chapter 13 the nature of storms. lesson 1 thunderstorms
TRANSCRIPT
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
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!
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter11/graphics/cf_xsect.jpg
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/tstorm/tst_detecting.html
Severe Thunderstorms
anvil
Precipitation
Rain Free Base
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? A giant spark of static
electricity
2. When does a lightning bolt form?
When there is an electrical imbalance between clouds (-) and the ground (+)
3. 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 positively-charged 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.srh.noaa.gov/jetstream/lightning/images/lightning8.jpg
http://www.eoearth.org/files/119701_119800/119773/Step5.jpg
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 Parkwayhttp://www.sciencephoto.com/images/download_lo_res.html?id=670034119
http://www.barransclass.com/phys1090/circus/JenkinsD/JenkinsD.html
Lightning Q&A and Safety…
http://www.srh.noaa.gov/jetstream/lightning/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. Abundant moisture over a limited area.
b. Rain falls faster than the ground can absorb it.
c. 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-photos-2011_n_861204.html#s279672&title=Mississippi_River_Flooding
Tornados…
A. A change in wind direction and speed creates a horizontal rotation.
B. Strong updrafts tilt the rotating air to a vertical position.
C. A tornado forms within the rotating winds.
http://www.weatherwizkids.com/tornado_formation.jpg
Tornado Alley - The Midwest!
http://midwestweather.net/archives/tornadoclimatology.htm
A cP air mass from Canada meets a mT air mass from the Gulf of Mexico forming a supercell.
A supercell is a giant, self-sustaining storm that can spawn tornados.
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
http://0.tqn.com/d/weather/1/0/i/C/-/-/fujita2s_600.jpg
Dr. Theodore Fujita
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. Move to a pre-designated shelter – to a basement if possible.
2. Move to an interior room/hall, lowest floor, under sturdy furniture.
3. Stay away from windows.4. Get out of vehicles!5. Don’t try to outrun a tornado.6. If outside, lie flat in a ditch or depression.7. 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…
Large, rotating, low pressure storm
2. We call these storms… hurricanes
3. 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. Air pressure in eyewall– decreasesb. Surface wind speeds – increase
6. What are two basic conditions that tropical cyclones require to form?
a. Lots of warm ocean waterb. Disturbance to lift the air
Tropical Cyclones…
7. Tropical cyclones move steadily towards… the west!
8. 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
http://www.srh.noaa.gov/shv/?n=hurricane_rita
Development of a Tropical Cyclone…
Tropical Disturbance – a weak, low-pressure system – group of thunderstorms collect
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.uvs-model.com/WFE%20on%20tropical%20cyclone%20(Hurricane).htm
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
http://www.weatherstockphotography.com/
Ivan2006
Dean 2007
Katrina 2005
Hurricane History…
http://www.nhc.noaa.gov/HAW2/english/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?
Saffir-Simpson
12. What are the three characteristics of a hurricane described by the scale?
a. Wind speed – how high?b. Air pressure – how low?c. Potential for damage –
how much?!
http://www.nhc.noaa.gov/sshws_table.shtml?large
Classifying Hurricanes…
The Saffir-Simpson Scale…a. Categories 1 – 5b. For a tropical storm to be considered a
cat. 1 hurricane – 74 mphc. The category that does the most damage
– 5d. Wind speed of a cat 5? > 155 mphe. Three most powerful storms to hit USA?
a. Florida Keys, 1935b. Camille, 1969c. Andrew, 1992
http://www.nhc.noaa.gov/pastint.shtml
Classifying Hurricanes…
14. A hurricane runs out of energy
a. When it moves over land
b. 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!