Ch 13 The Nature of Storms

Conditions for a Thunderstorm 1. Abundance of moisture in lower atmosphere (release of latent heat) 2. Air must rise (Cools to dew pt creating condensation) 3. The portion of atmosphere that clouds go through must be unstable.

Limits on growth Air will rise until it meets a layer of stable air that it can not over come. This caps most thunderstorms at around 18 km.

Two groups of thunderstorms A) Air mass: Unequal heating 1. Mountain (orographic) 2. Sea-breeze (tropic regions) B) Frontal: Advancing fronts 1. Cold fronts (majority) 2. Warm fronts (rarely)

There are 3 stages of development 1. Cumulus Stage: Updrafts transport moisture to upper levels. 2. Mature Stage: Strong updrafts and downdrafts 3. Dissipation Stage: The storm loses energy because there are only downdrafts

13.2 Severe Weather Supercells: Extremely powerful storms characterized by intense, rotating updrafts.

Lightning: Large discharge (100 million V) of static electricity within the atmosphere that heats up the surrounding air to 30,000 degrees C (5 times hotter than surface of the Sun)

Lightning: in the US alone causes an average yearly death rate of 93 and 300 injuries

Downbursts: Violent downdrafts of air (confused with tornadoes) that can reach up to 160 km/h winds.

Hail: Ice precipitation that forms from updrafts transporting the water to upper layers where it freezes, then falls back down collecting more moisture. If the up drafts are strong enough, then the water covered ice chunks go back up, freeze the new water and fall back down. The more this cycle repeats itself, the larger the hail gets.

Floods: The main cause of thunderstorm related deaths each year.

Tornadoes: violent, whirling column of air that comes in contact with the ground. -The fastest winds on Earth. -An average of 80 deaths and 1500 injuries occur each year in the US. *Is there anyone who can help?

Ways to reduce risk: -Obtain a weather alert radio or service. -Watch for signs of a tornado -Yoda Green tinge to sky -Rolling clouds (funnel clouds) -Keep an eye on powerful thunderstorm

More ways to reduce risk ***If a tornado is spotted: -Head to the basement or a neighbors basement

More ways to reduce risk ***If a tornado is spotted: -If no basement available run to a bathroom -Do not try to out drive a tornado -If caught outside, lie down in a low area like a ditch

13.3 Tropical Storms Tropical cyclone: Large rotating low pressure system. The energy for these storms are provided by the warm ocean water. Two needed conditions: 1. Warm ocean water 2. Disturbance (uplift of air) Guided by wind belts, the Hurricanes that effect our east coast start on the west coast of Africa and travel across the Atlantic.

13.3 Tropical Storms As soon as a hurricane makes land fall it begins to lose energy and becomes weaker.

PREVAILING WESTERLIES: GLOBAL WIND SYSTEMS THAT LIE BETWEEN 30 AND 60 DEGREES NORTH AND SOUTH LAT, WHERE SURFACE AIR MOVES TOWARD THE POLES IN AN EASTERLY DIRECTION TRADE WINDS: GLOBAL WIND SYSTEM THAT FLOWS 30 DEGREES NORTH AND SOUTH LAT WHERE AIR SINKS, WARMS, AND RETURNS TO THE EQUATOR IN A WESTERLY DIRECTION JET STREAM: HIGH ALTITUDE NARROW BAND OF WIND THAT IS WITH IN THE WESTERLIES AND CAN FLOW AS FAST AS 185 KM/HR

STORM TRACK: THE PATH OF THE STORM AS DETERMINED BY THE UPPER WIND BELTS STORM SURGE: OCCURS WHEN POWERFUL HURRICANE FORCE WINDS DRIVE A MOUND OF OCEAN WATER TOWARD SHORE, WHERE IT WASHES OVER THE LAND OFTEN CAUSING ENORMOUS DAMAGE HURRICANE: A TROPICAL CYCLONE WITH A WELL DEFINED EYEWALL AND A MINIMUM WIND SPEED OF 74 MPH SAFFIR/SIMPSON SCALE: CLASSIFIES HURRICANES ACORRDING TO WIND SPEED AIR PRESSURE AND POTENTIAL FOR PROPERTY DAMAGE FUJITA SCALE: A MEASURE OF THE INTENSITY OF TORNADOES BASED ON DESTRUCTION, WIND SPEED, AND DURATION.

1. Which is not a condition for a thunderstorm to form? A. Abundance of moisture B. Rising air C. Stable air D. Unstable air 2. Which is not a stage of development for a thunderstorm? A. Nimbus B. Mature C. Cumulous D. Dissipation

3. Which should you not do if there is the threat of a tornado? A. Stay away from windows B. Seek shelter in a Bathroom C. Hide in the basement D. Try to out drive it

4. Which should you not do if there is the threat of a Hurricane? A. Try to out drive it B. Hide in the basement C. Seek shelter on the roof D. Stay away from windows

Why does a hurricane get weaker as it makes landfall? Bonus ***How does Hail form?