Transcript Storms and human impact pptx

Review and warm up
• Kahoot first and fourth period
• Weather mapping review activity
• Read the directions carefully. Only use dry erase markers or
highlighters on the maps.
• Make sure that you show the maps to Mrs. Chapel so she can get a
grade for you.
• You have 10 minutes
Basic Concepts of Doppler Radar
Doppler Shift: A frequency shift in electromagnetic waves due to the motion of scatters
toward or away from the observer.
Doppler radar: obtains weather information (wind and precipitation) based upon returned
energy.. It emits a burst of energy. If the energy strikes an object (rain drop, bug, bird, etc),
the energy is scattered in all directions. A small fraction of that scattered energy is directed
back toward the radar
Radar Meteorology
M. D. Eastin
Basic Concepts of Doppler radar
• Doppler shift is negative (lower frequency, red shift) for objects
moving away from the radar (positive vr)
• Doppler shift is positive (higher frequency, blue shift) for objects
moving toward the radar (negative vr)
• These “color” shift conventions are often translated to radar displays:
Red: Moving away from radar
Blue/Green: Moving toward radar
Radar Meteorology
M. D. Eastin
Satallite mapping: Dozens of satellites keep a constant
watch over the earth each day.
Some are
geosynchronous (stay in the same position over the
earth) while others orbit around the earth.
Severe Storms
Most Violent weather is associated with low
pressure systems because air of different
properties mixes there
• Thunderstorms
• Tornadoes
• Hurricanes
• Winter Storms
How do tornadoes form?
• Scientists aren’t entirely sure
• Associated with low pressure system
• Associated with supercells which contain a deep and persistent rotating
updraft called a mesocyclone.
• An updraft is upward moving air currents, and a downdraft is downward
moving air currents.
Creating a tornado:
1. Air rotates because of wind shear-winds at different altitudes spin in
different speeds
2. Rising air within the thunderstorm updraft tilts the rotating air from
horizontal to vertical.
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, self-sustaining
storm that can
spawn tornados.
Most tornadoes
occur in May.
http://midwestweather.net/archives/tornadoclimatology.htm
In 2006, the NWS introduced the Enhanced Fujita Scale, an updated version of the F-scale
Watch vs. Warning
• Watch=conditions are favorable for a tornado
• Warning=tornado has been sited or indicated by weather radar
• Hazards?
Flying debris
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. (A bath tub is safest!)
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.
Where don’t you want to be when a tornado strikes?
How many does NC have per year?
• Approximately 16
On radar, often big tornadoes are seen with a
“hook echo”
Hurricanes
• Hurricane: Atlantic and East Pacific
• Typhoon: West Pacific
• Cyclone: Indian Ocean
• Intense Low-Pressure Systems
• Need 60 m (200 feet) of ocean water at 26.5 C or
warmer to form
When to expect
• Hurricane season is June through November
• Peak is in September
Tropical Cyclones…
1.
A tropical cyclone can be
described as a…
 Large, rotating, low
pressure storm
 Form near equator
where air is warm and
moist
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!
Classifying Hurricanes…
4. A hurricane runs out of energy
a.
b.
When it moves over land
When it moves over cold
water
• Need warm water for energy
• Decay rapidly over land
• Lose strength over cold
water
• Can still cause destructive
flooding long after cyclonic
structure is gone
• Degenerate into low
pressure systems
http://backyard.weatherbug.com/profiles/blogs/the-south-central-texas-445
Classifying Hurricanes…
3.
a.
b.
c.
The Saffir-Simpson Scale…
Categories 1 – 5
Category that does the most damage – 5
Wind speed of a cat 5? > 155 mph
http://www.nhc.noaa.gov/pastint.shtml
Classifying Hurricanes…
1. What scale is used to classify
hurricanes?

Saffir-Simpson
2. What are the four
characteristics of a hurricane
described by the scale?
a.
Wind speed – how
high?
b. Air pressure – how
low?
c. Potential for damage –
how much?!
d. Storm surge
http://www.nhc.noaa.gov/sshws_table.shtml?large
Hurricane Watch vs warning
• A hurricane poses a possible threat within the next 36 hours
• Hurricane conditions expected within 24 hours
Hurricane Hazards…
• Wind Pressure
• Flying Debris
• Storm Surge
• Flash Flooding
• Tornadoes
http://www.med.navy.mil/sites/nmcp/localarea/Weather/PublishingImages/def1.gif
Hurricane Safety
• Best plan is to evacuate
• Towns have voluntary evacuation during a watch, and some switch to mandatory
during a warning.
• Plan early in advance
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•
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If you choose to stay:
Board all windows
Prepare Flashlights, avoid candles
Stay tuned to radio
Stay indoors
How many does North Carolina get?
• a tropical cyclone makes landfall along the coastline about once every
four years
Hurricane and tornado posters
• You have the rest of the period to finish your posters
Closure
• Obtain a map analysis worksheet
• Turn the worksheet in as you leave.
• This is a grade