Download Severe Weather

Severe Weather
SPI 8.4 Analyze meteorological data to predict weather conditions
• Cyclones and anticyclones are
produced by differences in the air
pressure around them.
Air Pressure &
Weather
**Meteorologists keep track
and use these to predict the
weather.
• A cyclone is created when areas of
low pressure(warmer) surround it.
Cyclones happen when air masses
come together and rise.
• An anticyclone is created in areas
of high pressure (cooler).
Anticyclones have denser air. The
cooler, denser air moves out of the
center of the high pressure area
and move toward low pressure
areas.
Turn to page 196. Look at the
difference in how each moves.
What is Severe Weather?
• Severe weather is
weather that can cause
property damage,
injury and sometimes
death.
• Thunderstorms are small,
intense weather systems
that produce strong winds,
heavy rain, lightening and
thunder.
• They usually occur along a
cold front, but can also
develop in other places.
• There are only two
atmospheric conditions
required to produce a
thunderstorm:
1.
2.
Warm and moist air near Earth’s
surface
Unstable atmosphere
• Unstable atmospheres
happen when the
surrounding air is colder
than the rising air mass.
• Lightning is an electric discharge that occurs between a
positively charged area and a negatively charged area. It can
happen between two clouds. Between Earth and a cloud, or
even between two parts of the same cloud.
• Thunder is the sound that results from the rapid expansion
of air along the lightning strike.
• Thunderstorms can produce one or more of the following
conditions:
• High winds, hail, flash floods, and tornados
• A tornado is a small,
spinning column of air that
has high wind spends and
low central pressure. In
order to be considered a
tornado, it must touch the
ground. Otherwise, it is a
funnel cloud.
• A funnel cloud resembles a
tornado, but it has not yet
touched the ground. It is
the beginning of a tornado.
• Hurricanes are the most
powerful storms on Earth.
• A hurricane is a severe
storm that develops over
tropical oceans and have
strong winds that spiral in
toward the intensely lowpressure storm center.
A typhoon is a
mature tropical
cyclone (hurricane)
that develops in
the western part of
the North Pacific
Ocean between
180° and 100°E.
• A hurricane begins as a group of thunderstorms.
• Due to the Coriolis Effect, hurricanes spin counterclockwise in the
Northern Hemisphere and clockwise in the Southern Hemisphere.
Eye Wallsurrounds the
eye
Rain bands- produce heavy rains and
high winds.