chapter 10 thunderstorms. mid-latitude cyclone: counter-clockwise circulation around a low-pressure...
TRANSCRIPT
Chapter 10 Thunderstorms
Mid-latitude cyclone: counter-clockwise circulation around a low-pressure center
Where are thunderstorms located?Along the warm front or the cold front?
Tornado over Kansas - May 2004
Thunderstorms…
• Form in conjunction with MLC, but can also form on their own.
• Generate lightning and thunder, wind gusts and hail• Can cover a small area (single cloud) or a large area;
cluster of clouds• Have strong up and down (not spiraling counter clockwise)
movement of gusty, variable winds• Forms in unstable air.
Thunderstorm Scavenger Hunt
1. What are some other names/types of thunderstorms?2. Where are thunderstorms most common on Earth?3. During what time of day/season are thunderstorms most active?4. What three ‘ingredients’ are needed to form a thunderstorm?5. What is the size and duration of a thunderstorm?6. What are the warning signs that a thunderstorm is approaching?7. What is the #1 thunderstorm killer?8. What are “super-cells”, how big are they?9. What is a microburst?10. What are three stages of thunderstorm development?11. What is a mesocyclone?12. According to the National Weather Service (NWS), when is a severe
thunderstorm watch or warning issued?
Compare…
Pg. 287-Formation Size
Air Mass thunderstorm
Frontal thunderstorm
Air Mass Thunderstorms
• Air near surface is warmed during the day.• Warm air rises and condenses to form
cumulous clouds in the afternoon.• Scattered, isolated.• Most moisture evaporates
but eventually it accumulates into
taller clouds.
Forms along a Cold Front
8
Or…along a Warm Front
Unstable air mass
9
Orographic lifting over mountains
11
Forms when air converges, is forced up, cools adiabatically, form clouds
These tend to be brief, short-lived storms with moderately heavy downpours.
3 Stages of Development of a ThunderstormPg. 288
Cloud continues to grow as long as there is a supply of warm, moist air.Updraft occurs.
13
http://www.youtube.com/watch?v=DualOU_gBn0
Stage 1
Bergeron Process
Ice crystals collect water molecules and grow larger
while cloud droplets evaporate and get smaller.
Stage 2
• Mature stage
15
Stage 3
16
Fair-Weather Cumulus
DevelopingCumulonimbus
Well-Developed Cumulonimbus
Severe Thunderstorm Development along a Cold Front
19
???????????
• Where in the U.S. do thunderstorms occur most frequently?
• How many are occurring at any given time world-wide?
Average Number of Thunderstorm Days
Flash Floods - Number One Thunderstorm Killer
AtmosphericHazard
Bell work
1. T or F? A mature stage thunderstorm cloud can be as high as the mesosphere.2. Severe thunderstorms form along (cold, warm) fronts.3. Which can have the higher wind speeds – hurricanes or tornadoes?4. T or F? Thunderstorms have vertical air movement while tornadoes have spiral air movement.5. Does an updraft cause a “up-dog” ?
Supercell Thunderstorm
Supercell:
A single, very large (65,000 ft. high) massive cloud 12-30- miles in diameter,Lasts for many hours
Cluster of Supercell Thunderstorms
Temperature Inversion enhances formation of severe thunderstorms: dense, cold layer above prevents warm, moist air from rising.Surface air heats up, and finally erupts upward, producing an unusually large cumulus cloud
Mammatus Sky
Text book Questions pg. 315
1.
2.
4.
5.
6.
Microburst
Strong DOWNDRAFTSBeneath the thunderstorm
Small 2.5 miles across
Cold dense, sinking air
Last 2-5 minutes
Also called wind shears
http://www.youtube.com/watch?v=fjFTH3s6BlM