal area, small craft operators are advised to remain in port or not to venture into the open sea.

Small Craft Advisory:

A marine advisory generally issued for winds greater than 23 mph (20 knots) but less than 38 mph (33 knots).

Storm Surge:

A phenomenon caused by extremely low pressure and strong winds around the eye of a hurricane that cause a dome of water to form at levels higher than the surrounding ocean surface. Large swells, high surf, and wind-driven waves ride atop the dome as it impacts land areas causing extensive damage to facilities and the shoreline environment. This buildup of water can produce severe flooding in coastal areas, particularly when storm surge coincides with normal high tides. Storm surge may severely erode beaches and highways, and undermine bridges.

Storm Warning:

A marine warning issued to denote wind speeds of 48-63 knots (55-73 mph).

Super Typhoon:

A typhoon with sustained winds of 150 mph (130 knots) or greater.

Surf:

The sea-surface wave activity occurring between a shoreline and the outermost line of breakers.

Surface Pressure:

The pressure exerted by the atmosphere at a given location on the earth's surface.

Surf Advisories:

Issued to denote high surf for a particular beach or beaches. (In Hawaii, limits vary for selected beaches.)

Sustained Winds:

The wind speed obtained by averaging the observed values over a one-minute period.

Swell:

Wind waves that have moved out of their fetch or wind generation area. Waves generated by swell exhibit a regular and longer period than wind waves.

Synoptic:

Refers to the overall condition of the atmosphere at a given time.

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T

Tide:

The periodic rising and falling of the earth's oceans and atmosphere resulting from the gravitational forces of the moon and sun acting upon the rotating earth. This disturbance actually propagates as a wave through the atmosphere and along the surface of the waters of the earth.

Tide Table:

Annual tabulations of daily predictions of the times and heights of high and low water at various places. Such tables are constructed from astronomical data and the results of harmonic analysis of previous observations at the desired point.

Tropical Cyclone:

The general term for all cyclonic circulations that originate over tropical waters. Circulation is counter-clockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere. Related phenomena such as inland or coastal flooding due to heavy rainfall, high wind, landslides, hazardous-material release, storm surge, and/or high surf commonly occur during a tropical cyclone event.

Tsunami:

An ocean wave generated by a submarine earthquake, volcano, or landslide. Also known as a seismic seawave.

Typhoon:

A hurricane occurring west of the International Dateline (180 degrees west longitude).

U

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V

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W

Warning:

Issued when a threat is imminent or expected to occur within 24 hours or less. Actions for protection of life and property should begin immediately.

Watch:

Issued when a threat is expected within 24 to 36 hours. Preliminary precautions should be taken.

Wave Height:

The height of a water-surface wave generally taken as the difference between the wave crest and preceding trough.

Wave Length:

The distance between any two adjacent corresponding locations on the wave train, usually measured in one of three ways: crest to next crest, trough to next trough, or from the start of a wave cycle to the next starting point.

Western Pacific:

Pacific Ocean area extending west of the International Dateline to Asia and Australia.

Wind Advisory:

Issued for the occurrence of wind gusts between 40 and 57 mph (35 and 50 knots) for any duration.

Wind Direction:

The direction from which the wind blows.

Windward:

Of or on the side exposed to the wind or to prevailing winds. In Hawaii, those areas exposed to the northeast trade winds and typically the wet sides of the islands due to enhanced shower activity.

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X

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Y

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Z

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