Weather around the U.S

Today’s focus: AIR MASSES

AIR MASSES - Characteristics  A large amount of air that has the same: 1.Temperature 2.Moisture  A large amount of air that has the same: 1.Temperature 2.Moisture

Characteristic #1 - Moisture Two types of air masses form over land or the water.  Land - Called “Continental” (DRY)  Water - Called “Maritime” (WET) Two types of air masses form over land or the water.  Land - Called “Continental” (DRY)  Water - Called “Maritime” (WET)

Characteristic #2 - Temperature  The air masses that are in the NORTH are COLD.  The air masses that are in the SOUTH are WARM. 1.COLD = POLAR 2.WARM = TROPICAL  The air masses that are in the NORTH are COLD.  The air masses that are in the SOUTH are WARM. 1.COLD = POLAR 2.WARM = TROPICAL

Putting it together:  There are 4 types of air masses in the United States. They are: 1.Maritime-tropical (mT) 2.Maritime-Polar (mP) 3.Continental – Tropical (cT) 4.Continental – Polar (cP)  There are 4 types of air masses in the United States. They are: 1.Maritime-tropical (mT) 2.Maritime-Polar (mP) 3.Continental – Tropical (cT) 4.Continental – Polar (cP)

NORTH WEST COAST  Cold  Snow and Ice  Cold  Snow and Ice Maritime Polar (mP)

SOUTH WEST COAST  Warm  Rainy  Warm  Rainy Maritime Tropical mT

MIDWEST  Cold  Dry  Cold  Dry Continental Polar cP

MIDSOUTH  Warm  Dry  Warm  Dry Continental Tropical (cT)

SOUTH EAST COAST  Warm  Rainy  Warm  Rainy Maritime Tropical (mT)

NORTH EAST COAST  Cold  Snow and ice  Cold  Snow and ice Maritime Polar (mP)

What impacts the U.S the Most?

It is….  Maritime Tropical  Continental Polar  Maritime Tropical  Continental Polar

Review time! 1.What is a mass of air called if it formed over land? Water? 2.Where are all the “ polar ” air masses in the United States? 3.Where are all the “ tropical ” air masses in the United States? 4.What are the two characteristics of the following air masses: - Continental Polar, Continental Tropical, Maritime Tropical and Maritime Polar 1.What is a mass of air called if it formed over land? Water? 2.Where are all the “ polar ” air masses in the United States? 3.Where are all the “ tropical ” air masses in the United States? 4.What are the two characteristics of the following air masses: - Continental Polar, Continental Tropical, Maritime Tropical and Maritime Polar

Review time! 1.What is a mass of air called if it formed over land? Water? 2.Where are all the “ polar ” air masses in the United States? 3.Where are all the “ tropical ” air masses in the United States? 4.What are the two characteristics of the following air masses: - Continental Polar, Continental Tropical, Maritime Tropical and Maritime Polar 1.What is a mass of air called if it formed over land? Water? 2.Where are all the “ polar ” air masses in the United States? 3.Where are all the “ tropical ” air masses in the United States? 4.What are the two characteristics of the following air masses: - Continental Polar, Continental Tropical, Maritime Tropical and Maritime Polar Continental, Maritime In the North In the South cP – Dry and cold, cT – Dry and warm, mT – Wet and warm, mP – Wet and cold

What happens when they hit each other???

Types of “Fronts” A front is when two air masses meet. There are cold fronts, warm fronts and occluded fronts

Keep in mind that….  Cold fronts move faster than warm fronts

Warm Front  Warm air rises over the cooler air  It rises steadily. Produces…clouds!  Replaces the cold air with warm air  Warm air rises over the cooler air  It rises steadily. Produces…clouds!  Replaces the cold air with warm air

Weather from a warm front:  Warm air  Steady rain for a few days  Warm air  Steady rain for a few days

Cold Front  Cold air pushes warm air up…fast!!!  This creates rain and storms  You also get colder air!  Cold air pushes warm air up…fast!!!  This creates rain and storms  You also get colder air!

