1. Hurricane Hazards and Society 1
A. Hazard and Risk
B. Hurricane formation
C. Comparing hurricanes and seasons
2. A. Hazard or Risk?
1. In this cartoon,
what are the
hazards?
2. How could the
person minimize
her risk from
these hazards?
3. Geologic Hazard
• Phenomenon capable of causing harm to humans
– Tsunami Primary Hurricane Hazards
- Wind
– Flood - Storm Surge
- Rain
– Volcanic ash - Waves
– Lahar Secondary Hurricane Hazards
– Fire (caused by a primary hazard)
- Flooding
– Liquefaction - Fire
- Landslides
– Landslide - Coastal Erosion
…. Can you think of others?
4. Risk
The likelihood of a hazard happening to YOU
Factors:
• Cost
– human life
– damage to property and infrastructure
• Probability
– dependent on location
– large events are generally less likely than small
ones
Recall: Question for today…
6. What is a hurricane?
• Make a list of hurricane characteristics:
7. What is a hurricane?
• Formal definition:
An intense low pressure system with sustained
winds >74 mph
8. What makes a hurricane?
• 4 essential ingredients
9. What makes a hurricane?
1) Warm SST >26.5°C (80°F) over large area
10. What makes a hurricane?
1) Warm SST (>26.5 C) over
large area
2) Instability in atmosphere
(rising air mass)
11. What makes a hurricane?
1) Warm SST (>26.5 C) over
large area
2) Instability in atmosphere
(rising air mass)
3) Little/no vertical wind shear
through troposphere
(Klotzbach and Gray, 2010)
12. What makes a hurricane?
1) Warm SST (>26.5 C) over
large area
2) Instability in atmosphere
(rising air mass)
3) Little/no vertical wind shear
through troposphere
4) Sufficient latitude >5-10o off
equator
13. Hurricanes are powered by
• latent heat stored in water vapor Feedback between
the ocean and
– released when water condenses atmosphere
systems!
1. Warm water supplies sensible heat
& humidity to overlying air
2. Air decreases density; rises
3. Air cools; H2Ovapor condenses
4. Latent heat released
-- Heat warms air; rises faster
5. P gradient increases
-- Faster winds
-- More water vapor into system!
14. So… Can hurricanes cross the equator?
• Discuss with the person next to you.
• Why or why not?
15. Can hurricanes cross the equator?
– Discuss with the person next to you.
– Why or why not?
(Hurricane tracks 1851-2012; NASA)
16. North Atlantic Hurricane Season is
June-November
Most storms occur in which month?
4
3.5 Tropical Storms
Average number per month, 1851-
3 Hurricanes
2.5 Hurricanes w/US Landfall
2
1.5
2011
1
0.5
0
17. Which of these things would cause a
hurricane to lose energy?
a) Moving over colder water
b) Moving over warmer water
c) Making landfall
d) Crossing the ocean
21. As hurricanes make landfall, they
decrease in strength
Why?
Remember
what fuels
hurricanes…
Warm
water!
22. Draw:
• the relationships between the
ocean, atmosphere, and people in a hurricane
Summary
Hazard and risk
What is a hurricane?
- What 4 conditions are necessary for hurricane formation?
- What happens as hurricanes approach land?
Notes de l'éditeur
Sample answers:--Hazards: volcanic ejecta (pyroclastic material, ash); poisonous gases--Ways to Minimize Risk: avoid death/injury by not jumping into the volcano, or not jumping at all; in advance, plan a different route to avoid ash clogging engine
High windsWaves, floodingLow pressure weather systemsDangerous, sometimes lead to evacuationsImage: Hurricane Rita as a Category 5 hurricane. Source: http://www.nnvl.noaa.gov/hurseas2005/Rita2045zD-050921-1kg12.jpg
Image: Hurricane Rita as a Category 5 hurricane. Source: http://www.nnvl.noaa.gov/hurseas2005/Rita2045zD-050921-1kg12.jpg
http://www.osdpd.noaa.gov/data/sst/fields/FS_km10000.gifAnother… Daily contoured image of SST:http://www.ospo.noaa.gov/Products/ocean/sst/contour/index.html
Public domain image.Associated text from http://commons.wikimedia.org/wiki/File:Twaves.jpg: It has been recognized since at least the 1930s (Dunn 1940) that lower tropospheric (from the ocean surface to about 5 km [3 mi] with a maximum at 3 km [2 mi]) westward traveling disturbances often serve as the "seedling" circulations for a large proportion of tropical cyclones over the North Atlantic Ocean. Riehl (1945) helped to substantiate that these disturbances, now known as African easterly waves, had their origins over North Africa. While a variety of mechanisms for the origins of these waves were proposed in the next few decades, it was Burpee (1972) who documented that the waves were being generated by an instability of the African easterly jet. (This instability - known as baroclinic-barotropic instability - is where the value of the potential vorticity begins to decrease toward the north.) The jet arises as a result of the reversed lower-tropospheric temperature gradient over western and central North Africa due to extremely warm temperatures over the Saharan Desert in contrast with substantially cooler temperatures along the Gulf of Guinea coast. The waves move generally toward the west in the lower tropospheric tradewind flow across the Atlantic Ocean. They are first seen usually in April or May and continue until October or November. The waves have a period of about 3 or 4 days and a wavelength of 2000 to 2500 km [1200 to 1500 mi], typically (Burpee 1974). One should keep in mind that the "waves" can be more correctly thought of as the convectively active troughs along an extended wave train. On average, about 60 waves are generated over North Africa each year, but it appears that the number that is formed has no relationship to how much tropical cyclone activity there is over the Atlantic each year.While only about 60% of the Atlantic tropical storms and minor hurricanes ( Saffir-Simpson Scale categories 1 and 2) originate from easterly waves, nearly 85% of the intense (or major) hurricanes have their origins as easterly waves (Landsea 1993). It is suggested, though, that nearly all of the tropical cyclones that occur in the Eastern Pacific Ocean can also be traced back to Africa (Avila and Pasch 1995).It is currently completely unknown how easterly waves change from year to year in both intensity and location and how these might relate to the activity in the Atlantic (and East Pacific).Date 1 June 2001 SourceNOAAAuthor Chris Landsea
Have your students describe what they see in this graphichttp://www.photolib.noaa.gov/historic/nws/images/big/wea00416.jpg NOAA Photo Library] {{w:Storm surge}} during {{w:HurricaneEloise|Hurricane Eloise}}
http://earthobservatory.nasa.gov/Library/Hurricanes/Images/hurricane_structure.jpgHurricane structure. Image courtesy NOAA, but taken from NASA Earth Observatory website.
http://earthobservatory.nasa.gov/Library/Hurricanes/Images/storm_surge.gifHurricane storm surge. Graphic by Robert Simmon, NASA GSFC.
This imageis in public domain under the terms of Title 17, Chapter 1, Section 105 of the US Code.
TIME?Can end with next slide, or go 15 moreLets do this again another day, too?
