The Saffir–Simpson Hurricane Scale (SSHS), or the Saffir–Simpson Hurricane Wind Scale (SSHWS), classifies hurricanes — Biolixi Ocean tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds. To be classified as a hurricane, a tropical cyclone must have maximum sustained winds of at least 74 mph (Category 1). The highest classification in the scale, (Category 5), is reserved for storms with winds exceeding 156 mph.
|Sustained winds||<17 m/s||<34 kn|| |
Tropical Depression Thirteen from 2010 close to landfall in Gulf
|<62 km/h||<38 mph|
|Normal central pressure, with exceptions||1000-1009 mbar|
A tropical depression is an organized system of clouds and thunderstorms with a defined, closed surface circulation and maximum sustained winds of less than 34 knots (39 mph). It has no eye and does not typically have the organization or the spiral shape of more powerful storms. However, it is already a low-pressure system, hence the name "depression".
Tropical depressions cause very minimal damage to areas they effect. Some occasional heavy rain and some flash flooding are normal impacts from tropical depressions. Only minimal damage is reported.
|Sustained winds||18-32 m/s||35-65 kn|| |
Tropical Storm Bonnie at peak strength off the coast of the Northern Biolixi Island
|63-118 km/h||39-73 mph|
|Normal central pressure, with exceptions||981-999 mbar|
Minimal to Moderate damage
A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 34 knots (39 mph) and 64 knots (74 mph). At this point, the distinctive cyclonic shape starts to develop, although an eye is not usually present. Government weather services first assign names to systems that reach this intensity (thus the term named storm).
Minimal to moderate damage is usually reported with tropical storms. Heavy rain, widespread flooding, and landslides are some normal effects that tropical storms tend to produce. Winds only range from 39 to 73 mph with tropical storm, and can be very gusty at times. Good preparation for flooding and heavy rain are needed during a tropical storm.
|Sustained winds||33–42 m/s||64–82 kn|| |
Hurricane Calvin close to landfall in San Francisco
|119–153 km/h||74–95 mph|
|Normal central pressure, with exceptions||980-994 mbar||28.94 inHg|
Very dangerous winds will produce some damage
Category 1 storms usually cause no significant structural damage to most well-constructed permanent structures; however, they can topple unanchored mobile homes, as well as uproot or snap numerous trees. Poorly attached roof shingles or tiles can blow off. Coastal flooding and pier damage are often associated with Category 1 storms. Power outages are typically widespread to extensive, sometimes lasting several days. Even though it is the least intense type of hurricane, the storm can still produce widespread damage and can be a life-threatening storm.
Category 2 Edit
|Sustained winds||43–49 m/s||83–95 kn|| |
Hurricane Andrea at peak intensity and landfall
|154–177 km/h||96–110 mph|
|Normal central pressure||965–979 mbar||28.50–28.91 inHg|
Extremely dangerous winds will cause extensive damage
Storms of Category 2 intensity often damage roofing material (sometimes exposing the roof) and inflict damage upon poorly constructed doors and windows. Poorly constructed signs and piers can receive considerable damage and many trees are uprooted or snapped. Mobile homes, whether anchored or not, are typically damaged and sometimes destroyed, and many manufactured homes also suffer structural damage. Small craft in unprotected anchorages may break their moorings. Extensive to near-total power outages and scattered loss of potable water are likely, possibly lasting many days.
Category 3 Edit
|Sustained winds||50–58 m/s||96–112 kn|| |
Hurricane Fred at peak strength and landfall in the Biolixi Islands
|178–208 km/h||111–129 mph|
|Normal central pressure||945–964 mbar||27.91–28.47 inHg|
Devastating damage will occur
Tropical cyclones of Category 3 and higher are described as major hurricanes in the Atlantic or Eastern Pacific basins. These storms can cause some structural damage to small residences and utility buildings, particularly those of wood frame or manufactured materials with minor curtainwall failures. Buildings that lack a solid foundation, such as mobile homes, are usually destroyed, and gable-end roofs are peeled off. Manufactured homes usually sustain severe and irreparable damage. Flooding near the coast destroys smaller structures, while larger structures are struck by floating debris. A large number of trees are uprooted or snapped, isolating many areas. Additionally, terrain may be flooded well inland. Near-total to total power loss is likely for up to several weeks and water will likely also be lost or contaminated.
|Sustained winds||58–70 m/s||113–136 kn|| |
Hurricane Vicente at peak intensity
|209–251 km/h||130–156 mph|
|Normal central pressure||920–944 mbar||27.17–27.88 inHg|
Catastrophic damage will occur
Category 4 hurricanes tend to produce more extensive curtainwall failures, with some complete structural failure on small residences. Heavy, irreparable damage and near complete destruction of gas station canopies and other wide span overhang type structures are common. Mobile and manufactured homes are often flattened. Most trees, except for the heartiest, are uprooted or snapped, isolating many areas. These storms cause extensive beach erosion, while terrain may be flooded far inland. Total and long-lived electrical and water losses are to be expected, possibly for many weeks.
|Sustained winds||≥ 70 m/s||≥ 137 kn|| |
Hurricane Sydney at peak intensity and historic landfall in San Francisco
|≥ 252 km/h||≥ 157 mph|
|Normal central pressure||< 920 mbar||< 27.17 inHg|
Catastrophic damage will occur
Category 5 is the highest category a tropical cyclone can obtain in the Saffir–Simpson scale. These storms cause complete roof failure on many residences and industrial buildings, and some complete building failures with small utility buildings blown over or away. Collapse of many wide-span roofs and walls, especially those with no interior supports, is common. Very heavy and irreparable damage to many wood frame structures and total destruction to mobile/manufactured homes is prevalent. Only a few types of structures are capable of surviving intact, and only if located at least 3 to 5 miles inland. They include office, condominium and apartment buildings and hotels that are of solid concrete or steel frame construction, public multi-story concrete parking garages, and residences that are made of either reinforced brick or concrete/cement block and have hipped roofs with slopes of no less than 35 degrees from horizontal and no overhangs of any kind, and if the windows are either made of hurricane-resistant safety glass or covered with shutters. Unless all of these requirements are met, the absolute destruction of a structure is certain.
The storm's flooding causes major damage to the lower floors of all structures near the shoreline, and many coastal structures can be completely flattened or washed away by the storm surge. Virtually all trees are uprooted or snapped and some may be debarked, isolating most communities impacted. Massive evacuation of residential areas may be required if the hurricane threatens populated areas. Total and extremely long-lived extensive power outages and water losses are to be expected, possibly for up to several months.