Sem#2 Chap 2

Question 1

Thunderstorms

Answer 1

Towering clouds that produce lightning and thunder. May rise to the troppause
Typically <30 km diameter, with speed ~90 km/hr
Most occur over land within the tropics.

Question 2

Severe thunderstorms (defined by the NWS) may produce:

Answer 2

• Winds >93 km/hr
• Hail >2.5 cm in diameter
• A tornado

Question 3

Thunderstorm Development, Temperate climates:

Answer 3

• Thunderstorms are frequent during warm seasons.

Question 4

Thunderstorms are rare in :

Answer 4

• Within high latitudes
• Over subtropical deserts
• Over oceans

Question 5

Thunderstorm days:

Answer 5

• Days on which at least 1 thunderstorm occurs.

Question 6

3 conditions must be present for thunderstorm:

Answer 6

• 1. Moist air (mostly from oceans, lakes, and wetlands)
• 2. A lifting mechanism
• 3. Atmospheric instability

Question 7

5 Lifting Mechanisms Force Air to Rise

Answer 7

 Movement along a front:
 Gust fronts:
 Less distinct boundaries:
High relief (orographic lift):
 Convergence:

Question 8

 Movement along a front:

Answer 8

• Advancing cold air forceswarm, moist air up.

Question 9

Gust fronts:

Answer 9

• Thunderstorms create cold downdrafts.
• Downdrafts act like small cold fronts

Question 10

Less distinct boundaries:

Answer 10

• Warm areas may contain less dense, buoyant air.
• Cool air may move beneath warm air

Question 11

High relief (orographic lift):

Answer 11

• Mountains force air upslope.

Question 12

Convergence:

Answer 12

• Colliding air flows may create lift.

Question 13

Air May Rise Without Being _________.

Answer 13

Physically Lifted

Question 14

Air above ground becomes buoyant enough to rise. Which is common during…..

Answer 14

Common during the summer on plains and mountain slopes

Question 15

Unstable air:

Answer 15

• When an air parcel is less dense than its environment

Question 16

Adiabatic expansion:

Answer 16

• Air parcel expands as it rises.
• Air in a rising, expanding parcel will cool.

Question 17

 Environmental lapse rate:

Answer 17

The rate temperature drops with increasing altitude.
* Typical rate is 4°–9°C/km

Question 18

Unsaturated air parcels:

Answer 18

• Do not form clouds as they rise and cool

Question 19

Saturated air parcels:

Answer 19

• Form clouds as they rise and cool

Question 20

 Dry adiabatic lapse rate (DAR):

Answer 20

• Applies to unsaturated air parcels
• Cool at ~10°C/km
• Relative humidity increases as air parcel rises and cools.

Question 21

If DAR > than environmental lapse rate:

Answer 21

• Air parcel will cool, become stable, and stop rising.

Question 22

Moist adiabatic lapse rate (MAR):

Answer 22

• Applies to saturated air parcels
• Cool at ~6°C/km
• Slower rate is due to latent heat released during condensation.

Question 23

Conditional instability:

Answer 23

• An air parcel’s MAR < than the environmental lapse rate
• Air parcel remains warmer than environment.
• Air parcel remains buoyant and continues rising

Question 24

Thunderstorm development depends on 2 variables:

Answer 24

• The environmental lapse rate
• An air parcel’s moisture content

Question 25

Unsaturated air parcels:

Answer 25

* Cool more quickly than environment * Become dense, stable, and stop rising

Question 26

Saturated air parcels:

Answer 26

* Cool more slowly than environment * May become conditionally instable * Water condenses out, and a thunderstorm may develop

Question 27

Class Question #1 What happens to a rising air parcel if its moist adiabatic rate is less than the environmental lapse rate? a) The air parcel will sink, warm adiabatically, and condense its water vapor. b) The air parcel will sink, cool adiabatically, and condense its water vapor. c) The air parcel will rise, warm adiabatically, and not condense its water vapor. d) The air parcel will rise, cool adiabatically, and condense its water vapor

Answer 27

(No given answer)

Question 28

Ordinary Thunderstorms

Answer 28

Do not rotate around a vertical axis  Form where regional winds do not change direction or speed  Rarely produce hail, strong winds, or tornadoes  ~2,0000 are active at any time around the world.  The anvil shape on cumulonimbus cloud during a thunderstorm

Question 29

 Common development scenarios: for ordinary thunderstorms

Answer 29

* Late afternoon formation as sunlight warms ground * Formation on mountain slopes due to orographic lifting

Question 30

3 Stages of an Ordinary Thunderstorm

Answer 30

Developing, Mature, Dissipating

Question 31

Developing: Ordinary Thunderstorm

Answer 31

warm, moist air is lifted, expands, and cools. * Conditional instability develops. * Cloud spreads laterally at tropopause into anvil shape.

