Chapter 29 Air Masses and Fronts BFRB Pages

Air Masses Large areas (blobs) of the troposphere that have approximately the same weather, temperatures and humidity Air Mass Types - Named for where they develop over and come FROM Weather changes occur with changes in air masses

TYPES of Air Masses maritime Tropical (mT)- warm & humid airmaritime Tropical (mT)- warm & humid air continental Tropical (cT)- hot (warm) & dry aircontinental Tropical (cT)- hot (warm) & dry air maritime Polar (mP)- cold & humid airmaritime Polar (mP)- cold & humid air continental Polar (cP)- cold & dry aircontinental Polar (cP)- cold & dry air continental Arctic (cA)- very cold & dry aircontinental Arctic (cA)- very cold & dry air THESE ARE ALL LISTED IN THE ESRT’s ON PAGE 13 ON THE BOTTOM!THESE ARE ALL LISTED IN THE ESRT’s ON PAGE 13 ON THE BOTTOM! There are no mA air masses – WHY???There are no mA air masses – WHY???

Fronts boundary between two air massesboundary between two air masses bring changes in the weather (from west to east)bring changes in the weather (from west to east) VIF!!!! - Fronts are named for the air that is behind themVIF!!!! - Fronts are named for the air that is behind them The 4 types of fronts and their symbols are listed in the ESRT’s on Page 13 on the bottomThe 4 types of fronts and their symbols are listed in the ESRT’s on Page 13 on the bottom

COLD AIR MASS WARM AIR MASS

Air Mass Army Analogy Think of air masses as an army front (the army is BEHIND the frontline)Think of air masses as an army front (the army is BEHIND the frontline) At the Front there is FIGHTING and lots of VIOLENCE (stormy weather)At the Front there is FIGHTING and lots of VIOLENCE (stormy weather) Behind the front (inside the air mass) the general sits on his duff and watches the goings-on while enjoying the nice weather!Behind the front (inside the air mass) the general sits on his duff and watches the goings-on while enjoying the nice weather!

FIGHTING - STORMS NICE WEATHER

Cold Front Cold dense air pushes warm less dense air up and out of the wayCold dense air pushes warm less dense air up and out of the way Cold fronts usually move very quickly and bring short periods of showers/thunderstormsCold fronts usually move very quickly and bring short periods of showers/thunderstorms Lower temperatures are behind the frontLower temperatures are behind the front SYMBOL – the direction of the “arrows” points towards the direction the front is MOVINGSYMBOL – the direction of the “arrows” points towards the direction the front is MOVING

Cross Sectional View Overhead View on Map

Cross Section View – Why does the cold air mass stay near the ground and lift the warm air mass up?

Warm Front Warm air moves up and over the cold front as it slowly displaces the cold airWarm air moves up and over the cold front as it slowly displaces the cold air Warm fronts move slowly, and bring many days of steady precipitationWarm fronts move slowly, and bring many days of steady precipitation Higher temperatures are behind the frontHigher temperatures are behind the front SYMBOL – direction of “semi-circles” is the direction the front is movingSYMBOL – direction of “semi-circles” is the direction the front is moving

Cross Sectional View Overhead View on Map

Cross Section View – Why does the warm air mass slowly override the cold mass cause long periods of rain?

Stationary Front The air from the warm front and cold front meet, but do not moveThe air from the warm front and cold front meet, but do not move These fronts have similar weather conditions as warm frontsThese fronts have similar weather conditions as warm fronts SYMBOL – warm and cold fronts are moving in opposite directions, thus making a stationary conditionSYMBOL – warm and cold fronts are moving in opposite directions, thus making a stationary condition

Cross Section View – look at the spread out, horizontal stratus clouds

Occluded Front Cold air catches up to and overtakes a warm front (often squeezing it between another cold front)Cold air catches up to and overtakes a warm front (often squeezing it between another cold front) May produce precipitation for many daysMay produce precipitation for many days SYMBOL – cold and warm fronts “mix” hence the purple color - the “bumps” are also on the SAME SIDE OF THE LINE (sometimes just a mix of red & blue symbols)SYMBOL – cold and warm fronts “mix” hence the purple color - the “bumps” are also on the SAME SIDE OF THE LINE (sometimes just a mix of red & blue symbols)

Overhead View On Map Cross Sectional View

This is the jet stream. It moves from West to East in the US and dictates what our weather will be. What kind of air is being brought to NY right now?

LAKE EFFECT SNOW Great Lakes Region – NYSGreat Lakes Region – NYS cP air mass passes over the warmer & more humid lake air causing it to rise rapidly and form into cumulonimbus cloudscP air mass passes over the warmer & more humid lake air causing it to rise rapidly and form into cumulonimbus clouds HEAVY snowfall occurs rapidlyHEAVY snowfall occurs rapidly Western NYS is known as the SNOW CAPITAL of the USA!Western NYS is known as the SNOW CAPITAL of the USA!