ATPL Meteorology - Class 15: Fronts and Depressions.
Summary
TLDRThis meteorology lesson explores weather fronts, the boundaries between air masses with different temperatures and densities. It explains how warm and cold fronts cause changes in weather, with warm fronts leading to stratiform clouds and drizzle, and cold fronts resulting in cumulonimbus clouds and storms. The script also delves into occluded fronts, global frontal activities, and the formation of frontal and non-frontal depressions, including tropical revolving storms like hurricanes and typhoons. The video provides insights into predicting weather patterns and the atmospheric processes behind various weather phenomena.
Takeaways
- 🌍 Fronts are boundaries between different air masses and can predictably change local weather conditions.
- 🔍 Weather fronts can be identified from a distance, allowing for weather predictions over short to medium time frames.
- 🌡️ The meeting of air masses with different temperatures creates fronts due to density differences that prevent them from mixing.
- ☀️ Warm fronts occur when warm air moves into an area of colder air, typically represented by a red semi-circle symbol.
- 🌀 Warm fronts slope upwards at a ratio of 1:150, spreading out over large distances and moving at about a third of the 2000-foot wind speed.
- ❄️ Cold fronts are where cold air moves under warmer air, represented by a blue icicle symbol, and have a steeper slope of 1:50.
- 🌬️ Cold fronts travel faster than warm fronts, typically at two-thirds of the 2000-foot wind speed, causing gusty wind conditions.
- 🔄 An occluded front forms when a cold front catches up to a warm front, creating a V-shape with warm air sandwiched between cold air masses.
- 🌤️ Weather associated with fronts includes stratiform conditions with warm fronts and cumulaform conditions with cold fronts.
- 📉 Warm fronts cause a gradual drop in pressure as they approach, while cold fronts lead to a rapid increase in pressure after they pass.
- 🌐 Global frontal activities include the polar front, which moves with the seasons, and the intertropical convergence zone formed by equatorial heating.
Q & A
What is a weather front?
-A weather front is the border between two different air masses, often marked by a change in weather conditions. It is the point where air masses of differing temperatures and densities meet, leading to a transition from one type of weather to another.
How do weather fronts help in predicting local weather?
-Weather fronts can be observed from a distance, allowing meteorologists to make predictions about the weather in a local area for the coming days or weeks. The movement and interaction of air masses at the fronts can indicate the type of weather changes expected.
What is the difference between a warm front and a cold front?
-A warm front occurs when warm air moves into an area of colder air, typically characterized by a gradual slope and associated with stable, stratiform weather conditions like drizzle. A cold front, on the other hand, is when cold air moves under warmer air, creating a steeper slope and leading to more unstable, cumulaform weather such as thunderstorms and heavy rain showers.
What is the typical speed of a warm front compared to the 2000-foot wind speed?
-A warm front typically moves at about one-third the speed of the 2000-foot wind, which is outside the friction layer and represents the free stream flow of air.
How does the slope of a cold front differ from that of a warm front?
-The slope of a cold front is much steeper than a warm front, with a ratio of about 1 to 50, meaning for every one unit of distance forward, the front rises 50 units vertically. This is much steeper compared to the warm front's ratio of about 1 to 150.
What is an occluded front and how does it form?
-An occluded front forms when a cold front catches up to a warm front. It creates a V-shape with a wedge of warm air in the middle, sandwiched between two areas of cold air. This type of front is typically associated with wet weather conditions.
What types of clouds are associated with a warm front?
-With a warm front, one can expect to see cirrus clouds at the highest levels, followed by altostratus clouds in the mid-layers, nimbostratus clouds indicating rain, and eventually stratus clouds as the front approaches.
How does the pressure change as a warm front approaches?
-As a warm front approaches, the pressure tends to drop because the warm air is less dense and has fewer particles to exert pressure on the Earth's surface. This results in a gradual decrease in pressure.
