Storms Text Book Pages 450 459 What is

Storms Text Book : Pages 450 - 459

What is a storm? A violent disturbance in the atmosphere.

What is a storm? Involves sudden changes in air pressure Cause rapid air movement Conditions that bring one kind of storm in one area often cause other kinds of storms in the same area

Types of severe storms • Thunderstorms • Tornadoes • Snowstorms • Hurricanes

Thunderstorms

Severe Thunderstorms • • Torrential Downpours Strong winds at greater than 58 mph Hail ¾ inch diameter (or larger) Frequent lightning

Severe Thunderstorm Watch • Issued by National Weather Service • This means that conditions are favorable for a thunderstorm • Length is multiple hours.

Severe Thunderstorm Warning • Issued By Local Weather Service • Means a severe storm has been spotted by doppler radar • Usually only an hour

Lightning • A sudden spark or energy discharge, caused when electric discharges jump between parts of a cloud, nearby clouds, or between a cloud and the ground.

Why do we see lightning before we hear thunder? • Because light travels much faster than sound.

Thunderstorm/Lightning Safety • Stay indoors, away from doors and windows. • Avoid objects that conducts electricity, such as metal objects and bodies of water. • Do not seek shelter under the trees. • Do not use phones with cords. Remember: Cars are pretty safe…

Tornadoes Tornado Alley

What is a tornado? v. A tornado is a rapidly whirling, funnel shaped cloud that reaches down from a cloud to touch Earth’s surface.

How are tornadoes formed? v Same system that produces thunderstorms can produce tornadoes. v Late in the day, when earth’s surface is very warm, convection (the flow of heat through a material, causing hot parts to rise and cooler parts to sink) can get very strong. This can lead to a tornado.

Tornado Watch • Conditions are favorable for a tornado to form Tornado Warning • A tornado has formed.

Tornado Happenings 1. When the updraft in a convection cell is really strong, the air rushes in from all sides at high speeds.

Tornado Happenings 2. Air curves into a spin. This lowers the pressure even more. Air rushes in even faster, and the pressure gets even lower, and so on. v Like a skater who pulls her arms in close to her sides. The tornado spins faster and faster.

Tornado Happenings 3. As the tornado gets stronger, a funnel forms that can destroy anything in it’s path. The center of the tornado can reach speeds of 500 kilometers per hour (about 300 miles per hour) or more.

Where Do Tornadoes Happen? v. Tornadoes happen where dry, cold air masses mix with warm, moist air masses. v. More tornadoes occur in the United States than in any other country, especially in the area known as TORNADO ALLEY.

A Famous Tornado Grand Island, Nebraska June 3, 1980

On June 3, 1980, a series of tornadoes devastated the city of Grand Island, Nebraska. Seven tornadoes hit within a three hour period. The storm did massive damage and closed the city down for three days.

What is a snowstorm? v. All year round, most precipitation begins in clouds as snow. v. If the air is colder than 0 degrees all the way to the ground, the precipitation falls as snow.

Snowstorm Safety • Try to find a shelter from the wind. • Cover exposed parts of your body and try to stay dry.

What is a hurricane? • A tropical storm that has winds of about 119 kilometers per hour or higher (200 miles per hour). • Storm usually doesn’t last for more than 7 -10 days. • As it moves inland it continues to move across the land but it begins to weaken

Map Symbols

Intertropical Convergence Zone The ITCZ is an area of low pressure located roughly 5 degrees North and South of the Equator. It is a place where air converges, rises, and condenses (forming clouds). It is the rainiest place on Earth!

So What Does a Hurricane Need in Order to Develop? So a hurricane needs warm water, time to grow, and favorable upper level winds in the troposphere. If the winds are too strong, they will blow the hurricane apart – we call that wind shear!

Naming System • • A list of names from A-W (excluding Q) Alternate from male to female 6 lists, repeated in cycle Big name storms replaced

Hurricane Watch • A hurricane poses a possible threat within the next 36 hours Hurricane Warning • Hurricane conditions expected within 24 hours

The Saffir-Simpson Scale M E M I R O ! ! ! ZE http: //www. nhc. noaa. gov/aboutsshws. php Saffir-Simpson Wind Scale and Animations http: //www. nhc. noaa. gov/surge/ Storm Surge Overview and Animations

Hurricane Safety • Best plan is to evacuate – Towns have voluntary evacuation during a watch, and some switch to mandatory during a warning. • Plan early in advance

IF you choose to stay…. • • Board all windows Prepare Flashlights, avoid candles Stay tuned to radio Stay indoors