Thunderstorms
1
Three Conditions are
needed:
• 1) Abundant source of moisture in the lower
atmosphere
• 2) Moisture condenses, releasing latent heat.
Latent heat keeps the cloud warmer.
•
then the air around it. Keeps the upward
motion going to the
•
inside of the cloud.
• 3) Portions of the atmosphere needs to be
unstable.
2
Limits to Growth
Three conditions need to meet:
• · Air keeps rising
• · More moisture condensing and releases
latent heat
• · Continues until rising air reaches stable air
and growth stops
• *Most cumulonimbus clouds grow to the
height of 18,000 meters.
• *Most thunderstorms last 20 - 30 minutes
with a diameter of 24
• kilometers
3
Air Mass
Thunderstorm
• Classification by the lift
mechanisms.
• Air lifted upward due to the
unequal heating of the earth
within one air mass.
• Maximum heating occurs
during mid-afternoon optimum time for those
storms.
4
Air Mass
Thunderstorm
5
Air Mass
Thunderstorm
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Two common
thunderstorms
1) Mountain thunderstorms - air
mass rises over mountains
(orographic lifting)
7
Sea breeze
thunderstorm
• - local air mass
thunderstorm caused by
the temperature - the
difference between land
and water
8
Frontal
Thunderstorms
• Produced by advancing cold front and they
meet the warm fronts. Upward motion
produces a line of thunderstorms.
• Initial lift comes from the cold front, why?
Air is not dependent on day time heating occurs at night!
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Formation of frontal
Thunderstorm
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Frontal Thunderstorm
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Uplifting
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Warm Fronts
• Can develop thunderstorms. When the warm
front slides up and over a cold front within
stable air • mild thunderstorm.
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Typical Eye View
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Warm Front
15
Sea Breezes can cause
thunderstorms
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Thunderstorm
development
• Three stages of development - Stages
classified by the direction of air movement
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Three Stages of
Growth
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Cumulus Stage
• 1)
a. Begins with thermals created by
insulating heating in the g r
ground or
winds blowing over terrain
•
b. Winds force moisture upward
•
c. Moisture begins to cool and forms tiny
droplets of H2O
•
d. Water droplets accumulate and forms
cumulus clouds
•
e. Condensation process releases heat
into surrounding air
•
f. Heat causes updrafts and creates low
pressure under cloud
•
•
•
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Mature Stage
• a. Air cannot rise any farther
•
b. Cumulus clouds become cumulonimbus
clouds.
•
c. H2O droplets increase in size. Air cools
around it.
•
d. Rain falls quickly-creating downdrafts.
•
e. Updrafts and downdrafts create convection
cells that turn into gusty winds.
•
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Dissipating Stage
• Downdrafts - thunderstorms undoing the
convection cells that only exist with a supply
of warm air.
• Once the warm air supply is gone,
downdrafts continue until it runs out of
raindrops.
•
21
Severe Thunderstorm
•
•
•
•
•
•
•
Characteristics of a severe thunderstorm
1) Hail
2) Swirling tornadoes
3) 160 mph winds
How do they form?
Cold air moves over warm land that provides
a steady supply of moisture.
22
Super Cells
• Super Cells
• Thunderstorms with large temperature
gradients that exist between the upper and
lower atmosphere of the storm.
• · Air becomes more unstable producing
stronger updrafts and downdrafts.
• · Cold fronts more with low pressure systems
with pockets of cold air - creates super cell.
• · Super cells have intense updrafts (rotating )
can reach speeds of 240 km/hr. Only 10% of
100,000 thunderstorm reach that level
23
Super Cells
24
Super cell structure
25
Super cells
26
Lightning
• Electrical discharge caused by rapid
movement of air with in a cumulonimbus
cloud Friction between updrafts of air and of
downdrafts cause the airs to lose e- forming
Ions. These are (+) and (-) charged particles.
27
•
•
•
•
•
• Creates and electrical imbalance which in
turn creates an invisible channel of
negative charged air between the cloud
and the ground
•
• The channel meets the (+) charge round
in close areas - return strike is upward
towards the cloud - lightning
•
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29
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• Lightning bolts heat the air surrounding it to
30,000°C
•
• Thunder - rapid expansion and contraction of
air, caused by intense heat.