Question 32

Mature: Ordinary Thunderstorm

Answer 32

ice particles fall and melt into raindrops. * Rain initiates downdraft due to evaporative cooling. * Falling rain pushes down air and intensifies downdraft.

Question 33

Dissipating: Ordinary Thunderstorm

Answer 33

* Downdraft suppresses updraft, cutting off storm’s energy source.

Question 34

Squall-Line Thunderstorms

Answer 34

Thunderstorms organized in a line: A shelf cloud often develops:  Most intense thunderstorms arrive after shelf cloud passes:

Question 35

Thunderstorms organized in a line:

Answer 35

* Line may be a consolidated gust front, or a cold front.

Question 36

A shelf cloud often develops:

Answer 36

* Forms over the front, often has little precipitation * Straight-line winds may develop.

Question 37

Most intense thunderstorms arrive after shelf cloud passes:

Answer 37

* Lightning and heavy rain are common. * Wind is often gusty (variable velocity and direction)

Question 38

Warmer-Season Squall-Line Thunderstorms, develop.....

Answer 38

Develop from the gust fronts of many ordinary thunderstorms  Many gust fronts form a single, large, coalesced pool of cool air.  Single, coalesced gust front advanced into warm, moist air.  New thunderstorms develop along advancing gust front

Question 39

Radar:

Answer 39

* Initially: many individual thunderstorms are visible. * Later: a well-defined line of thunderstorms is visible.

Question 40

Frontal squall lines

Answer 40

* Thunderstorms occurring in a very long line * Often seen along the “tail” of a mid-latitude cyclone

Question 41

Derechos

Answer 41

Derecho: Spanish for “direct” or “straight”  Severe straight-line winds over a large geographic region  May develop along squall-line thunderstorms

Question 42

Supercell Thunderstorms

Answer 42

A thunderstorm with a longlasting, rotating updraft * Often produce tornadoes * Typically isolated from neighboring thunderstorms * Base diameter ~50 km Vertical wind shear must be present in troposphere.

Question 43

Supercell Thunderstorm Development

Answer 43

 Wind shear produces horizontal, rolling wind tube near ground.  Updrafts lift tube into an arch, and a cumulonimbus cloud develops.  Downdrafts splits the storm into two distinct thunderstorms.  Warm SSE air feeds the SE storm, while NW storm dies out. Chap#2 Slide 21

Question 44

Mesocyclones

Answer 44

 Counterclockwise-spinning, medium-sized storms High-altitude winds create asymmetrical anvil cloud.  Wall cloud develops at base of updraft.

Question 45

Forward flank

Answer 45

NE side of NE-moving supercell * Strong wind at forward flank downdraft (FFD)

Question 46

Rear flank

Answer 46

SW side of NE-moving supercell * Rear flank downdraft (RFD)

Question 47

NE tilt of storm

Answer 47

* FFD lies to NE of updraft, so storm can last for hours.

Question 48

Class Question #2 Identify one way that a squall-line thunderstorm can develop. a) from a consolidated gust front of several ordinary thunderstorms b) from a saturated air parcel sinking, warming adiabatically, and thereby producing intense precipitation c) from the rapidly-cooling air in a rear-flank downdraft (RFD) of a supercell thunderstorm d) from rapidly sinking air on the leeward slopes of a mountain range

Answer 48

(might be D as mentioned in class)

Question 49

Lightning

Answer 49

A charge separation develops in a thunderstorm’s clouds. Lightning is a huge electrostatic discharge. * Electrons jump from tiny ice crystals to large ice particles. * Ice crystals get (+) charge, ice particles get (–) charge.

Question 50

Name the two variations of lighting strikes...

Answer 50

Cloud to Ground and Cloud-to-cloud lightning, which is the most common.

Question 51

Updrafts carry tiny ice crystals (+ or - ?) to high altitude.

Answer 51

+

Question 52

Large ice particles (+ or -?) remain near cloud bottom.

Answer 52

-

Question 53

Air is an insulator, so charge separation is ________.

Answer 53

maintained

Question 54

Stepped leader:

Answer 54

Electrons in cloud base surge to ground in steps ~50–100 m long

Question 55

Charge separation develops between cloud base and ground.

Answer 55

* Negative charge of cloud base pushes away the ground’s electrons. * The ground and surface air develop a net positive charge.

Question 56

Positive streamer

Answer 56

Ionized (+) air molecules rise from ground to meet stepped leader

Question 57

Electron flow channel

Answer 57

* Forms when stepped leader and positive streamer meet * Main electrostatic discharge occurs (called a “return stroke”) * Process may repeat and produce multiple return strokes

Question 58

Positive-polarity cloud-to-ground lightning is rare:

Answer 58

* Electrons jump from ground to cloud’s positively charged anvil. * Requires an especially large electrostatic potential

Question 59

Protect yourself from lightning... list

Answer 59

* Stay indoors, away from conducting materials * Install lightning rods on rooftops to direct current

Question 60

Class Question #3 How is an electrical charge separation maintained in a thunderstorm? a) A push-force is created when the electrons on ice crystals chemically combine with supercooled water droplets. b) The air acts as an insulator and thereby keeps the positive and negatively-charged areas separated. c) Updrafts and downdrafts act in unison to keep the east and west sides of a thunderstorm electrically separated. d) Stepped leaders carry H2O ions up from the ground and into a thunderstorm, thereby creating and maintaining a charge separation.

