STORMS

THUNDERSTORM HAZARDS

• lightning

• downpours (of rain) / local flooding

• downbursts (of air) / gustfronts

• hail

• tornados

WHAT CAUSES LIGHTNING

1. Lightning comes from electrical charges that build up within a storm cloud. Thunderstorms form when warm, moist air rises high into the atmosphere. Rising air called UPDRAFT.

2. clouds form when water vapor in the air cools into water drops, called cloud droplets.

3. Some cloud droplets freeze into ice crystals and collide with cloud droplets making large particles called GRAUPEL.

4. we then get pos and neg charged particles. ice cry: positive and light. they go up. thundercloud is very neg, making a pos charge on ground.

5. when strong theres an electrical discharge and energy release in form of lightning. electrons flow in a massive current from the cloud to the ground !!

CLOUD TO GROUND LIGHTNING

Lightning often connects the negative charges in the cloud to positive charges on the ground.

WHY LIGHTNING HIT TREE TELEPHONE POLE OR TALL STRUCTURE FIRST

tallest object, so closest to the storm cloud.

INTRA-CLOUD LIGHTNING

lightning can stay within a cloud. it travel from neg charge to positive charge in another area within? the cloud.

CLOUD TO CLOUD LIGHTNING

lightning can travel between 2 cloud when travel from neg charge to positive charge in another cloud.

NEGATIVE STEP LEADERS

tiny, fast-moving channels of negative charge that move downward from the cloud toward the ground. CREATE THOSE BRANCH AHH THINGS.

POSITIVE UPWARD LEADERS

channels of positive charge that move upward from the ground (or from tall objects like trees, buildings, or towers). They usually start from the tallest object because the electric field is strongest there.

CAN YOU SEE POSITIVE UPWARD LEADERS

no. too fast. need special cameras.

RETURN STROKE

bright flash of lightning that shoots upward from the ground to the cloud after the leaders connect. It is the main lightning bolt.

2 MOST COMMON TYPE OF LIGHTNING

Intracloud (IC) Lightning ANDCloud-to-Ground (CG) Lightning

CLOUD TO GROUND LIGHTNING, HOW MUCH DO U NEED TO MAKE A SPARK

To make a spark in air, you need approximately 3 billion volts / km.

WHAT KINDA STRIKES CLOUD TO GROUND LIGHTNING HAS

Lightning from the anvil(positive strikes) travels a longer distance, which can happen only if it has more volts.

POSITIVE AND NEGATIVE STRIKES IN CG LIGHTNING:

NEGATIVE STRIKES

• are more numerous

• come from cloud base.

POSITIVE STRIKES:

• are less frequent,

• come from the anvil, (bottom)

• are often much stronger,

• are the primary cause of natural wildfires.

• 10 to 25% of Canadian CG lightning is positive.

PERCENT OF PPL WHO SURVIVE LIGHTNING STRIKE

90

HAZARDS OF LIGHTNING:

TREES: Hazard is shrapnel of tree bark exploding outward.

CARS CAN THEY SURVIVE LIGHTNING

If the electricity can make it from the sky to your car, it can make it from the car to the ground. the metal car is a Faraday cage which carries the electric current around you and into the ground

LIGHTNING IN THE WORLD

Florida is "lightning alley" in N. America. Africa has highest density of lightning worldwide.

LIGHTNING IN CANADA

~2.4 million cloud-to-ground strikes/year, causing 6 - 12 deaths/year.

LIGHTNING DETECTION NETWORKS

Crowd-sourced, world-wide network.

"Static" received from many stations (green dots) allows

TRIANGULATION AKA exact location (green lines) to find

the lightning (large red radar circle).

Each "+" shows a lightning stroke. Colour indicates how long ago. red 2h to white 20m shows recency.

look like a firework.

CANADIAN LIGHTNING DETECTION NETWORK

DE: detection deficiency. 95% of all strikes within this red line are detected

LIGHTNING DETECTION FROM SPACE

GOES weather satellites have special "optical transient detectors" to observe lightning

HOW FAR AWAY LIGHTNING IS

Sound travels MUCH more slowly than light.

• Count the number of seconds between when you see the lightning and hear the thunder.

• Divide that number by 3 to estimate the range in kilometers to the lightning. Examples: 9 second difference => 3 km

LIGHTNING SAFETY

MONITOR WEATHER CONDITIONS

30/30 RULE: If 30 seconds (10km away) or less between when you see the lightning flash and hear thunder, then move indoors and stay there until 30 minutes after last lightning or thunder.

