The Saffir-Simpson Hurricane Scale was renamed in 2010 to the Saffir-Simpson Hurricane Wind Scale. The barometric pressure and the storm surge potential have been sufficiently out of bounds in recent years causing confusion as to what to expect from a hurricane. New SLOSH models have been created to show the potential impact the storm surge may have on specific areas based on available geographic data. In 2012, the scale was slightly modified to assist with proper mathmatical computation of the scale, for applications such as ours. This slight adjustment allows the conversion from kts to MPH and kph to work flawlessly without intervention. For this, we sincerely thank the NHC!
Basically this means that there was enough confusion that a generic set of numbers were not enough to give the general public the detail they need in order to act on a hurricane coming their way, so the scale was changed to help everyone understand what to expect from each storm category.
|Tropical Depression||38 mph
|Tropical depressions are thunderstorm systems which have collected into a large mass of convection with a closed circulation. The same wind speeds are used to describe subtropical depressions, remnant lows post tropical depressions and more.|
|Tropical Storm||39-73 mph
|Tropical Storms have a closed circulation and have winds between 39 and 73mph. These storms can cause minor damage but are also known to be large rain events with the potential to cause various degrees of flooding when they move slowly over an area. They also cause mudslides and other rain related events, especially over mountainous terrain.|
|Damaging winds are expected. Some damage to building structures could occur, primarily to unanchored mobile homes (mainly pre-1994 construction). Some damage is likely to poorly constructed signs. Loose outdoor items will become projectiles, causing additional damage. Persons struck by windborne debris risk injury and possible death. Numerous large branches of healthy trees will snap. Some trees will be uprooted, especially where the ground is saturated. Many areas will experience power outages with some downed power poles. Hurricane Cindy (2005, 75 mph winds at landfall in Louisiana) and Hurricane Gaston (2004, 75 mph winds at landfall in South Carolina) are examples of Category One hurricanes at landfall.|
|Very strong winds will produce widespread damage. Some roofing material, door, and window damage of buildings will occur. Considerable damage to mobile homes (mainly pre-1994 construction) and poorly constructed signs is likely. A number of glass windows in high rise buildings will be dislodged and become airborne. Loose outdoor items will become projectiles, causing additional damage. Persons struck by windborne debris risk injury and possible death.. Numerous large branches will break. Many trees will be uprooted or snapped. Extensive damage to power lines and poles will likely result in widespread power outages that could last a few to several days. Hurricane Erin (1995, 100 mph at landfall in northwest Florida) and Hurricane Isabel (2003, 105 mph at landfall in North Carolina) are examples of Category Two hurricanes at landfall.|
|Dangerous winds will cause extensive damage. Some structural damage to houses and buildings will occur with a minor amount of wall failures. Mobile homes (mainly pre-1994 construction) and poorly constructed signs are destroyed. Many windows in high rise buildings will be dislodged and become airborne. Persons struck by windborne debris risk injury and possible death. Many 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. Hurricane Rita (2005, 115 mph landfall in east Texas/Louisiana) and Hurricane Jeanne (2004, 120 mph landfall in southeast Florida) are examples of Category Three hurricanes at landfall.|
|Extremely dangerous winds causing devastating damage are expected. Some wall failures with some complete roof structure failures on houses will occur. All signs are blown down. Complete destruction of mobile homes (primarily pre-1994 construction). Extensive damage to doors and windows is likely. Numerous windows in high rise buildings will be dislodged and become airborne. Windborne debris will cause extensive damage and persons struck by the wind-blown debris will be injured or killed. Most trees will be snapped or uprooted. Fallen trees could cut off residential areas for days to weeks. Electricity will be unavailable for weeks after the hurricane passes. Hurricane Charley (2004, 145 mph at landfall in southwest Florida) and Hurricane Hugo (1989, 140 mph at landfall in South Carolina) are examples of Category Four hurricanes at landfall.|
|Catastrophic damage is expected. Complete roof failure on many residences and industrial buildings will occur. Some complete building failures with small buildings blown over or away are likely. All signs blown down. Complete destruction of mobile homes (built in any year). Severe and extensive window and door damage will occur. Nearly all windows in high rise buildings will be dislodged and become airborne. Severe injury or death is likely for persons struck by wind-blown debris. 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. Hurricane Camille (1969, 190 mph at landfall in Mississippi) and Hurricane Andrew (1992, 165 mph at landfall in Southeast Florida) are examples of Category Five hurricanes at landfall.|
Wind Radii: Our forecast maps also contain wind radii information for the forecast plots. The colors below correspond to the colors of the wind radius.
|Forecast Wind Radii Color Codes|
|Max 34 kt Winds
|Max 50 kt Winds
Tropical Storm / Tropical Cyclone
|Max 64 kt Winds
Hurricane / Severe Tropical Cyclone / Typhoon
Saffir-Simpson Hurricane Scale (Retired)
Used prior to 2009 hurricane season
This version of the scale is being kept around for the weather geeks 🙂
The Saffir-Simpson Hurricane Scale was created to give mariners a way to determine how bad the storm really is, and to give those on land a way to know how far inland, or how far from sea-level they need to be in order to be safe from the winds and storm surge.
