When tropical weather starts to threaten, weather forecasts are filled with new terms and ideas that can be confusing especially to people new to South Florida and tropical weather. These terms should help demystify hurricane season, and help you to feel a bit more confident as we face the season of storms.
Tropical Wave
An inverted trough (an elongated area of relatively low pressure) or cyclonic curvature maximum moving east to west across the tropics. These can lead to the formation of a tropical cyclone. Also known as an easterly wave.
An inverted trough (an elongated area of relatively low pressure) or cyclonic curvature maximum moving east to west across the tropics. These can lead to the formation of a tropical cyclone. Also known as an easterly wave.
Tropical Disturbance
A tropical weather system with organized convection (generally
100-300 miles in diameter) originating in the tropics or subtropics, having a
non-frontal migratory character and maintaining its identity for 24 hours or
longer. It may or may not be associated with a detectable perturbation of the
wind field.
Tropical Depression
A tropical cyclone in which the maximum sustained surface wind speed is 38 MPH (33 knots) or less. Sustained winds are defined as one-minute average wind measured at about 33 ft (10 meters) above the surface.
A tropical cyclone in which the maximum sustained surface wind speed is 38 MPH (33 knots) or less. Sustained winds are defined as one-minute average wind measured at about 33 ft (10 meters) above the surface.
Tropical Storm
A tropical cyclone in which the maximum sustained surface
wind speed is between 39 -73 MPH (34-63 knots).
Hurricane
An intense tropical cyclone with maximum sustained surface wind
speeds of 74 MPH (64 knots) or higher. The term hurricane is used for
Northern Hemisphere tropical cyclones east of the International Dateline to the
Greenwich Meridian. The term typhoon is used for Pacific tropical cyclones
north of the Equator west of the International Dateline.
Eye Wall
An organized band of cumulonimbus clouds immediately surrounding
the center of the tropical cyclone.
Landfall
The intersection of the surface center of a tropical cyclone with a coastline. Because the strongest winds in a tropical cyclone are not located precisely at the center, it is possible for a cyclone’s strongest winds to be experienced over land even if landfall does not occur. Similarly, it is possible for a tropical cyclone to make landfall and have its strongest winds remain over the water.
The intersection of the surface center of a tropical cyclone with a coastline. Because the strongest winds in a tropical cyclone are not located precisely at the center, it is possible for a cyclone’s strongest winds to be experienced over land even if landfall does not occur. Similarly, it is possible for a tropical cyclone to make landfall and have its strongest winds remain over the water.
Tropical Cyclone
A low pressure system (not associated with a front) that
develops over tropical and sometimes sub-tropical waters and has organized deep
convection with a closed wind circulation about a well-defined center.
Extratropical Cyclone
A cyclone (of any intensity) for which the primary energy source is baroclinic (i.e., results from the temperature contrast between warm & cold air masses).
A cyclone (of any intensity) for which the primary energy source is baroclinic (i.e., results from the temperature contrast between warm & cold air masses).
Post-Tropical Cyclone
A cyclone that no longer possesses sufficient tropical
characteristics to be considered a tropical cyclone. Post-tropical cyclones can
continue to carry heavy rains and high winds. Note: former tropical cyclones
that become extratropical and remnant lows are 2 specific classes of
post-tropical cyclones.
Remnant Low
A class of post-tropical cyclone that no longer possesses the convective organization required of a tropical cyclone and has maximum sustained winds of less than 34 knots.
A class of post-tropical cyclone that no longer possesses the convective organization required of a tropical cyclone and has maximum sustained winds of less than 34 knots.
Storm Surge
An abnormal rise in sea level accompanying a hurricane or other
intense storm, and 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 high tide from the observed storm tide.
Storm Tide
The actual level of sea water resulting from the astronomic tide combined with the storm surge.
The actual level of sea water resulting from the astronomic tide combined with the storm surge.
Tropical Storm Watch
An announcement that sustained winds of 39 to 73 mph are possible within the specified area within 48 hours in association
with a tropical, subtropical, or post-tropical cyclone.
Tropical Storm Warning
An announcement that sustained winds of 39 to 73 mph are expected somewhere within the specified area within 36 hours in
association with a tropical, subtropical, or post-tropical cyclone.
Hurricane Watch
An announcement that sustained winds of 74 mph or higher are possible within the specified area in association with a tropical, subtropical, or post-tropical cyclone. 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.
An announcement that sustained winds of 74 mph or higher are possible within the specified area in association with a tropical, subtropical, or post-tropical cyclone. 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 sustained winds of 74 mph or higher
are expected somewhere within the specified area in
association with a tropical, subtropical, or post-tropical cyclone. Because
hurricane preparedness activities become difficult once winds reach tropical
storm force, the
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 dangerously high water and waves continue, even
though winds may be less than hurricane force.
Short Term Watches and Warnings
These warnings provide detailed information about specific hurricane threats, such as flash floods and tornadoes.
These warnings provide detailed information about specific hurricane threats, such as flash floods and tornadoes.
Source: FEMA
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