Buildings at Risk Terms - Wind

Question 1

Define “A Zone”

Answer 1

Includes the areas of the base flood plain inland of the V Zone where the wave action is less than 3 ft in height. Although the waves pose less of a threat in this zone, it is important to realize that high-velocity water may still occur due to the momentum of breaking waves. National Flood Insurance Program regulations for new construction require the lowest floor elevation to be above the base flood elevation such that flood waters will not inundate the structure or, for non-residential buildings, the floor levels below the BFE must be flood proofed.

Question 2

Anemometer

Answer 2

An instrument used to measure wind speed. Several types of anemometers are in use, the most common being mechanical anemometers that employ either a propeller or a set of rotating cups. Most of these devices will not survive wind speeds in excess of 150 mph. Some specifically designed mechanical anemometers are rated at wind speeds up to 200 mph.

Question 3

Anticy clone (or High)

Answer 3

An area of high pressure from the center of which air spirals out in all directions, implying sinking are and good weather. Cold anticyclones move rapidly south or southeastward out of the polar regions and are comparatively shallow or short-lived. Warm anticyclones are deep systems extending high into the upper atmosphere and are often stationary or quasi-stationary over the oceans. Their influence on atmospheric processes is profound.

Question 4

Atlantic Basin

Answer 4

The area including the entire Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico

Question 5

Basic Wind Speed ( ASCE 7-93)

Answer 5

Fastest-mile wind speed at 10m (33ft) above ground level in flat, open country having an annual probability of 0.02 of being equaled or exceeded (50-year return period).

Question 6

Basic Wind Speed (ASCE 7-95)

Answer 6

Peak 3-second gust wind speed at 10m (33ft) above ground level in flat, open country having an annual probability of 0.02 of being equaled or exceeded (50-year return period). This is currently the standard measure in the United States of wind speed

Question 7

Blizzard

Answer 7

A cold, northerly gale occurring in the northern part of the Midwestern United States, especially in North and South Dakota. Brining rapidly falling temperatures and fine crystalized snow, this suffocating wind often kills animals that are stranded out in the open.

Question 8

Boundary Layer

Answer 8

A region extending upward from the ground surfaces to a height of several hundred feet in which the wind speed is slowed by the ground roughness (buildings, trees, hills). the wind speed becomes zero right at the ground surface. Beyond the top of the boundary layer the wind speed is fairly uniform. Typically, the wind speed at a height of 30ft is 60-85% of the speed near the top of the boundary layer.

Question 9

Breeze .

Answer 9

The general name given to light winds blowing along seashores and lakes. During the daylight hours, when the land temperature is warmers than that of the water, the air over the land rises, creating low-pressure area. Cold air from the sea or lake then blows toward the land, beginning very gradually after sunrise, increasing to a peak in the afternoon and diminishing in the evening. At night, when the land temperature drops below that of the water, the process is reversed, and the flow of air is from the land to the water.

Question 10

Cyclones

Answer 10

Any atmospheric system in which atmospheric pressure diminishes progressively to a minimum value at the center and toward which the winds blow spirally

Question 11

El Nino (en)

Answer 11

A 12-18 month period during which anomalously warm sea surface temperatures occur in the eastern half of the equatorial Pacific. Hurricanes thrive over warm water. Moderate or strong El Nino events occur irregularly, about once every five to six years, on average. The presence of El Nino in the Pacific tends to reduce hurricane acivity in the Atlantic

Question 12

Eyewall

Answer 12

annular region of secondary circulation in a hurricane marking the transition between the calm eye and the region of strongest winds.

Question 13

Fastest-mile speed

Answer 13

the wind speed average over the time required for a mile-long column of air to pass a fixed point

Question 14

Fohn (or Foehn)

Answer 14

The general name given to all winds descending from the tops of mountains and moving down along their sides. This air, usually warm and dry, is compressed and its temperature rises. Typical of northern side of the Alps, the south fohn is strong and gusty, bringing warm, dry air that melts the snow and evaporates any clouds on the mountain top. The north fohn blows over the southern side of the Alps and has the same characteristics as the south fohn, although it is not as strong or as warm.