What is the intertropical convergence zone and how does it relate to weather fronts?
-The intertropical convergence zone (ITCZ) is an area around the equator where trade winds from the Northern and Southern Hemispheres meet, often resulting in a front due to differences in temperature and moisture levels. This zone fluctuates throughout the year and is associated with the equatorial lows and Hadley cells.
What is a polar front depression and how does it differ from a frontal depression?
-A polar front depression is a low-pressure system that forms when a warm air mass bulges into a cold air mass along the polar front, leading to a curved wind pattern and the formation of fronts within the system. It differs from a frontal depression in that it specifically involves the polar front and can lead to a series of weather changes as the fronts move around the depression.
What are some global frontal activities mentioned in the script?
-The script mentions the polar front, which moves north and south throughout the year, separating tropical maritime and polar maritime air masses. It also discusses the intertropical convergence zone formed by equatorial lows and Hadley cells, as well as thermal lows that can lead to monsoons or tropical revolving storms like hurricanes, typhoons, and cyclones.
Outlines
🌤️ Weather Fronts and Their Impact
The script introduces the concept of weather fronts as boundaries between different weather systems, which can be predicted to understand upcoming weather changes. It explains how air masses with varying temperatures meet, creating fronts that are characterized by their shapes and slopes. Warm fronts, represented by a red semi-circle, occur when warm air moves into a colder area, causing the air to rise slowly and leading to stratiform weather conditions such as cirrus, altostratus, nimbostratus, and stratus clouds. Cold fronts, symbolized by blue icicles, represent the denser cold air pushing under warmer air, resulting in steeper slopes and cumulaform weather with cumulus and cumulonimbus clouds. The speed of these fronts is related to the wind speed at 2000 feet, with warm fronts moving slower and cold fronts moving faster. An occluded front forms when a cold front catches up to a warm front, creating a V-shape with warm air in the middle and is typically associated with wet weather.
🌡️ Changes in Pressure and Wind Direction
This section delves into the effects of weather fronts on air pressure and wind direction. As a warm front approaches, the pressure drops due to the increase in warm, less dense air, which has fewer particles to exert pressure on the Earth's surface. Conversely, a cold front causes an increase in pressure as it advances, filling air columns with colder, denser air that exerts more pressure. The change in wind direction, or veering, is also discussed, with the wind direction changing sharply across the cold front and more gradually across the warm front. The script also touches on the global distribution of air masses and the formation of fronts in different regions, such as the polar maritime and tropical maritime regions over the North Atlantic Ocean.
🌍 Global Frontal Systems and Depressions
The script discusses global frontal systems, including the polar front, which fluctuates with temperature and seasons, and the intertropical convergence zone, where trade winds meet and form fronts. It explains how these fronts can lead to the formation of polar front depressions, which are low-pressure areas with distinct boundaries between warm and cold air masses. The weather associated with these frontal depressions includes a sequence of cloud types and weather conditions similar to those experienced when a warm front is followed by a cold front. The section also covers non-frontal depressions, such as thermal depressions, which form in areas of intense heating, like the Indian subcontinent during the summer monsoon season, and the formation of tropical revolving storms, including hurricanes, typhoons, and cyclones, which are extreme forms of thermal depressions.
🌪️ Formation and Characteristics of Tropical Revolving Storms
This part of the script focuses on the formation and characteristics of tropical revolving storms, such as hurricanes, typhoons, and cyclones. It describes how these storms form over warm, moist ocean areas, with low pressure and rising air leading to cloud formation and the release of latent heat, which further fuels instability. As these systems move away from the equator, the Coriolis force causes them to begin spinning, creating the characteristic eye of the storm and violent weather conditions at the edges. The script notes that these storms are most common at the end of summer when ocean temperatures are highest and can cause significant disruption in regions they impact, such as the Caribbean, Japan, and other areas prone to these weather phenomena.
