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

• Continental = _____________• Maritime = _______________• Tropical = __________________• Polar = ____________________• Arctic = _________________

Over land, dryOver water, wet

Lower latitudes, warmMid to upper latitudes, cool

Upper latitudes, cold

Air Masses Characteristics• mT = maritime tropical = ___________

• mP = _____________ = ___________

Warm and moist

Maritime polar Cool and moist

Air Mass Characteristics

cT = _________________ = ____________

cP = _________________ = ____________

cA = _________________ = ____________

Continental tropical Dry and warm

Continental polar Dry and cool

Continental Arctic Dry and Cold

ESRT Page 13

mP cP

mP

mT

cTmT

Tools Meteorologists Use

1. Station Models

• How the weather is plotted on a surface map

• ESRT page 13

Station Models

68

66

12

002

.10

Temperature

Dew Point

Visibility

Present Weather

Cloud Cover

Barometric PressureHas to be converted

Precipitation past 6 hours

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

• 995.7 = _______

• 1023.9 = _______

957

239

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 = ________

• 002 = ________

967.8

1000.2

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

_________________________• Isobars: Lines of equal

______________________• = isobars close on a weather map mean the

wind speed is __________(higher pressure gradient)

temperature

isobars

higher

Isobars – connect points of equal pressure