This work is supported by a National Science Foundation (NSF) collaboration between the Directorates for Education and Human Resources (EHR) and Geociences (GEO) under grant DUE Hurricane Formation: Ocean and Atmosphere Systems Interact to Create Hurricanes

Questions What is a hurricane? What four conditions are necessary for hurricane formation? What happens as hurricanes approach land?

What is a Hurricane? Make a list of hurricane characteristics:

What is a Hurricane? Formal definition: intense low pressure system with sustained winds >74 mph An intense low pressure system with sustained winds >74 mph

What Makes a Hurricane? Four essential ingredients

What Makes a Hurricane? 1)Warm SST >26.5°C (80°F) over large area

What Makes a Hurricane? 1)Warm SST (>26.5 C) over large area 2)Instability in atmosphere (rising air mass, beneath which surface winds converge)

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 atmosphere to tropopause (ocean) (atmosphere) (tropopause) Which wind profile has too much vertical shear for hurricanes to form?

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 >5-10 o off equator

Hurricanes are powered by: latent heat stored in water vapor latent heat stored in water vapor – released when water condenses 1.Warm water supplies sensible heat and humidity to overlying air 2.Air decreases density; rises 3.Air cools; H 2 O vapor condenses 4.Latent heat released -- Heat warms air; rises faster 5.P gradient increases -- Faster winds converge at the low pressure center -- More water vapor into system! Feedback between the ocean and atmosphere systems!

Can Hurricanes Cross the Equator? Discuss with the person next to you. Why or why not?

Can Hurricanes Cross the Equator? – Discuss with the person next to you. – Why or why not? (Hurricane tracks ; NASA)

North Atlantic Hurricane Season is June-November Most storms occur in which month?

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

As a hurricane approaches land

Wind and Rain (NOAA)

Storm Surge (NASA)

As hurricanes make landfall, they decrease in strength Why? Remember what fuels hurricanes … Warm water!

Draw: The relationships between the ocean, atmosphere, and people in a hurricane. Make sure you can now answer these: What is a hurricane? -What four conditions are necessary for hurricane formation? -What happens as hurricanes approach land? Make sure you can now answer these: What is a hurricane? -What four conditions are necessary for hurricane formation? -What happens as hurricanes approach land?

References Slides 4 and 5. Public Domain Image of Hurricane Rita as a Category 5 hurricane. Slide 6. Public Domain Image of SST. Slide 7. Public Domain illustration of tropical waves. Slide 9. Creative Commons illustration of hurricane forces: Slide 12. Public Domain image of hurricane tracks: Slide 15. Public Domain image of Hurricane Eloise approaching shore. Slide 17. Public Domain illustration of storm surge. Slide 18. Public Domain image of 2012 hurricane tracks. All other illustrations and text were created by Lisa Gilbert under a Creative Commons Attribution-NonCommercial- ShareAlike license You may reuse this item for non-commercial purposes as long as you provide attribution and offer any derivative works under a similar license.