Factbox-How hurricane classes forecast the dimensions of destruction By Reuters

© Reuters. Site visitors lights wave by robust gust of wind forward of Hurricane Ian, in Fort Myers, Florida, U.S. September 28, 2022. REUTERS/Marco Bello

(Reuters) – Hurricane Ian approached Florida’s Gulf Coast on Wednesday as a strong storm only one score shy of the best class designation given to storms in the US.

Storm power is outlined by the Saffir-Simpson Hurricane Wind Scale, which assesses hurricane programs on a score between 1 and 5, based on the Nationwide Hurricane Middle. The size, created by and named for wind engineer Herb Safari and meteorologist Bob Simpson, is used to forecast wind depth and potential harm.

Storm power is categorized by a hurricane’s most sustained wind velocity and may change all through the course of a climate occasion. It doesn’t contemplate different elements similar to storm surge, rain flooding and tornadoes.

Ian is a Class 4 with sustained winds of 155 miles per hour (250 km per hour), the NHC stated. Hurricanes rated a 3 or increased are thought of main storms.

Here’s a take a look at the hurricane scale:


Storms of this magnitude function sustained wind speeds of 74-95 mph (119-153 kph). Thought of “very harmful,” winds are able to defacing house exteriors, snapping tree branches and inflicting days-long energy outages. Individuals, livestock and pets face some danger of harm or dying.


These storms have sustained winds of 96-110 mph (154-177 kph). Decided to be “extraordinarily harmful,” winds can carry main harm to house exteriors, uproot timber that block roads and trigger near-total energy blackouts that would final weeks. A considerable danger of dying is current.


These main storms have sustained winds of 111-129 mph (178-208 kph). The winds are anticipated to trigger “devastating harm” to buildings, together with blown roofs, and uproot timber. Along with misplaced energy, water outages may happen from days to weeks after the storm passes. There’s a excessive danger of dying.


Class 4 storms, similar to Hurricane Ian, carry sustained winds of 130-156 mph (209-251 kph). Winds could cause “catastrophic harm” to houses, together with destroyed roofs and exterior partitions. Along with fallen timber, downed energy poles have potential to depart areas with out energy and uninhabitable for months. The danger of dying or harm is taken into account very excessive.


The very best designation given to hurricanes with sustained winds exceeding 157 mph (252 kph). Winds trigger “catastrophic harm” that go away many houses destroyed and residential areas remoted resulting from downed timber and energy poles. Given the intensive harm and lack of energy, areas may very well be left unlivable for months. Threat of harm and dying, even for these indoors, may be very excessive.

Learn extra:

The worst hurricanes in Florida’s historical past as Ian takes purpose

How hurricanes trigger harmful, harmful storm surges

How local weather change is fueling hurricanes

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