Download Ch 13 The Nature of Storms

Ch 13 The Nature of Storms
Conditions for a Thunderstorm
1. Abundance of moisture in lower
atmosphere (release of latent heat)
2. Air must rise (Cools to dew pt
creating condensation)
3. The portion of atmosphere that
clouds go through must be
unstable.
Limits on growth
Air will rise until it meets a
layer of stable air that it can
not over come.
This caps most thunderstorms
at around 18 km.
Two groups of thunderstorms
A) Air mass: Unequal heating
1. Mountain (orographic)
2. Sea-breeze (tropic regions)
B) Frontal: Advancing fronts
1. Cold fronts (majority)
2. Warm fronts (rarely)
There are 3 stages of
development
1. Cumulus Stage:
Updrafts transport
moisture to upper
levels.
2. Mature Stage:
Strong updrafts and
downdrafts
3. Dissipation Stage:
The storm loses energy
because there are only
downdrafts
13.2 Severe Weather
Supercells: Extremely powerful storms
characterized by intense, rotating updrafts.
Lightning: Large discharge (100 million V) of static
electricity within the atmosphere that heats up the
surrounding air to 30,000 degrees C (5 times hotter
than surface of the Sun)
Lightning: in the US alone causes an average yearly
death rate of 93 and 300 injuries
Downbursts: Violent downdrafts of air (confused with
tornadoes) that can reach up to 160 km/h winds.
Hail: Ice precipitation that forms from updrafts
transporting the water to upper layers where it
freezes, then falls back down collecting more
moisture. If the up drafts are strong enough, then
the water covered ice chunks go back up, freeze the
new water and fall back down. The more this cycle
repeats itself, the larger the hail gets.
Floods: The main cause of thunderstorm related deaths
each year.
Tornadoes: violent,
whirling column of
air that comes in
contact with the
ground.
-The fastest winds
on Earth.
-An average of 80
deaths and 1500
injuries occur each
year in the US.
*Is there anyone
who can help?
Ways to reduce risk:
-Obtain a weather alert radio or service.
-Watch for signs of a tornado
-Yoda Green tinge to sky
-Rolling clouds (funnel clouds)
-Keep an eye on powerful thunderstorm
More ways to reduce risk
***If a tornado is spotted:
-Head to the basement or a
neighbors basement
More ways to reduce risk
***If a tornado is spotted:
-If no basement available run to a
bathroom
-Do not try to out drive a tornado
-If caught outside, lie down in a
low area like a ditch
13.3 Tropical Storms
Tropical cyclone: Large rotating
low pressure system. The energy
for these storms are provided by the
warm ocean water.
Two needed conditions:
1. Warm ocean water
2. Disturbance (uplift of air)
Guided by wind belts, the
Hurricanes that effect our east coast
start on the west coast of Africa and
travel across the Atlantic.
13.3 Tropical Storms
As soon as a hurricane makes land fall it begins to lose
energy and becomes weaker.
PREVAILING WESTERLIES: GLOBAL WIND SYSTEMS
THAT LIE BETWEEN 30 AND 60 DEGREES NORTH
AND SOUTH LAT, WHERE SURFACE AIR MOVES
TOWARD THE POLES IN AN EASTERLY DIRECTION
TRADE WINDS: GLOBAL WIND SYSTEM THAT
FLOWS 30 DEGREES NORTH AND SOUTH LAT
WHERE AIR SINKS, WARMS, AND RETURNS TO THE
EQUATOR IN A WESTERLY DIRECTION
JET STREAM: HIGH ALTITUDE NARROW BAND OF
WIND THAT IS WITH IN THE WESTERLIES AND CAN
FLOW AS FAST AS 185 KM/HR
STORM TRACK: THE PATH OF THE STORM AS
DETERMINED BY THE UPPER WIND BELTS
STORM SURGE: OCCURS WHEN POWERFUL
HURRICANE FORCE WINDS DRIVE A MOUND OF
OCEAN WATER TOWARD SHORE, WHERE IT WASHES
OVER THE LAND OFTEN CAUSING ENORMOUS
DAMAGE
HURRICANE: A TROPICAL CYCLONE WITH A WELL
DEFINED EYEWALL AND A MINIMUM WIND SPEED
OF 74 MPH
SAFFIR/SIMPSON SCALE: CLASSIFIES HURRICANES
ACORRDING TO WIND SPEED AIR PRESSURE AND
POTENTIAL FOR PROPERTY DAMAGE
FUJITA SCALE: A MEASURE OF THE INTENSITY OF
TORNADOES BASED ON DESTRUCTION, WIND
SPEED, AND DURATION.
1. Which is not a condition for a thunderstorm
to form?
A. Abundance of moisture B. Rising air
C. Stable air
D. Unstable air
2. Which is not a stage of development for a
thunderstorm?
A. Nimbus
B. Mature
C. Cumulous
D. Dissipation
3. Which should you not do if there is the threat
of a tornado?
A. Stay away from windows
B. Seek shelter in a Bathroom
C. Hide in the basement
D. Try to out drive it
4. Which should you not do if there is the threat
of a Hurricane?
A. Try to out drive it
B. Hide in the basement
C. Seek shelter on the roof
D. Stay away from windows
5. Why does a hurricane get weaker as it makes
landfall?
Bonus
***How does Hail form?