2 nd hour rocks!!! Chapter 12 Fall 2012

Sandy v Irene v Katrina Sandy v Katrina Can’t catch a break

Hurricanes Tropical Cyclones (typhoons in Western Pacific and Cyclones in Indian Ocean) Found between 5 o – 20 o latitude over all tropical oceans except South Atlantic and eastern South Pacific Greatest number of storms in North Pacific (avg of 20 per year) Fewer than 5 develop in U.S. each year

Cyclone Development

Hurricanes Must have winds of at least 119km (74 miles) per hour Mature Hurricanes can be 600km (375miles) in diameter – Average = 60 – 1500km (60 – 930miles)

Anatomy of Hurricane Eye: precipitation ceases and lowest pressure Eye Wall: ring of cumulonimbus clouds, greatest wind speeds, heaviest rainfall

Anatomy of a Hurricane

Anatomy of Hurricane

Hurricane Formation Pressure drops from outer edge to center of hurricane, this generates rapid inward spiraling As air moves closer to the center of the storm, its velocity increases The rotation brings in warm, moist surface air

Hurricane Formation Tropical Disturbance – Disorganized array of clouds and thunderstorms in eastern North Atlantic – Initiated by powerful convergence and lifting associated with ITCZ – Others form when a trough from midlatitudes intrudes the tropics – Easterly Waves (waves from the east)

Convergence

Hurricane Depression Tropical Depression: – Winds do not exceed 61km (37 miles) per hour Tropical Storm – Winds 61 – 119 km (37 – 74 miles) per hour – Given a name (sticks with them to hurricane) – 80 to 100 develop each year

Hurricane Development

Tropical Depression to Storm

Hurricane Decay Diminish when they 1.Move over ocean water that cannot hold warm moist tropical air 2.Move over land 3.Reach a location where the large scale flow aloft is unfavorable

Hurricane Destruction Saffir-Simpson Scale: ranks the intensities of hurricanes – Based on observed conditions at a particular stage in the life of a hurricane and are viewed as estimates of the amount of damage a storm would cause if it were to make landfall without changing size or strength

Saffir-Simpson Scale

Hurricane Destruction Damage caused by hurricanes can be divided into three classes: – Storm Surge – Wind Damage – Inland Freshwater Flooding

Storm Surge Most devastating damages in the coastal zone Responsible for 90% of all hurricane- caused deaths Dome of water 65 to 80km (40 to 50 miles)

Storm Surge If all wave activity were smoothed out, the storm surge would be the height of the water above normal tide level

Storm Surge Worst surges occur in place like the Gulf of Mexico, where continental shelf is very shallow and gently sloping Local features (bays, rivers) can cause the surge height to double and increase in speed

Storm Surge

State Park

Delta of Bangladesh

Storm Surge Most important factor responsible for the development of a storm surge is the piling up of ocean water by strong onshore winds – Gradually the hurricane’s winds push water toward the shore, causing sea levels to elevate while also churning up violent wave activity – Always most intense on the right side of the eye where winds are blowing toward the shore

Wind Damage Effects a much larger area Can produce tornadoes (over half of all hurricanes that make landfall produce at least one tornado) Mobile homes vulnerable Flying debris causes most of the damage

Wind Damage

Hurricane Winds

Wind Damage

Inland Flooding Hurricane Agnes (1972) – Only a category 1, but inland flooding caused 122 deaths and $2 billion worth of damage – Flooding in the NE, specifically Harrisburg Pennsylvania and West Schurykill Harrisburg: 32cm (12.5in) in 24 hours W. Schuykill: 48cm (19in) in 24 hours

Hurricane Agnes

Inland Flooding Hurricane Camille (1969) – Greatest number of deaths associated with this storm occurred in the Blue Ridge Mtns of Virginia 2 days after the hurricane made landfall – 25cm (10in) in 24 hours, severe flooding, 150 dead

Hurricane Camille

Hurricane Watch Announcement aimed at specific coastal area that a hurricane poses a possible threat within 36 hours

Hurricane Irene

Hurricane Warning Issued when sustained winds of 119km (74miles) per hour within 24 hours or less – Have to account for adequate lead time – And have to attempt to keep over-warning to a minimum

Naming Hurricanes The World Meteorological Organization created six lists of names for tropical storms over ocean areas – Names are alphabetical – Names are retired if the storm is especially damaging

Naming Hurricanes