Transcript Air Masses and Fronts

Objectives
Define and described air masses.
 Define and describe weather fronts.
 Be able to name winds and air masses
 Understand differing cyclonic systems and
how to prepare for related emergencies.
 Compare high and low pressure systems.
 Read, label and analyze a weather map.
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Air Masses
 Large
areas (blobs) of air that have
the same weather, temperatures and
humidity and air pressure
 Air Mass Types - Named for where
they come FROM
 Weather changes occur with changes
in air masses
TYPES of Air Masses
The Bergeron Classification System
maritime Tropical (mT)- humid/moist air & warm
 continental Tropical (cT)- dry air & hot
 maritime Polar (mP)- humid/moist air & cold
 continental Polar (cP)- dry air & cold
 continental Arctic (cA)- dry air & very cold
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There are no mA air masses
Fronts
 boundary
between two air masses
 bring changes in the weather (from
west to east)
 Fronts are named for the air that is
behind them
Air Mass Army Analogy
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Think of air masses as an army front (the
army is BEHIND the frontline)
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At the Front there is FIGHTING and lots of
VIOLENCE (stormy weather)
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Behind the front (inside the air mass) the
general sits on his duff and watches the
goings-on while enjoying the nice weather!
NICE WEATHER
FIGHTING - STORMS
Cold Front
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Cold dense air pushes warm air out of
the way
Cold fronts move very quickly and bring
short periods of rain/thunderstorms
Lower temperatures are behind the front
SYMBOL – the direction of the “arrows”
points towards the direction the front is
MOVING
Warm Front
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Warm air moves up the cold front as it
slowly displaces the cold air
Warm fronts move slowly, and bring
many days of steady precipitation
Higher temperatures are behind the front
SYMBOL – direction of “half-moons” is
the direction the front is moving
Stationary Front
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The air from the warm front and cold
front meet, but do not move
These fronts have the same weather as
warm fronts
SYMBOL – warm and cold fronts are
moving in opposite directions, thus
making a stationary condition
Occluded Fronts
Sometimes a colder or cooler front follows right behind a
warmer front. A warm air mass pushes into a colder air
mass (the warm front) and then another cold air mass
pushes into the warm air mass (the cold front). Because
cold fronts move faster, the cold front is likely to overtake
the warm front. This is known as an occluded front.
Remember moving in the same direction and combind or
included.
There are two types of Occlusion
I. In a cold occlusion, the air mass overtaking the
warm front is cooler than the cool air ahead of the warm
front, and plows under both air masses
II. In a warm occlusion, the air mass overtaking the
warm front is not as cool as the cold air ahead of the
warm front, and rides over the colder air mass while
lifting the warm air.
Vocabulary
Prevailing Westerlies- typical
west wind at this latitude
 Trade winds- prevailing wind
from east below Florida's
latitude
 Jet stream- high altitude, high
speed “river of air”
 Storm track- path of a storm
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The Cyclone
A
Cyclone is any low pressure system
that has a counterclockwise rotation
(In the Northern Hemisphere)
Types of Cyclones:
Tornado- a small, compact storm with
strong winds
 AKA:

Twister
 Willy-Willy (Australia)
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Types of Cyclones
Hurricane- A large, organized storm with
strong winds and heavy rain
 AKA
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Typhoon- in the Pacific
Types of Cyclones
Mid Latitude Low- a low pressure system
in the middle latitudes
 We live in the middle latitudes (30-50
degrees North & South)
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Comma shaped
 AKA
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,
Nor’ Easter (North Easter)
 Alberta Clipper
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Prevailing Winds
Push weather around
 In N.C., the prevailing winds come from the
west
 Most of the time our winds come from the west
  (therefore) our weather will usually come
from the west
 Sometimes we will get wind from the Northeast,
which usually brings extreme weather.
“Nor’ easters”
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A nor'easter is a type of macro-scale storm along
the East Coast of the United States and Atlantic
Canada, so named because the winds come from
the northeast atlantic, especially in the coastal
areas of the Northeastern United States and
Atlantic Canada. But their reach can be down into
the atlantic southeast. The precipitation pattern is
similar to other extratropical storms. Nor'easters
also can cause coastal flooding, coastal erosion,
hurricane force winds, and heavy snow.
