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TONIGHT Midterm #2 Corrections (HW#11) Thunderstorms and Tornadoes (Chp 10) Homework #12 – “Perfect Climate” Next Week (Apr 28) Hurricanes (Chp 11) Air Pollution (chp 12) Climate Classifications May 5 Climate Change TERM PAPERS DUE May 12 FINAL EXAM Extra Credit Papers Due.

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Week 13 notes


    • Midterm #2 Corrections (HW#11)

    • Thunderstorms and Tornadoes (Chp 10)

    • Homework #12 – “Perfect Climate”

  • Next Week (Apr 28)

    • Hurricanes (Chp 11)

    • Air Pollution (chp 12)

    • Climate Classifications

  • May 5

    • Climate Change


  • May 12


    • Extra Credit Papers Due

Week 13 Notes

Midterm 2
Midterm #2

  • Class Average = 71 points

    • Scores adjusted by +4 points

  • pre-Midterm Review

    • w/ review: 77%

    • wo/ review: 61%

  • Changing answers

    • About 2/3 of changed answers were wrong

Midterm 2 corrections

  • Homework #11

  • Same as before

    • TYPED (no exceptions)

    • Correct Your Missed Questions

    • Must be 3 part answer

      • Correct answer

      • 1 paragraph (2 or 3 sentences) explaining the correct answer

      • Source of correct answer


      • Well-done complete corrections = 10 points

      • Points deducted for incomplete or not following directions

Midterm #2 Corrections

Example correction
Example Correction


# 39. C, Scattering

  • The sky is blue because of Rayleigh scattering. The size of oxygen and nitrogen molecules selectively scatter the shorter blue wavelengths. It is this prominent scattered blue light that our eyes see.

  • Ahrens text: pg 405 (or Atmospheric Optics PowerPoint, slide # 62)

Term papers and extra credit term papers

  • 6-10 Pages, typed, double-spaced (exclusive of figures, bibliography)

  • Scientific Style –

    • ABSOLUTELY NO 1ST PERSON.  This is a science paper.

  • Well-organized

  • Properly documented

    • At least 4 CREDIBLE reference sources (only half may be Internet only source). 


    • References Format: APA http://www.wisc.edu/writetest/Handbook/DocAPA.html

  • Grading: Maximum 200 points

    • Content, Accuracy - 150 points

    • Organization, Format - 30 points

    • Grammar, Style - 20 points

Term Papers(and Extra Credit Term Papers)

Thunderstorms and tornadoes
Thunderstorms and bibliography)Tornadoes

Thunderstorms bibliography)

  • Not Rare

    • 40,000 Times Each Day Overthe World

    • Frequency Is Different but Every Place in the World has T-storms

  • T-storm Hazards

    • Lightning

    • Flash Floods

    • Hail

    • Winds (Downbursts, Microbursts)

    • Tornadoes

    • Hurricanes

Thunderstorm formation
Thunderstorm Formation bibliography)

  • Warm Humid Rises into an Unstable Atmosphere

  • Trigger needed to Start Lift

    • Unequal heating

    • Frontal Lift

    • Terrain

  • Enhanced by Strong Diverging Winds Aloft

  • Cumulonimbus

  • Types

    • Ordinary (Air Mass) Thunderstorms

    • Severe Thunderstorms

Air mass thunderstorms
Air Mass Thunderstorms bibliography)

  • Most Common

    • Least Destructive

    • Limited Life of Less Than an Hour

    • Localized

  • Life Cycle

    • Cumulus Stage

    • Mature Stage

    • Dissipative Stage

Cumulus stage
Cumulus Stage bibliography)

  • Unstable Air Rises by Localized Convection

  • Vertical Motion 10 to 45 mph

  • Cloud Extends Above Freezing Level

    • Ice Crystals Form and Grow by Bergeron Process

    • Precipitation Begins to Fall

Mature stage
Mature Stage bibliography)

  • Heavy Rain Drags Air forming Downdrafts

  • Downdrafts Strengthened By Cooling From Evaporation

  • Most Vigorous Rain along edges of cloud

  • Updrafts Dominate Inner Part of Cloud

Mature thunderstorm
Mature Thunderstorm bibliography)

