Transcript Storms Nature Powerpoint

Chapter 13
The Nature of Storms
Lesson 1
Thunderstorms
Think About It…
During which months do
we get the most
damaging thunderstorms
here in the Piedmont?
Focus Question…
How do the major types of
thunderstorms form?
Average Number of Thunderstorm Days
Annually…
Types of Thunderstorms…

Air Mass - Mountain



Where… within one air mass over a mountain
Why… warm air rises over a mountain, forming storm
clouds!
When… midafternoon
http://web.mst.edu/~rogersda/umrcourses/ge301/press&siever12.3.png
Types of Thunderstorms…

Air Mass - Sea-Breeze



Where… coastal areas, esp. tropics/subtropics
Why… temperature differences between land
and sea create convection cells and updrafts
When… summer
http://apollo.lsc.vsc.edu/~wintelsw/MET1010LOL/web/notes/chapter11/ts_ingredients4summary.html
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter11/graphics/cf_xsect.jpg
Types of Thunderstorms…

Frontal - Cold



Where… at the leading edge of a cold front
Why… cold air pushes warm air rapidly up at the
steep cold-front boundary
When… anytime a cold front moves in!
Types of Thunderstorms…

Frontal – Warm



Where… at the
leading edge of a
warm front
Why… warm air
mass slides up over
a cold air mass
creating clouds
When… if a warm
front moves in with
enough moisture and
instability
http://www.atmoz.org/img/warm-front.png
Thunderstorms in the
Piedmont…
Which types of
thunderstorms do we
experience here in the
Piedmont?
 Frontal (warm and
cold)
 Local Air Mass (in the
summer)
http://www2.journalnow.com/mgmedia/image/0/354/118602/severe-storms-cause-damage-across-region/
Stages of Development of a
Thunderstorm…
http://chiefio.wordpress.com/2010/12/28/ignore-the-day-at-your-peril/
NSSL – Q&A
Thunderstorms…
The National Severe Storm
Laboratory is in Norman, OK.
 http://www.nssl.noaa.gov/primer/tstor
m/tst_detecting.html

Severe Thunderstorms
anvil
Rain Free Base
Precipitation
http://ed101.bu.edu/StudentDoc/Archives/ED101fa06/mattwall/Extreme%20Weather.htm
How Lightning Forms …
http://www.erh.noaa.gov/bgm/preparedness/swaw/ny/images/Light1.gif
Lightning…
1.
What is lightning?

2.
When does a lightning bolt
form?

3.
A giant spark of static
electricity
When there is an
electrical imbalance
between clouds (-) and
the ground (+)
What is a stepped leader?

An invisible channel of
negatively charged air
from a cloud
http://i.imwx.com/web/multimedia/images/blog/stepped_lightning2.jpg
Lightning…
4. What is return stroke
(positive streamer)?

A channel of positivelycharged ions from the
ground
5. How hot is lightning?

30,000 degrees Celsius
6. What causes thunder?

Super-heated air expanding
and contracting
http://www.eoearth.org/files/119701_119800/119773/Step5.jpg
http://www.srh.noaa.gov/jetstream/lightning/images/lightning8.jpg
http://www.barransclass.com/phys1090/circus/JenkinsD/JenkinsD.html
Lightning Damage…
7.
Describe the damage that lightning can do.



7500 forest fires/year
300 injuries/ 93 deaths/year
Property damage
Lightning-struck trees on the
Blue Ridge Parkway
http://www.sciencephoto.com/images/download_lo_res.html?id=670034119
Lightning Q&A and Safety…
http://www.srh.noaa.gov/jetstream/lightn
ing/lightning_faq.htm#10
Lesson 2
Severe Weather
Think About It…
Where is the safest place
to be during a tornado?
Focus Question…
How do tornados form and
how are they classified?
The Fury of the Wind…
1. What is a downburst?

A violent downdraft concentrated in
a local area
2. What are the two types of
downbursts?
macro- (big) and micro- (small)
3. Microbursts are deadly because they
are harder to detect and prepare for.

Floods…
4. What are 3 conditions that cause
floods to occur?
a.
b.
c.
Abundant moisture over a limited
area.
Rain falls faster than the ground can
absorb it.
Wind currents in the upper
atmosphere are weak so that
weather systems move slowly
The Flooding Mississippi
River
Slide show May 17, 2011…
http://www.huffingtonpost.com/2011/05/
12/mississippi-river-flooding-photos2011_n_861204.html#s279672&title=
Mississippi_River_Flooding
Tornados…
A.
B.
C.
A change in wind
direction and
speed creates a
horizontal rotation.
Strong updrafts tilt
the rotating air to
a vertical position.
A tornado forms
within the rotating
winds.
http://www.weatherwizkids.com/tornado_formation.jpg
Tornado Alley - The Midwest!
A cP air mass from
Canada meets a
mT air mass from
the Gulf of Mexico
forming a supercell.
A supercell is a
giant, selfsustaining storm
that can spawn
tornados.
http://midwestweather.net/archives/tornadoclimatology.htm
The Enhanced Fujita
Scale…EF0 or EF1
- % of all tornados…

