Hurricanes(tropical cyclones)

Basics and Hazards

Where and when

Same Storm Type, Different Names

Breeding Ground

What Hurricanes Must Have

1. Coriolis Strong (too weak near Equator) -- so form at latitudes typically from 5 to 20 degrees away from equator

2. Sea Surface Temperature (SST) at least 26°C (79°F) through a depth of ~60 m - "Hurricane Alley"

3. Few changes in wind speed and direction over the easterly flow (wind shear can disrupt a hurricane)

4. Lots of water vapor at low levels, thus requiring formation over tropical oceans

5. Some convergence as a trigger (typically easterly waves initiate hurricanes -- areas of low pressure, convergence in trade winds, travel east to west about 15-30 mph) that can turn into hurricanes,

What kills a hurricane?

• cool sea surface temperatures

• dry air at low levels of the atmosphere

• strong trade wind inversion (subsidence created by sub-tropical highs)

• strong upper level winds to create wind shear

• Land (hurricane moving over land shuts off the source of energy – moist air)

Classroom Resource

Cannot have wind shear. Need same winds at different elevations in atmosphere

Classroom Resources

Life Cycle Animation Hurricane Categories

Positive Feedback: Release of Latent Heat

LH -> Heat Release ->

Lower pressure ->

more convergence ->

More uplift & LH release

Growth CycleLow brings in air, then convergence, then

uplift, then release of latent heat, that intensifies low pressure, then MORE convergence…

Warmth in tropical Atlantic is important as a fuel source

Classroom Resources

Latent Heat release is the Key to Growth seen in these animations

Can see trail of cooler water after heat extracted

Hurricane Structure

Classroom Resources

Classroom Resources

Computer View Real View

New Insight: Hot Towers

New information reveals that “hot towers” forming along the boundary between the eye wall and the eye can help hurricanes intensify even more

Classroom ResourceMovie explaining how hot towers can

intensify a hurricane

Hurricane Storm Tracks & Timing

Knowing the track and timing is vital

for public

safety

Statistically, we know where

There are natural cycles. So it is

difficult to separate these cycle trends from claims that

human actions are to blame

To influence a hurricane’s

direction by human action is

notpossible. Certainly,

this is ludicrous.

Classroom Resources

How to forecast track Role of Bermuda High

Hurricanes as Hazards

1. Produce Tornadoes

2. Storm Surges

3. High Winds

4. Stream Flooding

5. Landsliding

Tornadoes (& waterspouts)

Hurricane Lily Over Miami

Storm Surge

Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm. Lower pressure from the Hurricane also raises sea level. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level 15 feet or more. In addition, wind driven waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides. Because much of the United States' densely populated Atlantic and Gulf Coast coastlines lie less than 10 feet above mean sea level, the danger from storm tides is tremendous.

Water transport

Storm Surge Classroom Resources

Katrina – big damage from storm surge

ClassroomResource

Movie

See the surge as it moves up the

Mississippi R. at New Orleans

Too much water =

levee break

Why Susceptible to Storm Surge

Other KatrinaBiloxi – Ocean Springs

Barrier Islands VERY dangerous

Hatteras Breach in 2003 typical and expected

Hurricane Camille• On August 15, 1969, Hurricane Camille

claimed 143 victims along the Mississippi Gulf Coast. Most were guilty only of being in the wrong place at the wrong time, unlike twenty who perished while attending a beachfront "Hurricane Party". Despite evacuation warnings delivered by earnest emergency teams, their festivities continued unabated. The party-goers defiantly declared that the concrete foundation and the second-floor location of their party provided plenty of protection from the impending hurricane.

• Their confidence proved to be tragically misplaced when a 24 foot wave slammed into the apartment, destroying the building and subjecting the partiers to gale-force winds and violent ocean surges.

• Most of these Hurricane worshippers were killed. A few survivors were swept miles away, cheated of a Darwin Award by the capricious hand of fate.

Source: http://www.DarwinAwards.com/darwin1988-04.html

Classroom Resources: Wind

Explains why right side is more dangerous

New Orleans got lucky being on the left side of Katrina

Hurricane Andrew Damage Classroom Resources

Flooding

• Hurricane Floyd flooding in North Carolina (satellite view, Sept 23, 1999)

• Flooding caused extensive damage along the eastern Carolinas northeastward into New England with at least 51 deaths in North Carolina. Damages exceeded more than a billion and a half in Pitt County, North Carolina, alone. More than 2.5 million evacuated their comes due to flooding with 7000 homes destroyed and 17,000 made uninhabitable and damage to 56,000 more in North Carolina alone.

Ivan

Rains in Arizona

We can get moisture Classroom Resource

Mass Wasting/Landslides• Hurricane Mitch (1998)• "In an awesome display of power and destruction, Hurricane Mitch will be

remembered as the most deadly hurricane to strike the Western Hemisphere in the last two centuries! Not since the Great Hurricane of 1780, which killed approximately 22,000 people in the eastern Caribbean, was there a more deadly hurricane. Mitch struck Central America with such viciousness that it was nearly a week before the magnitude of the disaster began to reach the outside world. The death toll currently is reported as 11,000 with thousands of others missing...Taking into account the orographic effects by the volcanic peaks of Central America and Mitch's slow movement, rain fell at the rate of a foot or two per day in many of the mountainous regions. Total rainfall has been reported as high as 75 inches for the entire storm.

• The resulting floods and mud slides virtually destroyed the entire infrastructure of Honduras and devastated parts of Nicaragua, Guatemala, Belize, and El Salvador. Whole villages and their inhabitants were swept away in the torrents of flood waters and deep mud that came rushing down the mountainsides. Hundreds of thousands of homes were destroyed... Though the final death toll will never be known, it is quite likely that Mitch directly killed more people than any Atlantic hurricane in over 200 years. More than three million people were either homeless or severely affected. In this extremely poor third world region of the globe, estimates of the total damage from the storm are at $5 billion and rising. The President of Honduras, Carlos Flores Facusse, claimed the storm destroyed 50 years of progress. Mitch is ranked number 2 in Deaths, a rank which will likely stand for a long, long time."

Hurricane Mitch

Planning is key

Online Resources

Hurricanes Visualizations

http://serc.carleton.edu/NAGTWorkshops/visualization/collections/hurricanes.html

Imagery seen in this presentation is courtesy of Ron Dorn and other ASU colleagues, students and colleagues in other academic departments, individual illustrations in scholarly journals such as Science and Nature, scholarly societies such as the Association of American Geographers, city,state governments, other countries government websites and U.S. government agencies such as NASA, USGS, NRCS, Library of Congress, U.S. Fish and Wildlife Service USAID and NOAA.