Question 15

Fujita Scale

Answer 15

A scale from F0-F5 specifying a range of wind speeds based on observed damage as depicted in words and a set of damage photographs. This scale is applied extensively by meteorologist and the news media in categorizing extreme wind events.

Question 16

Geostrophic Wind

Answer 16

When characterized by a state of equilibrium between pressure, gravity, and the Coriolis force.

Question 17

Gale

Answer 17

a wind measuring 32-63 mph

Question 18

Gust

Answer 18

the sudden increase in a winds speed, lasting only a few seconds

Question 19

Gust Effect Factor

Answer 19

A factor that accounts for the effects of wind gusts on the response of the structure or structural component, based on 3-second gust basic design wind speed. (ASCE 7-95)

Question 20

Gust Response Factor

Answer 20

A factor that accounts for the effects of wind gusts on the response of the structure or structural component, based on the fastest-mile basic design speed (ASCE 7-93)

Question 21

Gust Speed

Answer 21

The maximum speed averaged over a period from 1-5 seconds. Generally, the gust speed is 20% to 30% higher than the corresponding sustained speed (1 minute average)

Question 22

Hurricane

Answer 22

A system of spiraling winds converging with increased speed toward a center where they rise vertically around an area of relative calm. Spreading over an area between 50-600 miles in diameter, the hurricane travels over the ocean at speeds from 10-25 mph while tangential wind speeds varies from 40-200 mph. A hurricane is formed over the ocean by the rising hot, humid column of air that rotates in a counterclockwise direction in the northern hemisphere. As the warm air rises and cools, the vapor is condensed into rain, and the latent heat that is released is the energy source that feeds the hurricane system. Associated with the storm is a tied from 10-25 feet high that is produced by the low pressure of the air above the ocean waters. Usually lasting from 8 to 12 days, they occur predominantly from June 1 to November 30.

Question 23

Hurricane Day

Answer 23

Four 6-hour periods during which a tropical cyclone is observed, or estimated to have hurricane-intensity winds

Question 24

Hurricane Destruction Potential (HDP)

Answer 24

a measure of a hurricane’s potential for wind and store surge destruction defined as the sum of the square of a hurricanes maximum wind speed for each 6-hour period of its existence

Question 25

Intense Hurricane

Answer 25

a hurricane rated category 3 or higher on the Saffire-Simpson Scale

Question 26

Intense Hurricane Day

Answer 26

four 6-hour periods during which a hurricane has intensity of Saffir-Simpson Category 3 or higher

Question 27

Inversion

Answer 27

In meteorology, a departure from the usual decreased or increased with altitude of the value of an atmosphere property; the layer through which this departure occurs. As used here, inversion refers to a departure from the normal cooling of air with increased height at low and intermediate altitudes; from the base of the inversion, air grows warmer with increasing altitude until the inversion is passed, after which the air cools normally with increased height.

Question 28

Importance Factor

Answer 28

A factor introduced in codification to account for the degree of hazard to human life and damage to property. In ASCE 7, the importance factor adjusts the mean recurrence interval of the basic wind speed.

Question 29

Isotach

Answer 29

Line connecting points of equal wind speed on a map.

Question 30

Kohala

Answer 30

A gale in Hawaii

Question 31

Koilo

Answer 31

A gentle breeze in Hawaii

Question 32

Kona

Answer 32

a southerly wind in Hawaii

Question 33

Landfall

Answer 33

the transition of hurricane from over-water to over-land exposure

Question 34

Mean Recurrence Interval

Answer 34

the number of years, on average, that would elapse before wind event of approximately the same intensity or higher would revisit a given location

Question 35

Mountain Wind

Answer 35

Also downslope winds or drainage winds. Descending mountain winds that form the fohn family, which includes the Swiss and Austrian fohns, the Chinook of the Rocky Mountains, the Santa Ana of Southern California, the zonda of Argentina, The puelche of the Andes, the Canterbury north wester of New Zealand, and others. As the wind rises over mountain slopes, it expands, cools, and loses moisture through condensation. as the wind descends the other side of the mountain, it is dry and becomes hot by compression