Keep in mind that even though a storm may lose strength even a day before striking land, that would not be enough time to lessen the storm surge. Katrina was a lesson for everyone in that while she dropped to a category 4 hurricane in wind strength, her storm surge did not have enough time to fall as well. She surged in at over 23ft, much to the surprise of those in her path.
|Tropical Depression||38 mph
|Tropical Storm||39-73 mph
RSMC Tokyo’s Tropical Cyclone Intensity Scale
Any tropical cyclone that forms to the west of 180° and east of 100°E in the Northern Hemisphere is officially monitored by the Regional Specialized Meteorological Center in Tokyo, Japan. The Japan Meteorological Agency, which runs RSMC Tokyo, uses four different categories to measure the wind speed produced by a tropical cyclone. These classifications are based on the maximum sustained winds produced by the storm averaged over a 10-minute interval.
A tropical depression is the lowest category that the Japan Meteorological Agency uses and is the term used for a tropical system that has wind speeds not exceeding 33 knots (61 km/h, 38 mph). A tropical depression is upgraded to a tropical storm should its sustained wind speeds exceed 34 knots (62 km/h, 39 mph). Tropical storms also receive official names from RSMC Tokyo. Should the storm intensify further and reach sustained wind speeds of 48 knot (89 km/h, 55 mph) then it will be classified as a severe tropical storm.
Once the system’s maximum sustained winds reach wind speeds of 64 knots (118 km/h, 74 mph), the JMA will designate the tropical cyclone as a typhoon—the highest category on its scale. The JMA also unofficially divides typhoons into three further classifications—strong (強い, 64–84 knots), very strong (非常に強い, 85–104 knots), and intensive (猛烈な, ≥105 knots).
The United States’ Joint Typhoon Warning Center (JTWC) unofficially classifies typhoons with wind speeds of at least 130 knots (67 m/s; 150 mph; 241 km/h)—the equivalent of a strong Category 4 storm in the Saffir-Simpson scale—as super typhoons. However, the maximum sustained wind speed measurements that the JTWC uses are based on a 1-minute averaging period, akin to the U.S.’ National Hurricane Center and Central Pacific Hurricane Center. As a result, the JTWC’s wind reports are higher than JMA’s measurements, as the latter are based on a 10-minute averaging interval.
From 2009 the Hong Kong observatory started to further divide typhoon into two further classifications severe typhoon and super typhoon. A severe typhoon has winds of at least 80 knot (95 mph, 150 km/h) whilst a super typhoon has winds of at least 100 knot (115 mph, 185 km/h).
Further detail: Wikipedia: Tropical Cyclone Scales [Safari]
|Tropical Depression||< 61 km/h
|Tropical Storm||62 – 88 km/h
34 – 47 kts
|Severe Tropical Storm||89 – 117 km/h
48 – 63 kts
|Severe Typhoon||150 km/h
|Super Typhoon||185 km/h
Tropical Cyclones Intensity Scale (Australia)
The severity of a tropical cyclone is described in terms of categories ranging from 1 (weakest) to 5 (strongest) related to the zone of maximum wind gusts as shown in this table.
Note: corresponding sustained winds and central pressure are also provided as a guide. Stronger gusts may be observed over hilltops, in gullies and around structures.
Note: The scale below is based on a 10 minute average, where the US Saffir-Simpson Hurricane Wind Scale is based on a 1 minute average. Because of this, the intensity of the scales will differ, making an Australian Category 5 Tropical Cyclone a solid Category 4 Hurricane.
|Category||Strongest Gust (km/h)
Average Maximum Wind (km/h)
Average Maximum Wind (kts)
|Central Pressure (hPa)||Typical Effects|
63 – 88
34 – 47
|> 985||Negligible house damage. Damage to some crops, trees and caravans. Craft may drag moorings|
|2||125 – 164
89 – 117
48 – 63
|985 – 970||Minor house damage. Significant damage to signs, trees and caravans. Heavy damage to some crops. Risk of power failure. Small craft may break moorings.|
|3||165 – 224
118 – 159
64 – 85
|970 – 955||Some roof and structural damage. Some caravans destroyed. Power failures likely. (e.g. Winifred)|
|4||225 – 279
160 – 199
86 – 107
|955 – 930||Significant roofing loss and structural damage. Many caravans destroyed and blown away. Dangerous airborne debris. Widespread power failures. (e.g. Tracy, Olivia)|
|< 930||Extremely dangerous with widespread destruction. (e.g. Vance)|
Further detail: Tropical cyclone intensity [Safari]