Answer 60

(Pretty sure its B)

Question 61

Thunder

Answer 61

Lightning produces thunder  Lightning strikes instantly heat up and expand the air.  Air suddenly contracts when lightning strike ends

Question 62

Downbursts

Answer 62

Downbursts are especially intense downdrafts Downdrafts created by: * Evaporation causing air to cool and sink * Rain pushing air downward

Question 63

Microbursts

Answer 63

* A small downburst affecting ~5 km2 * Airplane lift is enhanced if taking off into a microburst. * Airplane lift is diminished if flying out of a microburst.

Question 64

Hailstones

Answer 64

Spherical lumps of solid ice Supercooled water droplets form at high altitudes.

Question 65

Hailstorm

Answer 65

When hailstones fall to the ground

Question 66

Hail swath

Answer 66

the path where hail falls to ground

Question 67

Class Question #4 Identify one variable that causes hailstorms in Mendoza, Argentina, to be so severe that farmers must install hail-nets to protect their crops. a) Dry air flows downslope from the Andes Mountains, creating counterclockwise-rotating gust fronts. b) Severe air pollution from Mendoza creates anthropogenic uplift patterns that frequently produce thunderstorms and hail. c) Moist air blows south, along the eastern slopes of the Andes Mountains, and often creates supercell thunderstorms. d) Regular weather patterns in Mendoza repeatedly create tornadoes, 30% of which spawn severe hailstorms.

Answer 67

(no given answer)

Question 68

Tornadoes

Answer 68

A violently rotating air vortex Extends from thunderstorm’s base to the ground

Question 69

World’s largest number of tornadoes is in ______.

Answer 69

Tornado Alley

Question 70

Tornado outbreaks

Answer 70

multiple tornadoes in a short time

Question 71

Supercell contains a _______.

Answer 71

mesocyclone. (A strong rotating updraft)

Question 72

Supercell contains 2 _______.

Answer 72

downdrafts * Forward flank downdraft (FFD) on NE side * Rear flank downdraft (RFD) on SW side

Question 73

Rear flank downdraft (RFD) creates _______

Answer 73

roll of rotating air. * Air spins on a horizontal axis.

Question 74

When rolling air passes beneath mesocyclone:

Answer 74

* Updraft pulls rolling air upward. * Rolling air stretches, thins, and wind speed increases. * Tornado forms if vortex contacts the ground.

Question 75

Funnel cloud visibility:

Answer 75

* A spinning cloud develops as updraft condenses moisture. * Debris is carried aloft, darkening the vortex.

Question 76

Multiple-Vortex Tornadoes

Answer 76

Tornado may break into several smaller vortices.  Very large tornadoes may have especially low pressure at vortex base.  Very low pressure may draw tornado core air downward.  Sides of tornado may be pushed outward from descending, core air.

Question 77

Non-Supercell Tornadoes

Answer 77

Develop along squall lines and in hurricanes Significant horizontal wind shear is needed: * Wind in opposite directions on either side of a front  If shear is strong enough, small vortices may develop. Updrafts may lift and stretch vortices into tornadoes. Hurricane rain band shear may also cause tornadoes.

Question 78

Defining Tornado Intensity

Answer 78

* Scale refined in 2007 to the Enhanced Fujita Scale

Question 79

Tornado classification is not based on ______.

Answer 79

wind speed

Question 80

Tornado Classification is based on ______

Answer 80

the damage tornadoes cause

Question 81

Tornado fatalities also occur from ....

Answer 81

* Vehicles are tossed. * Roofs collapse. * Walls are blown away. * Trees fall onto homes.

Question 82

Doppler radar

Answer 82

* Detects rotating winds * Detects tornado hook echoes

Question 83

Tornado watch

Answer 83

* Weather conditions favor tornado formation.

Question 84

Tornado warning

Answer 84

* A tornado has been seen or detected by radar.

Question 85

Class Question #5 Why must hospitals especially emphasize tornado safety drills? a) Because hospital administrators must lock all exterior doors, and secure all windows, immediately following a tornado warning. b) Because staff must move patients to safety, and this takes more than the typical lead time of NWS tornado warnings. c) Because backup electricity generators must be manually switched on following a NWS issued tornado watch, and this takes training. d) Because federal law mandates that all drugs be securely locked away within 5 minutes of a NWS issued tornado warning.

Answer 85

(Not given)