Steve Davis Meteorologist Senior Forecaster National Weather Service.

Steve DavisMeteorologistSenior ForecasterNational Weather Service

Watch/Warning responsibility For 20 counties in southeast and south central Wisconsin.

Watch/Warning responsibility For 20 counties in southeast and south central Wisconsin.

National Weather Service Forecast OfficeMilwaukee/Sullivan, WI

National Weather Service Forecast OfficeMilwaukee/Sullivan, WI

What causes the weather onplanet earth?

The Sun!

The sun heats the equatorial regionmore than the poles. The land and water heat (and cool) at different rates. Then throw in a spinning earth and all this leads to turbulent motions in the atmosphere.

Where was the hottest temperature everrecorded in North America? How hot did it get?

Death Valley, CA1340, July 10, 1913!!Death Valley, CA1340, July 10, 1913!!

How Does The Weather Work?How Does The Weather Work?

Sea surface temperatures measured from satellites. See how the equator iswarmer than the polar regions? What kind of big storms develop when the ocean gets really warm?

The earth rotates on a tilted axisaround the sun. Is the sun closer tothe earth in the winter or the summer?

The sun is about 91.4 million miles away in January and 94.4 million miles away in July!!

Air Masses: large volumes of air having a similartemperature, atmospheric pressure, and moisturecontent. Air masses cover many hundreds or thousands of square miles, and slowly change in accordance with the terrain they are over.

Air Masses: large volumes of air having a similartemperature, atmospheric pressure, and moisturecontent. Air masses cover many hundreds or thousands of square miles, and slowly change in accordance with the terrain they are over.

Cool and Moist

Cool and Moist

Warm and Moist

Warm and Moist

Cold and DryCold and Dry

Frontal BoundaryFrontal Boundary

Where was the coldest temperature ever recorded in North America? What was it?Where was the coldest temperature ever recorded in North America? What was it?

-81.40, Snag, Yukon, Canada -81.40, Snag, Yukon, Canada

The atoms and molecules that makeup the atmosphere, despite their tiny size, actually exert some weight on us. It is about14.7lbs per square inch. Gravity holds the atmosphere down. Think about the pressurein the deep water of a swimming pool.

The atoms and molecules that makeup the atmosphere, despite their tiny size, actually exert some weight on us. It is about14.7lbs per square inch. Gravity holds the atmosphere down. Think about the pressurein the deep water of a swimming pool.

Air pressure is almostalways changing.

This change in pressureis caused by changesin air density, and airdensity is related to temperature! Do you see how the Sun playsa big part in changes to Air Pressure?

Air pressure is almostalways changing.

This change in pressureis caused by changesin air density, and airdensity is related to temperature! Do you see how the Sun playsa big part in changes to Air Pressure?

The uneven heating of the earth creates the different Air Massesaround the globe. The different Air Masses have different densitiesand therefore create areas of High and Low pressure.

The uneven heating of the earth creates the different Air Massesaround the globe. The different Air Masses have different densitiesand therefore create areas of High and Low pressure.

What weather phenomenondo we feel almost everyday that tells us there is High and Low pressure around us?

What weather phenomenondo we feel almost everyday that tells us there is High and Low pressure around us?

Nature is constantly trying to get back into balance.

Can you think of other things that get out of balance in nature?

Nature is constantly trying to get back into balance.

Can you think of other things that get out of balance in nature?

HH LL

Air moves from Air moves from

High Pressure To Low PressureHigh Pressure To Low Pressure

Wait!! Since the earth is rotating, the wind is deflectedto the right of it’s path. This is called the Coriolis Force!Wait!! Since the earth is rotating, the wind is deflectedto the right of it’s path. This is called the Coriolis Force!

Air moves from high to low pressureAir moves from high to low pressure

Clockwise RotationClockwise Rotation Counter Clockwise RotationCounter Clockwise Rotation

- Usually means quiet weather. Sunshine generally occurs with high pressure.

- Usually means quiet weather. Sunshine generally occurs with high pressure.

- Usually means unsettled weather. Clouds and precipitation often accompany low pressuresystems.

- Usually means unsettled weather. Clouds and precipitation often accompany low pressuresystems.

Now that we have High and Low pressure systems pushing air around, it’s time to

introduce Cold / Warm Fronts

Now that we have High and Low pressure systems pushing air around, it’s time to

introduce Cold / Warm Fronts

Cool and Moist

Warm and Moist

A Low pressure systemwill bring air massestogether. The contrast ofdifferent air masses can cause all kinds of weather.

