Weather Patterns Severe Storms Chapter 20 smallarea storms

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Weather Patterns & Severe Storms Chapter 20

Weather Patterns & Severe Storms Chapter 20

 • small-area storms formed by the strong upward movement of warm, moist, unstable

• small-area storms formed by the strong upward movement of warm, moist, unstable air • always accompanied by lightning, thunder, and usually rain • formed from cumulonimbus clouds

Observe an animation of a thunderstorm.

Observe an animation of a thunderstorm.

Air-mass thunderstorm: • form in warm, moist air mass • occur in spring and

Air-mass thunderstorm: • form in warm, moist air mass • occur in spring and summer- last less than 1 hour • single, widely scattered

Frontal thunderstorm: • occur in lines along a frontal surface • stronger and may

Frontal thunderstorm: • occur in lines along a frontal surface • stronger and may last several hours • can produce heavy rain and flooding

Lightning: • a discharge of electricity from a thundercloud to the ground, or cloud

Lightning: • a discharge of electricity from a thundercloud to the ground, or cloud to cloud, or ground to cloud

 • temperature inside lightning flash can reach 28, 000°C • at this temperature,

• temperature inside lightning flash can reach 28, 000°C • at this temperature, air expands explosively-sudden expansion makes thunder!

an intense tropical lowpressure area with sustained winds starting at 75 mph

an intense tropical lowpressure area with sustained winds starting at 75 mph

storm surge: currents formed when hurricanes pile water up along the shore and blow

storm surge: currents formed when hurricanes pile water up along the shore and blow it inland most damaging part of a hurricane

eye: central area of sinking air; 15 to 20 km wide

eye: central area of sinking air; 15 to 20 km wide

Eye of hurricane Floyd

Eye of hurricane Floyd

 • Winds most violent just outside the eye

• Winds most violent just outside the eye

Check out this website! http: //www. weather. com/web/newscenter/specialreports/ hurricanes/inside/elements. html

Check out this website! http: //www. weather. com/web/newscenter/specialreports/ hurricanes/inside/elements. html

Tropical depression: wind speeds up to 38 mph; some circular rotation at surface

Tropical depression: wind speeds up to 38 mph; some circular rotation at surface

Tropical storm: wind speeds from 39 -74 mph; can be named, shows drop in

Tropical storm: wind speeds from 39 -74 mph; can be named, shows drop in pressure, distinct rotation

Hurricane: wind speeds up to 75 mph

Hurricane: wind speeds up to 75 mph

Movement of Air in a Hurricane

Movement of Air in a Hurricane

There are sometimes gaps in between these bands where no rain is found. In

There are sometimes gaps in between these bands where no rain is found. In fact, if one were to travel between the outer edge of the hurricane to its center, one would normally progress from light rain to dry back to slightly more intense rain again over and over with each period of rainfall being more intense and lasting longer until reaching the eye. Upon exiting the eye and moving towards the edge of the hurricane, one would see the same events as they did going in, but in opposite order.

A schematic of this banding feature can be seen in the diagram above. The

A schematic of this banding feature can be seen in the diagram above. The thunderstorms are now organized into regions of rising and sinking air. Most of the air is rising, but there is a small amount found in between the thunderstorms that is sinking.

a narrow, funnel-shaped column of spiral winds that extends downward from the cloud base

a narrow, funnel-shaped column of spiral winds that extends downward from the cloud base and touches the ground

 • strongest winds between 360 and 500 km/hr • funnel less than 500

• strongest winds between 360 and 500 km/hr • funnel less than 500 m across • always travel with a parent thunderstorm at speeds ranging from 40 to 65 km/hr

funnel is a mixture of clouds and dust pressure gets lower in center lowering

funnel is a mixture of clouds and dust pressure gets lower in center lowering of condensation level due to low pressure causes cloud to funnel air flows toward the funnel and cools to dew point- drops form Extremely low pressure-when it touches ground, acts like a giant vacuum

Waterspout: tornados over the waterweaker than tornados

Waterspout: tornados over the waterweaker than tornados

Tornados usually occur during spring and summer and most likely occur in late afternoon

Tornados usually occur during spring and summer and most likely occur in late afternoon

Fujita Scale: scale used for categorizing tornados

Fujita Scale: scale used for categorizing tornados