Welcome

Please register to have access to more features!

It is highly recommended that you have Javascript enabled; many features will not work unless you do. The recommended browsers are Firefox and Chrome; the board is also NOT mobile-friendly.

Please invite your friends!

If you were referred by someone (ex. me, Jessica) please put their username in the referral box on the registration page. Ask them if you don't know their username.

If you are visiting for TESTING PURPOSES ONLY, this is the test account information:


Username:
Test
Password: test123



Select a forum to post in:

Search found 1 match

Return to: Tornadoes

Tornadoes

General info
  • Generated in regions of already severe thunderstorms
  • Two prime factors for initiation: topography, local climate
  • Created over areas undisturbed by mountains
    • Very common in Midwestern US – “Tornado Alley” (TX, OK, KS, NB, IA)


Formation
  • Average dimensions: width – 75 yards; track length – 1-4 miles; time on ground – 5 min; forward speed – 25 mph
  • Timing – spring to summer; late afternoon to late evening (time of maximum local ground heating)
  • Structure
    • Combination of opposing wind patterns
      • High level, relatively dry/cooler winds from west
      • Lower level, warm/wet winds from east (originating in the Gulf of Mexico)
    • Rollers – winds form cyclonic rotation parallel to the ground
    • Large thunderstorms pull warmer air upward from low levels; warm/wet air provides energy for storm
    • Large updrafts can cause a roller to tip into a vertical position
    • Tornado is born upon touchdown with ground
    • Large storms can produce more than one tornado – called “families” or “swams”
      • Large tornado swarm in 1974; caused damage in 13 states from AL to OH; 148 tornadoes in ~16 hours; 307 killed, 6,000+ injured and $600 mil in damage
  • Severe pressure drops
    • Inside a twister can be as low as 3″ Hg
    • For comparison: average daily pressure is ~31-32″ Hg; large thunderstorm can be as low as 27″ Hg
  • Movement
    • Track direction generally SW to NE
    • Combination of prevailing wind direction from west and the counterclockwise rotation of tornado
by Jessica
April 27th, 2013, 12:38 pm
 
Forum: Science Topics
Topic: Tornadoes
Replies: 0
Views: 2,855

Return to: Tornadoes

cron
Reputation System ©'