Chapter 11

Hurricanes

Hurricane Katrina Flooded 80% of New Orleans

The US’s deadliest hurricane in terms of deaths happened in 1900 in Galveston, Tx. with 8000 who died. Due to continued developments along the coastal areas, we see increased damages and deaths.

Hurricane formations•A hurricane must have sustained wind speeds of at least 74 mph.

•The North Pacific has the greatest number of storms per year averaging 20.

•meteorological satellites have been the greatest advancement in observing tropical cyclones.

Equator lacks hurricanes

•Because the Coriolis effect is too weak to create rotation.

What’s in a name?

•Hurricane – Hurricanes in the Atlantic Ocean

•Typhoon – hurricanes in the western Pacific Ocean.

•Cyclone – hurricanes in Indian Ocean and Arabian Sea.

Tracks of Major Hurricanes

Form in the tropics where warm water temperatures are

found.

Storm Ratings intensity

•Tropical storm– most intense

•Tropical depression –•Tropical disturbance –•Tropical water – least intense

The Major Hurricane Formation Regions are associated with the trade winds as a general

circulation wind belt.

Locations

• Most hurricanes form between the latitudes of 5° and 20° over all tropical oceans except the South Atlantic and eastern South Pacific.

• Hurricanes do not generally strike the west coast due to the colder water currents.

Lowest Pressure and Weakest Winds in Eye

Highest Winds at Eye-Wall

Conservationof

Angular Momentum

is why the surface wind

speeds increase

toward the center of a hurricane.

Causes• A steep pressure gradient generates the rapid, inward spiraling winds of a hurricane.

• As the warm, moist air approaches the core of the storm, it turns upward and ascends to form the eye wall.

• At the very center of the storm, called the eye, the air gradually descends, precipitation ceases, and winds subside.

Cross Section of a Hurricane

Development• A hurricane is a heat engine fueled by the latent heat when huge quantities of water vapor condense.

• They develop in late summer when ocean waters have reached temperatures of 80°F or higher and are able to provide the heat and moisture to the air.

• The initial stage of a tropical storm’s life cycle is called a tropical disturbance.

• Tropical disturbances begin as large ripples in the trade winds known as easterly waves.

The eye is the

warmestpart of

the hurricane,

and is free of

clouds due to sinking

air motion.

Hurricane Intensity

• Hurricanes diminish in intensity whenever they

• (1) move over cool ocean waters that cannot supply warm, moist tropical air,

• (2) move onto land, or • (3) reach a location where large-scale flow is unfavorable.

Wind Speeds are highest at the eye-wall.

Fast winds are due to very strong pressure

gradient force.

Hurricane Damage

•Depends on the storms strength.

• The Saffir–Simpson scale ranks the relative intensities of hurricanes.

•A 5 on the scale represents the worst storm possible, and a 1 is the least severe.

Divisions of Hurricane Damage

•storm surge, is most intense on the right side of the eye where winds are blowing toward the shore,

•wind damage, and •inland freshwater flooding.

Stormsurges lead

to the greatest number of hurricane related deaths. Continued

damage is due to the

development along the coastal areas.

North Atlantic Hurricanes

•develop in the trade winds, which move these storms from east to west.

•because of early warning systems that help detect and track hurricanes, the number of deaths associated with these violent storms have been greatly reduced.

Dropsonde - Released

from Aircraftinto a

Hurricane used for

measuring wind speeds

throughout every level of a hurricane

Pilots Fly through Hurricanes Measuring Weather Elements

Doppler RadarImage

3-DSatellit

eImage ..

The conveyor belt model.

meteorological data

•Collected by satellites.

•aircraft reconnaissance,

•radar, and •data buoys.

Hurricane announcements

• hurricane watch, aimed at specific coastal areas threatened by a hurricane, generally within 36 hours.

• hurricane warning is issued when sustained winds of 119 kilometers per hour or higher are expected within a specified coastal area in 24 hours or less.

• Two important factors in the watch and warning decision process are (1) adequate lead time and (2) attempting to keep over-warning at a minimum.

Chapter 11

END