SAFE PLACES: (1) fully enclosed metal vehicle with windows up; or (2) substantial permanent building (but don't use hard-wired telephones!)

UNSAFE AREAS: 1. small structures, huts, rain shelters 2. nearby metallic objects (pole, fence) 3. trees, water, open fields, hill tops, etc.

OPEN LIGHTNING: do the "Lightning- Safety Crouch" with feet together, hands over ears

STEPS TO LIGHTNING SAFETY CROUCH

Crouch on the ground

Weight on the balls of your feet

Heels together

Head lowered

Eyes closed

Ears covered

IF OTHERS STRUCK BY LIGHTNING

preform CPR.

THUNDERSTORMS

thick clouds with lightning & thunder, looks a bit like an anvil or mushroom depeneds.

MEASURMENT OF CLOUD TOP NEAR TOP OF TROPOSPHERE

10-15km

MEASUREMENT OF CLOUD BASE NEAR GROUND

altitude ~1km

HOW A THUNDERCLOUD GETS THEIR SHAPE

• strong updrafts & downdrafts (turbulent)

• if very strong updrafts, then dome of clouds overshoot above the anvil

• anvil can be 100s km in diameter.

• main updraft (stem of mushroom) is 15 km diameter.

• storm energy from temperature &

humidity

DESCRIPTION OF A THUNDER CLOUD

OVERSHOOTING TOP OR DOME: it be ontop of the anvil

ANVIL: look like the top of an anvil

MAMMATUS: weird bubbles at the end of anvil

MAIN UPDRAFT: a lump underneath anvil

STRIATIONS: look like a wind

RAIN: yk what that is

FLANKING LINE: the base of the cloud

WALL CLOUD: little thing under the base of cloud

FUNNEL CLOUD OR TORNADO: underneath everythings.

THUNDERSTORM CELLS

cumulonimbus (thunderstorms) are made of large cells that evolve during about 15-45 min.

MULTICELL THUNDERSTORMS

most thunderstorms contain 2 or more cells, each in different stages of evolution. They typically last for longer than any individual cell

THUNDERSTORM CELL LIFE CYCLE

1. CUMULUS STAGE: updraft, no rain, no anvil

2. MATURE STAGE: up & down-drafts, heavy rain, crisp anvil

3. DISSIPATING: downdraft, light rain, fuzzy anvil

THUNDERSTORM CELL LIFE CYCLE MULTICELL VERSION

Each cell only lasts 15-45 minutes, but the cluster, made up of multiple cells at various stages in their lifecycle, can last for several hours.

1. NEWEST CELL CUMULUS STAGE:

2. CUMULUS STAGE:

3. MATURE STAGE:

4. DISSIPATING STAGE:

STORM ENERGY

Sun - The Source of Atmos. Heat

3 DIFF HEIGHTS STORM ENERGY IS ABSORBED AT

TOP (thermosphere). Absorption of non-visible light

MIDDLE (stratopause). Absorption of ultraviolet by "good" ozone .

BOTTOM (earth surface). Light shines through lower atmosphere with little direct heating of air, but heats the ground instead.

Then the warm ground heats air in troposphere (the bottom 11 km), and powers storms.

SURFACE HEAT BUDGET FOR STORM ENERGY

Some solar energy reflects back into space from clouds and the ground. Some is absorbed by the ground making the ground warmer and the warm ground affects the air as follows

SENSIBLE HEAT (warms the air): air temperature increases.

LATENT HEAT: (evaporates water from lakes, vegetation, etc.) -> air humidity increases

Both temperature and humidity are important because they are the fuel for storms!

DAILY CYCLE FOR STORM ENERGY

• solar heating during day => input (like charging a battery)

• infrared radiation (IR) cooling day & night -> loss (like discharge)

• ==> greatest accumulation of heat, near sunset every day (at end of each charging cycle) .

Late afternoon and early evening => most likely time of day for Tstorm formation.

FAVOURABLE STORM LOCATIONS WHEN IT COMES TO STORM ENERGY

Favorable locations at greatest supply of heat and moisture:

• Closer to equator -> warm ocean currents -> warm, humid air.

• In USA -> Florida , Gulf states.

• In Canada -> prairies and central, because of Advection (warm humid air carried by the wind) and high temperatures

OBSERVING AND MONITORING USING REMOTE SENSORS

A remote sensor is an instrument that is remote from (outside of) the storm, but can still measure the storm. includes..

