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Damage descriptors and wind speeds will also be readily updated as new information is learned. [21] Some differences do exist between the two scales in the ratings assigned to damage. An EF5 rating on the new scale requires a higher standard of construction in houses than does an F5 rating on the old scale.
The Saffir–Simpson hurricane wind scale (SSHWS) is a scale that classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguished by the intensities of their sustained winds.
Direction shown by smoke drift but not by wind vanes 2 Light breeze 4–6 knots 4–7 mph 6–11 km/h 1.6–3.3 m/s 1–2 ft 0.3–0.6 m Small wavelets still short but more pronounced; crests have a glassy appearance but do not break Wind felt on face; leaves rustle; wind vane moved by wind 3 Gentle breeze 7–10 knots 8–12 mph 12–19 km/h
The expanded and refined damage indicators and degrees of damage standardize what was somewhat ambiguous. It also is thought to provide much better estimates of wind speeds and sets no upper limit on the wind speeds for the highest level, EF5. Environment Canada began using the Enhanced Fujita scale in Canada on April 1, 2013. [22]
For the IF scale, only wind speeds measured at or below 10 metres (11 yd) can be used to determine a rating. Doppler weather radar measurements are also able to be used to determine a rating if they are measured within damaging distance. For radar measurements, any readings below 60 metres (66 yd) can be used to determine a rating. [4] [3]
These warnings use a 1-minute sustained wind speed and can be compared to the Saffir–Simpson hurricane wind scale, however, regardless of intensity in this basin the JTWC labels all systems as tropical cyclones with TC numbers (plus any parenthesized names or placeholders, like typhoons and North Indian Ocean cyclones above). [18]
The National Weather Service in Birmingham, Alabama, noted the rating for this tornado was F4 on the Fujita scale, which has a wind speed range of 207 to 260 miles per hour (333 to 418 km/h). However, the wind speeds assigned to this tornado was between 210 and 261 miles per hour (338 and 420 km/h), indicating the potential that this tornado ...
Though this reading is just short of the theoretical F6 rating, the measurement was taken more than 100 feet (30 meters) in the air, where winds are typically stronger than at the surface. [citation needed] In rating tornadoes, only surface wind speeds or the wind speeds indicated by the damage resulting from the tornado, are taken into account ...