A Low pressure systemwill bring air massestogether. The contrast ofdifferent air masses can cause all kinds of weather.

When cold air overtakes warmair – it is a cold front. When cold air overtakes warmair – it is a cold front.

Air density is very important!

Cold air is more dense than warm air. It is harder for warmair to displace, or push out, coldair.

Air density is very important!

Cold air is more dense than warm air. It is harder for warmair to displace, or push out, coldair.

When warm air overtakes coldair – it is a warm front. When warm air overtakes coldair – it is a warm front.

Question: Which is heavier, dry air or very humid, moist air?

Hold on! Before we talk about rain, snow or clouds, we should

talk about the earth’s Water Cycle.

Hold on! Before we talk about rain, snow or clouds, we should

talk about the earth’s Water Cycle.

What is the Water Cycle?

It is the recycling of water betweenthe earth and the atmosphere.

Water travels from the oceans and the land up into the atmosphere

and eventually falls back to earth as rain, only to repeat the cycle.

What is the Water Cycle?

It is the recycling of water betweenthe earth and the atmosphere.

Water travels from the oceans and the land up into the atmosphere

and eventually falls back to earth as rain, only to repeat the cycle.

Let’s look at a picture!Let’s look at a picture!

Let’s followa water droplet,beginning fromthe ocean.

(You couldstart anywhere)

The water wedrink is as oldas the earth.

The water we drink is the same waterthe dinosaurs drank, washed inand even…well never mind!

Let’s followa water droplet,beginning fromthe ocean.

(You couldstart anywhere)

The water wedrink is as oldas the earth.

The water we drink is the same waterthe dinosaurs drank, washed inand even…well never mind!

High LevelHigh Level

LowLevelLowLevel

MiddleLevelMiddleLevel

The Cloud ChartThe Cloud Chart

Low Level: Low clouds are of mostly composed of water droplets since their bases generally lie below 6,500 feet (2,000 meters). However, when temperatures are cold enough, these clouds may also contain ice particles and snow.

Low Level: Low clouds are of mostly composed of water droplets since their bases generally lie below 6,500 feet (2,000 meters). However, when temperatures are cold enough, these clouds may also contain ice particles and snow.

Fog is a low cloud stuck on the ground!Fog is a low cloud stuck on the ground!

This one is called PyrocumulusThis one is called Pyrocumulus

Middle Level: The bases of mid-level clouds typically appear between 6,500 to 20,000 feet (2,000 to 6,000 meters). Because of their lower altitudes, they are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are cold enough.

Middle Level: The bases of mid-level clouds typically appear between 6,500 to 20,000 feet (2,000 to 6,000 meters). Because of their lower altitudes, they are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are cold enough.

This is Cumulonimbus MammatusThis is Cumulonimbus Mammatus

The Best Of All: CumulonimbusThe Best Of All: Cumulonimbus

This Is How They Look From The Space StationThis Is How They Look From The Space Station

High Level: High-level clouds form above 20,000 feet (6,000 meters) and since the temperatures are so cold at such high elevations, these clouds are primarily composed of ice crystals. High-level clouds are typically thin and white in appearance, but can appear in a magnificent array of colors when the sun is low on the horizon.

High Level: High-level clouds form above 20,000 feet (6,000 meters) and since the temperatures are so cold at such high elevations, these clouds are primarily composed of ice crystals. High-level clouds are typically thin and white in appearance, but can appear in a magnificent array of colors when the sun is low on the horizon.

Let’s Talk About Severe Weather SafetyLet’s Talk About Severe Weather Safety

Lightning Is Dangerous…Only If You Are CarelessLightning Is Dangerous…Only If You Are Careless

If you look at your friend and they look like this, take cover immediately!

If you look at your friend and they look like this, take cover immediately!

It might be too late if they look like this!

LightningLightning

At any given moment, there can be as many as 2,000

thunderstorms occurring acrossthe globe. This translates to

more than 14.5 MILLION storms each year. NASA satellite

research indicated these storms produce lightning flashes about 40 times a second

worldwide.

At any given moment, there can be as many as 2,000

thunderstorms occurring acrossthe globe. This translates to

more than 14.5 MILLION storms each year. NASA satellite

research indicated these storms produce lightning flashes about 40 times a second

worldwide.

How Lightning WorksHow Lightning Works

The thunderstorm creates an imbalance between positive and negativeelectrons. The air is a good insulator…allowing the opposing charges tobuild. When a tall object comes in between the ground and the storm, the charges are “encouraged” to jump toward each other.