•
• Know safety tips - Table 13.1 p 336
31
Downburst
• Violent downdraft in small areas
• · Areas that are 5 km wide are called
macrobursts - last 30
• minutes wind speed - 200 mph
• · Areas less than 3 km wide are called
microbursts - 10
• minutes or less - wind speeds 250 mph can cause
• extensive damage but difficult to detect
•
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Microburst
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Spreading microsburst
in the desert
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Wind Shear
• When wind changes speed, direction and
magnitude quickly and/or violently
•
35
36
Wind Shear Damage
37
• Hail - Precipitation that falls as ice balls occurs interior section of the U.S. -spring
• Two Conditions for hail:
• · Droplets in upper atmosphere reach
temperature below
• freezing - become ice pellets
• · Strong updrafts and downdrafts carry the
pellets up and down with other super- cooled
water droplets added on. The balls of ice fall
to the ground because of the pull of gravity
38
Hail Formation
39
Hail Storm
40
Baseball Size Hail
usually in Oklahoma
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Floods
• Floods - slow moving storms unleash rain
over a restricted area - ground saturated.
No where for water to go.
•
42
Flash Flood from
melting snow
43
Hazardous Driving
44
Characteristics of
Floods
45
Tornados
• Violent whirling column of wind in the air called funnel clouds -sparked by super cells.
When winds’ speed and direction changes
quickly with height.
• There are an average of 800 tornados
nationwide per year.
• Tornadoes are made visible by debris.
•
46
47
48
Damage
49
EF4 Tuscaloosa Ala
2011
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Tuscaloosa tornado
Damage 2011
• Click on Link beloe]w
• http://video.search.yahoo.com/video/play;_y
lt=A0S00MrywPlQhBgARHj7w8QF;_ylu=X3oD
MTBvcXNvNnBqBHNlYwNzcgRzbGsDdmlkBHZ
0aWQDVjEzMw-?p=tornado+damage+in+tuscaloosa+ala&vid
=14e2bc9e81f5f643c29a32662c125a3b&l=00
%3A13&turl=http%3A%2F%2Fts1.mm.bing.n
et%2Fth%3Fid%3DV.5007017859481864%26
pid%3D15.1&rurl=http%3A%2F%2Fwww.yout
ube.com%2Fwatch%3Fv%3DTeUwIZ7Kqk&tit=Tuscaloosa+Tornado+Damage+429-11&c=11&sigr=11au0jv3e&b=31&tt=b
51
EF5 Joplin Missouri
20011
52
Joplin Video Damage
53
Narrow Vortex
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Wide Vortex
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What can happen
before a tornado hits
an area?
• 1. Hail tumbles to the ground.
• 2. Erie silence, still motionless
• 3. Green like sky
• 4. Train sound
• 5. Cloud of debris
• 6. Sight of a Funnel cloud
• 7. Calm behind a storm.
Night time tornados are invisible so the train
sound is evident
Man made warning: a long siren
Check with the area you live in to see what their
tornado warning system is.
57
Tornado sounds
• Click on link below
• http://www.youtube.com/watch?v=2A3BYtc0
0I8
• Click on link below
• http://video.search.yahoo.com/video/play;_y
lt=A0S00MnLuflQj1kANjz7w8QF;_ylu=X3oD
MTBvcXNvNnBqBHNlYwNzcgRzbGsDdmlkBHZ
0aWQDVjEzMw-?p=tornado+sounds+in+a+rainstorm&vid=05
5ba555fc8fa60f7761b8a888ab2e85&l=&turl=
http%3A%2F%2Fts2.mm.bing.net%2Fth%3Fid
%3DV.4684822355181625%26pid%3D15.1&r
url=http%3A%2F%2Fwww.youtube.com%2Fw
atch%3Fv%3D4tnwJe6vvrE&tit=Rain+Storm+
and+the+sounds+of+a+Tornado&c=0&sigr=1
1af4js5n&fr=yfp-t-701&tt=b
58
Tornado Alley
No other country in the world receives more
tornadoes than the United States.
States in the south central area of the United
States experience the greatest number of
tornadoes, thus the name “Tornado Alley.”
Conditions for the violent windstorms in this
region are often time ideal.
When cool, dry air from the north meets
warm, moist air from the Gulf of Mexico,
tornadoes are frequently the result of this
meeting.
•
•
•
59
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Tornado Peak
Occurrances in the U.S.
61
Weather Patterns
62
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Tornado Siren
• http://video.search.yahoo.com/video/play;_y
lt=A0S00Mn0vvlQyGoA3Oj7w8QF;_ylu=X3oD
MTBvcXNvNnBqBHNlYwNzcgRzbGsDdmlkBHZ
0aWQDVjEzMw-?p=tornado+warning+siren&vid=4f3626062a
53c0560eaeb43035ad6043&l=00%3A15&turl
=http%3A%2F%2Fts3.mm.bing.net%2Fth%3Fi
d%3DV.4810879608488038%26pid%3D15.1&
rurl=http%3A%2F%2Fwww.youtube.com%2F
watch%3Fv%3Dnuu2iNisoQc&tit=Tornado+Sir
en&c=1&sigr=11atm4k29&fr=yfp-t-701&tt=b
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Shelter
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Fujita Scale
• Tornadoes are classified into five categories, F-0
through F-5. F-0 tornadoes are the mildest. F-5
tornadoes are the most dangerous (and the
rarest).
