Presentation on theme: "Geography 1000 For Quiz #3 (covers most of Chapters 7-9) Part 1 of 4 Parts “Super-Storm Sandy” in October, 2012 caused more than $55 Billion in financial."— Presentation transcript:
Geography 1000 For Quiz #3 (covers most of Chapters 7-9) Part 1 of 4 Parts “Super-Storm Sandy” in October, 2012 caused more than $55 Billion in financial losses and cost more than 300 lives. Most of these losses were preventable. People living along the sea coast are “gamblers” - - hoping that a big storm won’t really affect them. As of October, 2013, some people in New Jersey still do not have electricity and/or drinking water. People in New Jersey can say the same thing about us: we think that a big earthquake won’t really be that bad.
Photo taken by a friend of Nick Urban, who was a Geography 1700 student Fall 2013 Consider that counter-clockwise (cyclonic) rising air is condensing vapor back into liquid water as it rises, decompresses and cools. In the center, rain is falling as the “bucket” over-fills. Downdrafts may occur there also. At the edges, a ‘wall cloud’ and a funnel cloud may form due to rapidly rising air. Great turbulence and severe wind can result from air rising and falling.
U.S. Storms Tornadoes in 2011 killed more than 550 Americans. At least one tornado in 2013 was among the largest ever recorded – more than two miles wide on the ground and exhibiting wind speeds above 300 miles per hour. The 1925 “Tri-State Tornado” may have been much larger than any tornado ever ‘recorded.’ This one cyclone lasted for hours – killing more than 700 people. Cyclones can occur anywhere cold/dry and warm/wet air meet, usually in mid-latitudes where large continents create extremes and where coriolis force is active.
Katrina (2005) and Super-Storm Sandy (2012) add more than $200 Billion to this chart, not counting other U.S storms since projection was for $200 Billion combined, not PLUS.
Severe Weather and World-Class Storms The United States is regarded as having the greatest variety of bad weather. Why? Typhoons in the Pacific Ocean and ‘cyclones’ in the Indian Ocean have killed as many as 500,000 people in one storm alone. Even so, the USA can be worse due to having more cold-dry air than Bangladesh, which collides with wet-warm. Why does it matter that Americans tend to be some of the world’s best gamblers? More than 90% of the world’s tornadoes occur in the USA.
Anatomy of ‘bad’ weather The “Big Six” Attributes of the Atmosphere -Differential heating of the earth causes air pressure -air moves from higher pressure to lower pressure as wind. -Moving air and heat evaporate water – energy becomes latent in water vapor, called humidity. -Wind carries water vapor and heat to other places. -When that air cools, latent heat and liquid water return as warm clouds. -Precipitation occurs when liquid or frozen water falls from clouds.
How a rainy day can turn violent. “Sometimes Mikey likes it” Any time air becomes laden with moisture it will tend to be more buoyant than drier air elsewhere. When that air also becomes warm it can become even more buoyant. It could start rising on its own (convective rising). In dry Utah, when wind moves air upward over a mountain, the cooling effect can cause condensation, releasing heat and producing clouds. If air is wet enough, a simple rainy episode on the mountainside could turn into a genuine ‘convective’ uplift, leading to more substantial precipitation, stronger wind and so on. So, humidity that moves through Utah might not have turned into a genuine stormy day were it not for mountains that started the air moving upward. Afterward, the humid took over and caused its own rising and more storminess. A few times each year, there is enough water in Utah air to cause a strong convective uplift that could produce a tornado. Important
This photo of Tooele County illustrates how Utah can have severe weather anytime there is enough moisture in the air. Humidity is water vapor that contains latent (hidden) heat.
