Billion Dollar US Weather disasters

Chapter 25 Weather

2013: Category 4 Tornado, Oklahoma City, Moore & Newcastle. >90 killed, including 20 children.

2012: National drought. 123 deaths, $40 billion in damages SE & Ohio valley. 75 tornadoes, $4 billion in damages, 42

deaths Texas. 22 tornadoes, $1.3 billion in damages Midwest. 98 tornadoes hit OK, KS, NE, IA, $2 billion, 6 deaths Midwest. 38 tornadoes, large hail, Hit StL hard, $4 billion, 1

death 27 tornadoes over several states, $2.5 billion, 1 death SW. 25 tornadoes, hail damage over $1 billion in CO alone

Midwest. $4 billion, 28 deaths Hurricane Isaac. $2.3 billion damages, 42 deaths Western wildfires. $9.1 million acres, est. between $1-2 billion Hurricane Sandy. Est. $82 billion , 132 deaths

2011: Over 55 billion in damages, 646 deaths (Most deadly year in a decade)

25.1 – Air Masses Air Mass – large body of air with uniform temperature

and moisture content.May be thousands of km in diameter.

Air mass classifications

Maritime polar (mP)Maritime tropical (mT)

Continental polar (cP)Continental tropical (cT)

Polar Air MassesContinental Polar Canadian (cP)

– form over land covered in ice and snow Maritime Polar Pacific (mP)

– form over north Pacific; Aleutian IslandsMaritime Polar Atlantic (mA)

– form over north Atlantic; between Greenland and Iceland

Tropical Air MassesContinental Tropical (cT)

– flow over N.A. only in summer; hot dry air to the SWMaritime Tropical Gulf & Atlantic (mT)

– form over the Gulf of Mexico & tropical N. Atlantic; move northward over eastern US; bring mild winters, and hot,humid summers with thunderstorms and hurricanes

Maritime Tropical Pacific (mT)- form over the warm areas of the N. Pacific; rarely reach the

coast

25.2 FrontsFront – occur where there are two unlike air massesDensity keeps the air separate. (cold vs. warm)

May be several hundred km to several thousand km long.

Fronts do not exist in the tropics because there is not temperature differences.

Cold front

Warm front

http://www.youtube.com/watch?v=bN7E6FCuMbY

Squall line – long line of heavy thunder storms; may occur just ahead of fast moving cold front (write down for homework!)

Stationary Front

Two masses meet, and neither one is displaced

Winds blowing parallel to the front(not perpendicular) help it stay in place

Symbols point toward air type.

Occluded front

Sometimes a cold front follows right behind awarm front. Because cold fronts move faster,the cold overtakes the warm.At an occluded front, the cold air mass from the cold front meets the cool air that was ahead of the warm front. The warm air rises as these air masses come together. Usually forms around areas of low pressure.

Polar FrontBoundary where cold polar air meets the warmer air of middle latitudes.

Circles the earth between 40° – 60° latitude in each hemisphere.

p. 503-4

Moves toward equator in winter.Recedes in the summer.

Wave Cyclone - forms at the boundary of a polar front.

Warm and Cold winds blow in opposite directions.

An intensified low-pressure region forms in the center.

Page 503-504

Hurricanes – most severe tropical storm, with wind speeds starting at 120 km/hr.

Develop over warm, tropical oceans

Most common in the western Pacific (20/yr) where they are called typhoons

Hurricanes & Typhoons

Very warm, moist air rises off the water.

As the air rises, it cools and condenses, releasing energy, increasing the force of rising air.

The eye itself is a region of calm, clear, sinking air.

An average hurricane has the KE (wind energy) of about half the world-wide electrical generating capacity.

ThunderstormsStorm accompanied by thunder, lightning, and strong winds.

Occur when warm, moist air (mT) is heated and rises.Occur most often in late afternoon or early evening.

Tornadoes

The smallest, most violentand shortest-lived storm.

Dallas, TX April 2012

https://www.youtube.com/watch?v=uSs45dJGOlE

https://www.youtube.com/watch?v=0L-XExpb3pY

Moore, OK 2013 EF5

p. 507-8

A tornado over the ocean is called a “Water Spout”http://www.telegraph.co.uk/news/worldnews/australiaandthepacific/australia/9686072/Rare-waterspout-forms-off-Australia.html