Question 36

Named Storm

Answer 36

A hurricane or a tropical storm

Question 37

Named Storm Day

Answer 37

Four 6-hour periods during which a tropical storm is observed or estimated to have attained tropical storm or hurricane intensity winds

Question 38

Nor’easter

Answer 38

A cold, violent wind; of the same family as a blizzard. It is typical of New England, blowing from the northeast

Question 39

Norther

Answer 39

A wind generated by a low pressure in Texas or in the Gulf of Mexico, pulling cold polar air from the north. The norther lasts for about one day

Question 40

Pressure

Answer 40

air pressure in excess of or less than ambient. Negative values are less than ambient, positive values exceed ambient

Question 41

Ridge

Answer 41

In meteorology, the opposite of a trough- an elongated area or relatively high atmospheric pressure, commonly used to distinguish this form of the closed circulation of an anticyclone; a ridge may include a High, an upper-air ridge may be associated with surface High, and a High may have one or more distinct ridges radiating from its center.

Question 42

Roughness Length

Answer 42

A theoretical quantification of the wind-turbulence-inducing nature of particular type of terrain.

Question 43

Saffir-Simpson Hurricane Scale

Answer 43

A numerical scale used to rate the intensity of hurricanes from 1 (least intense) to 5 (most intense). The scale considers factors such as wind speed, type and intensity of damage, and height of storm surge

Question 44

Standard exposure

Answer 44

The conditions under which official wind speed measurements are made. In particular, standard exposure means an anemometer height of 10 meters (33ft) in flat, open terrain typical of airport locations

Question 45

Santa Ana

Answer 45

A dry, hot, northerly or northwesterly descending wind, blowing into the Los Angeles basin from the Mojave Desert in southern California. It is the cause of the very warm winters in this area.

Question 46

Storm Surge

Answer 46

the gradual increase in coastal water depth as a hurricane approaches land. The increase in depth depends on several factors, such as wind speed and direction, barometric pressure, coastline geometry and normal water depth

Question 47

Sustained Speed

Answer 47

the wind speed average over a period of one minute.

Question 48

Tornado

Answer 48

a very intense funnel-shaped storm (vortex) with a diameter that is typically less than 1,000 ft. The tangential speeds in a tornado are the heights known wind speeds and may exceed 200 mph. Although tornadoes usually are associated with intense thunderstorms, they can be spewed by hurricanes

Question 49

Trade Winds

Answer 49

a prevailing wind blowing over the ocean in a belt extending around the world from 30 degrees south latitude. In the Northern Hemisphere, this wind blows in a northeasterly direction, while in the Southern Hemisphere, its direction is southeasterly

Question 50

Tropical cyclones

Answer 50

the general term for cyclones that originate over the tropical oceans, from tropical disturbance to hurricane or typhoon

Question 51

Tropical Storm

Answer 51

a tropical cyclone with maximum sustained winds between 39-73 mph

Question 52

Trough

Answer 52

In meteorology, an elongated area of relatively low atmospheric pressure, commonly used to distinguish this from the closed circulation of a cyclone; a large trough may include one or more lows, an upper-air trough may be associated with lower level Low, and a Low may have one or more distinct troughs radiating from it

Question 53

Typhoon

Answer 53

a hurricane on the Pacific Ocean

Question 54

Waterspout

Answer 54

a phenomenon similar to a tornado only less violent and destructive. Forming over water, it consists of winds spiraling around a fresh or saltwater core due to vapor condensation that rises into the funnel-shaped mother cloud. They can occur over lakes as well and can travel on land for short periods of time

Question 55

V Zone

Answer 55

Encompasses areas within the base flood boundary subjected to velocity wave action of three feet or more in height. The coastal V Zone presents an extreme hazard to life and structures because of the height water velocity and additional forces resulting from the wave action.