Severe storms are caused by heat stored as water vapor in the atmosphere. Modern science is now able to provide minutes of warning ahead of cyclones. Severe storms are part of the normal water cycle. Without hurricanes, Florida would have persistent drought. Dangerous cyclones in India, Myanmar and Bangladesh are part of the vital monsoon season that helps prevent famine and starvation. Understand adjustments that can minimize damage and personal injury from coastal cyclones Know the prudent actions to take for hurricane or extra-tropical cyclone watches and warnings
Cyclones An area or center of low pressure with rotating winds – Counter-clockwise in Northern Hemisphere – Clockwise in Southern Hemisphere Tropical or extra-tropical – Based on origin and core temperature – Tropical storms may become more intense as they move out of the tropics and into the sub-tropics and mid-latitudes
Some major regional storm categories Nor’easter - Extra-tropical cyclone that moves along northward along East Coast U.S. Hurricanes - Tropical cyclones in Atlantic and eastern Pacific Oceans Typhoon - Tropical and Extra-tropical cyclones in Pacific Ocean west of International Dateline and north of the equator Cyclones – same kind of storm, but in the Indian Ocean. Monsoon – a seasonal shift in wind, but often brings too much rain (or not enough)
Category 1 Category 5
Tropical Depressions and Tropical Storms Tropical depressions – Tropical disturbance wind speeds increase and begin to spin. – A low pressure center is formed. Tropical storm – Winds increase to 63 km (39 mi) ph. – Storm is given a name.
Hurricanes, cont. Rain bands – Clouds that spiral inward around center – Increase in intensity towards the center of the hurricane Eyewall – Innermost band of clouds – Contain the greatest winds and rainfall Eye – Area of calm at center of the hurricane – Often sunny and even downdrafts – After storm ‘eye’ passes, 2 nd half of hurricane will arrive
Hurricane Structure Warm, moist air spirals upward around eyewall. Air rises and cools, then condenses out clouds and hidden heat Release of heat and moisture promotes more rising air, sometimes with increasing speed Upward rotation draws air from eye, causing dry air to sink back into center. Upward rotation also causes air to flow out the top of the storm concentrated in exhaust jets. Allows additional warm, wet air to feed in at the base of the storm Storm will continue until warm, wet air supply ends at the base
Cross-Section of a meso-scale cyclone
What sustains “extra-tropical” storms? – A cyclone will run out of energy when the difference in moisture and temperature inside the storm is not much greater than the drier/cooler air outside. – Passing over dry land or over cool water will tend to drain a cyclone of energy. – However, an extra-tropical storm that collides with a relatively cold blizzard or “Nor’easter” can rebuild temporarily by having something cooler and drier to use for ‘pushing-off’ and rising again for a while.
Extra-tropical Cyclone Development Low pressure develops along fronts. – Cold front on southwest, warm front on east. – Cold air circulates counter-clockwise. – Warm air rises on the southeast side. – Dry air aloft feeds the cyclone from behind the cold front. Occluded front develops, trapping warm air aloft. Pressure gradient weakens and storm dissipates. Air will flow when there is a ‘gradient’ or “slope” between high and low pressure. Air pressure results from differences in temperature. High pressure flows to low pressure. WIND.
Warm, wet air rises above cool/dry air classic “frontal” storm. Here we see how the jet stream (with storm track) helps pull low and high pressure cells toward each other. The difference between warm/wet and cool/dry helps produce rising air, high wind, precipitation, hail, lightning.
Hurricanes in East and Gulf Coasts Figure 9.21 Usually, take one of three paths Season starts June 1 and ends Nov 30
Geographic Regions at Risk for Cyclones, cont. What makes the USA so unusual in severe storms? Because, we should have desert in Alabama - - but we don’t. Instead, we have “fight club” -- ”tornado alley”. Westerlies
Track of Extra-Tropical Storms Trade winds from east to west collect ocean transfer ocean heat to air vapor where it can collide with drier air further north. Hurricanes west of Mexico tend to blow away from land because of the same trade winds that blow hurricanes toward land in the Gulf and Atlantic. This red arrow is probably wrong. Hurricanes do not reach Los Angeles.
Geographic Regions at Risk for Cyclones Our definition of ‘cyclones’ should include “tornado alley”. The coast is “hurricane” country, but cyclones include tornadoes that occur across much of the USA. Hurricane regions are also tornado regions. All together, the United States collects more than 90% of the world’s tornadoes.
North American Regions at Cyclone Risk – Atlantic coast of eastern USA and Gulf Coast and islands – Baja California and West Coast Mexico – Hawaii – Winter windstorms in Pacific Coast – Winter snow Sierra Nevada, Rocky Mountains, and east – Spring and summer thunderstorms and tornadoes in U.S. and Canada