Dissipating stage
Dissipating Stage bibliography)

  • As Precipitation and downdrafts dominate then updrafts cut off

  • Only 20% of Moisture Falls as Rain – the Rest Evaporates

Severe thunderstorms
Severe Thunderstorms bibliography)

  • Defined as

    • Wind Speeds Exceed 58 mph

    • Hailstones Greater Than ¾” diameter

    • Can Spawn Tornadoes

  • Extreme Downdrafts and Updrafts Intensify Storm

  • Scale: 6 to 60 mi Across Mesoscale

Severe thunderstorms1
Severe Thunderstorms bibliography)

  • Large Area Allows Several Storms to Cluster (Multi Cell Storms)

    • Mesoscale Convective Systems (MCSs)

    • Oval Clusters Are Mesoscale Convective Complexes (MCCs)

    • Linear Bands Are Squall Lines

    • SupercellsContain a Single Updraft Zone

      • Appear in Isolation or as Part of MCCs

      • Individual ButStorms Develop From A Common Origin

Mesoscale convective systems mcss
Mesoscale Convective Systems ( bibliography)MCSs)

  • Cover Large Parts of States

  • Life Span: up to 12 Hours or more

  • Accounts for 60% of All Rain in Middle of US and Canada

  • Surrounding Air and Inflow Supports Stronger Winds and Heavier Precipitation

Mesoscale convective systems mcss1
Mesoscale bibliography) Convective Systems (MCSs)

Week 13 notes

Mesoscale Convective Complexes ( bibliography)MCCs)

  • Oval or Roughly Circular

  • Organized Systems Containing Numerous ralTstorms

  • Not All Produce Severe Storms But They Are Self-Propagating

  • Create Downdrafts That Produce Other Cells

  • Consider Large Cluster of Thunderstorms

    • Warm Humid Air at Surface (mT, Wind S)

    • Dry Air Above (CT, Mexico, Wind SW)

    • Wind Shear

    • Downdraft From Other Storms

    • Outflow Boundary

Squall lines
Squall Lines bibliography)

  • Large Number of Individual Storm Cells

    • Linear Band ~ 300 mi in Length

    • Form 60 to 180 mi ahead of Cold Front

Squall lines1
Squall Lines bibliography)

Gusts fronts
Gusts Fronts bibliography)

Gusts front
Gusts bibliography)Front

Supercell thunderstorms
Supercell bibliography) Thunderstorms

Supercell thunderstorms1
Supercell bibliography) Thunderstorms

Supercell thunderstorms2
Supercell bibliography) Thunderstorms

  • Diameter 12 to 30 mi

  • Smaller than Squall Line or MCCs

  • Most Violent

  • Life Span:

  • 2 to 4 Hours

Supercell structure
Supercell bibliography) Structure

Thunderstorm moisture
Thunderstorm Moisture bibliography)

Thunderstorm distribution
Thunderstorm Distribution bibliography)

Avg. Number of Thunderstorm Days per year

Lightning formation
Lightning Formation bibliography)

  • Excess negative and excess positive charges

  • Lightning: attempt to equalize electrical differences

  • Air is a poor conductor, thus electrical potential (charge differences) must be very high before lightning will occur

Lightning formation1
Lightning Formation bibliography)

  • Stepped leader: advancing, branching shaft of negative charges

  • As stepped leader approaches ground, a spark of positive charges surges upward from the ground

  • Stepped leader and upward surge create a path for current flow

Lightning formation2
Lightning Formation bibliography)

  • Negative current flows downward from cloud

Lightning formation3
Lightning Formation bibliography)

  • Return stroke: positive current flow upward

  • Lightning is a sequence of strokes and return strokes

  • • Usually 2-3 strokes; sometimes up to 20 strokes

Lightning causes
Lightning bibliography)Causes

  • Most Common Theory

  • Collusion of Hail stone and Ice Crystal

    • Ice Crystal is Positive Charged – Colder Lighter - Carried to Top of Cloud

    • Hailstone - Negative Charged - Heavier Stays More in Bottom of Cloud

Types of lightning
Types of Lightning bibliography)


Within Cloud



Thunder bibliography)

  • Air in Column is Heated to 50,000° F

  • Heated Air Expands Explosively

  • Shockwave heard as a Loud Noise

  • Speed Difference Flash and Sound

    • Sounds Travels at 1100 feet per second

    • Light Travels at 186,000 miles per second

    • Each 5 seconds between flash and sound is a mile.

