Weather: Maps, Symbols, and Basic Concepts

Without a knowledge of weather basics, we must depend on the…professionals. Sometimes the weather is just CRAZY!

Which is heavier? HIGH PRESSURE LOW PRESSURE Contains mostly dry air Contains more moisture Nitrogen Mass = 14 units Hydrogen Mass = 1 unit Oxygen Mass = 16 units ( X 2 = 2 units) Oxygen Mass = 16 units TOTAL MASS = 30 units TOTAL MASS = 18 units So, drier air is nearly twice as “heavy” as air in which the nitrogen and oxygen has been replaced with water molecules. This is why “fair weather” is associated with HIGH PRESSURE and rainy weather is associated with LOW PRESSURE.

High and Low Pressure Areas High pressure causes air to sink; rotates clockwise Usually results in several days of clear sunny skies Air rises; forms clouds; rotates couterclockwise Usually results in rain and storms

Types of Clouds

Air masses are like people… …they take on the characteristics associated with their surroundings.

Tornado Alley

Fronts A front is the boundary separating air masses of different densities Fronts extend both vertically and horizontally in the atmosphere

Fronts: Five Types of Fronts 1. Cold Front: The zone where cold air is replacing warmer air In U.S., cold fronts usually move from northwest to southeast Air gets drier after a cold front moves through

Fronts: Five Types of Fronts 2. Warm Front: The zone where warm air is replacing colder air In U.S., warm fronts usually move from southwest to northeast Air gets more humid after a warm front moves through

Fronts: Five Types of Fronts 3. Stationary Front: When either a cold or warm front stops moving When the front starts moving again it returns to either being a cold or warm front

Fronts: Five Types of Fronts 4. Occluded Front: Formed when a cold front overtakes a warm front This occurrence usually results in storms over an area In U.S., the colder air usually lies to the west

Fronts: Five Types of Fronts 5. Dry Line (Dew Point Front): Boundary separating a dry air mass from a moist air mass This occurrence can result in tornadoes being formed Usually found in western part of U.S.

Isotherms Lines on a weather map that connect places of equal temperature

The Doppler Effect

What does it mean? The Doppler Effect, or Doppler shift, is the apparent change in the frequency of a wave caused by the fact that the source is moving TOWARD or AWAY from the detector

The disadvantage of the Doppler Effect….

How you get busted….

How it works with weather:

Typical Doppler Radar tower….

Sample images… “Hook echo”