Storms 4: Hail, Mamatus clouds, Atmospheric Rivers

mammatus clouds

form below anvil (underside)

What effects do winds have?

1) cause damage directly

2) blows in more warm humid air (ex. storm fuel!)

moisture advection

blow in warm humid air to feed storm

• positive feedback

• longer-lasting storms

Force equation

F= m x a

• force mass x acceleration

• newtons second law

• if you push on an object harder (bigger force), it will accelerate faster in the direction you push it

Acceleration

• the change in velocity during time

• (V new - V old)/ time

• SPEED & DIRECTION

• ex. car increases speed 50 to 90 km in 15 seconds, it accelerates.

• if car maintain 50km/h, acceleration = 0

Air parcel

hypothetical blob of air about size of a city block

Forecast Equation for the Wind

wind (horizontal or vertical)

V new = V old + [(f/m) x delta t]

• tells us how wind will increase or decrease or change direction depending on forces that act on the air parcel

What does buoyancy force cause in storms?

• vertical movement

• causes up & downdrafts

What does Pressure-gradient force (PGF) in storms?

• horizontal or vertical movement

• hortizontal winds

Warm air rises, cold air sinks cause what phenomena in storms?

updrafts and downdrafts

why?? temperature affects density affects buoyancy

Buoyancy of air parcel depends on

Parcel temp vs Temp of surrounding air

Buoyancy drives Thunderstorms

• condensation in thunderstorms release latent heat

• latent heat warms thunderstorm (latent—>sensible heat) , making it buoyant, causes air to rise

• Drives violent updraft of thunderstorm

Pressure equation

P = F / A

• Pressure = force/area

Temperature alters Pressure to drive horizontal winds!!

Pressure differences important because,,

pressure difference across a distance is called PRESSURE GRADIENT

• these pressure gradients form in hurricanes

Where in a hurricane are there lots of thunderstorms?

in the core! condensation in the core makes the core even warmer

What happens as warm air expands in core?

warm air less dense than cool air—> takes up more space

pressure at top of core is > surrounding pressure

Pressure gradient drives..

• drives horizontal winds

• creatures outward spiralling winds

• winds remove molecules from the core

How does the storm—> spiral inflow into bottom of hurricane?

• low pressure at bottom of core creates pressure gradient that sucks in air

• the inflow advects in more fuel

Summary of pressure gradients driving horizontal winds

• horizontal changes in temp—>

• horizontal changes in pressure increase with height—>

• pressure gradient increase at higher altitudes

• drives faster winds @ higher altitude

-drives violent winds in hurricanes

-drives atmospheric rivers

Hurricane anatomy

• occluded front

• cold front

• warm front

• know location of high and low pressure

atmospheric rivers

• giant flowing streams of water vapor

• weaker ones bring rainfall, extreme ones can cause flooding and mudslides

• caused by pressure gradients

Air molecules (continuity concept)

• air molecules spread evenly

• don’t leave gaps

• don’t get bunched together

Continuity causes circulations

1) buoyant parcel rises (hole where it used to be—> partial vaccum (lower pressure than surrounding air)

2) surrounding air molecules get sucked in to fill hole (maintain continuity)

3) above the rising parcel, molecules compressed ( higher pressure) expands laterally

initial VERTICAL MOTION due to buoyancy (generates)

HORIZONTAL MOTION in surrounding air

—> CIRCULATION

vertical horizontal motions linked by effect of ..

continuity

Hail Safety

1) wear safety glasses

2)if possible, turn away from storm and drive away

3) stay under a roof, inside a car, under farm tractor. to protect from falling hail

Rain Hazards

Hazards:

• downpours cause flash floods, reduced visibility while driving

Safety:

• move to high ground, dont drive though water of unknown depth

Hail Hazards

Occurence

can come from any large thunderstorm- most common with supercell Low precipitation

Hazards

• injury, death, dent metal cars, break windows, flatten crops, kill livestock

Safety

• get indoors

• park under a roof

• close eyes to keep shards out

What is true about the eye of a hurricane?

1) It occupies more space because its warmer (particles more spread out)

2) High Pressure @ the top

3) Low Pressure @ the bottom