  • Nearby Thunder Is Sharp

  • Distant Thunder Echoes and “Rumbles”

Types of lightning1
Types of Lightning bibliography)

  • Cloud-to-Cloud

    • 80% of All Lightning

  • Sheet Lightning

    • Flash is Obscured by Clouds

    • Sky Lights Up Uniformly

  • Cloud-to-Ground (Water)

    • 20%

    • Negative Charges at Base of Cloud

Other lightning types
Other Lightning Types bibliography)

  • Ball Lightning

    • Appears as a Round, Glowing Mass, Basketball Size

    • One Form Avoids Electric Conductors and Another is Attracted

  • Saint Elmo’s Fire

    • Ionization of Air Just Before Cloud-to-ground Strike

    • Causes Church Steeples and Ship’s Mast to Glow Green-blue, Giving Out Sparks That Hiss

Other lightning types1
Other Lightning Types bibliography)

Lightning statistics
Lightning Statistics bibliography)

  • 12,000 fires/yr in US are started by lightning

    • 5.2 million acres

    • $50 million worth of timber destroyed

  • Total Lightning Losses/ Year: $5 billion

  • Deaths:

    • Avg =62/year

    • 2008

      • 27 killed

      • 302 injured

Lightning bibliography)

  • Electrical Charge Builds in Air Before Lightning Strikes

  • If Nothing Else Can be Done Flatten Out on Ground Get Away From High Points (Trees)

Lightning safety
Lightning Safety bibliography)

  • Lightning can strike up to 15 miles from where it’s raining

  • Take cover in a building

  • Stay away from electrical appliances

  • Get Out of the Water

  • Stay in the Car Unless It Is a Convertible

Downbursts bibliography)

  • Downbursts

    • Strong Downdrafts up to 165 mph

    • Spread in All Directions to Form Intense Horizontal Winds

    • Damage Sometimes Mistaken for Tornado

  • Microburst

    • Downburst Less Than 4 km (2.5 mi) in Diameter

    • Airport Danger due to Strong Wind Shear

      • Headwind for Lift Followed by Tailwind Causing Negative Lift

Downbursts bibliography)

Worst tornado movies
Worst Tornado Movies bibliography)

  • Twister

  • Revenge of the Twisters

  • Category 7

  • Any other movie with a tornado in it … Except

    • The Wizard of Oz

Tornadoes bibliography)

  • Extremely Rapid, Rotating Winds Beneath the Base of Cumulonimbus Clouds

  • Most Rotate Cyclonically (CCW NH)

  • Shapes

    • Some Very Thin rope-shaped Columns

    • Others Characteristic Funnel Shape Smallest at Surface

  • Result From an Extraordinarily Large Pressure Difference Over a Few Tenths of a mile (100 mb)

Tornado characteristics
Tornado Characteristics bibliography)

  • Wide Variety of Shapes and Sizes

  • Majority Have Diameters = 100 to 2000 feet

  • Time Span a Few Minutes to Several Hours

  • Forward Speed 30mph

  • Path of Destruction 2-2.5 mi

  • Wind Speed 40 mph to 280 mph

Tornado path
Tornado Path bibliography)

Tornado formation
Tornado Formation bibliography)

  • Development Situations

    • Frontal Boundaries

      • Squall Lines

      • Mesoscale Convective Complexes (MCCs)

      • Supercells

      • Tropical Cyclones

  • Not Very Well Understood

  • Most Intense and Destructive Are From Supercells

Tornado development
Tornado Development bibliography)

