Thunderstorms and Severe Weather

1
Thunderstorms and Severe Weather
2
All Thunderstorms begin as Cumulus Clouds
3
(No Transcript)
4
This is runaway convection cumulonimbus over
the Plains. These clouds can grow to 70,000
feet (14 miles) high!
5
Mature thunderstorms have both downdrafts and
updrafts. The precipitation forms in the updraft
and falls out into the downdraft.
6
(No Transcript)
7
Thunderstorm Hazards
? Lightning
? Tornadoes/downbursts
? Hail
? Flash Floods
8
Every year 100-200 people die from lightning
strikes
9
There are actually nine cloud-to-cloud strokes
for each cloud-to-ground stroke
10
In the U.S., the greatest number of thunderstorms
and lightning fatalities (5-10 per year) occur
annually in Florida.
11
Cloud-to-Ground strokes are the most dangerous.
12
Notice the segmented pathway to the ground.
Also, some of the lighting didnt contact the
ground.
13
Lightning doesnt always hit the tallest object
14
but it often does. In the middle ages, the
church towers were used to store gunpowder, with
predictable results. Mosques, on the other hand
were struck but rarely suffered damage. Can you
see why?
15
Did Franklin really do this?
www.codecheck.com/cc/BenAndTheKite.html
16
Benjamin Franklin Drawing Electricity from the
Sky" by Benjamin West (1738-1820). The
Philadephia Museum of Art
17
The cloud-to-ground stroke heats the air to
around 30,000 K, making it the brightest stroke.
18
By holding the shutter open, several strokes are
captured in this image. There were also lots of
air discharges.
19
An air discharge is a stroke which peters out in
the air.
20
(No Transcript)
21
(No Transcript)
22
Florida gets a lot of lightning and we used to
launch the space shuttle from there.
23
Lightning can hit outside the thunderstorm!
24
Notice the positive streamers at a, b, and c
25
When the stepped leaders charge is approaching,
you might give off positive streamers! Dont be
the lightnings conduit. Get inside during
thunderstorms.
Read survivor stories here http//www.lightningsa
fety.noaa.gov/survivors.htm.
26
The fellow inside the metal cage is safe. Its
called a Faraday Cage. Lightning travels around
him, not through him.
27
Inside your vehicle is actually a safe place.
Its a kind of Faraday Cage. Dont touch the
metal parts.
28
Out on the golf course is NOT a safe place during
a thunderstorm.
29
Lightning in the ground is so hot it will fuse
sand. The resulting formations are called
Fulgarites
30
The heating of the air causes rapid expansion.
The compession is sound. We hear it as thunder.
The sound of thunder travels at right angles to
the lightning bolt. It travels at 1100 ft/sec so
count to 5. The sound has traveled about one
mile.
31
Tornadoes
32
Blue dots are high winds, Green dots are large
hail, Red dots are tornadoes
33
Tornadoes never occur without a parent
thunderstorm. There are over 1000 tornadoes in
the U.S. most years.
34
Miami, Florida tornado
35
A large, cone tornado. It might be a mile wide
at the ground.
36
(No Transcript)
37
Oklahoma City F5 tornado May 3, 1999
38
(No Transcript)
39
Here are all the 2011 tornadoes (1894)
40
All the tornadoes in 2014 so far (1000)
41
The number of tornadoes observed in the U.S.
appears to be increasing. Or are we just getting
better at finding them?
http//stormhorizon.org/Ustornadoes1953-2009.jpg
42
Tornadoes in the Great Plains tend to be the most
destructive
43
On radar, often big tornadoes are seen with a
hook echo
44
Greensburg, KS tornado hook echo
45
Greensburg High School
(http//environment.nationalgeographic.com/environ
ment/photos/kansas-tornado/greensburg-kansas-schoo
l.html)
46
http//www.youtube.com/watch?vbJPGuMfnty4
47
Watches and Warnings
48
(No Transcript)
49
Damage from the May 31, 1998 tornadoes in Albany,
NY. On the Fujita scale, where does this fit?
50
In 2006, the NWS introduced the Enhanced Fujita
Scale, an updated version of the F-scale
51
Tornadoes do damage on a very small scale
Houses demolished
Houses untouched
House untouched
House damaged
52
In 2011, almost 1900 tornadoes were reported in
the U.S.!
53
(No Transcript)
54
Tuscaloosa EF4
https//www.youtube.com/watch?vNjVW0Du2ZIo https
//www.youtube.com/watch?vmPcUDIXX2G4 https//www.
youtube.com/watch?vCW7i4CbYLEQ
55
Where dont you want to be when a tornado strikes?
56
Hail
Large hail is not a killer, but does considerable
damage
57
Falling from 20,000 feet or higher, large
hailstones pack quite a punch!
58
Average annual number of days with hail
59
This is the biggest hailstone known. It fell at
a town called Aurora, NE on June 22, 2003.
60
The Aurora hailstone was 7 inches in diameter.
Imagine that falling on your head from 20,000
feet up!
61
This is the previous record-holder, the
Coffeyville hailstone with some props (egg, hand)
for comparison.