🌬️ Frontal Dynamics and Global Weather Patterns
The final paragraph summarizes the dynamics of weather fronts and their global implications on weather patterns. It reiterates the movement speeds and symbols associated with warm and cold fronts, and the weather conditions they bring, such as drizzle for warm fronts and thunderstorms for cold fronts. The script also explains how occluded fronts form and the weather sequence they produce. It discusses the global frontal activities, including the polar front's seasonal movement and the intertropical convergence zone's role in creating trade winds and fronts. Additionally, it mentions the impact of thermal effects, such as local heating over land or sea, which can lead to the formation of non-frontal and frontal depressions, contributing to the variety of weather experienced in different regions of the world.
Mindmap
Keywords
💡Weather Fronts
💡Warm Front
💡Cold Front
💡Occluded Front
💡Air Mass
💡Pressure Changes
💡Isobars
💡Polar Front
💡Intertropical Convergence Zone (ITCZ)
💡Frontal Depression
💡Thermal Depression
Highlights
Fronts are the border between weather systems and can be identified by changes in weather conditions.
Weather fronts can be predicted from a distance, aiding in forecasting local weather over days or weeks.
Air masses meeting due to temperature differences create fronts with distinct shapes and sizes.
Warm fronts occur when warm air moves into an area of colder air, represented by a red semi-circle symbol.
Cold fronts are characterized by cold air moving under warmer air, symbolized by blue icicle shapes.
The slope of a warm front is much gentler than that of a cold front, affecting weather spread and travel speed.
Occluded fronts form when a cold front catches up to a warm front, creating a V-shape of warm air between cold air masses.
Weather at fronts is influenced by air mass density differences, leading to stratiform or cumulaform conditions.
Pressure changes occur as fronts approach, with warm fronts causing a drop and cold fronts an increase.
Isobars show distinct patterns around fronts, indicating changes in wind direction and pressure.
Global frontal activities include the polar front and the intertropical convergence zone, influenced by seasonal temperature fluctuations.
Polar front depressions form when a warm air mass bulges into cold air, creating a low-pressure area with distinct fronts.
Thermal depressions occur due to surface heating causing air to rise and form low-pressure areas with unstable conditions.
Tropical revolving storms or hurricanes are extreme forms of thermal depressions, causing significant atmospheric instability.
Frontal depressions bring a sequence of weather changes, from warm front conditions to cold front instability.
Non-frontal depressions like thermal lows can also influence weather, especially in regions with intense surface heating.
The interplay of fronts, air masses, and pressure systems drives the complexity and predictability of weather patterns.
Transcripts
fronts are the border between one
weather system and another and they come
in various shapes and sizes but what
happens when these fronts approach and
pass over our location
let's find out
[Music]
hi i'm grant and welcome to class 15 in
the meteorology series
today we're going to be taking a look at
weather fronts weather fronts bring with
them a change in the weather conditions
it could be for the better could be for
the worse but in any case it is a change
and we can often see these fronts
approaching from quite far away so it
can help us to make predictions about
what's going to happen to the weather in
our local area for example over the next
couple of days or even couple of weeks
when air masses move over the earth they
sometimes meet other air masses which
are hotter or colder and because of the
temperature difference that means that
there's a density difference
and the air masses tend not to mix and
instead there is a quick transition from
one air mass to the other which we call
a front this is the border between two
different air masses
and fronts come in a few different
shapes and sizes
the first one is a warm front
a warm front is when warm air moves into
the area of colder air unsurprisingly
the line on the earth will look like
this and have sort of semi circles
think of as half sun shapes is what i do
to remind me that it's a hot front and
it's usually red in color
and that'll show the line at the earth's
surface
and the front itself doesn't stay
vertical it instead slopes up towards
um the colder air because the hot air is
rising above the cold air the ratio of
what it does this is about one to one
hundred fifty so we go up one meter and
a long 150 meters so it's quite shallow
and it spreads out quite far it could be
in the region of about 600 700 nautical
miles in total length that this warm
