Tornado
Rapidly whirling, funneled-shaped cloud (called a vortex) that reaches down from a storm cloud to touch Earth’s surface. Since air is invisible, the vortex that we see is water droplets, dust, and debris sucked up from the ground.
Caution: Take shelter in a basement or in the center of a building immediately when tornado warnings are issued for your area. Stay away from windows.
Usually brief, touching the ground approximately 15 minutes or less
Wind speeds may reach 480 km/hr (230 mph)
Counterclockwise in both the Northern and Southern Hemispheres
Stages of Tornado Formation:
Overshooting top
Wall cloud descends below base of cloud and slowly rotates
Funnel cloud descends from wall cloud
Funnel cloud touches ground
Tornado Watch – tornadoes are possibly in your area
Tornado Warning – tornadoes have been seen in the sky or on weather radar
Occur most often in the US
Approx. 800 tornadoes a year
Tornado Alley - Warm humid air mass moves north from Gulf of Mexico and meets a cold dry mass that is moving south from Canada; SD, Iowa, Nebraska, Kansas, Missouri, Oklahoma, TX, NM, and Arkansas
Enhanced Fujita Scale- Measuring intensities of tornadoes based on a scale developed by Dr. Theodore Fujita at the University of Chicago in the 1960s
EF0 Gale 65-85mph
EF1 Weak 86-110 mph
EF2 Strong 111-135 mph
EF3 Severe 136-185mph
EF4 Devastating 186-200 mph
EF5 Incredible over 200 mph
The deadliest tornado on record in the United States was the tri-state tornado outbreak of March 18, 1925. Several tornadoes demolished portions of Missouri, Illinois, and Indiana, killing 747 people and injuring over 2000 more.
Homework Assignment #2
What should you do if you’re caught outside during a lightning storm?
Why do you see lightning before you hear thunder?
What is the difference between a severe thunderstorm watch and a severe thunderstorm warning?
In what direction do tornadoes spin in NJ?
What is the difference between a tornado watch and a tornado warning?
Where is tornado valley?
Tropical Storms and Hurricanes
Tropical storms form over warm ocean waters. They begin as a tropical disturbance which is nothing more than a cluster of big thunderstorms. When this growing storm begins to rotate, it becomes a tropical depression. When wind speeds reach 40 miles per hour it is called a tropical storm.
Hurricanes are tropical storms that have winds of 119 km/hr
Usually occur between June and November in the eastern US
Hurricanes that occur in western US are called typhoons.
Size can be 220-700 km in diameter
Eye – center of a hurricane
Storm Surge - Hurricane pulls up ocean water an average of 1 cm per 1 mb of air pressure drop; Regions along shores and coasts are inundated with water being pushed ahead of the hurricane
Stages of Hurricane Development:
Tropical Disturbance
Mass of thunderstorms begin to organize
Light wind circulation
Tropical Depression
Wind speed 20-34 knots
Central low pressure developing with rotation of thunderstorms
Tropical Storm
35-64 knots
Strong central low pressure
Increasing wind speeds
Forward movement across oceans
Hurricane
64 knots or more
Well developed central low pressure; eye may be visible
Moving to west along with global winds (NE or SE Trades)
Can move up to 50 knots over open ocean
Highest wind speed on the forward traveling side
Saffir Simpson Scale – measures hurricane intensity by comparing wind speed and air pressure
Tropical Storm – 39-73 mph winds
Category 1 – 74-95 mph
Category 2 – 96-110 mph
Category 3 – 111-130 mph
Category 4 – 131-155 mph
Category 5 – 156 mph and up
Naming Hurricanes:
Initial tracking of hurricane was by latitude and longitude
WWII – use of military terms to identify individual hurricanes (Alpha, Bravo, Tango…)
Early 1950s – use of female names
Late 1970s – Male and female names are used; alternate male/female name for Pacific or Atlantic hurricanes
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