Hurricanes - the predictable hazards? Alistair McNaught Overview of lecture Nov Nov 2001 Predictable? Unpredictable? The year so far?

Hurricanes - the predictable hazards? Alistair McNaught Predictable times? Predictable places? Predictable impacts?

Hurricanes - the predictable hazards? Alistair McNaught Predictable times? Short term annual patterns To make a hurricane take warm ocean - 27ºC upper atmosphere weather a dash of Coriolis force - the spinning effect of the Earth’s rotation N.hemisphere - J F M A M J J A S O N D S.hemisphere - J F M A M J J A S O N D

Hurricanes - the predictable hazards? Alistair McNaught Predictable times? Medium term patterns To make a hurricane take warm ocean - 27ºC upper atmosphere weather a dash of Coriolis force El Niño / La Niña Antarctic circum- polar wave Pacific decadal oscillation

Hurricanes - the predictable hazards? Alistair McNaught Predictable impacts? Wind * Waves * Rain * Surge Saffir Simpson Scale mph (70m/s) Impacts on: Buildings: Loss as % value Windspeed (m/s) SS4 SS5 Source - Swiss Re Insurance publication Agriculture: Forestry: Ecosystems: Infrastructure:

Hurricanes - the predictable hazards? Alistair McNaught Predictable impacts? Wind * Waves * Rain * Surge

Hurricanes - the predictable hazards? Alistair McNaught Predictable impacts? Wind * Waves * Rain * Surge Eg Sept 99: Hurricane Floyd 14 inches (35cm) rain in 3 hrs. Rivers rising feet ( m) Oct 1998: Hurricane Mitch 25 inches rainfall (63cm) in 36 hours

Hurricanes - the predictable hazards? Alistair McNaught Predictable impacts? Wind * Waves * Rain * Surge Galveston (Texas) 8 Sep One of US most prosperous cities - built on island 2 - 3m above sea level. Hurricane surge = 5m. Combination of damage to wooden houses - * Wind damage * Flotation deaths due to storm surge.

Hurricanes - the predictable hazards? Alistair McNaught Predictable places? Global scale patterns To make a hurricane take warm ocean - 27ºC upper atmosphere divergence a dash of Coriolis force Too cool Too little spin

Hurricanes - the predictable hazards? Alistair McNaught Predictable places? Local scale patterns To make a hazard take A vulnerable location Coastal plain / Barrier Island Island eg Floyd Sept 99 - USA River flood plain eg Cyclone Eline Feb 2000 Mozambique

Hurricanes - the predictable hazards? Alistair McNaught Predictable places? Micro scale patterns To make a hazard take A vulnerable location Sample result Where to avoid

Hurricanes - the predictable hazards? Alistair McNaught Enter the Unpredictables Speed of system The system moves at speeds determined by the energy supply. This depends principally on temperature of sea A warm sea fuels the hurricane, cooler sea slows it. But the hurricane may move across warm currents, gaining energy OR may mix the water, altering its potency as a fuel. Hurricane Dennis - Sept 99 impacts on the Gulf Stream...

Hurricanes - the predictable hazards? Alistair McNaught Upper atmosphere weather Accelerator brakes and steering (upper atmosphere weather patterns) Accelerator (warm water) and brakes (cold water) Steering Enter the Unpredictables Location of landfall US Weather Service accuracy at predicting landfall location 24 hours before landfall (km from actual landfall site): Date Km error See Flash movieFlash movie

Hurricanes - the predictable hazards? Alistair McNaught Enter the Unpredictables Behaviour of landscape - eg Hurricane Mitch Oct/Nov 1998 Landscape Relief Mountainous in region where Mitch stalled Drainage Steep, dense networks - 70% roads impassable in Nicaragua after Mitch Slope stability Weak volcanic ash Vegetation 80,000 hectares/yr tropical rainforest cleared in coastal Honduras

Hurricanes - the predictable hazards? Alistair McNaught Enter the Unpredictables People Decision makers Preparation, planning, warning systems, emergency shelters Behaviour of people Communities Mitch - flooding in Tipitapa alerted by locals, first aid contacts via locals, refugee camp water pipe laid by locals Individuals Stay to protect property? Attract aid? Avoid vulnerability?

Hurricanes - the predictable hazards? Alistair McNaught Enter the Unpredictables Events Hurricane Mitch - Casitas Volcano produces lahar due to crater lake collapse

Hurricanes - the predictable hazards? Alistair McNaught Conclusions: More predictable than they used to be; Galveston (Texas) 8 Sep 1900 with deaths due to a 5 metre surge at night with no warning wouldn’t happen today. But prediction does not equate to preparedness. Orissa Cyclone 1999 killed 20,000 people in India. There was a metre surge and the cyclone stalled for 8 hours. But 100,000 people were evacuated before the cyclone hit. “the dead are mostly daily wage labourers, fishermen and women.” Poverty is the single biggest predictor of hurricane impact.