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Tropical Storm and Hurricane Glossary of Terms

When Is Hurricane Season?

The official hurricane season set by the National Hurricane Center runs from June 1 to November 30 of each year.

Cyclone

An atmospheric closed circulation rotating counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Tropical Depression

A tropical cyclone in which the maximum sustained surface wind speed is 33 kt (38 mph or 62 km/hr) or less.

Tropical Storm

A tropical cyclone in which the maximum sustained surface wind speed ranges from 34 kt (39 mph or 63 km/hr) to 63 kt (73 mph or 118 km/hr).

Storm Warning

A warning of sustained surface winds of 48 kt (55 mph or 88 km/hr) or greater, either predicted or occurring, not directly associated with tropical cyclones.

Hurricane Watch

An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified 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 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.

Saffir-Simpson Hurricane Wind Scale

The Saffir-Simpson Hurricane Wind Scale uses a rating scale of 1 to 5 based on the hurricane's intensity at the indicated time.

When winds in a tropical cyclone equal or exceed 74 mph (64 kt or 34 m/s) it is called a hurricane. Hurricanes are further designated by categories on the Saffir-Simpson scale. Hurricanes in categories 3, 4, 5 are known as Major Hurricanes, or Intense Hurricanes.

Category 1 74-95 mph
Category 2 96-110 mph
Category 3 111-130 mph
Category 4 131-155 mph
Category 5 156+ mph

Longitude of Key Areas Frequented by Atlantic Hurricanes

15°	Senegal
25°	Cape Verde Islands
60°	Lesser Antilles
70°	Dominican Republic
80°	Miami
90°	New Orleans

Saharan Air Layer (SAL)

Saharan Air Layer (SAL)

The Saharan Air Layer (SAL) is an intensely dry, warm and sometimes dust-laden layer of the atmosphere which often overlays the cooler, more-humid surface air of the Atlantic Ocean. In the Sahara Desert region of North Africa, where it originates, it is the prevalent atmosphere, extending from the surface upwards several kilometers. As it drives, or is driven, out over the ocean, it is lifted above the denser marine air. This arrangement is an inversion boundary where the temperature increases with height; this suppresses or "caps" any convection in the marine layer. Since it is dry air, the lapse rate within the SAL is steep, that is, the temperature falls rapidly with height.

Disturbances over North Africa periodically result in vast dust and sand storms, some of which extend as high as 20,000 feet. These can be driven out to sea within the SAL as far west as North America. These clouds of dust are visible in satellite photos. (courtesy of WikiPedia)

Map Atlas of Selected Tropical Areas

Bahamas	Caribbean Sea
Turks & Caicos Islands, Hispanola	Greater & Lesser Antilles
	Lesser Antilles: Leeward & Windward Islands
Cape Verde Islands	Cuba
Florida Keys & Key West	Mexico and Central America

Surface Fronts on Weather Maps

A quick explanation of how cold fronts, warm fronts and other fronts are depicted on weather maps (from NHC).

Barometric Pressure Conversion
Standard Atmospheric Pressure:
29.92 inHg or 1013.2 mb
1 knot = 1.15 mph

read more about the conventions used in Wind Barbs