Hurricane Season: Know the Lingo

 

Invest - When a tropical weather center (like the National Hurricane Center) is interested in collecting special datasets for an area of disturbed weather, they call it an "invest," because they are investigating the system for potential development. The designation of "invest" doesn't correspond to any likelihood of development, but it does mean there's an area of disturbed weather, and the organizations are looking into it.

Tropical Cyclone - A generic term for warm-core weather systems that occur in the tropics, like tropical storms and hurricanes.

Tropical Depression - A tropical cyclone in which the maximum sustained surface wind speed is less than 39 mph (34 knots).

Tropical Storm - A tropical cyclone in which the maximum sustained surface wind speed ranges from 39 mph (34 knots) to 73 mph (63 knots).

Hurricane - A tropical cyclone in which the maximum sustained surface wind is 74 mph (64 knots) or more.

Major Hurricane - A hurricane with winds greater than 111 mph (category 3 or higher on the Saffir Simpson hurricane wind scale).

Storm Surge - An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide. Storm surge can reach heights well over 20 feet and can span hundreds of miles of coastline.

Hurricane Warning - An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.

Hurricane Watch - An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.

Tropical Storm Warning - An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are expected somewhere within the specified area within 36 hours.

Tropical Storm Watch - An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are possible within the specified area within 48 hours.

Short Term Watches and Warnings - These watches/warnings provide detailed information about specific hurricane threats, such as flash floods and tornadoes.

Saffir Simpson Hurricane Wind Scale

Category	Wind Speed	Expected Damage
1	74 - 95 mph 64 - 82 knots	Very dangerous winds will produce some damage - Minor damage to exterior of homes - Toppled tree branches, uprooting of smaller trees - Extensive damage to power lines, power outages
2	96 - 110 mph 83 - 95 knots	Extremely dangerous winds will cause extensive damage - Major damage to exterior of homes - Uprooting of small trees and many roads blocked - Guaranteed power outages for long periods of time—days to weeks
3	111 - 129 mph 96 - 113 knots	Devastating damage will occur - Extensive damage to exterior of homes - Many trees uprooted and many roads blocked - Extremely limited availability of water and electricity
4	130 - 156 mph 114 - 135 knots	Catastrophic damage will occur - Loss of roof structure and/or some exterior walls - Most trees uprooted and most power lines down - Isolated residential due to debris pile up - Power outages lasting for weeks to months
5	Greater than 156 mph Greater than 135 knots	Catastrophic damage will occur - A high percentage of homes will be destroyed - Fallen trees and power lines isolate residential areas - Power outages lasting for weeks to months - Most areas will be uninhabitable

Source: www.ready.gov

History

The initial scale was developed by Herbert Saffir, a structural engineer, who in 1969, went on commission for the United Nations to study low-cost housing in hurricane-prone areas. While performing the study, Saffir realized there was no simple scale for describing the likely effects of a hurricane. Mirroring the Richter magnitude scale in describing earthquakes, Saffir devised a 1–5 scale based on wind speed that showed expected hurricane damage to structures. Saffir gave the scale to the National Hurricane Center, and Meteorologist Robert Simpson added the effects of storm surge and flooding.