• F-0 40-72 mph, Light damage, chimney damage,
tree branches broken
• F-1 73-112 mph, Moderate damage, mobile
homes pushed off foundation or flipped over
• F-2 113-157 mph, Considerable damage, mobile
homes demolished, trees uprooted
• F-3 158-205 mph, Severe damage, roofs and walls
torn down, trains overturned, cars thrown around
• F-4 207-260 mph, Devastating damage, wellconstructed walls leveled
• F-5 261-318 mph, Violent damage, homes lifted
off foundation and carried considerable
distances, autos thrown as far as 100 meters.
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Water Spout
• Intense column vortex that occurs over a
body of water, connected to a cumuliform
cloud.
• Non super cell tornado over water.
• They do not suck up water. The water seen is
droplets formed by condensation,
• 2 kilometers wide.
• Weaker than a tornado
67
Waterspout
• Five part life cycle
• 1. Formation of a dark spot on the water
surface
• 2. spiral pattern on the water surface
• 3. formation of a spray ring
• 4. development of the visible condensation
funnel
• 5. Ultimately decay.
68
Where do they occur?
• Locations in higher latitude within the
temperate zones
• Reports in Europe and the Great Lakes,
Florida etc.
69
Waterspout Diagram
70
3 spouts on Lake
Huron 1999
71
Tornadic water spout from a
thunderstorm.
They travel from land to
water.
72
Tropical Cyclones
• Tropical Cyclones - large rotating low
pressure system
• Season - summer and fall
• Origin - sunny tropics
• Energy - from the amount of energy of warm
moist tropical ocean water
73
•
•
•
•
•
•
U.S. Hurricanes
Indian Ocean: Cyclones
West Pacific: Typhoons
Development: water evaporates from ocean
surface. Latent heat is released when air rises
and H2O vapor condenses into clouds and
rain falls - created a low pressure system.
•
74
Coriolis Effect and Low
Pressure Center
• This causes the system to turn counter clock-wise
in the N.H. (Northern Hemisphere) as moving air
is added it begins to rotate faster. System
increases in speed and more energy is released
through condensation. Air usually rises because
of a disturbance in the Tropics along the ITCZ.
Pressure decreases in the center.
• Surface Winds - speeds can increase and exceed
240 km/hr
•
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Hurricane Formation
•
•
•
•
•
•
Conditions:
1) abundant supply of warm moist air
2) Disturbance to lift air
3) Air keeps rising
Found in all oceans except the South Atlantic
and Pacific Ocean west of South America.
Why? Cooler bodies of H2O and ITCZ is
farther north.
•
• Movement - wind currents guide them
• Tropics - home to subtropical high pressure
systems - move west, then towards the
poles on the edges of high pressure systems.
Here the prevailing westerlies guide the
movement - unpredictable.
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Hurricane
77
What does a Hurricane
Need?
78
90% of the deaths are
from drowning
79
Weather disturbances
• Eye forms - calm center
• Eye walls - have the strongest winds - 40 to
80 km wide
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Saffir-Simpson hurricane
scale
Classifies hurricanes:
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82
• Hurricanes last until they run our of energy; if
they run on land, they lose energy hurricanes
have: thunderstorms; tornadoes and rain.
•
•
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• Hurricane Hazards - winds that are more
than 60km/hr . can be as far as 400 km from
the eye; storm surges are driven by hurricane
force winds that force large amounts of
ocean water onto the coastal areas.
•
• Northern Hemisphere - right side of the
hurricane has the strongest winds. floods can
occur. National Hurricane center tracks these
storms; observes 36 hours in advance; gives
warning - 24 hours in advance. Advises
position, strength, movement.
• Hurricanes are named due to the excessive
number of storms being tracked at one
• time.
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Hurricane Sandy
85
Storm Surge
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Water logged soils
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Jersey Boardwalk
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Satellite picture
Sandy
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Frankenstorm?
•
•
•
•
1. Largest in Atlantic History
2. Gale force winds 1040 miles wide
3. Ocean temps 5 degrees above normal.
4. Transitioned from a warm core hurricane onto
an extra low tropical pressure system, a classic
Nor easter
• 5, High pressure blocking pattern near Greenland
• Major cause Global warming!
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