Transcript Storms PowerPoint

Thunderstorms
1. At any one time, nearly 2,000
thunderstorms are occurring around the
world.
2. The three conditions necessary for a
thunderstorm to form are: 1) lots of
moisture in the lower atmosphere 2) The
now warmer air begins to rise 3) the
atmosphere must be unstable
3. There are air mass thunderstorms that
form due to differences in air masses.
4. Frontal thunderstorms form by an
advancing cold front usually.
Stages of a Thunderstorm
Stages of thunderstorm development
13.2-Severe Weather
6. A supercell is a self-sustaining,
extremely powerful storm that has intense,
rotating updrafts.
Mammantus
7. Lightening is electricity caused by the
rapid rush of air in a cumulonimbus cloud.
8. When lightening occurs, the air expands
out rapidly, causing the sound of thunder.
9. A downburst is a violent damaging
thunderstorm wind concentrated in a local
area.
Downburst
Hail
10. Hail is precipitation in the form of balls or
lumps of ice. They form in severe storms.
Indicator of tornadoes!
Hail formation
11. A tornado is a violent, rotating column
of air in contact with the ground.
12. A change in wind speed and direction
cause wind shear which creates a
horizontal rotation. When it’s close enough
to an updraft, it becomes vertical and thus
a tornado.
Anatomy of a tornado
First photographed tornado- 1884
Salt Lake City Tornado
A dual funnel tornado
14. Weak tornadoes (F0-F1) make up 80% of all
tornadoes. Last 1-10 minutes. On ground up to 3
miles. Wind speeds- 60-115 mph
15. Strong ones (F2-F3) make up 19%. Last up
to 20 min. On ground up to 15 mi. Winds- 110205 mph
16. Violent ones (F4-F5) make up only 1%. Last
up to 1 hour. On ground up to
50 mi. Winds- over 200!
Hook Echo
Wind shear & Hook Echo
April 3-4, 1974 Tornado Outbreak
Waterspout
Three Waterspouts!
Tornado Alley!
18. More than 700 tornadoes occur each
year in the U.S.
Tornadoes & Hurricanes
13.3 Tropical Storms
1. A tropical cyclone is a large, rotating, lowpressure storm formed over warm, ocean water
in the summer or fall.
2. Our storms form off the coast of Africa near the
equator and move west/northwest.
Hurricane formation
3. A tropical depression is an organized
system of clouds and thunderstorms with a
defined surface circulation and maximum
sustained winds of 38 mph or less.
4. A tropical storm has maximum
sustained winds of 39-73 mph.
5. A hurricane is an intense tropical
weather system of strong thunderstorms
with a well-defined surface circulation and
maximum sustained winds of 74 mph or
higher.
Saffir-Simpson Scale
25. Some famous hurricanes to strike NC are:
Hugo (1989), Fran (1996), Floyd (1999), Isabel
(2003)
26. Record hurricanes in the US: Andrew (1992),
Katrina (2005)
27. The 2005 hurricane season set new records
with 28 storms. With only 24 names, the last 4
storms were given letters (Alpha, Beta, etc.)
Fifteen of these became hurricanes, seven were
major hurricanes, with five that were category
fours and four became category fives!!
• A hurricane watch is issued when
hurricane conditions are possible within 36
hours. Begin family's disaster plan,
needed supplies, evacuation routes, etc.
• A hurricane warning is issued when
hurricane force winds are expected within
24 hours. Complete planning process and
prepare for the storm.
Hurricane Isabel (infrared)
Isabel Radar
Inland during a hurricane, it’s the
rainfall that does the most damage!
Flooding from Isabel
Overwash from Isabel
Fran approaching …
Infrared Image of Floyd
Hurricane Wilma
August 1995 Satellite image
Storm Surge
Katrina and Sea Surface Temperatures
Saffir-Simpson