tornadoes and hurricanes weather: severe -...
TRANSCRIPT
Severe
Weather:
Tornadoes
and
Hurricanes
Tornadoes
Grab Toto!!
TORNADOES
∙Are a low pressure storm that usually forms over land
∙in an average year, 800 tornadoes are reported in the U.S.
∙a tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground… the rotating column of air is called the vortex
∙the vortex is only visible when debris and dirt gets carried up with the winds THE HOOK
Where do they come from?
Tornadoes come from the energy released in a thunderstorm.
What makes them dangerous (as compared to hurricanes) is that their energy is concentrated in a small area, only a hundred yards across
Most common east of the Rocky Mountains and west of the Appalachian Mountains.
They occur mostly during the spring and summer (April-June) They usually occur during the late afternoon and early evening.
Usually happen along cold fronts
When & Where do they occur?
How long is a tornado usually on the ground?
Can range from a few seconds to several hours ... 5 minutes is average
How fast do tornadoes move?
Movement can range from virtually stationary to more than 60 miles per hour ... Average is 10-20 miles per hour.
Watch—means conditions are favorable for tornado to develop
Warning—means that tornado has been spotted
THE WIND!
• Take a look at this piece of
wood that was driven into the
palm tree.
LOOK
AT
THESE
MEASURING DESTRUCTION
The Enhanced Fujita Scale rates tornadoes based on the amount and type of wind damage produced.
EF-0. Light damage
Wind 65 to 85 mph. Causes some damage to siding and shingles
EF-1. Moderate damageWind 86 to 110 mph. Considerable roof damage.
Winds can uproot trees and overturn single-wide mobile homes. Flagpoles bend.
EF-2. Considerable damageWind 111 to 135 mph. Most single-wide mobile
homes destroyed. Permanent homes can shift off foundation. Flagpoles collapse. Softwood trees
debarked.
EF-3. Severe damageWind 136 to 165 mph. Hardwood trees debarked. All
but small portions of houses destroyed.
EF-4. Devastating damageWind 166 to 200 mph. Complete destruction of well-
built residences and large sections of school buildings
EF-5. Incredible damage.Wind +200 mph. Significant structural deformation of mid- and high
rise buildings.
Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 yards
May 25th, 2008Catastrophic damage was reported in Parkersburg as much of the town was
destroyed, with reports of flattened houses and debarked trees. Six people were killed in Parkersburg and at least two fatalities were reported where a housing development was
destroyed. At least 70 people were injured
At 9:45 p.m. on May 4, 2007, Greensburg was hit by an EF5 tornado. The tornado was estimated to be 1.7 miles (2.7 km) in width and traveled for nearly 22 miles (35 km). Ninety-five
percent of the city was confirmed to be destroyed, with the other five percent being severely damaged. The National Weather Service estimated winds of the tornado to reach 205 mph
(330 km/h). This was the first tornado to ever be rated EF5 since the update of the Fujita scale.
Hurricanes
HURRICANES
∙Low pressure systems that form over warm, tropical waters near the equator
∙Most form between 5 and 20 degrees north latitude — they almost never form in the South Atlantic
Different names are given to hurricanes depending on where they form
1. Atlantic—we call them hurricanes
2. Pacific—they are called typhoons
3. Indian Ocean—they are called cyclones
•Mature hurricanes average about 350 miles across
•They have the lowest barometric pressures ever recorded with any storm (905 millibars is lowest recorded)
•These huge air pressure differences is what creates the rapid, inward spiraling of winds
When winds have developed speeds
from 39 to 73 miles per hour, it is called a
tropical storm (storms are given names when they
begin to have winds of this speed).
HURRICANE
DEVELOPMENT
2005 Katrina Developing
The storm becomes a hurricane when it reaches
a wind speed of over 74 mph
Hurricane Formation
∙When a season is
very active, Greek
letters are used to name
tropical storms after
the letters of the
alphabet had been
used.
THE END OF A HURRICANE
When a hurricane travels over land or cold water, its energy source (warm water) is gone and the storm weakens, quickly dying.
HURRICANE SEASON
•Occurs from June through November
•Most hurricanes form during the late summer months because the ocean is still retaining heat from the warmer earlier months
MEASURING DESTRUCTION
∙We use the Saffir-Simpson scale to rank hurricane intensitiesSaffir-Simpson Scale
CATEGORY WIND SPEED STORM SURGE
DAMAGE
1 74-95 mph 4-5 feet Minimal
2 96-110 mph 6-8 feet Moderate
3 111-130 mph 9-12 feet Extensive
4 131-155 mph 13-18 Extreme
5 Greater than 155
Greater than 18
Catastrophic
Video Clip on Wind Tunnel
STORM SURGE ACCOUNTS FOR 90% OFHURRICANE-CAUSED DEATHS
Category 5 Status includes:
Hurricane Wilma (October 2005) -- Gulf of Mexico, Yucatan Peninsula, Mexico, Cuba, and Southern Florida
Hurricane Rita (September 2005) -- hit Texas, Louisiana
Hurricane Katrina (August 2005) -- hit southern Louisiana, Mississippi and Alabama
Hurricane Isabel (September 2003) -- hit North Carolina, Maryland, Delaware, Virginia, and Washington, D.C.
Hurricane Andrew (August 1992)-- hit southeastern Florida and southeastern Louisiana
Hurricane Camille (August 1969) -- hit Mississippi, SE Louisiana, and Virginia
AMAZING EARTH SCIENCE FACTS
_______ pressure systems move clockwise and outward
_______ pressure systems (ex. hurricanes) move counterclockwise and inward.
Low
High