SATTELITE

RADAR

HOW TO DETERMINE A TSTORM FROM A SATTELITE

Note the oval shape of the anvil cloud.

See the shadow under the anvil cloud.

See the lumpy region of updraft overshoot, which pin-points the violent stem portion of the mushroom cloud.

These are clues to help identify Tstorms

HOW TO SEE SATELLITE IMAGES OF A TOP OF ANVIL CLOUD

they look like circles from birds eye view.

HOW TO READ RADAR MAP FOR BIRD MIGRATION

bird are dark blue spots on map. the combo of bird bats and insects are green. and greeny red ish is STORMS.

dBZ

A Disaster Intensity Scale for Radar-echo Strength. (an indicator of Rainfall-Rate) dBZ = radar echo intensity (in decibels)

Radar Loop (video) of Thunderstorms dBZ

By tracking past movement of Tstorm cells on radar, we can warn people in their paths. This allows them to warn people who are in the direct path of the storm

SQUALL LINE

a line of thunderstorms so "linear", or somewhat-linear ("quasi-linear"). Often form along a cold front. go down like \ but they go up like this

SUPERCELL THUNDERSTORM

a very large, rotating single-cell thunderstorm forms. They can cause the most violent tornadoes, large hail, frequent lightning, heavy rain, strong winds. A rotating thunderstorm is called a mesocyclone.

SUPERCELL types

low precipitation, classical, high precipitation

HOW TO RECOGNIZE MAMMATUS CLOUD

they look like bubbles under the anvil top thing.

3 TYPES OF SUPERCELL

(1) low precipitation (LP) supercell. It can produce lots of hail. Also termed "mesocyclone" because they rotate. you see bro in action

(2) classic supercell, (with rainy downdraft & rain-free updraft) looks like the anvil is taking over yk like covering everything

(3) high precipitation (HP) supercell, updraft mostly surrounded by rain. so damn foggy bc so much RAIN.

Some are in-between or contain features of 2 or more types, and are called "HYBRID" or "MIXED MODE" storms.

HOW TO RECOGNIZE A SUPERCELLS

STRITATIONS, OR STACKED PLATES! basically layers of cloud around the meso-cyclone

MOIST AIR FOR STORM ENERGY

acts as fuel for storms. Storms have special organization and capability to:

• draw in humid air,

• condense the moisture in this air

• release its heat into the storm, increasing the strength of the storm

This results in precipitation & violent winds

HUMIDITY IN STORM ENERGY

Humidity is the amount of water vapour in the air. A Humidity Variable: Mixing Ratio (r). the amount of water vapour divided by the amount of all other gases r = watervapour/gases.

SATURATION IN STORM ENERGY

Water vapour is special -> can easily condense into liquid

Constant exchange of H2O molecules occurs between vapour & liquid:

· (vapour to liquid) = condensation

· (liquid to vapour) = evaporation

The mixing ratio tends to approach an equilibrium where condensation matches evaporation. This equilibrium is called saturation. saturation value is the maximum humidity air can hold

IMPORTANCE OF SATURATION VALUE IN STORM

Saturation value is important in controlling atmospheric humidity. Warmer air can hold more water vapour at equilibrium than colder air!! Air that contains the maximum amount of water vapour = saturated (i.e., cloudy or foggy). Air holding less = unsaturated (i.e., not cloudy)

SATURATION MIXING RATIO AND TEMP

Increases exponentially w temp. temp on x mixing ratio on y axis.

LATENT HEAT IN STORM ENERGY

The release of latent heat increases the strength of the storm

If the Saturation Humidity value becomes smaller than the actual Humidity, then condensation occurs. 3 things happen.

1. releases the stored latent heat back into sensible heat to make storms warmer - this can make the storms even stronger

2. reduces the humidity down to the equilibrium (saturation) value

3. produces or increases liquid cloud drops, which can grow to become rain drops.

ADVECTION AND ADIABATIC COOLING IN STORM ENERGY

ADVECTION = movement of air by the wind. Water vapour can be advected into a thunderstorm by the wind.

When a thermal of unsaturated air rises ADIABATICALLY = with no heat transfer to the surrounding environment....

the air cools roughly 10°C/km of rise (because of pressure differences)

• Cooler air can hold less water as vapour

• Therefore, some vapour must condense into liquid droplets. But condensation releases latent heat, providing energy for the storm....

AIRMOTIONS

"Winds"

• cause damage directly, and

• blow in more warm, humid air (i.e., storm fuel).

This is called "moisture advection".