Nor'easters can occur at any time of the year but
are mostly known for their presence in the winter
season
Windward and Leeward Winds
Rain Shadow
Windward Side
Leeward Side
A rain shadow is a dry area on the
mountainside facing away from the
direction from which the wind comes. The
mountains block the passage of rainproducing weather systems, casting a
"shadow" of dryness behind them. Warm
moist air is "pulled" by the prevailing
winds over a mountain. Then it condenses
and precipitates and the dry air moves
foreword leaving a rain shadow behind
the mountain. Usually a desert.
Surface Winds
The Mid Latitude Low
N
This weather
system starts
when cool
and warm air
masses meet.
Then a Low
develops over
the interface.
S
The Low
continues to
spin, creating a
warm front and
a cold front.
Rain will fall
in front of
the warm
front and
right on top
of the cold
front.
Hurricanes
Massive storms with a size that can be
more than 300 miles in diameter.
 Feed on warm water
 Biggest danger is the storm surge in
coastal areas
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High Pressure Cells
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A high-pressure area is a region where the
atmospheric pressure at the surface of the planet is
greater than its surrounding environment.
High-pressure areas are generally associated with
cooler, drier air as well as clearing skies due to their
formation within areas of atmospheric subsidence, or
areas of large scale air descent.
A low pressure area is commonly associated with
inclement weather, while high pressure area is
associated with light winds and fair skies.
Clockwise
Low Pressure Cells
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Wind is initially accelerated from areas of high
pressure to areas of low pressure.[
Stronger areas of low pressure are associated
with stronger winds.
The stronger the pressure difference, or
pressure gradient, between a high pressure
system and a low pressure system, the stronger
the wind
A low pressure area is commonly associated
with inclement weather, while high pressure
area is associated with light winds and fair skies.
Counter-clockwise
High and Low Pressure
Hurricane far off shore
Rough surf
hundreds of
miles away.
Storm Surge
Hey! Let’s
check out the
storm!
Hurricane Tracks
Tornadoes
form from very powerful thunderstorms
(cumulonimbus clouds)
 These are funnel shaped columns of spiraling
winds that extend down to the ground from the
base of a cloud
 The winds move into a tornado (low pressure),
and can reach a maximum of 318 mph!
 Spin COUNTER CLOCKWISE (like a
hurricane)
 The actual funnel is made by water droplets
(clouds) and dust
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Tornadoes are especially dangerous
because it is so difficult to predict where
they will form
 Damage is usually along a narrow path
where the tornado traveled
 They usually last less then one hour
 Most fatalities are caused by flying debris
 Tornadoes are rated on the Fujita scale
(F0 – F6)
 An F6 is very rare, and can have wind
speeds up to 318 mph
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TORNADOES!
Tornadoes will pick
up dust and debris
from the ground
when then “touch
down” – this
creates a wider
swirl at the bottom
of the tornado
For those of you who aren't familiar with tornadoes,
here is a short glossary to help you understand.
Fujita Scale: Scale used to measure wind speeds of a
tornado and their severity.
F1: Laughable little string of wind unless it comes
through your house, then enough to make your
insurance company drop you like a brick. People enjoy
standing on their porches to watch this kind.
F2: Strong enough to blow your car into your house,
unless of course you drive an Expedition and live in a
mobile home, then strong enough to blow your house
into your car.
F3: Will pick your house and your Expedition up
and move you to the other side of town.
F4: Usually ranging from 1/2 to a full mile wide,
this tornado can turn an Expedition into a Pinto,
then gift wrap it in a semi truck.
F5: The Mother of all Tornadoes, you might as
well stand on your front porch and watch it,
because it's probably going to be quite a last
sight.
F6: Is theoretical and has never been reported.
It is known as “the finger of god’ or “the finger
of fate.” The implication, is that the power and
destructive force is incalculable and unguided.
Meteorologist: A rather soft-spoken, mild-mannered type
person until severe weather strikes, and they start
yelling at you through the TV: "GET TO YOUR
BATHROOM OR YOU'RE GOING TO DIE!“
Storm Chaser: Meteorologist-rejects who are pretty
much insane but get us really cool pictures of tornadoes.
