Download Violent tornadoes

Air Masses and Fronts
Definition
Air mass- huge section of the lower troposphere that have the same kind of weather
humidity) throughout.
Properties of Air Masses
cause changes in the weather
are classified by where they form
form over oceans and land
amount of moisture (humidity) depends on where the mass develops.
named for source region or places of origin
Source Regions
Source regions for cold air masses are polar areas and are labeled P
Source regions for very cold air are arctic areas and are labeled A
Source regions for warm air are masses are tropical areas and are labeled T
Air masses over oceans are called martime and are labeled m
Air masses over land are called continental and are labeled c
Types of air masses
5 major types of air masses
mP- maritime polar
is cold and humid
brings cooler temperatures to Eastern US
Brings fog to California and western states
Maritime tropical
mT maritime tropical
holds warm moist air
in summer- brings very hot, humid weather
in winter- if this air meets with cold air mass, rain or snow will fall
(temperature and
Continental tropical
cT continental tropical
originates in tropical land areas and desert areas of SW US
are hot and dry
Continental polar
cP continental polar
originates over land in N Canada
are cold and dry
causes very cold temp in the US in the winter
Continental arctic
cA continental arctic
very cold and dry
come from ice covered Arctic regions
Air masses change as they move from their source region.
they diverge from areas of high pressure and converge in areas of low pressure
are very large and take several days to pass through a region.
Fast moving air masses spend less time over any one area and bring more extreme weather
Rawinsonde
balloon carried package of instruments, used to measure humidity, temp., and winds
measurements made twice daily
very detailed
Fronts
boundary between air masses that have different temp. and humidity.
when two air masses meet a front forms
an approaching front means a change in weather
almost always brings ppt.
four types of fronts
forceful lifting- when two contrasting air masses meet, the lighter warmer of the two is lifted or rises
above the cooler, denser air mass. MAJOR CAUSE OF PPT in the US.
Cold Front
forms when a mass of cold air meets and replaces a mass of warm air
cold air forces the warm air mass upward
violent storms are associated with cold front
has a steep slope
often forms a line of thunderstorms called a squall line
Warm Front
forms when a mass of warm air overtakes a cold air mass and moves over it
Drizzle may accompany a warm front
hot humid weather follows
gentle slope
Occluded Front
forms when cold front overtakes a warm front (cold front travels faster then a warm front)
warm air is pushed upward and the cold air meets cool air
weather is complex and extreme
Occluded Front
forms when cold front overtakes a warm front (cold front travels faster then a warm front)
warm air is pushed upward and the warm air meets cool air
weather is complex and extreme
Stationary Front
warm air mass meets a cold air mass
no movement occurs
rain may fall for days
Cyclone
Cyclone Development
A wavelike kink develops- warm air is pushing N, (warm front) cool air is pushing S (cold front)
Cold front moves more rapidly and overtakes warm front producing unstable air and cloud development
Occluded front is produced.
Cyclone
Anticyclone
high pressure area containing cold dry air
clockwise direction
clear dry weather
isobars usually farther apart , winds are weaker
Tornadoes
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A violently rotating column of air in contact with the ground
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associated with cumulonimbus clouds and intense low pressure
categorized as weak, strong or violent
Types of tornadoes
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Weak- ropelike appearance, windspeeds no greater than 110 mph
Strong- funnel shaped cloud with speeds between 110-200mph. 3 in ten tornadoes are classified as
strong
Violent tornadoes
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violent tornadoes- 2 % of all tornadoes reach this strength. Wind speeds are greater than 200mph
Important terms
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Wall cloud- large, rotating, dark cloud used as an indication of tornodic development
Tornado Alley- Kansas, Missouri, Texas and Oklahoma most tornadoes occur here
waterspout- a tornado over water
mesocyclone- rising, spinning column of air
funnel cloud- a tornado that has not reached the ground
Weather Alerts
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watch- issued when there is a potential for tornado development
warning- issued when a tornado has been spotted.
Wall Cloud
Tornado safety
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Have a safety plan
Stay away from windows and doors
take shelter in an interior room or basement
if you are in an open area look for a ravine or ditch or other low lying area
Have an emergency kit- What should it include?
Other tornado information
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Most occur from 5-9 PM
June is the month in which most tornadoes occur
Tornadoes are associated with hail, heavy rain and lightning.
Fujita Scale is used to measure tornado intensity
The US has more tornadoes than any where else in the world.
HURRICANES!!!
Hurricanes
Tropical cyclones with winds that exceed 64 knots
blow in a counterclockwise direction
also called a cyclone or typhoon
develop on the western side of oceans
most common in late summer and early fall
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do not last long after they reach land because source of moisture is cut off
Development
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Start as a Tropical depression - 20-34 mph
gain speed and circulation to become a Tropical Storm- 34-64 mph
once wind speeds reach 75 mph classified as a hurricane.
The center has extremely low pressure which causes a strong pressure gradient to form.
Form when cold air mass of unstable air is over water with temp. greater then 81 oF
Important terms
Eye- the center of sinking air. It is a calm, clear, warm area
eye wall- intense thunderstorms that surround the eye.
Storm surge- unusually high seas, cause of greatest hurricane damage
Saffir-Simpson Scale- rates the intensity of a hurricane
Naming system
List alternate between male and female names, ex. The next two names on the list for 2000 Atlantic
storms are Alberto and Beryl
A storm is named once it reaches tropical storm status.
A name is retired if the hurricane is an exceptional one.
Watches and Warnings
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Hurricane watch- hurricane conditions possible
Hurricane warning- hurricane is expected within 24 hours.
Hurricane Safety
Have an emergency plan and an emergency kit which should include….
Board and tape windows
remove damaged trees
move outdoor items inside.
Weather Forecasts
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Daily forecasts are based on weather maps and computer models
Data is collected by rawinsonde, satellites, and commercial aircraft
Using data collected, forecasts are made at Weather Service Forecast Offices four times a day. May be
issued more frequently during severe weather.
Computer models are produced twice a day.
Satellites and Radar
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Satellites are used more and more to fill in data-poor regions
geostationary satellites are over the same area at all times and keep time with the earth rotation.
Radar- the different colors of radar gives an indication of the amount of rain and severity of the
associated weather.
Station Model
20 different weather observations may be plotted next to each station on a weather map.
This information is expressed in symbols and called a station model.
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The symbols are always located in the same location.
Symbols
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Highlighted portion represents
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Highlighted portion represents
dew point
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Highlighted portion represents
Sea level pressure
% cloud cover
Symbols
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Highlighted portion represents
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Highlighted portion represents
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Highlighted portion represents
temperature
Weather Symbol
wind speed and direction