-> positive feedback = longer-lasting storms

(this is how storms can become " organized ")

RELATES TO:

• forces

• acceleration

• buoyancy

• pressure.

FORCES W/ AIR MOTIONS

FORCES CREATE WINDS.

In the atmosphere, forces create winds.

The relationship between forces & motion is described by

Newton's Second Law: If you push on an object harder then it accelerates faster in the direction you push it.

Force (N) = mass (kg) times acceleration (m/s^2)

ACCELERATION W/ AIR MOTIONS

Acceleration (a) = change of velocity (v) during time interval ( ∆𝑡𝑡 ),

where velocity has both speed and direction.

Acceleration is measured as velocity (m/s) change per time

(s)

(m/s2).

A= Vnew - Vold / TIME where it has speed and direction

FORECASTING THE WINDS

Combining these relationships (Newton's Law, & definition of acceleration) gives a

"forecast method" (also called a "prognostic equation"):

VIVFDAT... NOOOOOOOOOOOOOOOOOOO

AIR PARCELS

hypothetical blob of air about teh size of a city block

AIRPARCEL MOVEMENT

wind (horizontal or vertical) It tells how winds will increase or decrease or change direction, depending on the forces that act on air parcel.

FORCES IN ATMOSPHERE and relation to AIR MOTION

buoyancy force (vertical) ==> causes up & downdrafts

pressure-gradient force / PGF (horiz. or vert.) horizontal PGF -> horizontal winds

TEMP ALTERS BUOYANCY TO DRIVE VERTICAL WINDS

warm air rise - > updraft

cold air sink - > downdraft

Temperature affects the density of air,

and density affects buoyancy.

WHAT BUOYANCY OF AN AIR PARCEL DEPENDS ON

1. parcel temperature

2. temperature of the surrounding air.

BUOYANCY AND THUNDERSTORMS

it drives thunderstorms!

1. Condensation in Tstorms releases latent heat.

2. Latent heat warms the Tstorm air, making it buoyant and causing the air to rise.

3. This is what drives the violent updrafts in thunderstorms.

TEMP ALTERS PRESSURE TO DRIVE HORIZONTAL WINDS

P(ressure) = Force (F) / unit AREA (A)

where we are concerned only with the component of force PERPINDICULAR to the surface area

PRESSURE UNIT: N / m^2

FORCES CAN DRIVE WINDS. VIVFDAT.

PRESSURE DIFFERENCES (IMPORTANT)

change in pressure triangleP yk what that is. like the formula.

- pressure at only one place is not important here. the DIFFERENCE between opposing pressures is important.

pressure pushing on one side of air parcel vs. pressure pushing on other side

PRESSURE GRADIENT

pressure difference across a distance. Hurricanes are

strengthened by pressure-

gradient forces

TEMPERATURE ALTERS PRESSURE TO DRIVE HORIZONTAL WINDS

HOW IT WORKS:

• horizontal changes in temperature ==>

• horizontal changes in pressure that increase with height ==>

• pressure gradient increasing at higher altitudes ==>

• drives faster winds at higher altitudes.

This type of pressure-gradient force drives the violent winds in hurricanes. It also drives Atmospheric Rivers.

CONTINUITY LINKS VERTICAL AND HORIZONTAL WINDS

CONTINUITY CONCEPT:

• Air molecules tend to spread themselves

smoothly and evenly

• They don't leave any gaps (i.e., they don't

leave a vacuum)

• They don't get bunched together

AIR IS SPREAD RELATIVELY EVENly

CONTINUITY LEADS TO CIRCULATION

a) Air molecules are smoothly and evenly distributed in space

b) Buoyant air parcel rises, leaves hole where it used to be => a (partial) vacuum: has lower pressure than surrounding air.

c) Surrounding air sucked in to fill hole: maintain continuity

d) Air above the rising parcel is compressed: has

higher pressure, expands laterally

e) Net result: initial VERTICAL MOTION due to

buoyancy generates HORIZONTAL MOTION in

surrounding air ==> CIRCULATION !

CIRCULATIONS

CIRCULATIONS:

irl, circulations dev smoothly and continuously to try to maintain continuity as air parcels start to move.

Circulations can be driven: by buoyancy in the vertical, or by horizontal pressure gradients.

Vertical & horizontal motions are linked by the effect of continuity.

