Chapter 19 (Tornadoes)

Of the about 1000 tornados that occur globally each year, what percent occur in the United States? Why do we have so many?

-75% of all tornadoes occur in the us, as a result of latitude, air masses, and topography

Explain the difference between a funnel cloud and a tornado.

-funnel cloud : funnel shaped cloud of water droplets, associated with a rotating column of wind. When a funnel cloud touches the ground, it becomes a tornado.

You do not need to memorize any statistics from the 'Tornado Winds and Size/Life' slide, but do be able to tell me: (1) the percent pressure drop inside a tornado, and (2) if the Coriolis Effect is responsible for the typically cyclonic rotation of tornados.

1) 10% pressure drop inside or tornadoes. 2) yes, the coriolis effect is responsible for the direction of tornado rotation.

What is the difference between a tornado watch and a tornado warning?

A tornado watch is issued for when tornado conditions are favorable, and a warning is issues if a tornado is believed to be present in a given area.

Use the conservation of angular momentum to explain how velocity changes as radius decreases.

Conservation of angular momentum explains that stretching of a tornado reduces radius, thus increasing rotational velocity.

Explain how dust devils are formed. Are they a type of tornado?

Dust devils, which are not a type of tornado, are formed from localized convection/instability, and wind shear

Contrast the strength of tornados from supercells versus non-supercell tornados.

Non supercell tornadoes are typically very weak.

Discuss what two features we look for (other than rotation) on Doppler Radar that might signal a tornado is present or likely to form. If we don't 'see' a hook echo with radar, does this mean the thunderstorm is not a supercell?

Other then rotation, we often look for a 1) "hook echo", or for a debris ball that shows up on radar. If we dont see a hook echo, the storm could still be a super cell because not all supercells have a hook echo.

Compare weak tornados to strong tornados. Which: (1) lasts longer? (2) is more common? (3) is more deadly?

Strong tornadoes last much longer, and are much more deadly. 75% of all tornadoes are EF0 and EF1 class twisters.

How important are thunderstorm downbursts (gust fronts) in this process?

They are essential in tornado formation, as descending air behind the gust front and ascending air ahead of it create rotation. as gust front moves under updraft, low level mesocyclone rotation stretches beneath mid level mesocyclone to form a tornado.

Have tornadoes occurred in California? Are they typically weak or strong? How might our cold ocean current or our mountainous topography be affecting tornado probability and/or strength?

Tornadoes have occured in california but they are typically very weak. Cold ocean currents and mountainous topography prevent super cells from forming and gaining strength.

Where do tornados form under a supercell and if the storm is approaching you, would you be able to see the tornado? Why or why not?

Tornadoes often form behind the rain curtain, which makes it very difficult to see if the storm is approaching you.

What is a suction vortex and how is the occurrence of central downdrafts within the core of a tornado related to suction vortex formation?

a suction vortex is one of multiple vortices inside a larger tornado. Central downdrafts within the core of a tornado cause the formation of suction vortices.

Describe how a sequence of tornado formation and dissipation from a supercell relates to the often 'start and stop' and slightly offset pathway of destruction left on the ground.

a tornado will often dissipate, and the a new updraft along the forward flank downdraft brings fresh fuel and air causing reformation, and a stop and start destruction pattern.

While we have records or more tornados in the USA in recent decades, what other factors than global warming might be leading to this trend? (See USA Tornado Occurrence slide)

an increase in population and technology could be the cause of the trend of increasing tornado frequency.

Discuss what causes tornadoes to dissipate.

cool dense air from the rear flank downdraft pushes the tornado outwars away from the storm. This cool air eventually wraps around and dissipates the tornados updraft.

Discuss the geography of US tornados and their peak timing.

every state has tornado hot spots, but florida has the most tornados (which are typically weak) and oklahoma is #2 but with the most strong tornadoes. Tornados begin to increase frequency in march, with a peak in may, and the surge dying off by late summer / early fall.

Discuss the general rules for tornado safety.

general rules for tornado safety include, 1) staying away from windows, 2) being on the lowest floor of the house, 3) hiding in a closet or bathroom in the middle of the house. In a car 1) lie down flat in a ditch and cover your head, 2) think about personal safety and not car safety.

Describe the Enhanced Fujita scale and how scientists typically determine rotational wind speed.

the EF scale varies from <65 mph winds being EF0 and 200+ mph winds being EF5. Typically rotational wind speed is guessed because it is difficult to measure.

What National Weather Service center forecasts severe weather and tornados?

the NWS storm prediction center in norman oklahoma is responsible for forecasting severe weather and tornadoes

Discuss the conditions necessary for tornado formation (tornadogenesis), the two main steps (step 1 - mesocyclone and step 2 - wall cloud) and the two leading theories for step 3 (the tornado itself.)

the conditions necessary for tornado formation include: 1) vertical wind shear inducing horizontal rotation, 2) strong updrafts cause axis of rotation to tilt into vertical, and lastly 3) rotation within the t-storm itself. The two main steps in the formation process include 1) t storm rotation (aka mesocyclone formation). Next, 2) a forward flank gust front leads to wind shear and rotation, that forms a wall cloud. The final step of formation has two major theories , one being that 1) a rear flank gust front creates shallow near ground wind shear and rotation. The other theory is called the dynamic pipe, and states that constriction in mid level mesocyclone causes lower air to constrict, and this constriction zone travels down to the ground.

Describe the general life-cycle of a long-lived tornado and be able to identify whether the tornado is new or fading from a photo or a diagram/cross-section of its shape.

the life cycle of a tornado is 5 steps. 1) a dust whirl stage in which a dust cloud begins to swirl under the t storm. 2) Organizing stage: in which the cloud funnel touches the ground. 3) Mature stage: in which the tornado is thick and vertical, the tornado has stengthened, and the pressure in the core has decreased. 4) Shrinkng stage: storm is moving faster then the bottom of the tornado, and the tornado starts to tilt and strech out. 5) Decaying stage: tornado is rope like and weak.

Explain why wall clouds can appear below the lifting condensation level / cloud base and how they are related to tornadoes.

wall clouds get pulled down via circulation about the down burst ( gust front) . they are the localized drop in the base of the cloud, and if they rotate are 'pre-tornadic'.