Weather Flashcards
One atmosphere is how many PSI?
14.7 PSI
Wind Isobars
Contour lines on a weather chart representing equal pressures.
Pressure Gradient
Is indicated by the spacing between isobars. Strength of wind is dependent on the Pressure Gradient. The closer the “contour lines” on a weather map the steeper the pressure gradient.
Wind Velocity
Varies based directly with the pressure gradient.
Direction
The direction from which the wind flows.
Fetch
The distance over which the wind contacts the water (in the direction the wind is blowing.
Swells
After being formed in the area of fetch, SWELLS can travel thousands of miles before breaking in shallow waters.
Breakers
Formed by the distant wind / fetch.
Width of the fetch area.
Wind duration.
Water depth.
Wave Trough
Lowest part of the wave
Wave Crest
Highest part of the wave
Wave Dimensions
Height = Trough to Crest
Length = Trough to Trough distance
Period = Time in seconds between Crests
Northern Hemisphere
Wind flows counter clockwise around a LOW and clockwise around a HIGH.
Buy Ballots Law
In the Northern Hemisphere if you stand with your back to the wind, the low pressure area will be on your left side.
Backing Wind Shift
COUNTER clockwise shift of wind.
Example: SE Wind shift to a NE Wind
Pressure system will pass to your south
Veering Wind Shift
CLOCKWISE shift of wind.
Example: SW wind shift clockwise to West Wind
Pressure system will pass to north
Sea Breeze
High pressure cool air blowing off the water into warm air heated by the land.
Warm Front
Occurs when a warm air mass advances and overtakes colder air mass.
-Less dense and slow moving
-Several days of grey rainy weather generally follow
Cold Front
Occurs when a cool air mass advances and overtakes a warm air mass.
-Cold air is denser and buries under warm air, lifting it up.
-Cold fronts are faster and more intense than warm fronts.
Note: Cold fronts are frequently associated with:
-A line of clouds
-Sharp changes in wind direction
-Squalls
Occluded Front
Formed when a cold front overtakes a warm or quasi-stationary front, pushing the warmer air up over the two cooler air masses.
Types of Clouds
Cirrus, Cumulus, Stratus, Altocumulus, Cirrocumulus, Altostratus.
Northern Hemisphere Storms
Dangerous RIGHT HAND semi-circle
Navigable LEFT HAND semi-circle
Advection Fog
-Warm moist air moves over cold water.
-Known as coastal fog.
-Can last for days because the temp of seawater is fairly constant.
Radiation Fog
Produced at night over the land when radiation cooling reduces air temp to or below the dew point.
Also called ground fog.
Steam Fog
Cooler air lies over warmer air
Also called sea smoke
Frontal Fog
Rain falls from warm air, down through cold air. Additional water vapor causes air to reach dew point.
Also called rain fog
Frost
USCG describes frost as a light feathery deposit of ice caused by the sublimation of water vapor directly into crystalized form, on objects whose temperatures are below freezing.
