Transcript Chap 30 - murdoP2Wiki

Storms and Weather Forecasts
Chapter 30
Thunderstorm
• Small area storms
formed by a strong
upward movement of
warm, unstable moist
air.
Air-mass thunderstorm
• Form within a warm,
moist air mass.
• Often single storms.
• Occur mostly in
spring and summer.
• Usually last less than
an hour.
Frontal thunderstorm
• Usually form in warm,
moist air on or ahead
of a cold front. Some
do occur in front of
warm fronts.
Squall Lines
• Line of heavy
precipitation and tstorms in front of a
cold front.
Lightning
• A discharge of
electricity from a
thundercloud to the
ground, another cloud,
or cloud to ground.
• 28,000oC, 50,400oF
Thunder
• Sound created as
lightning “superheats”
and it expands
(explodes) rapidly.
• Approximately 3
seconds for sound to
travel 1 kilometer.
Tornado
• Narrow, funnel shaped
column of spiraling
winds that extend
downward from the
cloud base and touches
the ground.
• Fujita scale F0-F5,
damage related.
Tornado Peak Season
• From late spring to summer.
• Occur most frequently in late afternoon.
• Temperature lag is the cause. The Earth is
responsible for heating the lower
atmosphere.
Waterspouts
• A tornado that has
formed over a body of
water.
• Usually weaker than a
land born tornado.
Severe Thunderstorms
• Has wind gust of at
least 80 m.p.h., hail
about 2 cm in diameter
or greater, and
presence of a funnel
cloud or tornado.
Watch
• Covers an area of
100km by 200km or
larger. Severe tstorms and tornadoes
possible.
Warning
• Is issued when a severe thunderstorm or tornado
has been spotted.
Hurricane
• Intense low-pressure
tropical area with
sustained winds of 120kph
(74mph) or greater.
• Strong winds and heavy
rains produce major
damage.
• It has no fronts, powered
by evaporation.
• Source regions include
Gulf of Mexico,
Caribbean Sea and east
coast of Africa.
Hurricane Peak Season
• From late summer to
early fall.
Storm Surges
• Formed when a
hurricane “piles up”
water along the shore
and blows it inland.
Most damaging during
high tides.
Eye
• Central area of sinking
air, usually 15-20km
in diameter.
• No rain, calm winds,
high pressure.
Eye Wall
• Area of intense
thunderstorms
surrounding the eye of
the hurricane.
Tropical Cyclones/Typhoons
• Hurricane near
equator.
Naming Hurricanes
• Prior to 1953:
– Identified by their date.
• From 1953 to 1979:
– Given female names, alphabetically.
• 1979 to the present:
– Given male and female names, alphabetically.
Blizzard
• A snowstorm with
high winds and low
temperatures.
Moisture Supply Differences
• In the United States,
the midwest-Gulf of
Mexico; the west
coast-Pacific Ocean;
the east cost-Atlantic
ocean.
Computer Model
• A copy of the
atmosphere in the
computer that contains
wind, temperature,
pressure, humidity,
clouds and
precipitation.
Geostationary
• Means “stationary” in
respects to the Earth.
GOES
• “Geostationary
Operational
Environmental
Satellite” positioned to
picture the 50 states.
Doppler Affect
• Effect caused by the
movement of light,
sound or wind relative
to a stationary point.
Winds moving toward
the radar appear to
have a shorter
wavelength than
particles moving away
from the radar source.
Station Model
• National Weather
Service based
information from each
recording station.
Weather station model
Information is encoded to save space. It is placed in the same location on
every model to avoid possible confusion.