front um
covers
and the warm front travels at a certain
speed and it's usually a third
of the speed of the 2000 foot wind and
why the 2000 feet wind well
at 2000 feet we're sort of outside the
friction layer so it's the free stream
flow of air and the warm front moves a
third of that speed
the opposite to a warm front is a cold
front
and this is where cold air mass moves in
and forces its way
under warmer air
due to it being higher density and it's
given this symbol which is sort of like
icicles i think of it as and it'll be
blue in color
the slope of a cold
front
is much steepers normally has a ratio of
150 so we go forward one and up 50 which
is a lot steeper than the warm front and
this means that it's not as spread out
typically
uh only nears a distance of around 100
nautical miles in total length
and a cold front can often be held at
the surface by surface friction and it
can lead to an overhang forming which is
known as a cold nose
and this cold nose repeatedly forms and
collapses and forms and collapses which
leads to sort of gusty wind conditions
as it's doing that
the speed of travel of a cold front is
faster than a warm front it's typically
two-thirds of the two thousand foot wind
or two-thirds of the wind outside of the
friction layer
occasionally
a
cold front
will catch up to a warm front this is
because the cold front is obviously
moving at two-thirds the wind speed and
warm front is only one third the wind
speed so occasionally they catch up and
we get something known as an occluded
front
an occluded front basically forms a v
shape of warm air
in the middle where the two fronts
become connected and ahead of it you get
cold air behind it you get cold air just
with this little sandwich of warm air in
the middle
an occluded front front is normally just
associated with wet weather conditions
so weather is formed at the fronts
because
some air mass is being forced to rise
above another air mass because of those
different densities
with a warm front we see
stratiform weather
so the ascending air is forced up quite
slowly because of this gradual
slope
and we'll see
fairly stable stratiform conditions and
it will lead
the actual line of the front on any
charts because the line
shows it on the surface and obviously
we're sloping towards that so you'd
start off with maybe cirrus clouds very
high up
getting towards alto stratus clouds
again stable in that mid layer
nimbostratus
around sort of this region and
eventually stratus behind it
and you'll basically see the cloud base
the lowest level of cloud lowering
as the
front approaches your position if we
were standing here and this is passing
over us
our cloud base starts all the way up
here and starts to lower as this front
approaches in contrast
a cold front forces its way
underneath warm air at quite a quick
rate at 1 in 50.
and so it causes the warm air
located here to rise quite rapidly
and makes that unstable conditions which
is cumulaform weather producing as a
result so you get cumulus nimbus clouds
those storm clouds you get cumulus
clouds and eventually you get
altocumulus up in this sort of region up
here
and with an occluded front we see
a wedge of warm air produced
in between the two colder air masses and
as a result we get a bit of a stratiform
area leading in and a cumuliform
area after the front and again you get
nimble stratus and cumulative just
associated with wet weather in general
if we think of a few columns of air
where a front passes we can
easily figure out what happens to the
pressure as these fronts approach so
first we'll have a little look at a warm
front
so each column of air
will have a different proportion of warm
air and cold air due to the slope of
this front you can see this has a lot of
cold air whereas this has a lot of warm
air
warm air is less dense which means there
are fewer particles per unit area
so this column on the right has a small
proportion of air with not many
particles in it
and the particles are being pulled down
by gravity and imparting a pressure onto
the surface of the earth that surface
pressure that we're going to measure
as we move to the left or you can think
of it as this warm front passing over
this same column and this just being
three
time shots
of that same column
and
basically more and more of the column
is made up of this warmer less dense air
and that means that there's fewer
particles in the air and that means that
there's fewer particles being pulled by
down by gravity and imparting that
pressure onto the surface
so overall you can see that as a warm
front approaches
the pressure drops as a result you get
one zero one zero
one double eight one two six and so on
and so on as the pressure
drops as the front approaches
a cold front is a bit different because
the cold air is forcing its way under
the warm air
and if we have a look at the columns of
