1st Edition ATMS 120 Lecture 14 Outline of Last Lecture I US hurricane fatalities II Stages of hurricane development III Size duration and strength IV Naming V More on hurricane tracks VI Inside a hurricane Outline of Current Lecture I Hurricane structure II Ingredients conducive for development III Destructive forces IV Storm surge V Inland flooding VI High winds Current Lecture I Hurricanes have eyes for two reasons 1 Air descends in the eye The extremely low pressure in the center allows gravity to slowly pull the air down 2 Descending air warms This promotes evaporation Descending air clears the sky The eye of the hurricane is the warmest place Air is trying to escape upwards but battles the force of gravity In the eye because the pressure is so low gravity wins and pulls the air downward descending which warms the air Graph on next page These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Greater slopes equal faster winds In the top three graphs pressure wind speed and rainfall the eye has the minimum values As just mentioned in the eye the temperature is warmer than in the rest of the hurricane The storm surge is skewed to the right of the eye As discussed in previous lectures the hurricane hits hardest on the right hand side eastern side in the northern hemisphere II Four things are needed for hurricane development 1 Sea surface temperatures at least 81 degrees Measured with IR satellite and buoys The strength of a hurricane is directly related to the sea surface temperature 2 Deep 200 feet layer of warm water Hurricanes extract heat from the ocean 30 100 foot waves churn up a lot of cold water from below Cold water shuts down hurricanes Hurricanes leave behind a lot of cold water that they have churned up which is why the next hurricane doesn t follow the previous one s path 3 No vertical wind shear no change in wind speed and direction with height Spreads out the heat weakens the storms Disrupts the vortex shears it apart 4 Must be at least 5 degrees north or south of the equator No Coriolis Force to help the system circulate III 4 types of destructive forces that go along with hurricanes 1 Storm surge A rise in sea level due primarily to wind blown water Only affects the coastline why deaths from surges are minimal those people evacuate first 2 Inland flooding Hurricanes can drop 10 50 inches of water Widespread Biggest killer 3 High winds Primarily contained in the eyewall Can exceed 200 mph 4 Tornadoes Can be very numerous Often very weak EF 0 to EF 1 Hard to distinguish damage Can generally be ignored for purposes of this class IV Storm surges are greatest on the right hand side of hurricanes where there is a 5 30 foot rise in sea level The worst location to be in in terms of storms surges is near a bay or inlet Storms surges are enhanced by tides and the shape of the coast line Storm surges are different from tsunamis Tsunamis are one giant wave whereas storms surges are successive waves the next one bigger than the last Tsunamis are caused by earthquakes but storm surges are caused by winds V The worst conditions for inland flooding are slow moving hurricanes locations with a lot of terrain and locations with poor land management A good example of this last point is Haiti vs the Dominican Republic Haiti has little forest coverage as a result of using wood for its resources as compared to the Dominican Republic Little coverage leads to the soil becoming saturated with water during hurricanes which can cause landslides Flooding is the deadliest weather disaster in the United States VI High winds during hurricanes are caused by very strong pressure gradients Hurricane force winds can extend 50 miles from the eye They are very destructive because the winds change direction