Transcript Thunderstorms, Tornados , and Hurricanes

Thunderstorms, Tornados, and Hurricanes
Thunderstorms
• Requirements
– Warm moist air
– Lifting mechanism
What is the result of lifting?
• Most Probable Location?
Fig. 15.15
Thunderstorm
formation
2. Mature Stage
•condensation
3. Dissipating
Stage
in uppermost
reaches produces ice
Cloud
ends1. Cumulus Stage
crystals formation
(which can
merge)
Evaporation
Falling
precipitation of some of the
warm air is forced vertically
generates friction against
falling
rains
updrafts
– creates
a removes
downward
column
of the system,
energy
from
movement – downdraft
creates updrafts
Failing
air warmsthe
– melts
cooling
air
some ice to produce rain
formation
of
a
cumulus
cloud
other ice
hail stable and
Cool
airfallsisasmore
Passing updrafts and
prevents
downdrafts
causeupdrafts
polarization of charges
no
precipitation
occurs
during
between
ice
particles
and
Light rain and dissipation of
droplets in the clouds
this stage
(causes
lightning)
clouds
• 3 stages:
upward cooling quickly,
as warm air rises and expands
Lightning
• Lightning joins centers
of opposite charges.
– Top of cloud to middlebottom
– Bottom of cloud to land
surface
Fig. 15.17
Tornadoes
• Narrow, funnel-shaped spirals
of rapidly converging and
rotating air associated with
thunderstorms
• Center around low-pressure
• Winds are associated with
high pressure gradients
– Midlatitude cyclones have
gradients of 0.04 mbar/km
– Hurricanes have gradients of
0.2 mbar/km
– Tornados have gradients up to
100 mbar/km
• The higher the gradient the
greater the winds
Tornado formation
• 3 stages
– Early – slow air
movement at the ground
surface shears with rapid
vertical movement,
produces rolling spiral of
wind
– Updraft – updraft of
thunderstorm pulls the
spiraling air up vertically,
creates mesocyclone
– Tornado – rotation
becomes tighter and
faster, air extends
downward
Hurricanes
• Characterized by high sustained winds
• Heavy rainfall
• Storm surges (elevated water levels) along
coastlines
• Occur over the globe, but have different
names
– Pacific Ocean – typhoons
– Indian Ocean - cyclones
Formation
• Our “hurricanes” begin as winds coming off of
northern Africa
Formation - continued
• Air moves over warm water (at least 27 oC)
• Ocean water evaporates and subsequently
condenses in the atmosphere (What has
happened in terms of energy and temperature?)
• Warm humid air continues to be drawn into the
air mass and is forced upwards (creating a greater
pressure gradient).
• Prevailing winds create cyclonic rotation
(counterclockwise)
Formation - continued
• Lowest pressure develops at the center where
air is being forced upwards
• Continued evaporation of warm waters
increases the movement of air and
strengthens the storm
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Fig. 15.23
Daily Question
8
Tornadoes
Using a Venn
Diagram, compare
and contrast
midlatitude cyclones,
tornadoes, and
hurricanes. Provide 1)2)
3)
a minimum of 7
4)
items.
5)
1
4
Hurricanes
9
12
10
5,
6, 7
2
Midlatidude
cyclones
11
3
Destructive winds 8) Short duration
Rain
9) Require warm water
Cold front advances 10) form over land
on a warm front
11) Geographically
Form off of Africa
affects a large area
Center around low 12) Moves west to east
pressure
6) Counter clockwise
air movement
7) Associated with
thunderstorms