air then as the front approaches
nothing's actually happening it's only
once the front hits that we start to get
parts of these columns made up of
that colder more dense air because it's
more dense there's more particles more
particles get cooled down by gravity
therefore more pressure
as a result and you will see
that
it will increase the pressure rapidly
just after the front's passed and it'll
be rapid because you've got that steep
um steeper angle
so quickly you get more and more
of these columns made up of colder
basically higher pressure air so both
fronts will do something interesting to
isobars let's just take a look at the
cold front for example so we know that
the pressure increases rapidly after the
front has passed so we've got 1006
here and here and then it goes to 1008 1
0 1 0 and so on so if we
were to draw these individual pressures
joined up
in isobars
then we'll see something quite
interesting
so once the lines are all joined up on
all these spot pressures joined up we
can see that there's a very definite
change as we pass over the cold front in
terms of the direction
of these isobars there's a very
sharp angle at the front and that
basically means the wind direction
changes as well
so at the surface you would get one
that's not exactly aligned with the
isobars because
in the northern hemisphere the wind
backs as it goes down
but then if you still take a
fairly standard backing of maybe like 40
degrees and apply over here as well
you can see that the wind has changed in
angle
by the same proportion as the isobar has
changed
so as a cold front passes the wind veers
round
and the same thing happens when a warm
front passes as well
so across the world there are different
air masses that dominate certain regions
such as the tropical maritime
region and the polar maritime region
over the north atlantic ocean
and where these air masses meet a front
is formed and depending on the time of
year this polar front this boundary will
be higher in latitude or lower in
latitude
as the warming areas warm and cold areas
sorry fluctuate with the temperature and
the seasons
they will also vary with pressure
patterns and other factors such as
competing ear masses
and this front changes and it's very
rarely a straight line like this and it
can cause bumps and
indentations into each other's air
spaces
and something
that forms sometimes is called a polar
front depression which we're going to
have a look at just after i've explained
something else
another common frontal zone exists
around the equator in something known as
the intertropical convergence zone
so what happens is at the equator
it's very hot so that surface heating
causes
air to rise out which ascends up
it spreads out starts to cool down and
then descends back to earth in the
hadley cells i've mentioned them before
in previous classes this creates high
pressure areas around the tropics
air likes to flow from high to low
pressure so it flows back in towards the
low pressure area caused by this surface
heating at the equator as it starts to
flow it gets pulled round to the right
in the northern hemisphere and to the
left in the southern hemisphere this
creates some predictable winds known as
the trade winds which are north east in
direction in the northern hemisphere and
south east in direction in the southern
hemisphere
where these winds meet a front is
produced because the air masses will
have slightly different temperature and
moisture levels
and it will vary throughout the year in
the same way as this polar front does
through the seasons
so i talked earlier about how the front
between the tropical and polar maritime
air masses kind of fluctuate and bulge
and sometimes a frontal depression will
form a polar front depression we call it
this is when a warm air mass or the
tropical maritime air mass bulges up
into the cold air and the wind starts to
curve around the air the bulge as a
result and a low pressure area is formed
at the tip of the warm air and forms a
shape that looks like this
the air masses will have distinct
boundaries with the warm air moving
northeast
and the colder air mass moving southeast
and a front forming at the cold and the
warm areas respectively this low
pressure area is a depression and it has
fronts in it hence the name frontal
depression and the fronts will then be
moved with the prevailing wind around
the depression and the depression itself
will move in the direction of the wind
in the warm sector so you get these
fronts starting to move round the low
pressure zone like this but the overall
bulge will move horizontally like this
and this is why in europe we experience
a lot of these frontal depressions these
waves of weather coming in and you might
associate
places like ireland
uk with constantly having
rain
and storms and stuff like that this is
one of the reasons why because these
