Weather Terminology

Hurricane Season - June 1st through November 30th is officially designated as hurricane season.

Tropical Depression - A circulation at the surface of the water with a sustained wind speed of 38 mph or less.

Tropical Storm - Distinct circulation with sustained wind speeds of 39 to 73 mph.

Tropical Storm Watch - The alert given when a tropical storm poses a threat to a certain coastal area within 36 hours.

Tropical Storm Warning - A tropical storm is expected to strike within 24 hours with sustained winds of 39 to 73 mph.

Hurricane - A tropical cyclone that rotates counterclockwise with sustained winds of 74 mph or greater.

Hurricane Watch - The alert given when a hurricane poses a threat to a certain coastal area within 36 hours.

Hurricane Warning - A hurricane is expected to strike within 24 hours with sustained winds of 74 mph or more accompanied by heavy rain and high waves.

Small Craft Advisory - An advisory to alert mariners of expected or occurring conditions which are considered potentially hazardous to small weather sensitive boats. This statement is highlighted in the marine forecast when winds are expected to be greater than 20 knots or seas 7 feet or higher.

Small Craft Should Exercise Caution - Precautionary statement issued to alert mariners with small, weather sensitive boats. This statement is highlighted in the marine forecast when winds are expected to be 15 to 20 knots or seas to 6 feet.

Special Marine Warning (SMW) - Issued to warn mariners of short-lived hazardous marine weather situations. Examples of these would be strong thunderstorms or waterspouts.

Gale Warning - A warning to mariners for expected or occurring conditions where winds are sustained between 34 and 47 knots for extra tropical systems.

Land/Sea Breeze - A coastal breeze blowing toward the ocean/land, caused by temperature differences when the sea surface is warmer (land breeze) or cooler (sea breeze) than nearby land. Therefore it usually blows during the night (land breeze) or day (sea breeze).

Marine Weather Statement (MWS) - Issued to advise the public and marine community of minor coastal marine problems such as: Heavy surf, beach erosion, rip currents, and winds less than 35 knots. These statements can also be issued to provide additional information when a marine warning or advisory is in effect.

Rip Currents - Also known as rip tide. A strong water-surface current of short duration flowing seaward from the shore. Usually appears as a band of agitated water. Swimmers also know this as undertow.

Swells - Ocean waves that have traveled out of their place of origin. Swells are characterized by a more regular and longer period and flatter crests than wind waves.

Tides - Alternating rise and fall in sea level produced by the interactions between the earth and primarily the moon and sun. Tides affect bays, sounds and extend up rivers. Other factors that influence the tides include coastline shape, water depth, ocean-floor topography and meteorological effects of different scales.

Force 0: Calm. Winds less than 1 mph.

Force 1: Light air. Winds 1-3 mph. Ripples on the water's surface.

Force 2: Light breeze, 4-7 mph. Small wavelets developing.

Force 3: Gentle breeze, 8-12 mph. Large wavelets with scattered whitecaps.

Force 4: Moderate breeze, 13-18 mph. Waves 2-3 feet with whitecaps becoming numerous.

Force 5: Fresh breeze, 19-24 mph. Waves 4-7 feet. Sea spray begins.

Force 6: Strong breeze, 25-31 mph. Waves 7-14 feet. White caps everywhere. Spray increasing.

Force 7: Near gale, 32-38 mph. Seas 14-18 feet. Foam begins to blow in streaks.

Force 8: Gale, 39-46 mph. Blinding foam begins blowing in streaks.

Force 9: Strong gale, 47-54 mph. 20 foot waves.

Force 10: Storm. Wind 55-63 mph. Waves 20-30 feet.

Force 11: Violent storm, 64-73 mph. Waves 30-45 feet.

Force 12: Hurricane, 74-82 mph. Air filled with foam. Waves as high as 50 feet.

Weather Fronts
Fronts form when air masses of different temperatures collide. When a cold air mass catches up with warm air, the heavier cold air pushes under the warm air mass and lift it, causing stormy weather. In a warm front, the warm air rides up and over the cold, generally producing less sever storms than a cold front.

By knowing the normal sequence of weather as a front passes through, you can predict the weather conditions fairly accurately.

Cold Fronts
Cold fronts move at speed from 10 to 50 knots. In winter they are 2 or 3 times faster than in summer. A fast-moving cold front may be preceded by a squall line, a roll of black, threatening clouds with violent storms. Wind shifts suddenly along the front, and wind velocities increase dramatically. Behind the squall line are heavy rains, then clearing, and gusty winds, usually followed by several days of clear, cool weather.

Warm Fronts
Warm fronts are quite different. The high, thin cirrus clouds that form when the warm air climbs up and over the retreating cold air mass can extend as far as 1,000 miles ahead of the front. these clouds thicken and lower as the front advances, and winds increase steadily. As the clouds lower, rain or snow begins to fall, continuing until after the front passes. The winds shift clockwise and decrease. The temperature begins to rise and visibility becomes poor.

Behind the warm front are thick, low stratus clouds and possibly more rain. Once the front passes, the skies clear and wind normally blows from the southwest. Since cold fronts frequently follow a passing warm front, the duration of good weather may be short.

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