80
- Path…

up to 3 miles
- Wind Speed…

60-115 mph
- Duration…

1 – 10 minutes
Dr. Theodore Fujita
http://0.tqn.com/d/weather/1/0/i/C/-/-/fujita2s_600.jpg
The Enhanced Fujita
Scale…EF2 or EF3
- % of all tornados…

19
- Path…

15+ miles
- Wind Speed…

110 - 165 mph
- Duration…

20+ minutes
The Enhanced Fujita
Scale…EF4 or EF5
- % of all tornados…
 1 (Thankfully!)
- Path…
 50+ miles
-
-
Wind Speed…
 200+ mph
Duration…
 1+ hours
http://thedailycap.com/alabama-tornado-2011
Tornado Safety…
1.
2.
3.
4.
5.
6.
7.
Move to a pre-designated shelter – to a
basement if possible.
Move to an interior room/hall, lowest floor,
under sturdy furniture.
Stay away from windows.
Get out of vehicles!
Don’t try to outrun a tornado.
If outside, lie flat in a ditch or depression.
Abandon a mobile home for a shelter.
Lesson 3
Tropical Storms
Think About It…
From which direction do
the hurricanes which hit
our east coast come?
Focus Question…
How does a hurricane
form?
Tropical Cyclones…
1.
A tropical cyclone can be
described as a…

2.
We call these storms…

3.
Large, rotating, low
pressure storm
hurricanes
Tropical cyclones derive a
tremendous amount of energy
from…

Warm, tropical
oceans
http://www.nhc.noaa.gov/HAW2/english/history.shtml
Tropical Cyclones…
4.
Which direction do
tropical cyclones turn in
the northern hemisphere?


Counterclockwise
It is a low
pressure system!
Fran, 1996, Cape Fear, NC
Name was retired!
Tropical Cyclones…
5.
As a hurricane strengthens, what do
the following components do?
a.
b.
6.
Air pressure in eyewall– decreases
Surface wind speeds – increase
What are two basic conditions that
tropical cyclones require to form?
a.
b.
Lots of warm ocean water
Disturbance to lift the air
http://www.srh.noaa.gov/shv/?n=hurricane_rita
Tropical Cyclones…
7.
8.
Tropical cyclones move steadily towards…
 the west!
Which wind system moves across the USA and usually
guides hurricanes out into the Atlantic Ocean?
 the prevailing westerlies
Hurricane Rita – 2005, 3rd lowest pressure in Atlantic (897 mb), hit as cat. 3
Development of a Tropical
Cyclone…
Tropical Disturbance – a weak, low-pressure
system – group of thunderstorms collect
http://www.uvs-model.com/WFE%20on%20tropical%20cyclone%20(Hurricane).htm
Development of a Tropical
Cyclone…
Tropical Depression – a disturbance begins
to rotate around the center of low pressure
Katrina as a tropical depression
http://www.weatherstockphotography.com/
Development of a Tropical
Cyclone…
Tropical Storm – a depression is labeled a
storm when the wind speeds reach 39 mph.
Tropical Storm Dalila, July 2007
http://www.weatherstockphotography.com/
Development of a Tropical
Cyclone…
Tropical Hurricane – pressure drops and the
wind speeds reach 74 mph
Dean
2007
Ivan
2006
Katrina
2005
Hurricane History…

http://www.nhc.noaa.gov/HAW2/englis
h/history.shtml#galveston
Anatomy of a Hurricane…
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter15/vertical_circ.html
Classifying Hurricanes…
11.
What scale is used to
classify hurricanes?

12.
What are the three
characteristics of a
hurricane described by the
scale?
a.
b.
c.

Saffir-Simpson
Wind speed – how high?
Air pressure – how low?
Potential for damage –
how much?!
http://www.nhc.noaa.gov/ssh
ws_table.shtml?large
Classifying Hurricanes…
The Saffir-Simpson Scale…
a.
Categories 1 – 5
b.
For a tropical storm to be considered a
cat. 1 hurricane – 74 mph
c.
The category that does the most damage
–5
d.
Wind speed of a cat 5? > 155 mph
e.
Three most powerful storms to hit USA?
a.
b.
c.
Florida Keys, 1935
Camille, 1969
http://www.nhc.noaa.gov/pastint.shtml
Andrew, 1992
Classifying Hurricanes…
14.
A hurricane runs
out of energy
a.
b.
When it
moves over
land
When it
moves over
cold water
http://backyard.weatherbug.com/profiles/blogs/the-south-central-texas-445
Hurricane Hazards…
15.
The
strongest
winds in a
hurricane
are in …

The eye
wall
http://www.med.navy.mil/sites/nmcp/localarea/Weather/PublishingImages/def1.gif
Hurricane Hazards…
16.
What is a storm surge?
1.
When hurricane force winds drive a mound
of ocean water towards coastal areas
http://www.chathamemergency.org/images/storm%20surge%202.png
Hurricane Hazards…
17.
What hurricane hazard is caused by
great amounts of rain?

floods
Flooding from
Hurricane Fran
http://pubs.usgs.gov/of/1996/of96-499/text/PHOTOS.html
Hurricane Hazards…
18.
Which agency is
responsible for
tracking and
forecasting
hurricanes?

The National
Hurricane Center
in Miami, FL at
the FIU Campus
(NOAA)
Lesson 4
Recurring Weather – Review
handout!