fronts
move in and hit
ireland in the uk all the time the
weather associated with a frontal
depression is the same as if we had a
warm front then followed by a cold front
so at the warm front we will see slowly
rising air over a long distance which
means we get
cirrus clouds up top
and then altostratus and nimbostratus
and stratus clouds the cloud base will
be lowering as the front approaches our
position
and as the front passes over our
position we'll see a temperature
increase as we go into the warm sector
we will see an increase in the humidity
of the air and therefore a higher dew
point as a
result and we'll also see the pressure
falling off as we saw earlier
and
again with that pressure and that
frontal drop off we'll see the isobars
changing so we'll get a change in the
wind direction in the warm sector we'll
see low stratus clouds as the warrior is
maritime air it's full of moisture but
the low
the high temperature air is slightly
more stable so we don't associate with
very cumuloformed clouds and as the cold
front approaches and passes we will
start to see the rapid ascent of this
warmer air leading to unstable
conditions thunderstorms heavy rain
showers etc and as the front passes
we'll see the pressure increasing the
temperature will fall as we go back into
the colder air which means the dew point
falls and the humidity falls as well
eventually we will get occluded fronts
forming where the cold front catches up
to the warm front
this happens first where they're closest
together so it'll be at that tip of the
um the sort of triangular pattern
and
then they'll start to spread down and
eventually you end up with a fully
occluded front it's almost like if you
zip up
the polar front depression that's how
the occluded fronts form so just as
there are depressions with fronts in
them frontal depressions there's also
some without fronts in them which are
non-frontal depressions surprisingly
there is one
sort of non-frontal depression that
there is worth adding a bit of extra
information about
and which is called a thermal depression
so these form in certain areas year
round like the equity equatorial lows
and hadley cells that we looked at
previously but they can also form in
specific areas depending on the season
so thermal lows form because the surface
temperatures heat up and cause the air
to rise creating an area of convergence
at the surface
and rising unstable air in the center of
the low pressure area something that
also happens
is
as a cloud is formed by the rising air
and the
um
condensing air into clouds
some latent heat is released from the
air mass itself and that means that the
rising air is now warmer than the
surrounding air because of this latent
heat release which can cause even more
unstable conditions
a common place that this happens is
somewhere like india
throughout the summer gets very hot and
as a result there's a large low pressure
area
which is formed over the land and it can
move over the ocean
lead to a lot of air rising over the
ocean moisture filled air huge clouds
and storms
form as a result towards the end of the
summer which is the monsoon season
tropical revolving storms or
hurricanes cyclones or typhoons
are another version of these thermal
depressions but in its most extreme form
so a very deep depression will form in a
warm equatorial region
over the ocean
these areas of low pressure start to
move away from the equator and if they
move over dry land then there's not
enough evaporation to form any storms so
it's no issue but if they move over the
ocean then there's more moisture in the
air it's a more humid environment and it
rises and it condenses to form clouds
this releases a large amount of latent
heat and causes even more instability in
the atmosphere
once this area of low pressure and cloud
moves sufficiently far away from the
equator about 500 kilometers then it
starts to feel the effect of the
coriolis force and a spin starts to form
this spinning motion starts to spread
the clouds away from the center and an
eye
form the eye of the storm
and at the edge of the eye we have the
most
violent weather conditions experienced
so violent in fact that of course it
causes massive disruption to
places like the caribbean or you know
japan gets hit by these quite hard and
it's only certain places that these form
because we need very specific conditions
we need a warm ocean
with a low pressure area that is very
large
so
they tend to happen
normally at the end of summer as well
because the oceans had a large amount of
time
to heat up and form this low pressure
area
so over the atlantic when they hit
places like the united states and the
caribbean we call them hurricanes what
happened towards the end of summer in
july october time
in the pacific in general in japan
and
places like the philippines
they would call them typhoons usually
