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Hurricane Terminology

Storm Structure

The process by which a disturbance forms and subsequently strengthens into a hurricane depends on at least three conditions. Warm waters, moisture, and a wind pattern near the ocean surface that spirals air inward. Bands of thunderstorms form, allowing the air to warm further and rise higher into the atmosphere. If the winds at these higher levels are relatively light, this structure can remain intact and allow for additional strengthening.

  • Hurricane
  • Tropical Storm
  • Non-Tropical Storm
  • Marine

A hurricane is a tropical cyclone in the Atlantic, Caribbean Sea, Gulf of Mexico, or eastern Pacific, which the maximum 1-minute sustained surface wind is 64 knots (74 mph) or greater, either predicted or occurring, and not directly associated with a tropical cyclone.
Eye - The relatively calm center in a hurricane that is more that one half surrounded by wall cloud. The winds are light, the skies are partly cloudy or even clear (the skies are usually free of rain) and radar depicts it as an echo-free area within the eye wall.
Eyewall - It is an organized band of cumuliform clouds that immediately surrounds the center (eye) of a hurricane. The fiercest winds and most intense rainfall typically occur near the eye wall. VIP level 3 (moderate to heavy rain) or greater are typical. Eye wall and wall cloud are used synonymously, but it should not be confused with a wall cloud of a thunderstorm.
Storm Surge - An abnormal rise in sea level accompanying a hurricane or other intense storm, whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic tide from the observed storm tide.
Advisory - Highlights special weather conditions that are less serious than a warning. They are for events that may cause significant inconvenience, and if caution is not exercised, it could lead to situations that may threaten life and / or property.
Hurricane Watch - An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.
Hurricane Warning - An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds. The warning can remain in effect when dangerously high water or a combination of dangerosly high water and waves continue, even though winds may be less than hurricane force.

Tropical Depression - A tropical cyclone in which the maximum 1-minute sustained surface wind is 33 knots (38 mph) or less.
Tropical Storm - A tropical cyclone in which the maximum 1-minute sustained surface wind ranges from 34 to 63 knots (39 to 73 mph) inclusive.
Tropical Storm Watch - An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are possible within the specified coastal area within 48 hours.
Tropical Storm Warning - An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are expected somewhere within the specified coastal area within 36 hours.
Gale Watch - A watch for an increased risk of a gale force wind event for sustained surface winds, or frequest gusts, of 34 knots (39 mph) to 47 knots (54 mph), but its occurrence, location, and / or timing is still uncertain.
Gale Warning - A warning of sustained surface winds, or frequest gusts, in the range of 34 knots (39 mph) to 47 knots (54 mph) inclusive, either predicted or occurring, and not directly associated with a tropical cyclone.
Storm Watch - A watch for an increased risk of a storm force wind event for sustained surface winds, or frequent gusts, of 48 knots (55 mph) to 63 knots (73 mph), but its occurrence, location, and / or timing is still uncertain..
Storm Warning - A warning of sustained surface winds, or frequest gusts, in the range of 48 knots (55 mph) to 63 knots (73 mph) inclusive, either predicted or occurring, and not directly associated with a tropical cyclone.
Coastal Waters Forecast (CWF) - The marine forecast for areas, including bays, harbors, and sounds, from a line approximating the mean high water mark (average height of high water over a 19-year period) along the mainland or near shore islands extending out to as much as 100 NM.
Marine Weather Statements - A National Weather Service product to provide mariners with details on significant or potentially hazardous conditions not otherwise covered in existing marine warnings and forecasts. Marine weather statements are also used to supplement special marine warnings.
Special Marine Warning (SMW) - A warning product issued for potentially hazardous weather conditions usually of short duration (up to 2 hours) producing sustained marine thunderstorm winds or associated gusts of 34 knots or greater; and / or hail 3/4 inch or more in diameter; and / or waterspouts affecting areas included in a Coastal Waters Forecast, a Nearshore Marine Forecast, or a Great Lakes Open Lakes Forecast that is not adequately covered by existing marine warnings. Also used for short duration mesoscale events such as a strong cold front, gravity wave, squall line, etc., lasting less than 2 hours and producing winds or gusts of 34 knots or greater.

 

 

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