Weather Systems Flashcards
What two things are always in motion to distribute heat energy on and around the Earth?
- Ocean Currents
- Global Wind Systems
What explains why the poles are never very warm?
The Sun’s rays do not hit the Earth as directly at the poles as compared to the tropics. Sunlight must be spread over a larger area near the poles.
Air Masses:
- Continental Tropical - cT
- Maritime Tropical - mT
- Continental Polar - cP
- Maritime Polar - mP
- Arctic - A
Continental Air Masses: Maritime Air Masses: Polar Air Masses: Tropical Air Masses: Arctic Air Mass:
Continental - Dry Maritime - Humid Polar - Cool/Cold Tropical - Warm Arctic - Very Cold
Polar Easterlies:
- Direction
- Location by Latitude
- East
- Located between 60 degrees latitude and the pole in both hemispheres.
Prevailing Westerlies:
- Direction
- Location by Latitude
- West
- Located between 30 and 60 degrees latitude in both hemispheres.
- This is the wind system that directs fronts across our country.
Trade Winds:
- Direction
- Location by Latitude
- East
- Located between the equator and 30 degrees latitude in both hemispheres.
Intertropical Convergence Zone (ITCZ)
- The area near the equator where the trade winds converge from 2 different directions.
- Air is forced up and creates an area of low pressure. (Remember – warm air rising!)
- The ITCZ provides the moisture for many of the world’s tropical rainforests.
Doldrums
- Another name for the Intertropical Convergence Zone (ITCZ)
- It is sometimes called the “horse latitudes”
- Around the 30 degrees latitude, sinking air creates a belt of high pressure which causes weak winds.
Polar Jet Stream
- Narrow bands of fast, high altitude westerly winds (which resemble jets of water).
- Polar jet stream (separates polar easterlies from prevailing westerlies).
Subtropical Jet Stream
- Jet streams follow the boundaries between hot and cold and are strongest in the winter.
- Subtropical jet stream (where the trade winds meet the prevailing westerlies.
Cold Front
- Symbol
- Weather
- Cold, dense air displaces warm air and forces it up a steep front.
- Symbolized by blue triangles (icicles!)
- Clouds, showers, and thunderstorms.
Warm Front
- Symbol
- Weather
- Advancing warm air displaces cold air and moves up slowly.
- Symbolized by red semicircles (like lava rocks!)
- Extensive cloudiness and precipitation
Stationary Front
- Symbol
- Weather
- Two air masses meet and neither advances.
- Blue icicles alternate with red semicircles.
- Some clouds and precipitation - can have rain for several days in a row.
Occluded Front
- Symbol
- Weather
- A cold air mass moves so rapidly that it overtakes a warm front and wedges the warm air up.
- Purple Alternating semicircles/icicles.
- Precipitation on both sides of the front.
High Pressure System:
- Air temperature and movement
- Weather type
- Direction of Rotation
- Symbol
- Cold air sinking
- Fair weather
- Rotates clockwise
- Represented as a blue “H”
Low Pressure System:
- Air temperature and movement
- Weather type
- Direction of Rotation
- Symbol
- Warm air rising
- Clouds and precipitation
- Rotates counter-clockwise
- Represented as a red “L”
Thermometer
- Measures temperature
- Measured in degrees Celsius (C°) or Fahrenheit (F°).
- Contain liquids when heated
Barometer
- Measures air pressure
- Measures in millibars or inches of mercury.
- May contain mercury or a vacuum inside a metal chamber that contracts or expands with changes in air pressure.
Anemometer
- Measures wind speed
- Measures in mph or km/h.
- Has cupped arms that rotate as the wind blows.
Hygrometer
- Measures relative humidity
- Percentage of water is holding compared to how much it can hold.
- Uses wet and dry bulb thermometers and determines how fast the water evaporates from the web bulb.
Radiosonde
A radiosonde is a balloon-borne package of weather sensors.
Radar
- Radio Detecting and Ranging
- Works by bouncing radio waves off of large rain drops.
- The waves that bounce off are picked up by a receiver, processed by a computer, and displayed on a screen as a “radar” image.
Doppler Effect
The change in wave frequency that occurs in energy, such as sound or light as that energy moves toward or away from an observer.
Isobars
Lines on a map connecting points having the same atmospheric pressure at a given time or on average over a given period.
Station Model
A record of weather data for a particular site at a particular time.
Digital Forecasting
A digital forecast relies on numerical data. This is the main method used in modern forecasting.
Analog Forecasting
An analog forecast involves comparing current weather patterns to patterns that took place in the past.
Thunderstorms (and types)
- Florida gets the most thunderstorms of U.S. states (tropical area)
Types of Thunderstorms:
- Orographic (Mountain)
- Sea Breeze
- Frontal-Cold
- Frontal-Warm
Air Mass- Orographic (Mountain) Thunderstorm:
- Location
- Why it forms
- When
- Within one air mass over a mountain.
- Warm air rises over a mountain, forming storm clouds!
- Mid- afternoon
Air Mass- Sea Breeze Thunderstorm:
- Location
- Why it forms
- When
- Coastal Areas, especially tropical and subtropical areas.
- Temperature differences between land and sea create convection cells and updrafts.
- Summer
Frontal- Cold Thunderstorm:
- Location
- Why it forms
- When
- At the leading edge of a cold front.
- Cold air pushes warm air rapidly up at the steep cold-front boundary.
- Any time a cold front moves in!
Frontal- Warm Thunderstorm:
- Location
- Why it forms
- When
- At the leading edge of a warm front.
- Warm air mass slides up over a cold air mass creating clouds.
- If a warm front moves in with enough moisture and instability.