PRESSURE GRADIENTS DRIVING ATMOSPHERIC RIVERS

Atmospheric rivers can carry more than twice the volume of the Amazon River

RAIN

When the air hits mountain ranges and is forced to rise, the air cools at the adiabatic lapse rate (10°C/km), causing water vapour to condense, and rain to form

HURRICANE HAZARDS

• contain thunderstorms

• storm surge / coastal flooding

• high waves

• coastal erosion

DOWNPOURS

Extremely large rainfall rates (i.e., Downpours) can cause Flash Floods

FLASHFLOOD SAFETY

DON'T GO INTO FAST FLOWING WATER, EVEN IN A CAR. It takes just 30cm (12 inches) of flowing water to carry off a small car. More than half of the deaths from flooding each year in the US happen in vehicles

DOWNBURSTS AND GUST FRONTS

are created when a thunderstorm produces dense air where rain falls. precipitation evaporates before hitting the ground. GUST FRONT is leading edge of the cold, horizontal, straight-line winds created by a downburst. downburst air hits ground & spreads outward in straight lines

• Downdraft speeds of 20 to 90 km/h.

• Horizontal wind speeds near ground of up to 250 km/h.

• Microbursts are small diameter (≈ 1 km) downbursts.

INDICATORS OF A GUST FRONT AND WHAT YOU CAN POSSIBLY SEE

HABOOB: A dust or sand storm created if the ground is dry.

GUSTNADO: "gust storm". Small, vertical swirls of dust and debris that can form along the front.

ARC CLOUD: A line of clouds that forms if the surrounding air is moist.

HAIL

begins as tiny crystals of ice that are

swept into a thunderstorm's updraft (usually

a supercell/lowprecip). Them ice embryos collide with supercooled water w/ a temp below freezing. water freezes, causing the embryo to grow... leaves layers of clear or cloudy ice as the hailstone moves around inside a thunderstorm

HAIL SAFETY

1. Bring or wear safety glasses, in case hail breaks the windows in your car.

2. If possible, turn away from the storm and drive away.

3. Stay under a roof, inside a car, under a farm tractor, etc. to protect yourself from falling hail.

RISKS OF DOWNBURSTS

Often invisible, but a hazard to aircraft.

RISKS OF GUST FRONTS

can blow down large trees and destroy weak structures (mobile homes; out- buildings); hazard to aircraft during take-off/landing

DOWNBURST AND GUST FRONT SAFETY

avoid weak buildings & trees that could fall. Airports have sensors; flights avoid; pilots trained.

ROAD MAP TO STORM TOPICS

hazards, fundamentals and energy dependant on each day of a storm

1. Lightning (H), Thunderstorm Basics (F), Sun, radiation, Surface heating (E)

2. Rain Downpours, Air Downbursts (H) Supercells, mesocyclone. Observe: radar, satellite (F) moisture, condensation, latent heating (E)

3.Tornadoes (H) Wall cloud, striations, Doppler radar (F)

4. Hail, Flooding Atmos. (H) rivers (F) heat to motion, forces, winds (E)

5. Flooding, winds, waves, storm surge (H) Hurricanes (F) energy in warm ocean, Coriolis (E)

RECOGNIZING TORNADOS

Most tornadoes are made visible by...

1. cloud-water droplets (the funnel cloud) a cloud that look like upside down cone.

2. dust and debris from the ground (the debris cloud). dust underneath the funnel cloud. sometimes looks like a reflection of it like it goes like this /\

TORNADO SHAPES

cannot tell intensity based on it.

ROPE

kinda funky looking like a snake

CYLINDER

just the name is accurate. straight, no cone shape

CONE

looks like upside down traffic cone

V-SHAPED

does look like a V, since u see the tip.

WEDGE

like a big cone basically

TORNADOS BEING ATTACHED TO TSTORMS

Only (20-30%) of supercell thunderstorms produce tornadoeS. SUPERCELL STORM = strongest storms. strong tornadoes are most likely associated with supercell storms.

DIRECTION OF TORNADOS AND TSTORMS

move from southwest (SW) toward the northeast (NE). in NORTH AMERICA

BEST WAY TO VIEW THUNDERSTORMS

• off to the side of the storm path

• preferred side is to the southeast of the storm (at X)

• look at the storm toward northwest

• resulting supercell storm looks like the sketch at upper left

HOW TO RECOGNIZE SUPERCELL ROTATION

• striations around the mesocyclone

• a rotating wall cloud (close to the bottom of the cloud)

WALL CLOUD

an isolated lowering of cloud base ...

• beneath rising cumulus towers ...

• on the SW flank of the storm ...

• outside of (SW of) the precipitation region.