and again it would be the northern
hemisphere end of summer so july to
october
and in the indian ocean over the south
of the indian ocean
they tend to call them cyclones
and they'll happen in the
at the end of the summer
for the southern hemisphere which would
be sort of january to march time but if
they hit the indian ocean in the
northern hemisphere it would happen
again at the end of summer which would
be july to october but still called
cyclones in summary then you've got a
warm front which moves at one third of
the 2000 foot wind speed it's got a
slope of about 1 to 150 it's given this
little red
half sun symbol
it slopes up very slowly and gradually
leading to stratiform conditions which
lead ahead of where this cold front
sorry the warm front actually is on the
surface you get cirrus altostratus
nimbostratus and stratus clouds typical
stable sort of conditions
and drizzle that sort of thing
a cold front is the opposite it moves at
two-thirds of the 2000 foot wind speed
it's got a slope of one to 150
and it
forces its way under warmer air causing
that warm air to rise rapidly it can
lead to very cumulaform clouds
as a result
and cumulonimbus big storm clouds and
it's given the symbol of this sort of
pointy blue line
and
most of the weather will be in and
around the cold front itself
and because it's not got this very low
gradual slope leading ahead of it it
actually slopes behind it
because of the cold front moving faster
than the warm front eventually the cold
front will catch the warm front ahead of
it
and you get an occluded front as a
result which basically means you get
warm front weather
followed by cold front weather
and the warm sectors kind of squeezed up
into this v shape it's given the symbol
which is just a combination of the two
for cold front and warm front so as the
front approach interesting things happen
to the pressure think of the columns of
air
and the warmer air being less dense
colder air being more dense
uh air that is less dense fewer
particles to push down on the earth and
create pressure
so if we look at the warm front first
which is these figures up the top we'll
see that as the warm front approaches
more and more of these columns are made
up of hot air
and or warm air and the pressure drops
as a result quite gradually
a cold front would be the opposite
we see that the pressure
increases
rapidly after the cold front has passed
because there's more
cold air in each of these columns more
dense more particles more amount of
particles pushing down on the earth's
surface and it's faster change than the
slope
because of the
it's a faster change than the warm front
because of the slope difference between
the two so you get various global
frontal activities you get the polar
front which moves north and south
throughout the year it's the board line
between the tropical maritime and the
polar maritime
you get the equatorial or sorry the
inter-tropical conversion zone which is
formed by the equatorial lows and the
hadley cells
the warm air the equator rises creates
low pressure zone that air starts to
spread out falls back down to earth
creating high pressure the
tropical zones
air flows from high to low gets pooled
around with the coriolis force we get
the trade winds as a result which are
north easterly in the northern
hemisphere southeasterly in the southern
hemisphere where those winds meet
into tropical convergence zone a front
is formed there we also get more local
versions of this sort of thermal effect
and where we get
a lot of heating
over land causes a lot of air rising or
even over the sea
and the most extreme version would be a
tropical revolving storm we got a large
area of low pressure lots of rising air
because it's so full of moisture
those clouds start to condense out
as they condense it creates heat that
heat leads to these parcels of air being
even more unstable more rising and as it
moves away from the equator it starts to
spin causing a lot of damage as it does
so hurricanes typhoons cyclones whatever
you want to call them tropical revolving
storms so as you get non-frontal
depressions we get frontal depressions
frontal depressions basically form from
a bulge in the polar front or indeed it
could be the intertropical conversion
zone
and essentially you see
weather from a warm front then a warm
sector where there's low stratus clouds
and then you see weather from a cold
front so as one of these passes you'll
see the pressure start to drop it'll
start to stabilize for a bit and then it
will increase rapidly behind
you get all the weather that's
associated with it you get the wind
direction changing
um
and this sort of thing happens a lot to
northern europe these
polar front depressions
blow over the atlantic and we've got
lots of frontal activity in northern
europe as a result
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