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. 

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]

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.