Hurricanes
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Hurricanes. A ‘Survival Guide’ Project W4400: Dynamics of Climate Variability and Climate Change Emily Firth, Bali White. What are hurricanes? (AKA cyclones and typhoons). intense low pressure disturbances Form, migrate over tropical ocean regions

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Hurricanes

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Hurricanes

Hurricanes

A ‘Survival Guide’ Project

W4400: Dynamics of Climate Variability and Climate Change

Emily Firth, Bali White


What are hurricanes aka cyclones and typhoons

What are hurricanes?(AKA cyclones and typhoons)

  • intense low pressure disturbances

  • Form, migrate over tropical ocean regions

  • conditions required: high SST (> 26°C) and weak vertical wind shears.

  • intense winds and very strong convective activity

  • -> thunderstorms and large amounts of rainfall.

  • takes days or a week to form

  • spreads over a radius of a few hundred kilometers.

  • surrounded by rings of towering thunder clouds spiraling up to a small circle at the center of the storm--the eye.

  • winds here can reach a speed of 100+ km/hour and the most intense rainfall occurs.

  • inside eye, air is still and convection suppressed by (subsidence). has a radius of 30-40 km.

  • major damage potential / loss of life when they make landfall.


A regional snapshot

A regional snapshot

 Typhoon Durian, Philippines Dec 2006

North Atlantic Ocean

West Pacific Ocean

East Pacific Ocean

North Indian Ocean

South Indian Ocean

SW Pacific Ocean

 This map shows the tracks of all Tropical cyclones which formed worldwide from 1985 to 2005


Migration of hurricanes

Migration of Hurricanes

  • hurricane tracks curve eastward and they speed up north of ~30°N

  • active in the "trade wind" belts - north or south of the equator where the winds blow steadily from east to west

  • initiated by weak pressure perturbations that exist in the tropics.

  • move west with the trade winds in a steady, relatively slow motion (10-20 km/hour).

  • intensify primarily through release of latent heat in surrounding clouds; small percentage reach full hurricane intensity.


Global warming and hurricanes

Global warming and hurricanes

  • Tropical sea surface temperature (SST) increase of 0.25-0.5C over past several decades

  • Future projections linking global warming to hurricane trends are hotly debated

  • Role of Global Climate Models

  • Uncertainties and limitations

    • Year-to-year and multidecadal variability in SST and hurricane activity

    • Variation in historical and regional hurricane data

    • Temporal limitations: reliable satellite data only last 30 years


Three take home points

Three ‘take home’ points

  • A likely increase in hurricane intensity with rising tropical SSTs

  • Regions of hurricane origin likely to remain unchanged

  • Uncertainty surrounding impacts of increasing SSTs on hurricane frequency


Useful resources

Useful resources

  • HURDAT: Atlantic basin hurricane database www.aoml.noaa.gov/hrd/hurdat

  • Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report. Climate Change 2001: The Scientific Basis. http://www.grida.no/climate/ipcc_tar/wg1/index.htm

  • Wikipedia: The Free Encyclopediawww.wikipedia.org/wiki/Hurricanes

View of the eyewall of Hurricane Katrina taken on Aug 28, 2005.


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