Weather from a cold front:  Cold air  Storms that do not last as long as the rains from a warm front  Cold air  Storms that do not last as long as the rains from a warm front

Occluded front  When a cold front over takes a warm front You get: Rain! (Could be light rain or heavy rain)

Stationary Front  Warm and Cold air do not move  Gentle rain is the result  Warm and Cold air do not move  Gentle rain is the result

Symbols on a weather Map:

Animation old_occlusion.gif

Let’s Recap Type of FrontWeatherOther info Warm Front Cold Front Stationary Front Occluded front

Type of Front WeatherOther info Warm Front Steady, gentle rain Weather warms up Air gets pushed up slowly. Cold FrontStorms, lots of rain in a short amount of time. Weather cools down Air gets pushed up quickly. Stationary Front Long periods of steady rain Both fronts do not move Occluded front Light or Heavy rainA cold front catches a warm front

Mid-Latitude Cyclones  Large centers of low pressure that generally travel from west to east and cause stormy weather

STAGE 1  Formation of a front

STAGE 2  The front takes on a wave shape  One side a cold front  One side a warm front  The front takes on a wave shape  One side a cold front  One side a warm front

STAGE 3  The fronts start rotating counterclockwise around a low pressure system

STAGE 4  The cold front catches the warm front  Produces an occluded front  The cold front catches the warm front  Produces an occluded front

STAGE 5  The cyclone weakens after the occluded front forms

A B C D

Weather Recap…  A  After a cold front came through. So the weather is COLD.  B  After a warm front came through. So the weather is WARM.  C  As a cold front is coming through. So the weather is STORMY.  D  As a warm front is coming through. So the weather is STEADY RAIN.  A  After a cold front came through. So the weather is COLD.  B  After a warm front came through. So the weather is WARM.  C  As a cold front is coming through. So the weather is STORMY.  D  As a warm front is coming through. So the weather is STEADY RAIN.

Putting it all together

Thunderstorms  Occur when there is upward movement of warm moist air into the atmosphere  Gusty winds, heavy precipitation  Stages: Cumulus Stage-warm air moves up and builds cumulus cloud “wall”  Mature Stage-thunderstorm occurs but still has warm air moving up into atmosphere to feed the thunderstorm  Dissipating stage-colder air descends along with remaining precipitation  YouTube - Thunderstorm Time Lapse YouTube - Thunderstorm Time Lapse  Occur when there is upward movement of warm moist air into the atmosphere  Gusty winds, heavy precipitation  Stages: Cumulus Stage-warm air moves up and builds cumulus cloud “wall”  Mature Stage-thunderstorm occurs but still has warm air moving up into atmosphere to feed the thunderstorm  Dissipating stage-colder air descends along with remaining precipitation  YouTube - Thunderstorm Time Lapse YouTube - Thunderstorm Time Lapse

TORNADO  A rotating column of air  Very unpredictable  Winds can exceed 500 mph inside tornado  Mostly occur in spring  YouTube - tornado destroy a house? YouTube - tornado destroy a house?  YouTube - Tornado YouTube - Tornado  A rotating column of air  Very unpredictable  Winds can exceed 500 mph inside tornado  Mostly occur in spring  YouTube - tornado destroy a house? YouTube - tornado destroy a house?  YouTube - Tornado YouTube - Tornado

Tornado  Stages-Thunderstorms  Mesocyclone-horizontal winds roll and are forced upward by a strong updraft within the thunderstorm  Tornado/vortex-the rotating column of air in the clouds connects with the mesocyclone  Measured by the Fujita Scale (F0-F5)-based on damage produced by the storm  ml ml  Stages-Thunderstorms  Mesocyclone-horizontal winds roll and are forced upward by a strong updraft within the thunderstorm  Tornado/vortex-the rotating column of air in the clouds connects with the mesocyclone  Measured by the Fujita Scale (F0-F5)-based on damage produced by the storm  ml ml

HURRICANE  Form over ocean near the equator – Need warm, moist air to form  Winds spin counter- clockwise (Low pressure)  Lowest pressure is at the eye  The strongest storms on earth  YouTube - How a hurricane is born - The Science Of Superstorms - BBC YouTube - How a hurricane is born - The Science Of Superstorms - BBC

Hurricane  Stages-Tropical Disturbance  Tropical Depression-thunderstorms over oceans  Tropical Storm-sustains winds of about 40-75mph  Hurricane  Measured by the Saffir Simpson Scale (1-5)-based on wind speed  Stages-Tropical Disturbance  Tropical Depression-thunderstorms over oceans  Tropical Storm-sustains winds of about 40-75mph  Hurricane  Measured by the Saffir Simpson Scale (1-5)-based on wind speed