Air Masses
Definition
Large body of air having similar temperature
and moisture
Air masses extend several miles up and
cover lots of “ground”
There can be several different air masses
over the US at any given time
Source Region
• Geographic Region where the air mass
originated
Over land, dry
• Continental = _____________
• Maritime = _______________
Over water, wet
• Tropical = Lower
__________________
latitudes, warm
Mid to upper latitudes, cool
• Polar = ____________________
• Arctic = _________________
Upper latitudes, cold
Air Masses Characteristics
• mT = maritime tropical = ___________
Warm and moist
Maritime polar = ___________
Cool and moist
• mP = _____________
Air Mass Characteristics
cT = _________________
Continental tropical = ____________
Dry and warm
Continental polar
Dry and cool
cP = _________________
= ____________
cA = _________________
Continental Arctic = ____________
Dry and Cold
ESRT Page 13
mP
cP
mP
cT
mT
mT
Tools Meteorologists Use
1. Station Models
• How the weather is plotted on a surface
map
• ESRT page 13
Station Models
Cloud Cover
Temperature
68
Visibility
002
Barometric Pressure
Has to be converted
1
2
Present Weather
66
.10
Precipitation past
6 hours
Dew Point
Wind Direction and Wind Speed
ESRT Page 13
Converting the air pressure for the
station model
• If the air pressure is 986.8 mb  drop the
9 and the decimal and put 868 on your
station model
• If the air pressure is 1009.8  drop the 10
and the decimal and put 098 on your
station model
• Examples
957
• 995.7 = _______
239
• 1023.9 = _______
Reading the air pressure from the
station model
• Look at your station model number, if its
greater than 500, add a 9 and put a
decimal between the last 2 numbers
• Look at your station model number, if its
less than 500, add a 10 and put a decimal
between the last 2 numbers
Examples
• 678 = ________
967.8
1000.2
• 002 = ________
2. Surface maps
• Station models are plotted and then analyzed• Usually for isotherms and isobars, high and low
pressure, fronts, precipitation, etc.
• Isotherms: Lines of equal
temperature
_________________________
• Isobars: Lines of equal
______________________
isobars
• = isobars close on a weather map mean the
higher
wind speed is __________
Isobars – connect points of equal
pressure