The thunderstorm creates an imbalance between positive and negativeelectrons. The air is a good insulator…allowing the opposing charges tobuild. When a tall object comes in between the ground and the storm, the charges are “encouraged” to jump toward each other.

Rule Of ThumbSound travels about 1 mile in 5 seconds.

If you see lightning, you can estimatehow far away it is by counting how long it takes the thunder to reach your ears.

Flash – Bang: The lightning is too close!2 seconds: Less than ½ mile away5 seconds: 1 mile away10 seconds: 2 miles away15 seconds: 3 miles away

Lightning: What To DoLightning: What To Do

If lightning approaches, go indoors. An open sided shelter is not very safe.A car is safer than being exposed outdoors, but not as safe as a building.

Don’t take a bath during a lightning storm! Don’t talk on a corded phone. Your cordless phone is safe.Stay away from windows.

If you are caught outdoors (on a soccer / football / baseball field), get into the lightning crouch!

If lightning approaches, go indoors. An open sided shelter is not very safe.A car is safer than being exposed outdoors, but not as safe as a building.

Don’t take a bath during a lightning storm! Don’t talk on a corded phone. Your cordless phone is safe.Stay away from windows.

If you are caught outdoors (on a soccer / football / baseball field), get into the lightning crouch!

Safety!Safety!

Weather Watches and Warnings From The National Weather Service

Severe Thunderstorm or Tornado WATCHConditions are favorable for the development of severe weather. Be alert (watch) and be ready to take action if a WARNING is issued.

Severe Thunderstorm or Tornado WARNINGSevere weather is imminent or a tornado has been spottedor detected on radar. TAKE COVER IMMEDIATELY!

Weather Watches and Warnings From The National Weather Service

Severe Thunderstorm or Tornado WATCHConditions are favorable for the development of severe weather. Be alert (watch) and be ready to take action if a WARNING is issued.

Severe Thunderstorm or Tornado WARNINGSevere weather is imminent or a tornado has been spottedor detected on radar. TAKE COVER IMMEDIATELY!

Tornado: What To DoTornado: What To DoIf You Are Indoors:If You Are Indoors:

Stay away from windows. Don’t waste time opening them!Stay away from windows. Don’t waste time opening them!

If you have a basement, go there right away. Take a flashlight and a radio and getunder something sturdy, like a table.

If you have a basement, go there right away. Take a flashlight and a radio and getunder something sturdy, like a table.

If you don’thave a basement, hide in a closet or the bathroom.

If you don’thave a basement, hide in a closet or the bathroom.

Tornado: What To DoTornado: What To DoIf You Are Outside:If You Are Outside:

Make every effort to get inside!

If you are in your car, get out and find a ditch to lie in. Crouch low near abuilding. Cover your head!

Make every effort to get inside!

If you are in your car, get out and find a ditch to lie in. Crouch low near abuilding. Cover your head!

How Does Hail Form?How Does Hail Form?

When, where and how big was the largest

hailstone found in the United States?

When, where and how big was the largest

hailstone found in the United States?

FedEx Planes and Thunderstorms

Red sky at night, sailors delight.

Red sky in morning, sailors take warning.

If crows fly low, winds going to blow.

Dark bases by noon, rain will come soon.

Man's preoccupation with weather has been well documented throughout history. Each culture has sought to understand weather through stories that explain how the Sun was created, how and why the wind blows, why we have frost.

Red sky at night, sailors delight.

Red sky in morning, sailors take warning.

If crows fly low, winds going to blow.

Dark bases by noon, rain will come soon.

Man's preoccupation with weather has been well documented throughout history. Each culture has sought to understand weather through stories that explain how the Sun was created, how and why the wind blows, why we have frost.

Is it a way to forecast the weather?

Is it a way to forecast the weather?

Let’s look at the red sky folklore…Let’s look at the red sky folklore…

We’ve come a long way!We’ve come a long way!

You have to like (maybe love) math!You have to take a lot of science classes.You have to have good writing skills. You have to go to college for at least 4 years. Usually more. You will use lots of computers.

You can work on TV. You can work for the National Weather Service.You can work for companies that are affected by weather.

For example – Chocolate CompanyUtility CompaniesAirlines

You have to like (maybe love) math!You have to take a lot of science classes.You have to have good writing skills. You have to go to college for at least 4 years. Usually more. You will use lots of computers.

You can work on TV. You can work for the National Weather Service.You can work for companies that are affected by weather.

For example – Chocolate CompanyUtility CompaniesAirlines

Any questions?Any questions?