Download File - MXMS Science

Earth Processes
MXMS 7th Grade Science
Weather
Air Mass Properties
• Pressure
L
LOW
“Low & Loose – Counterclockwise”
vs.
H
HIGH
“High & Tight – Clockwise”
Pressure
• Isobars-shown on weather maps as lines
of equal pressure (998 mb line, 996 mb
line, 994 mb line, etc.)
Air Mass Properties
• Temperature
COLD
vs.
WARM
Air Mass Properties
• Wind Speed & Direction
Air Mass Properties
• Observable Conditions
Air Mass Types
• Polar air (P)
– 60°N & northward
– Cold air
• Tropical air (T)
– 25°N & southward to equator
– Warm air
Air Mass Types
• Marine air (m)
– Located over the ocean
– Moist air
• Continental air (c)
– Located over a land mass
– Dry air
Air Mass Types
• m + P = mP = Maritime (Marine) Polar
– Moist & Cold
• m + T = mT = Maritime (Marine) Tropical
– Moist & Warm
Air Mass Types
• c + T = cT = Continental Tropical
– Dry & Warm
• c+ P = cP = Continental Polar
– Dry & Cold
Air Mass Types
cA = Continental Arctic (within Arctic Circle)
•
•
•
Very cold (frigid) air temperatures
Very dry
Found mainly during winter
Air Mass Types
Courtesy of Stormstalker
Fronts
• Boundary zone where two different “air
masses” meet
• Noticeable change in air mass properties
(pressure, temperature, wind, etc.)
• Zone width can range from a few miles to
several dozen miles
Fronts
• Cold Front
– Pressure falls ahead of front
– Temperature falls behind front
– Dew point falls behind front
– Noticeable wind direction shift
– Frequently includes storms (rain, lightning,
etc.) ahead of front
Fronts
• Cold Front
Fronts
• Warm Front
– Pressure rises, then falls behind front
– Temperature rises behind front
– Dew point rises behind front
– Slight wind direction shift
– Light to moderate precipitation ahead of front
Fronts
• Warm Front
Fronts
• Stationary Front
– No motion or very little motion
– Noticeable differences across front
(temperature, wind, etc.)
– Cloudy along front
– Usually an extended period of precipitation
along front
Fronts
• Stationary Front
Fronts
• Occluded Front
– Pressure falls ahead of front
– Temperature…
• Falls behind front (cold-type)
• Rises behind front (warm-type)
– Dew point…
• Slight fall behind front (cold-type)
• Slight rise behind front (warm-type)
– Noticeable wind direction shift
– Light to heavy precipitation ahead of & behind
front
Fronts
• Occluded Front
Fronts
Identify which front type is most likely to have passed
between 2 PM and 3 PM, based on the data given in
the table.
Weather Obs at KRDU (7-3-2010)
Time
Temp.
Pressure
Dew Pt.
Wind Dir.
2 PM
84°F
1000 mb
69°F
SW
3 PM
69°F
1005 mb
64°F
NW