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Subject: D1) How are Atlantic hurricanes ranked?
Contributed by Chris Landsea (NHC)
The USA utilizes the Saffir-Simpson hurricane intensity scale
(Simpson and Riehl 1981) for the Atlantic
and Northeast Pacific basins to give an estimate of the potential flooding and
damage to property given a hurricane's estimated intensity:
Saffir-Simpson Scale
Saffir-Simpson Category |
Maximum sustained wind speed |
mph | m/s |
kts |
1 |
74-95 |
33-42 |
64-82 |
2 |
96-110 |
43-49 |
83-95 |
3 |
111-129 |
50-58 |
96-112 |
4 |
130-156 |
59-69 |
113-136 |
5 |
≥157 |
≥70 |
≥137 |
Note : Classification by central pressure was ended in the 1990s, and wind
speed alone is now used. Surge values are no longer referenced in this
scale. The actual storm surge experienced will depend on offshore bathymetery
and onshore terrain and construction. A minor modification was made to the
limits of Categories 3, 4, and 5 on May 15, 2012 to resolve rounding errors.
Damage
Category | Level | Description | Example |
1 |
MINIMAL |
Hurricane Dolly (2008) |
People, livestock, and pets struck by flying or falling debris could be injured
or killed. Older (mainly pre-1994 construction) mobile homes could be destroyed
, especially if they are not anchored properly as they tend to shift or roll
off their foundations. Newer mobile homes that are anchored properly can
sustain damage involving the removal of shingle or metal roof coverings, and
loss of vinyl siding, as well as damage to carports, sunrooms, or lanais. Some
poorly constructed frame homes can experience major damage, involving loss of
the roof covering and damage to gable ends as well as the removal of porch
coverings and awnings. Unprotected windows may break if struck by flying
debris. Masonry chimneys can be toppled. Well-constructed frame homes could
have damage to roof shingles, vinyl siding, soffit panels, and gutters.
Failure of aluminum, screened-in, swimming pool enclosures can occur. Some
apartment building and shopping center roof coverings could be partially
removed. Industrial buildings can lose roofing and siding especially from
windward corners, rakes, and eaves. Failures to overhead doors and unprotected
windows will be common. Windows in high-rise buildings can be broken by flying
debris. Falling and broken glass will pose a significant danger even after the
storm. There will be occasional damage to commercial signage, fences, and
canopies. Large branches of trees will snap and shallow rooted trees can be
toppled. Extensive damage to power lines and poles will likely result in power
outages that could last a few to several days.
| 2 |
MODERATE |
Hurricane Frances (2004) |
There is a substantial risk of injury or death to people, livestock, and
pets due to flying and falling debris. Older (mainly pre-1994 construction)
mobile homes have a very high chance of being destroyed and the flying debris
generated can shred nearby mobile homes. Newer mobile homes can also be
destroyed. Poorly constructed frame homes have a high chance of having their
roof structures removed especially if they are not anchored properly.
Unprotected windows will have a high probability of being broken by flying
debris. Well-constructed frame homes could sustain major roof and siding damage
. Failure of aluminum, screened-in, swimming pool enclosures will be common.
There will be a substantial percentage of roof and siding damage to apartment
buildings and industrial buildings. Unreinforced masonry walls can collapse.
Windows in high-rise buildings can be broken by flying debris. Falling and
broken glass will pose a significant danger even after the storm. Commercial
signage, fences, and canopies will be damaged and often destroyed. Many
shallowly rooted trees will be snapped or uprooted and block numerous roads.
Near-total power loss is expected with outages that could last from several
days to weeks. Potable water could become scarce as filtration systems begin
to fail.
|
3 |
EXTENSIVE |
Hurricane Ivan (2004) |
There is a high risk of injury or death to people, livestock, and pets due
to flying and falling debris. Nearly all older (pre-1994) mobile homes will be
destroyed. Most newer mobile homes will sustain severe damage with potential
for complete roof failure and wall collapse. Poorly constructed frame homes can
be destroyed by the removal of the roof and exterior walls. Unprotected windows
will be broken by flying debris. Well-built frame homes can experience major
damage involving the removal of roof decking and gable ends. There will be a
high percentage of roof covering and siding damage to apartment buildings and
industrial buildings. Isolated structural damage to wood or steel framing can
occur. Complete failure of older metal buildings is possible, and older
unreinforced masonry buildings can collapse. Numerous windows will be blown out
of high-rise buildings resulting in falling glass, which will pose a threat for
days to weeks after the storm. Most commercial signage, fences, and canopies
will be destroyed. Many trees will be snapped or uprooted, blocking numerous
roads. Electricity and water will be unavailable for several days to a few
weeks after the storm passes.
|
4 |
EXTREME |
Hurricane Charley (2004) |
There is a very high risk of injury or death to people, livestock, and pets
due to flying and falling debris. Nearly all older (pre-1994) mobile homes will
be destroyed. A high percentage of newer mobile homes also will be destroyed.
Poorly constructed homes can sustain complete collapse of all walls as well as
the loss of the roof structure. Well-built homes also can sustain severe damage
with loss of most of the roof structure and/or some exterior walls. Extensive
damage to roof coverings, windows, and doors will occur. Large amounts of
windborne debris will be lofted into the air. Windborne debris damage will
break most unprotected windows and penetrate some protected windows. There will
be a high percentage of structural damage to the top floors of apartment
buildings. Steel frames in older industrial buildings can collapse. There will
be a high percentage of collapse to older unreinforced masonry buildings. Most
windows will be blown out of high-rise buildings resulting in falling glass,
which will pose a threat for days to weeks after the storm. Nearly all
commercial signage, fences, and canopies will be destroyed. Most trees will be
snapped or uprooted and power poles downed. Fallen trees and power poles will
isolate residential areas. Power outages will last for weeks to possibly months
. Long-term water shortages will increase human suffering. Most of the area
will be uninhabitable for weeks or months.
|
5 |
CATASTROPHIC |
Hurricane Andrew (1992) |
People, livestock, and pets are at very high risk of injury or death from
flying or falling debris, even if indoors in mobile homes or framed homes.
Almost complete destruction of all mobile homes will occur, regardless of age
or construction. A high percentage of frame homes will be destroyed, with total
roof failure and wall collapse. Extensive damage to roof covers, windows, and
doors will occur. Large amounts of windborne debris will be lofted into the
air. Windborne debris damage will occur to nearly all unprotected windows and
many protected windows. Significant damage to wood roof commercial buildings
will occur due to loss of roof sheathing. Complete collapse of many older
metal buildings can occur. Most unreinforced masonry walls will fail which can
lead to the collapse of the buildings. A high percentage of industrial
buildings and low-rise apartment buildings will be destroyed. Nearly all
windows will be blown out of high-rise buildings resulting in falling glass,
which will pose a threat for days to weeks after the storm. Nearly all
commercial signage, fences, and canopies will be destroyed. Nearly all trees
will be snapped or uprooted and power poles downed. Fallen trees and power
poles will isolate residential areas. Power outages will last for weeks to
possibly months. Long-term water shortages will increase human suffering. Most
of the area will be uninhabitable for weeks or months.
|
Note that tropical storms are not on this scale, but can
produce extensive damage with rainfall-produced flooding. Note
also that category 3, 4, and 5 hurricanes are collectively
referred to as major (or intense) hurricanes. These major
hurricanes cause over 83% of the damage in the USA even though
they account for only 21% of tropical cyclone landfalls
(Landsea 1993).
Last Modified : May 12, 2012
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