Lightning:
- Formation
- Stepped leader
- Return Stroke
- Temperature
- It is a giant spark of electricity in thunderstorms
(It is an electric current - a discharge of atmospheric electrical energy). - Lightning bolts occur when negative charges (electrons) in the bottom of storm clouds want to link with the positive charges on the ground.
- A “stepped leader” is the flow of negative charge (electrons) which rushes to the ground and attracts with the positive charges.
- The “return stroke” is when a strong electric current carries the positive charge into the clouds. It creates the electric flash we see as lightning.
- About 50,000 degrees Fahrenheit
Downburst
- A downburst is a violent downdraft concentrated in a local area.
Two types of downbursts…
- Macrobursts (more than 2 ½ miles wide/ 130 mph winds/ 5-20 min)
- Microbursts (2 ½ miles wide/ 168 mph. winds/ less than 10 min.)
- Microbursts are deadlier because they are hard to detect and plan for.
Hail
Precipitation in the form of balls or lumps of ice
Causes of Floods:
- Wind currents in the upper atmosphere are weak so that weather system move slowly.
- Abundant moisture over a limited area
- Rain falls faster than the ground can absorb it.
- Groundwater levels are high and water can not infiltrate the ground.
Formation of Tornadoes
- A change in wind direction and speed creates a horizontal rotation
- Strong updrafts tilt the rotating air to a vertical position
- A tornado forms within the rotating winds.
Tornado Alley (formation):
- The area in the U.S. that get’s the most tornadoes
- A cP air mass from Canada meets a mT air mass from the Gulf of Mexico
- There is not a lot of mountains to break up the meeting of cP and mT air masses.
- Most tornadoes occur in May.
The (Enhanced) Fujita Scale
- Path
- Wind Speed
- Duration
- Percentage of all tornadoes
- This scale is used to classify a tornado AFTER the tornado has passed by looking at the damage and effects of the tornado.
- EF0 to EF1 – 3 miles; 60 - 115mph; 1 - 10 min; 80% of all tornadoes
- EF2 to EF3 – 15+ miles; 110-165 mph; 20+ min; 19% of all tornadoes
- EF4 to EF5 – 50+ miles; 200+ mph; 1+ hr; 1% of all tornadoes
Tornado Safety:
- Move to a pre-designated shelter – to a basement if possible.
- Move to an interior room/hall, lowest floor, under sturdy furniture. (A bath tub is safest!)
- Stay away from windows.
- Get out of vehicles!
- Don’t try to outrun a tornado.
- If outside, lie flat in a ditch or depression
- Abandon a mobile home for a shelter. Usually occur in May.
Tropical Cyclone
- Hurricanes
- Large, rotating, low pressure storms
- Pressure drops and wind speeds reach 74mph.
- 74 mph. Or greater
Hurricanes and Cyclones :
- Turning Direction
- Pressure system
- Air pressure
- Surface wind speeds
- Spins counter-clockwise
- Low pressure system
- Air pressure on the eyewall decreases as hurricanes strengthen.
- Surface wind speeds increase as hurricanes strengthen.
Conditions for Cyclone Formation:
- Direction
- Which wind system guides them in the Atlantic?
- Lots of warm, ocean water
- Disturbance to lift the air
- Moves west
- The prevailing westerlies guides hurricanes in the Atlantic.
Tropical Disturbance / Depression
- Definition
- Sustained winds
Disturbance - A weak, low-pressure system – group of thunderstorms collect.
- Less than 23 mph.
Depression - A disturbance begins to rotate around the center of low pressure.
- 23 to 39 mph.
Tropical Storm
- A depression is labeled a storm when the wind speeds reach 39 mph.
- 39 to 73 mph.
Scale used for Hurricane Classification:
- Four characteristics
- Listed/Rated
- Windspeeds for the lowest / highest categories
- Saffir-Simpson Hurricane Scale
- Wind speed (how high?)
- Air pressure (how low)
- Potential for damage (how much?!)
- Storm surge (flooding)
- 1 to 5 (5 is highest)
- Category 1 is 74mph.
- Category 5 is 155mph.
Storm Surge
- Strongest winds are at…
- Effects of storm surge
- Agency for tracking…
When hurricane force winds drive a mound of ocean water towards coastal areas.
- Strongest winds are at the eye wall
- Floods
- The National Hurricane Center in Miami, FL, at the FIU Campus (NOAA)
Smog
- Causes
- Chemicals
A yellow-brown photochemical haze.
- Caused by the action of solar radiation on an atmosphere polluted with hydrocarbons and nitrogen oxides, mostly from car exhaust.
- Ozone Chemicals
Particulate Matter
- Ash, dust, pollen, and Asbestso fibers.
- These are forms of SOLID pollutants in the air.
Greenhouse Effect
It is the heat from the sun being trapped by the gases in our atmosphere.
- Allows for life in the atmosphere by keeping the Earth warm.
Ozone Depletion
- Ozone blocks the UV rays from the sun!
- It is caused by Chlorofluorocarbons (CFCs), which reacts with Ozone to break apart the O3 (Ozone).
- CFCs are used as refrigerants, coolants, propellants in aerosol cans, and Styrofoam.
CFC Regulations:
CFCs were banned in the late 1980s in industrialized nations.
- “Under the 1987 Montreal Protocol developing countries committed themselves to halving consumption and production of the CFCs by 2005 and to achieving an 85% cut by 2007.”
Acid Rain
- Formation
- Source
- Effects
- It is precipitation with a pH level of less than 5. (Normal is from 5 to 5.6)
- Acid precipitation forms when sulfur dioxide and nitrogen oxides combine with atmospheric moisture to create sulfuric acid and nitric acid.
- Coal-burning power plants (mostly in midwestern USA)
- Damage to aquatic ecosystems and vegetation. Affects freshwater, plants, and soil
