The word radar is an acronym from "Radio Detection and
Ranging". Radar images are useful for locating precipitation.
A radar sends a pulse
of energy into the atmosphere and if any precipitation is
intercepted by the energy, part of the energy is scattered
back to the radar. These returned signals, called "radar echoes", are
assembled to produce radar images.
Sending and Receiving Signals (detecting a target)
The
radar creates an electromagnetic energy pulse which is focused by an antenna
and transmitted through the atmosphere. Objects in the path of this
electromagnetic pulse, called targets, scatter
the electromagnetic energy. Some of that energy is scattered back toward the
radar.
The
receiving antenna (which is normally also the transmitting antenna) gathers
this back-scattered radiation and feeds it to a device called a receiver.
The location of the colored radar echoes indicate where
precipitation is falling and the various colors indicate the intensity of the
precipitation through the color code in the lower left corner of the image.
Satellites:
A
satellite is defined as a man-made object put into orbit around a celestial
body, like the earth or the moon.
Satellites
serve a wide variety of purposes from transmission of television signals via
communication satellites to guidance and tracking systems of defense
satellites. For meteorologists, satellites provide a comprehensive view of the
world's weather. On April 1, 1960, the first weather satellite was launched
into orbit from the United States. Since then, weather satellites have been
launched into orbit and their capabilities have improved significantly. Satellites
carry imager
and sounder
instruments enabling them to image clouds,
monitor earth's surface
temperature and water vapor
fields, and sound the atmosphere for its vertical thermal and
vapor structures. Today, not only do satellites observe clouds, but
measure other non- visible radiation from the earth and atmosphere. This helps
us to estimate such aspects as crop and soil conditions.
Acknowledgement: The above information is taken from the following website:
A front can
best be described as the border between two different air masses. A warm front
is the leading edge of a milder or warmer air mass. A warm front travels in
such a way that it results in warm air replacing colder air. This happens as
the warm air rises up and over the cold air below. As the warm air travels
upwards, it begins to mix with the cold air aloft and condenses to form clouds.
You can usually expect periods of rain or drizzle for many hours as the front
approaches.
Cold Front
A cold front is
the leading edge of colder air. In front of it, you usually have warmer, more
humid air. Behind the front lies much cooler or colder and drier air. The cause
for cold fronts is colder air masses migrating southward from the polar
regions. It is part of the world's natural energy circulation or cycle, this is
how the earth "balances" out the warm and cold air masses around the
earth.
High Pressure Centre
Indicates an
area of high pressure. In a high pressure system, air will slowly descend and flow out in a
clockwise direction at the ground. Normally a high will bring mainly sunny
skies to an area.
Low Pressure
Centre
Indicates an
area of low atmospheric pressure. In a low pressure system, air is flowing counterclockwise
into the centre of the Low. The air will rise and cool often resulting in
clouds and precipitation.
Trough
An elongated
area of low pressure.
Jet Stream
The jet stream
is like a current or river of air in the upper atmosphere, 7,000 to 13,000
meters up. It's created when cold and warm air masses come together. In the
mid-latitudes of the Northern Hemisphere winds will tend to move from the west
to the east. The jet stream, quite simply put, is the apex of these winds in
the upper atmosphere. The minimum criterion for jet stream speed is 93
kilometers per hour. The location and orientation of the jet stream changes
from day to day. Weather patterns are influenced by the position, strength and
orientation of the jet stream.
Acknowledgement: This information is derived from the following website.
When we look at tomorrow’s forecast for Regina, SK. We observe
that there is a slight difference between those forecasts. I think this is because
of using different instruments and people reading them.
History Behind Predicting Weather
Man has always tried to predict weather as his survival has
depended on weather and other natural conditions. The
Babylonians in around 650 BC and Chinese
Astronomers in 300 BC used observation
and calenders to predict weather.
Around 340 B.C., the Greek philosopher
Aristotle wrote Meteorologica, he made some remarkably observations
concerning the weather. Throughout the
centuries, people have attempted to make forecasts based on weather lore and
personal observations. Galileo Galilei (1564-1642, Italian) invented an early
thermometer in 1592. The following article sheds more light on this subject.
Would finally
build into a tornado...near Strathmore.
