Weather Patterns and Maps Atmospheric Variables at Work
Weather Forecasting Synoptic Map: Weather Maps that show field qualities such as: 1.)Temperature 2.)Air Pressure 3.)Precipitation 4.)Front Systems 5.)Wind Speeds At a specific time over a large geographic area
Isotherms: represent lines of equal temperature on a weather map- in Fahrenheit or Celsius
Drawing Isotherms
Isobar: represent lines of equal pressure Measured from sea level on a synoptic map Varies from 960mb – 1050mb (normal is 1013.2)
Drawing Isobars
What is the Coriolis Effect? Results from the rotation of the Earth Causes: Wind Ocean Currents And anything traveling on or in them *To be deflected! The path of travel is affected! Coriolis Effect
The Coriolis Effect on Wind Deflection Winds are Deflected due to the rotation of the Earth If Earth were Stationary-Not Quite! Missile and Target Example.
Wind Deflection and Direction Northern Hemisphere: Winds are deflected to the RIGHT (they appear to be deflected left if traveling south) Southern Hemisphere: Winds are deflected to the LEFT Weather in 2013 video
Travel Path and Deflection:
Planetary Wind and Pressure Belts
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Convection around the globe Air rises at equator (Low pressure) and sinks at 30˚ N & S (High Pressure) Air again rises at 60 ˚ N & S in an area of low pressure and sinks at 90˚ N and S (H) Because air flows from highlow pressure, this creates our typical wind patterns called PREVAILING WINDS
Global Perspective: How prevailing winds affect seasonal weather
Coriolis Effect On wind and Pressure Systems High: Clockwise and out(Anticyclone) Lo+66w: Counter-Clockwise and IN (cyclone) Northern Hemisphere
Pressure Systems and Air Flow
Question Checkpoint Using what you just learned, what is the typical direction (called a storm track) that a storm will travel that originates in the central U.S?
Cyclone: a low pressure system “L” on a synoptic map Cyclone: a low pressure system “L” on a synoptic map. This is a zone of convergence at ground level because rising air at the center draws in air L http://www.redlasso.com/ClipPlayer.aspx?id=d93fcb1a-28dd-4f36-afa7-d9669c4cf363
Anticylone: “H” on a synoptic map/center of a high pressure system Anticylone: “H” on a synoptic map/center of a high pressure system. These are areas of Divergence at ground level where sinking air at the center causes winds to blow outward
Air Masses large bodies of air with uniform temperature, pressure and humidity Source Region: Where the air mass comes from maritime Tropical (mT)- warm & humid air continental Tropical (cT)- hot & dry air maritime Polar (mP)- cold & humid air continental Polar (cP)- cold & dry air continental Arctic (cA)- very cold & dry air There are no mA air masses
Air mass origins
Front Systems represents as a boundary between 2 different air masses Fronts are named after the air mass BEHIND them and bring about temperature & other weather changes There are 4 types of fronts: Warm, Cold, Stationary, and Occluded
The Cold Front 1.) They pass very quickly! 2.) Forces warmer air to rise, expand, cool & causes rapid cloud formation. This leads to intense precipitation as the front passes Summer: Cause bad thunderstorms and lightning Winter: Snow storms 4.) Is followed by cooler, drier weather and High Pressure
Cold Front
Cold Front warm cold
The Warm Front 1.)Moves Slowly 2.)Warm air flows in to replace a retreating cold air (warmer conditions follow) 3.)Warm moist air rises over cooler air & cools by expansion, which leads toformation of high wispy clouds which thicken over time. Light to moderate precipitation, but steady as the front approaches 4.)Associated with warm, hazy weather followed by LOWER atmospheric pressure after front passes.
Warm Front
The Occluded Front Occurs when an advancing cold air mass pushes a lighter warm air mass completely above the ground as it overtakes it mixes 1.)Associated with large areas of rainy, unsettled weather 2.)Once it’s passed the conditions are similar to a cold front
Formation of an Occluded Front
Occluded Front
The Stationary Front -Occurs when winds blow in opposite directions along a cold and warm air boundary -little or no movement (a.k.a. stationary) -clear, partly cloudy or light precip. but nothing severe unless there is a lot of moisture in the air
Typical Mid latitude-low storm system Where is it warm and where is it cold?
How we predict weather from fronts
Jet Stream: upper level winds (tropopause/stratosphere that form where cold, polar air meets warmer tropical air. VERY FAST! Aid in jet travel. Are WESTERLY in U.S.
There are two jet streams (high altitude winds moving West East): Polar Jet and Subtropical Jet- They shift position over the year
Where the jet stream is positioned brings changes in weather (ex: storms)