- HURRICANE DEFINITIONS
Know your hurricane season terminology
|
- Tropical depression: A tropical system in which the maximum sustained
surface w.nd is 33 knots (38 mph) or less. Though the wind speeds
are significantly less than those in a hurricane, tropical depressions
are capable of producing tremendous rainfall amounts.
|
- Tropical storm:
A tropical system in which the maximum sustained surface wind
ranges from 34 to 63 knots (39 to 73 mph). These systems are
also intense rainfall producers, but often cause enough wind
and waves to cause some beach erosion and minor boat damage.
|
- Hurricane:
A tropical system in which the maximum sustained surface wind
is 64 knots (74 mph) or greater. This is the worst and strongest
of all tropical systems.
|
- Hurricane eye:
A relatively calm area in the center of the storm. In this area,
winds are light and the sky often is only partly covered by clouds.
Never go outside in the eye of the storm. This period of calm
may only last 10 to 20 minutes before hurricane force winds and
torrential rains return.
|
- Storm surge:
An abnormal rise in sea level accompanying a hurricane or other
intense storm. The height of the storm surge is the difference
between the observed level of the sea surface and the astronomical
tide that would have occurred in the absence of the storm.
|
- Tropical storm watch: An announcement that a tropical storm or tropical
storm conditions pose a threat to coastal areas generally within
36 hours.
|
- Tropical storm warning: A warning that a tropical storm or tropical storm
conditions, including sustained winds of 39 to 73 mph, will affect
a specified coastal area within 24 hours or less.
|
- Hurricane watch:
An announcement for specific areas that a hurricane or hurricane
conditions pose a possible threat to coastal areas generally
within 36 hours.
|
- Hurricane warning: A warning that hurricane conditions including
sustained winds of 74 mph or greater associated with a hurricane
are expected in a specified coastal area within 24 hours or less.
Any preparedness measures must be rushed to completion once the
warning is issued. High winds and coastal flooding will develop
many hours before the eye of the storm actually comes ashore.
|
- Inland high wind watch for hurricane
force winds: An announcement for
inland areas that sustained winds of 74 mph or greater associated
with a hurricane are anticipated beyond the coastal areas though
the actual occurrence, timing and location are still uncertain.
|
- Inland high wind warning for hurricane
force winds: An announcement for
inland areas that sustained winds of 74 mph or greater associated
with a hurricane are anticipated beyond the coastal areas in
the next six to twelve hours.
|
- Hurricane local statement: A public release prepared by your local National
Weather Service office in or near the threatened area giving
specific details on weather conditions, evacuation decisions
made by local officials, and other precautions necessary to protect
life and property.
|
|
Saffir/Simpson Hurricane Scale:
The Saffir-Simpson Hurricane Scale is used to rate
the intensities of a hurricane in Categories from 1 to 5 and
assess the damage potential in each category.All hurricanes are
dangerous, but some are more so than others. The way storm surge,
wind, and other factors combine determines the hurricane's destructive
power. To make comparisons easier, and to make the predicted
hazards of approaching hurricanes clearer to emergency forces,
National Oceanic and Atmospheric Administration's hurricane forecasters
use a disaster-potential scale which assigns storms to five categories.
Category 1 is a minimum hurricane; category 5 is the worst case.
This can be used to give an estimate of the potential property
damage and flooding expected along the coast with a hurricane.
The criteria for each category are shown below.
-
| Category |
Definition-Effects |
| ONE |
Winds
74-95 mph: No real damage to building structures.
Damage primarily to unanchored mobile homes, shrubbery, and trees.
Also, some coastal road flooding and minor pier damage. |
| TWO |
Winds
96-110 mph: Some roofing material, door, and window
damage to buildings. Considerable damage to vegetation, mobile
homes, and piers. Coastal and low-lying escape routes flood 2-4
hours before arrival of center. Small craft in unprotected anchorages
break moorings. |
| THREE |
Winds
111-130 mph: Some structural damage to small residences
and utility buildings with a minor amount of curtainwall failures.
Mobile homes are destroyed. Flooding near the coast destroys
smaller structures with larger structures damaged by floating
debris. Terrain continuously lower than 5 feet ASL may be flooded
inland 8 miles or more. |
| FOUR |
Winds
131-155 mph: More extensive curtainwall failures with
some complete roof structure failure on small residences. Major
erosion of beach areas. Major damage to lower floors of structures
near the shore. Terrain continuously lower than 10 feet ASL may
be flooded requiring massive evacuation of residential areas
inland as far as 6 miles. |
| FIVE |
Winds
greater than 155 mph: Complete roof failure on many
residences and industrial buildings. Some complete building failures
with small utility buildings blown over or away. Major damage
to lower floors of all structures located less than 15 feet ASL
and within 500 yards of the shoreline. Massive evacuation of
residential areas on low ground within 5 to 10 miles of the shoreline
may be required. |
|