Supercell tornado development
Supercell bibliography) Tornado Development

  • Formation of a Slow Horizontal Rotation of a Large Segment of the Cloud

    • Up to 12 mi in Diameter

    • Deep in Cloud Several thousand feet in air

    • Results in Large Vortices

    • Mesocyclone Precedes Tornado by ~30 min

    • Depends on Wind Shear

      • A Rapid Change in Direction Rolling Motion About Horizontal Axis

      • Updraft Tilts to Form Mesocyclone

Supercell tornado development1
Supercell bibliography) Tornado Development

Supercell tornado development2
Supercell bibliography) Tornado Development

Tornado damage
Tornado Damage bibliography)

  • Most Damage Is From the High Winds

  • Most Injuries Caused by Flying Debris

  • Most Violent Tornadoes Have Small Zones of Intense Rotation

  • Small High Intensity Vortices

    • No suction

    • Can Destroy One Home Leave Next Door OK

Fujita scale
Fujita Scale bibliography)

Fujita scale1
Fujita Scale bibliography)

F# Wind Speed Damage

F0 40-72 mph Minor, branches broken

F1 72-112 Peels roofs, cars moved

F2 113-157 Roofs torn, boxcars, trees

F3 158-206 Roofs & walls, trains

F4 207-260 Houses destroyed

F5 261-318 Houses lifted, debark trees

Tornado damage1
Tornado Damage bibliography)

F172-112 mph Peels roofs, cars moved

F2113- 157 mph Roofs torn, boxcars, trees

Tornado damage2
Tornado Damage bibliography)

F3158-206 mphRoofs & walls removed, trains moved

F4207 - 260 mph Houses destroyed

Tornado damage3
Tornado Damage bibliography)

F5261- 318 mphHouses lifted, debark trees

F5 Path of DestructionLaPlata, MD 2002

Enhanced fujita scale
Enhanced Fujita bibliography)Scale

  • Based on Consistent Assessment of Damage

  • Enhance description of damage with examples and photos that include not only structures, but also vegetation

  • Base damage assignment on more than one structure, if available

Tornado frequency
Tornado Frequency bibliography)


Number of tornadoes Avg. Number per 10,000 mi.2

Worldwide tornadoes
Worldwide Tornadoes bibliography)

Waterspouts bibliography)

  • Waterspouts

    • Tornadoes Over Water

    • Typically Smaller Diameters and Weaker

  • Some Form Initially Over Water but

  • Majority Form Over Water

    • Fair Weather

    • Unstable when Warm Water Heats Air From Below

    • Rope-like Structure

    • Water Not Sucked Up

Waterspouts bibliography)

Waterspouts bibliography)

Week 13 notes

HAIL FORMATION bibliography)

  • Particle forms in area of weak updrafts to about 1 mm

  • Begins to fall

  • Swept back up by strong updrafts

  • Particles collides with supercooled particles that freeze to it

  • Lifting and falling occur many times (layers)

  • Large enough to fall or get into downdraft (entrainment)

Week 13 notes
HAIL bibliography)

  • Spherical or irregular chunks of ice greater than 5 mm diameter

  • Cross-section shows many layers

  • Lethal missiles

    • Injure or kill

    • Damage in US alone is hundreds of millions of dollars

Diameter: 140mm (5.5in)Weight 0.75kg(1.7lbs)Speed: 45m/s (100mph)

Hail climatology
HAIL CLIMATOLOGY bibliography)

Avg. Number of Hailstorms per year

Weather hazards
Weather Hazards bibliography)

Homework 12 your perfect climate
Homework #12 - Your Perfect Climate bibliography)

  • In a brief paragraph, describe your “perfect” climate and why?

    • Hot sunny days? Cool and foggy”

    • Rain, Snow?

    • Different seasons?

    • Weather related activities you enjoy?

  • Then find a location (NOT in California) that best fits your idea of a perfect climate

    • Provide details of its average temperatures, rainfall, snow, etc.

    • A good source will be “Climate Charts” in the Week #1 Additonal Resources.