We release them from the mental institution every time
it starts thundering, just to see what they'll do.
Moore, Oklahoma: A favorite gathering place for
tornadoes. They like to meet here and do a little
partying before stretching out across the rest of the
Midwest.
Bathtub: Best place to seek shelter in the middle of a
tornado, mostly because after you're covered with
debris, you can quickly wash off and come out looking
great.
Severe Weather Radio: A handy device that sends out
messages from the National Weather Service during a
storm, though quite disconcerting because the high
pitched, shrill noise just as an alarm sounds
suspiciously just like a tornado. Plus the guy reading
the report just sounds creepy.
Tornado Siren: A system the city spent millions to
install, which is really useful, unless there's a storm or a
tornado, because then of course you can't hear them.
Storm Cellar: A great place to go during a
tornado, as it is almost 100% safe, though
weigh your options carefully, as most are not
cared for and are homes to rats and snakes.
May-June: Tourist season in Oklahoma, when
people who are tired of bungee jumping and
diving out of airplanes decide it might be fun to
chase a tornado. These people usually end up
on Fear Factor.
Mobile Home: Most people are convinced mobile
homes send off some strange signal that triggers
tornadoes, because if there's one mobile home park
in a hundred mile radius, the tornado will find it.
Twister: Slang for 'tornado' and also the title to a
movie starring Helen Hunt, which incidentally
everyone thought was corny and unrealistic until
May 3rd, 1999.
TORNADO RECORDS
· Highest Recorded Wind: 318 mph,
Bridge Creek/Moore, OK, May 3, 1999. **
· Widest Observed Path: 2.5 miles,
Hallam, NE, May 22nd, 2004.+
· Longest Observed Path: 219 miles, Tri
State Tornado, March 18, 1925.
Additionally, here are some phrases you might want to learn and
be familiar with:
"We'll have your electricity restored in 24 hours," which means
it'll be a week.
“We're going to be out for a week, so buy a lot of supplies and
an expensive generator," means it's going to be on in twelve
hours, probably as soon as you return from Wal-Mart.
"It's a little muggy today." Get outta town. It's getting ready to
storm.
"There's just a slight chance of severe weather today, so go
ahead and make your outdoor plans." Ha. Ha ha ha ha.
The BIG STORM TIP of the day:
When your electricity goes out, and you go to bed at
night, be sure to turn off everything that was on
before it went out, or when it is unexpectedly
restored in the middle of the night, every light, every
computer, your dishwasher, your blow dryer, your
washing machine, your microwave and your fans will
all come on all at once. 1) You'll just about have a
heart attack when they all come on at the same time,
waking you from a dead sleep. And 2) Your breakers
will blow, leaving you in the dark once again.
•small area storms formed by the strong
upward movement of warm, moist air
•usually occurs ahead of a cold front as the
colder, denser air shoves the warmer air
upward
•This forms the cumulonimbus clouds that
produce thunderstorms
•These storms are accompanied by heavy
rain, thunder, lightning, sometimes hail, and
can also produce tornadoes
All thunderstorms produce lightning
 Lightning is the discharge of huge
amounts of static electricity (think of
walking across a carpet in your socks and
then touching something-ZAP)
 Lightning can travel from the cloud to the
ground, cloud to cloud, or even from the
ground to a cloud!
 Thunder is the result of the air quickly
expanding from the heat of the lightning
bolt (causes a sound wave)
 You cannot have lightning without
thunder!!
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Supercell
Thunderstorm
formations – will form
SEVERE storms and
tornadoes! THIS IS ONE
BIG STORM SYSTEM!
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European Storms:
http://www.youtube.com/watch?v=68d2EfeHYf
A&safety_mode=true&persist_safety_mode=1
NWS Hurricane Plane:
http://www.youtube.com/watch?v=aOaktKIoVX8
NOAA 1988: Weather Plane
http://www.youtube.com/watch?v=KWVMcLQioQs&feat
ure=related
Videos/Games
Grade Swap
 http://reviewgamezone.com/game.php?id=
1838
Air Mass Video
 http://www.youtube.com/watch?v=Kmhizd
4De2E&safety_mode=true&persist_safety
_mode=1&safe=active