Storms

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Reading Assignment	Browse through the Audubon Field Guide to the Weather pp. 93-154, and look at the accompanying photos.
Reminders	Come see The Mars Show, Friday nights at 8 p.m.! Free admission for GNSC 320 students. (Bring a friend for $2.)

Class notes:

Lightning

• Kills more people than all other storms
• May strike the same place (or person) twice
• Cloud-cloud, cloud-ground, ground-cloud
• Count seconds after thunder
  • Thunder and lightning occur together, superheated air around lightning bolt
  • Sound travels 1 mile in 5 seconds
• "Bolt from the blue" miles from storm
• Lightning do's and don'ts
  • Don't use telephone; stay away from TV
  • Don't go into small, stand-alone building
  • Don't go under large stand-alone tree
  • Don't touch anything metal
  • Don't use water faucet, sinks, tubs, shower
  • Get off water, if in boat
  • Get off hilltop, if in open field
  • In field, crouch on knees, bend over, don't let head touch ground, nor lie down
  • Get inside a house or large building
  • Get inside a hard-top car

Twister!

• "Tornado" is a violently rotating air column touching the ground (if not, "funnel cloud")
• Usually small and short-lived (15 minutes)
• April 4, 1974 super outbreak
  • 148 tornados, 13 states, 315 fatalities, 6000 injuries, $600 million damage
• March 18, 1925 Tri-state tornado
  • 3.5 hours, 219 miles in Missouri, Illinois, Indiana, 689 fatalities
• Classification
  • Severe, winds 158-206 mph
  • Devastating, winds 207-260 mph
  • Maxi-tornados, winds 261- >300 mph
  • Devasting and maxi-tornados only 2%
• Tornado formation
  • Thunderstorm: right rear quadrant
  • Mesocyclone: large-scale rotation from top to bottom
  • Wall cloud: Low cloud mass, lower portion of mesocyclone
  • TVS: tornado vortex signature; smaller, within mesocyclone less than 50% of the time
• Often preceded by large hail
• Often multiple (watch your back!)
• Roar like locomotives
• Usually April - June, afternoon and evening
  • May occur anytime, even in winter!
• Have occurred in all 50 states
• What state has most tornados per sq. mile?
  • Oklahoma tornados: 10 to 100 per year (1982, 101 tornados)
  • Oklahoma county 70 tornados 1950-1994
  • Oklahoma City 32 times in last 90 years
  • 1986, 7 tornados within 15 miles of ch. 9
  • Woodward, 1947
  • Red River Valley outbreak
  • Wichita Falls, TX, April 10, 1979
• Tornado safety
  • Watch vs. Warning
  • Houses do not explode
    • Windward wall falls inward, others outward
    • Don't take time to open windows
  • Damage due to high winds, injuries to flying debris
    • stay away from windows and doors
    • Get under mattress or heavy blanket
  • Go to storm cellar or basement
  • Get under staircase, in bathroom or central closet, in central hallway
  • Get away from mobile home or large rooms (gyms, cafeterias, auditoriums)
  • Over half of deaths due to attempted flight in cars
  • Lie flat in ditch and cover head

Downbursts

• Upper-level winds create downdraft in cumulonimbus anvil
• Deflected horizontally at ground level
• Straight-line winds up to 100 mph for short distances
• Often mistaken for tornados
• Downburst wind shear

Blizzard

• Whiteout = visibility < 10 feet due to wind-whipped powdery snow
  • Air pressure, Jan 10, 1975, Kirksville, MO: 29.05 inches Hg in a.m.; 3 hours later 28.85 inches Hg
  • 2 feet of snow fell Jan 11 in Minnesota
  • 20 ft. drifts, 80 mph wind gusts
  • 60 fatalities, $15 million damage
• Prepare: It's too late once the storm hits
  • Single storm: 189 inches snow; Feb 13-19, 1959 Mt. Shasta Ski Bowl, CA
  • 24 hours: 75.8 inches; April 14-15, 1921 Silver Lake, Colorado
  • Month: 390 inches (32.5 feet); Jan, 1911 Tamarack, CA
• Winter car supplies
  • Bag of sand for traction
  • Bright cloth for antenna signal
  • Coins for pay phone
  • Blanket, Flashlight, extra layers of clothes
  • Raisins, peanuts, chocolate for quick energy
  • First aid kit, water
  • Crack windows when car is running

Hurricanes

• Hurricanes in Atlantic Ocean; Typhoons in Pacific Ocean
• Categories 1 to 5 based on wind speed and storm surge
  • Category 5: Winds > 150 mph and storm surge > 18 feet
• Hurricane Andrew, August 1992, Florida
• Hurricane Hugo, September 1989, Carolina
• Chesapeake-Potomac, August, 1933

Flash Floods

• Express-train wall of water, often without warning (seconds count)
• Never drive into moving water
• Get out if your car is trapped; don't waste time trying to drive out
• Climb out of canyons (or caverns), even when dry, if it's raining upstream
• Check insurance rates before buying house