Ch. 19 Tornadoes

24 terms by leslier 

Ready to study?
Start with Flashcards

Create a new folder

Advertisement Upgrade to remove ads

tornadoes &notes from 3/29-end

Tornado

• Tornado: intensely rotating column of air touching/contacting the ground
• You can tell b/c there is debris rotating on the ground
• tornado made of: debris and cloud
• you can have though a rotating column of air w/o cloud!! Esp if you can see debris on ground
• Northern HEMI=rotating counter clockwise
MUST HAVE UPDRAFT TO SUSTAIN
o (if it's bright behind it, and the Flanking line is being wrapped up, you still have to keep the intensity of the cloud in mind because it could start to reform again)
• Tornado: violently rotating column of air rotating under a cumulonimbus cloud

Tornadogenisis

formation of a tornado that occurs near the time the supercell''s forward and rear flank downdraft meet under mesocyclone

Double Vortex Stretching

• Wind is stronger up higher and weaker close to ground
• indicates strong wind speed, hear w/ height
• one vortex that was going as a horizontal roll and a strong updraft comes and forces it up and now you have 2 vortices that are tilted vertically, stretched it, and vorticity increases
o think of ice skaters rotating on ice
• vertical wind speed shear, wind simply getting stronger w/ height just off ground—answer to what causes it!

Conservation of Angular Momentum

air stretched in narrower and narrower column will rotate faster and faster
• Wall cloud: isolated lowering of cloud base in vicinity of mesocyclone (strongest updraft) you can have wall cloud w/o mesocyclone
• mesocyclone w/in a tornado radius gets smaller and starts to spin faster
• Whats happeing in that area?
o There is updraft, as pressure decreases in center and air is brought into surface convergance and rapidly brought up, air is ingested into storm

Supercell Tornadoes

• Double Vortex Stretching (titlting)
• stretching and coservation of angular momentum
• mesocylcomnes (less tha 20% produce tornadoes)
• tornadoes
• supercell waterspouts (covered later)
o most come as result of very disorganized cloud band, many aren't even supercells or thunderstorms

Suction Vortices

small extremely violent rotating air columns embedded w/in rotating circulation of large tornadoes
a result of a downdraft being created among the rotating updraft that makes a tornado very wide developing suction vortices
the most severe winds happen here

more tornadoes can result in Tornado families

Tri-State Tornado 1925

• March 18, 1925
• worst tornado in US history
• track length 179 miles
• avg forward speed: 60-65 mph
• avg width in MO: 1/4 mi
• "" in IL: 1/2-1 mi
• killed 695
• injured 2,027
• damage: $16.5 million

CAPE

measures how unstable the atmos is and how strong a thunderstorm's updraft will be
higher CAPE=higher chance for severe thunderstorms

Non-Supercell Tornadoes

• landspouts
o non-supercell (non-Mesocycloe)
o thunderstorms
o often on frontal boundaries
• Tropical cyclone Related Tornadoes
o right forward side of tropical cyclone
o embedded w/in rainbands
• ATX has history of these
• difficult to see
• very quick moving

Waterspouts

• tornado over the water
• "fair" weather waterspouts
o cumulus congestus cloud lines (not necessarily rain producing)
o weak short lived waterspouts
o huge #!
• supercell waterspouts
o cumulonimbus clouds
o associated w/ supercells/ mesocyclones longer lived/ stronger tornadoes
o smaller #

Other Tornado-like Vorticies

• Gustnadoes
o short lived and weak
o often on gust front/outflow boundary
o circulation w/in boundary/friction layer
• cold air funnels
o develop from elevated convective clouds that develop over colder air
o often form under cumulous clouds in the circulation of large, upper air cut off lows
• dust devils
o associated w/ dry convection (hot surfaces)

Tornado Stats

• "tornado alley of USA
• only 25% of all tornadoes globally on avg are outside US

World Tornado Climatology

• you gotta have maritime tropical air, they occur on boundaries (warm moist air, latent heat available)
• you gotta have upper air wind pattern to ensure wind drafts
• longer path linked to more damaging tornadoes

Tornado Detection

• Storm spotters/ storm chasers
• WSR88D Doppler radar (velocity mode)
• surface observations
o they are pretty widely separated when it comes down to scale of tornado
• DOWs (doppler on wheels)
o University of Oklahoma
o TAMU

Storm Chasers vs. Spotters

• Storm chaseres vs. storm spotters diff= spotters stay in one spot, chasers follow tornado, can be very dangerous, beneficial b/c like Dallas tornadoes, could get live feed
• basics of storm spotting

Tornado Forcasting

• Hourly surface analysis charts
• constant height charts
• thermodynamic diagrams
• hodographs
• comp models
• composite charts
• SPC severe weather outlooks/guidance
• Atmospheric Stability Indices:
o CAPE (j/kg)
o Lifted Index (degrees C)
o storm relative helicity (m2/s2)
o energy helicity Index

Post Storm Surveys

• Was the damage caused by a tornado or by straightline winds?
• ground & Aerial surveys
• construction diff & standards
• general rule of thumb:
• convergent damage patter=tornado
• divergent damage patter=straightline winds

Tornado Strength

• weak tornadoes: page 26
o 80% of all US tornadoes
• strong tornadoes:
o 19% of all tornadoes
o less than 30% US fatalities
• Violent:
o 1% of all US tornadoes
o 70% of all fatalities
o 60 min or more
o 200-318 mph

EF0

• EF0—KNOW TYPES OF DAMAGES, first bold in supp text
o light damage
o 65-85 mph wind—3 second gust
o branches broken
o signs damaged

EF1

o moderate damage
o 86-110 mph
o trees snapped
o shingles blown off
o large signs bent
o windows broken

EF2

o Considerable damage
o 111-135 mph
o large trees uprooted
o roofs torn off buildings
o outbuildings/barns destroyed
o cars scooted off highways
o increasing danger/flying debris

EF3

o severe damage
o 136-165 mph
o extreme danger from flying debris
o frame home exterior walls blown down
o homes shifted slightly off foundations
o cars become airborne for short distances
o interior walls generally left standing

EF4

o devastating damage
o 166-200 mph
o frame homes reduced to foundation as poles of debris immediate downwind
o cars airborne considerable distances
o skyscrapers twisted
o effects of flying debris become spectacular
o little above ground shelter
o suction vortices appear

EF5

o incredible damage
o 201-318 mph wind
o frame homes disintegrate w/ debris carried downwind over a wide area (foundation left bare)
o car/trucks airborne ½ mile or more and reduced to chasses and wrapped around objects
o considerable damage to steel reinforced buildings
o well developed suction vortices common

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set