Wall Cloud: A wall cloud is an abrupt lowering of a rain-free cumulonimbus base into a low-hanging accessory cloud. A wall cloud is usually situated in the southwest portion of the storm. A rotating wall cloud usually develops before tornadoes or funnel clouds.
Funnel Cloud: A funnel cloud is a rotating cone-shaped column of air extending downward from the base of a thunderstorm, but not touching the ground. When it reaches the ground it is called a tornado.
Snowflakes are made of ice crystals. Each snowflake is six-sided and made of as many as 200 ice crystals. Snowflakes form in clouds where the temperature is below freezing. The ice crystals form around tiny bits of dirt that has been carried up into the atmosphere by the wind. As the snow crystals grow, they become heavier and fall toward the ground.
Some of the weather related events are as follows:
Rain and
flood
Air contains water vapors. When warm air moves up in the sky,
water vapors in it gather to form clouds. If the clouds are big enough and have
abundant water droplets, these droplets bang together and form bigger drops.
When the drops get heavy, they fall because of gravity, and we have a rainfall.
If rain is heavy and it falls for days or there is a lot of
snow and there is a meltdown, it can cause rivers to overflow causing a flood.
Thunderstorm
A
thunderstorm is a storm with lightning and thunder along with the gusty winds,
heavy rain and sometimes hail. A thunderstorm is formed when there is abundant
moisture in the air which causes clouds and precipitation to form and when
there is an uplift of the air. The uplift must be very strong to produce
cumulonimbus cloud that reaches high above in the atmosphere.
An unstable or active air circulation system comes into being
because of a big temperature difference between the cold air of the high
altitude and the warm air on the ground.
Hail
Hail is created when
small water droplets are caught in the updraft of a thunderstorm. These water
droplets are lifted higher and higher into the sky until they freeze into ice.
Once they become heavy, they will start to fall. If the smaller hailstones get
caught in the updraft again, they will get more water on them and get lifted
higher in the sky and get bigger. Once they get lifted again, they freeze and
fall. This happens over and over again until the hailstone is too heavy and
then falls to the ground.
Tornadoes
A tornado is a very active rotating column of air extending
from a thunderstorm to the ground. The most violent tornadoes can cause
tremendous destruction with wind speeds of up to 500 km/h. They can destroy
large buildings, uproot trees and hurl vehicles A tornado’s damage path can exceed
one kilometer wide to 30 kilometers long. Most
tornadoes form from thunderstorms.In North
America when warm, moist air from the Gulf of Mexico and cool, dry air from Canada
meet, they create instability in the atmosphere. A change in wind direction and
an increase in wind speed with increasing altitude create an invisible, horizontal
spinning effect in the lower atmosphere. Rising air within the updraft tilts
the rotating air from horizontal to vertical. An area of rotation, 4-10
kilometers wide, now extends through much of the storm. Most strong and
destructive tornadoes form within this area of strong rotation.
Winter Storms
Winter
storms get energized when two air masses of different temperatures and moisture
levels clash. In North America winter storms usually form when an air mass of
cold, dry, Canadian air moves southward and collides with a warm, moist air
mass moving north from the Gulf of Mexico. The point where these two air masses
meet is called a front. If cold air advances and pushes away the warm air, it
forms a cold front. When warm air advances, it rides up over the denser, cold
air mass to form a warm front. If neither air mass advances, it forms a
stationary front.
Classification
of some severe weather events according
to Environment Canada’s website:
Blizzard:A Blizzard warning is issued when winds
of 40 km/hr or greater are expected to cause reduced visibility of 400 meters
or less, due to blowing snow,
or blowing snow in addition to falling snow,
for at least 4 hours.
Blowing
Snow:When blowing snow is caused by winds of at least 30 km/h, is expected
to reduce visibility to 800 meters or
less for at least 3 hours then a blowing snow warning is issued.
Freezing Rain/ Drizzle:When rain or drizzle falls onto below zero ground
and freezes on
contact forming a layer of ice causing slippery roads then a freezing rain
warning is issued.
Severe Thunderstorm: A severe thunderstormwarning is issued when windgusts of 90 km/h or greater, there is heavy rainfall along with hail of 2 centimeters in diameter or larger.
