Winds, cyclones and tornadoes Flashcards
what is wind?
Wind can be defined as motions of the atmosphere driven by atmospheric pressure differences. It is the movement from high pressure (more molecules) to low pressure (fewer molecules)The molecules want to equalize so the extra molecules at high-pressure flow to the area of low pressure.
what is the unit for air pressure
millibars (mbar or mb)
what is the average sea level air pressure
Sea‐level average pressure:1013.25 mb.
what is the highest ever recorded sea level pressure
1050 mb
Lowest recorded sea‐level pressure:
870 mb
what are iscobars
Isobars are lines on a map connecting areas of equal pressure.
in the northern hemisphere, how do winds rotate
counter clockwise
in the southern hemisphere, how do winds rotate§
clockwise
what weather is caused by a high-pressure system
fair weather
how is fair weather created by high-pressure systems?
the air sinks, which suppresses the upward motions required for clouds to develop, which causes fair weather.
what weather is caused by low-pressure systems
opposite of fair weather so clouds and precipitation occur
high pressure zone is…
low pressure zone is..
The high-pressure zone is an anticyclone and the low-pressure zone is a cyclone.
what is the The Beaufort wind speed scale
the Beaufort scale goes from 0-17, judging the effects of the wind.
what is 0 and what is 17 on the Beaufort wind speed scale
0 is calm and 17 is a hurricane.
how many knots does the wind have to be traveling at to be considered a hurricane
The wind is not classed as a hurricane until speed gets above 100km/hr or 64 knots
what are the three stages of tropical cyclones
depression - tropical storm - hurricane
tropical depression
20 - 30 knots - starting to define itself
tropical storm
34 to 64 knots - stronger winds, starting to form circular pattern
hurricane !!!
over 64 knots - clearly defined storm with rotation and eye.
what is the scale used for hurricanes
the saffir Simpson scale, goes to 1 to 5
what factors are needed to form a hurricane
ocean temp more than 26degrees. water depth more than 50m, velocity to give hurricane initial rotation, an area of high pressure above the low-pressure system.
how do hurricanes weaken
Tropical storms and hurricanes weaken when their source of heat and moisture is cut off. When hurricanes move over land, they lose their source of energy. However, if they move over an area of water with the correct conditions, they can re-intensify.
what surrounds the eye of the hurricane what is the windspeed like here
the eye wall, fastest windspeed, densest cloud
secondary hazards from hurricanes
storm surge, flooding, tornadoes, and riptides.
