Hazardous Weather ND Test 2
Card Set Information
Hazardous Weather ND Test 2
What is a drought?
prolonged period of dry weather that dramatically lowers the water level
What are droughts caused by?
What is desertification?
process that turns productive desert into non-productive desert as a result of poor land management
occurs in semiarid areas bordering deserts
What causes desertification?
cultivating of marginal lands
destruction of vegetation in arid regions
poor grazing management
incorrect irrigation processes
increasing human population and poverty
What are heatwaves?
long periods of extreme heat that are longer and hotter than normal
close to the ground so they affect humans, pets and vegitation
What are ice storms?
caused by freezing rain
rain turns into ice on contact, causing everything to be slippery and causes extra weight on power lines and roofs
What are the 3 conditions for freezing rain?
source of moisture
warm air over a layer of cold air
ground temperatures at or below freezing
What are blizzards?
severe winter storms with large amounts of snow, high winds, and low visibility for extended periods of time
What causes blizzards?
interaction between upper level low pressure trough and surface low pressure
What causes Colorado & coastal storms?
moist ocean air
What causes Alberta Clippers?
dry air with less snow and cold temperatures
What causes Nor'easters?
hurricane winds, heavy snows, intense precipitation, high waves
What are the atmospheric conditions for a thunderstorm?
warm, humid air in the lower atmosphere
cold air above warm air
updraft must force air into the upper atmosphere
What are the different stages in a thunderstorm?
What is required to be a severe thunderstorm?
winds greater than 58 mph
hailstones bigger than .75"
or generates a tornado
What are the necessary conditions for a severe thunderstorm?
greater wind sheer, greater storm
high water vapor content in lower atmosphere
updraft of air
dry air mass above a moist air mass
What are the types of severe thunderstorms?
MCSs (mesoscale convective systems) most common
What are MCSs?
large clusters of self-propagating storms
What are squall lines?
long lines of individual storm cells
anvil shaped clouds form
can develop along drought lines
What are supercells?
smaller than other two but more damaging
spawn the most tornadoes
12-30 miles in diameter
last between 2 and 4 hours
What are tornadoes?
vortex extending downward from the cloud and touching the ground
Where do tornadoes form?
form where there are large differences in atmospheric pressure over short distances
What are the three stages of a tornado?
What occurs in the organizational stage?
updrafts tilt horizontally, rotating the air vertically
cloud begins to lower and funnel descends
What occurs in the mature stage?
funnel extends to ground
moist air is drawn up
suction and damage occur
What occurs in the shrinking stage?
warm air is reduced
tornado begins to thin
What occurs in the rope stage?
funnel moves erratically and then disappears
What is the Fujita scale?
measures internal windspeeds and damage produced
measured F0 to F5
updated in 2007
now based on detailed wind measurements and long-term damage records