Download Thunderstorms and Tornadoes

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

page
1
page
2
page
3
page
4
page
5
page
6
page
7
page
8
page
9
page
10
page
11
page
12
page
13
page
14
page
15
page
16
page
17
page
18
page
19
page
20
page
21
page
22
page
23
page
24
page
25
page
26
page
27
page
28
page
29
page
30
page
31
page
32
page
33
page
34
page
35
page
36
page
37
page
38
page
39
page
40
page
41
page
42
Document related concepts
no text concepts found
Transcript 
Chapter 14
Thunderstorms
A storm containing lightening and
thunder; convective storms may have
heavy rain hail
 Ordinary Cell Thunderstorms

 Air-mass thunderstorms: limited wind sheer
 Stages: cumulus, mature, dissipating
 Entrainment, downdraft, gust front
A dissipating thunderstorm
Thunderstorms

Multi-cell Thunderstorms
 Thunderstorms that contain a number of
convection cells, each in a different stage of
development, moderate to strong wind
shear; tilt, over shooting top
Multicell storm
Thunderstorms

Multi-cell Thunderstorms
 Micro-bursts: localized downdraft that hits
the ground and spreads horizontally in a
radial burst of wind; wind shear, virga
Dust clouds from microbursts
Thunderstorms

Multi-cell Thunderstorms
 Gust Front: leading edge of the cold air out-
flowing air; shelf cloud, roll cloud, outflow
boundary
Thunderstorms

Severe thunderstorms: one of large hail,
wind gusts greater than or equal to
50kts, or tornado, tilted
updraft/downdraft
Shelf cloud
Thunderstorms

Multi-cell Thunderstorms
 Squall-line thunderstorms; line of multi-cell
thunderstorms, pre-frontal squall-line,
derecho
Pre frontal
Squall
line
Pre frontal
Squall
line
The thunderstorms are producing strong straight-line winds called a derecho
Thunderstorms

Multi-cell Thunderstorms
 Meso-scale Convective Complex: a number
of individual multi-cell thunderstorms grow in
size and organize into a large circular
convective weather system; summer,
10,000km2
Thunderstorms

Supercell thunderstorms
 Large, long-lasting thunderstorm with a




single rotating updraft
Strong vertical wind shear
Outflow never undercuts updraft
Classic, high precipitation and low
precipitation supercells
Rain free base
A supercell thunderstormwith a tornado sweeps over Texas
Thunderstorms

Supercell thunderstorms
 Strong vertical wind shear
 Surface, 850mb, 700mb, 500mb, 300mb
conditions
 low-level jet
Thunderstorms

Supercell thunderstorms
 Cap and convective instability
Thunderstorms

Thunderstorms and the Dryline
 Sharp, horizontal change in moisture
 Thunderstorms form just east of dryline
 cP, mT, cT
Fig. 14-23, p. 384
Thunderstorms

Floods and Flash Floods
 Large floods can be created by training of
storm systems, Great Flood of 1993
 Flash floods rise rapidly with little or no
advance warning; many times caused by
stalled or slow moving thunderstorm
downtown Des Moines, Iowa, during July, 1993
Fig. 14-25, p. 387
Thunderstorms

Topic: Big Thompson Canyon
 July 31, 1976, 12 inches of rain in 4 hours
created a flood associated with $35.5million
in damage and 135 deaths
 Slow moving Thunderstorm
Fig. 1, p. 386
Flash Floods
Slow moving or Stalled thunder Storm, especially in
canyon areas
135 deaths in 1976 flood
12 inches of rain in 4 hours
(normal ~16 inches /year)
Thunderstorms

Distribution of Thunderstorms
 Most frequent Florida, Gulf Coast, Central
Plains
 Fewest Pacific coast and Interior valleys
 Most frequent hail Central Plains
Related documents