Saffir Simpson hurricane wind scale

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The Saffir-Simpson hurricane wind scale ( Saffir-Simpson hurricane wind scale (SSHWS)), until 2009 Saffir-Simpson hurricane scale (SSHS) is a wind scale for categorizing Hurricanes, i.e. tropical cyclones. It applies north of the equator, in the Atlantic and in the Pacific east of the date line. It was developed in 1969 by Herbert Saffir and Bob Simpson , a former director of the US National Hurricane Center , based on studies of the effects of hurricanes , especially Hurricane Camille , and was officially introduced by the National Hurricane Center in 1972.

The scale uses wind speed to classify storms into five categories. The Saffir-Simpson hurricane scale used until 2009 also included the height of the ocean waves generated by the storm and the air pressure in the center ( eye ) of the hurricane. Because these parameters correlate very poorly with the wind speed, a pure wind force scale was used.

The scale was developed first and foremost for seafaring, which is why the exact range limits are defined in nodes. The border between tropical low and tropical storm (34 knots) corresponds to the border between wind force 7 and 8 on Beaufort and the border between tropical storm and hurricane (64 knots) corresponds to the border between wind force 11 and 12 on Beaufort. However, the wind speed in is the United States traditionally in miles per hour ( miles per hour ) indicated.

Former version (until the end of 2011)

Until the end of 2011, the scale had the following classification:

Saffir-Simpson hurricane scale up to 2011
Level / category Wind speed
node mph km / h m / s
Tropical low ≤ 33 ≤ 38 ≤ 62 ≤ 17
Tropical storm 34 to 63 39 to 73 63 to 118 18 to 32
Category 1 hurricane 64 to 82 74 to 95 119 to 153 33 to 42
Category 2 hurricane 83 to 95 96 to 110 154 to 177 43 to 49
Category 3 hurricane 96 to 113 111 to 130 178 to 209 50 to 59
Category 4 hurricane 114 to 135 131 to 155 210 to 250 60 to 69
Category 5 hurricane from 136 from 156 from 251 from 70

An expansion to a sixth category requested by various media was not officially adopted.

Current categorization (since 2012)

Since 2012, the measurements for the published wind speeds have been converted as follows:

  1. The value measured in whole knots (kn) averaged over one minute is rounded to whole multiples of 5 kn.
  2. For public reports, the wind speed rounded in knots is converted to miles per hour (mph) or km / h and rounded again (to 5 mph or 5 km / h).

Due to this double rounding, the following problem arose in the area of ​​the 4th hurricane category:

Wind
speed
rounded to 5 kn 		Classification in
category according to
the value in knots 		Conversion
to mph 		Rounding
to 5 mph 		Classification in
category according to the value
in miles per hour
105 Cat 3 120.8 120 Cat 3
110 Cat 3 126.6 125 Cat 3
115 Cat 4 132.4 130 Cat 3
120 Cat 4 138.1 140 Cat 4

When converting knots to miles per hour, there is a change in the category assignment for 115 knots. A similar problem arises when converting 135 knots to km / h:

Wind speed, rounded to (5 kn) Classification in category according to the value in knots Conversion in km / h Rounding to 5 km / h Classification in category according to the value in km / h
135 Cat 4 250.0 250 Cat 5

To solve these problems, the lower and upper limits of category 4 have been adjusted for all units of measurement (kn, mph and km / h) (change by 1 kn). In addition, corresponding changes have been made to the upper limit of category 3 and the lower limit of category 5. The problem no longer arises and the scale has had the following limits since then:

Saffir-Simpson hurricane scale since 2012
Level / category Wind speed
node mph km / h m / s
Tropical low ≤ 33 ≤ 38 ≤ 62 ≤ 17
Tropical storm 34 to 63 39 to 73 63 to 118 18 to 32
Category 1 hurricane 64 to 82 74 to 95 119 to 153 33 to 42
Category 2 hurricane 83 to 95 96 to 110 154 to 177 43 to 49
Category 3 hurricane 96 to 112 111 to 129 178 to 208 50 to 58
Category 4 hurricane 113 to 136 130 to 156 209 to 251 59 to 70
Category 5 hurricane from 137 from 157 from 252 from 71

See also

swell

  1. ^ Information from the National Weather Service Headquarters

Web links