The Nature of Storms. Chapter 13. 13.1 Thunderstorms. At any given moment, nearly 2000 thunderstorms are occurring around the world. . Abundant source of moisture in the lower levels of the atmosphere A mechanism to lift the air to allow moisture to condense and release latent heat
At any given moment, nearly 2000 thunderstorms are occurring around the world.
Occasionally weather events come together in such a way that there is a continuous supply of surface moisture, causing more severe storms.
A lightning bolt forms when friction between updrafts and downdrafts separates electrons from some of their atoms creating positive ions and negative ions.
This creates regions of air with opposite charges.
A channel of negatively charged air moves toward the ground and a channel of positively charged ions rushes upward from the ground to meet it, creating an illumination called lightning.Lightning
Lightning heats the air to around 30000°C, whichis five times HOTTER than the surface of the Sun!
Hail: precipitation in the form of balls or lumps of ice, occurring most frequently in the central US. Most common during Spring
A tornado is caused by wind shear, which is when wind speed and direction change suddenly with height– causing a horizontal rotation near the Earth’s surface
An updraft can shift this rotating air into the vertical position
As updrafts speed up the rotation, air pressure in the center decreases, creating a pressure gradient between the inside and outside of the tornado – creating violent winds
Although devastating, tornadoes typically last only a few minutes.
The Fujita Tornado Intensity Scale ranks tornadoes according to the path of destruction, wind speed, and duration
Tornadoes can occur at any time and at any place, although some times and locations are more conducive to their formation
The most violent storm on Earth is within the calm, sunny tropics.
As water evaporates from the ocean, heat is stored in the form of latent heat
The heat is released as the air rises and water vapor condenses into clouds and rain
The rising air creates a low pressure system at the ocean surface and more air moves in to replace it
The Coriolis Effect causes the air to turn counterclockwise, resulting in the rotation of the cyclone
Air moving towards center rises and rotates faster, further decreasing pressure in the center
Tropical Cyclones / Hurricanes require two basic conditions to form:
These conditions exist in all tropical oceans except the South Atlantic Ocean and the Pacific Ocean west of the South American coast because waters in these areas are cooler.
Tropical Depression - when a disturbance acquires a cyclonic rotation around a center of low pressure
Tropical Storm - when winds of the depression reach 65km/hr
Hurricane - when winds of the storm reach 120km/hr
Eye - calm center of the storm
Eyewall - a band immediately surrounding the eye where the winds are the strongestStages of a Hurricane
Saffir-Simpson Hurricane Scale - classifies hurricanes according to wind speed, air pressure in center, and potential for property damage
Persistent or repetitive weather can negatively affect agriculture, transportation, and recreation.
A Cold Wave is an extended period of below normal temperatures, which can be caused by high pressure systems of continental polar (cP) or Arctic air
Wind-Chill: because wind transports heat away from the body, the temperature may feel cooler than it really is
The wind-chill factor tells how cold it actually feels to the human body
The heat index tells how warm it feels to the human bodyHeat Index