ATMS 120 1st Edition Lecture 13 Outline of Last Lecture I Tropical cyclones II Hurricane tracks III Atlantic hurricane season Outline of Current 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 Current Lecture I The average cleanup costs in the US per year due to hurricanes are 10 billion The average number of deaths per year in the US due to hurricanes is 47 In the late 1970 s geostationary satellites were launched giving hurricane warnings up to 4 days in advance allowing the average death toll per year to fall The places in the world that are the most dangerous to live in in terms of tropical cyclones are Haiti and Bangladesh II In the northern hemisphere hurricanes spin counter clockwise If a hurricane in the northern hemisphere were heading to the north the eastern side of the hurricane is where you would expect to find the fastest winds and greatest storm surge If a hurricane in the southern hemisphere were heading to the south the eastern side of the hurricane as well is where you would expect to find the fastest winds and the greatest storm surge Tropical disturbance Cluster of tropical thunderstorms Watched or investigated for further development Tropical depression Organized cluster of tropical thunderstorms with sustained winds between 22 28 mph 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 Surface low pressure area develops in the center of the storm Tropical depressions are assigned a number Tropical storm Cluster of intense thunderstorms circulating around a deep low pressure center with sustained winds of 39 73 mph Tropical storms are assigned a name Hurricane Large organized system of intense tropical thunderstorms circulating around a very deep low pressure center 74 mph sustained winds torrential rains and storm surge 5 30 feet III The Saffir Simpson scale is what s used to categorize hurricanes based on their wind speed This scale ranks the storms using the maximum 1 minute sustained wind speeds Category 1 storms have the weakest wind speed while Category 5 storms have the strongest The average diameter of a hurricane is between 400 600 miles Super Typhoon Tip had a diameter of 1350 miles wide The average lifetime of a hurricane is between 2 7 days at hurricane strength Hurricane Ginger had a lifetime of 27 days IV Naming hurricanes in the United States reflect Spanish English and French geographic regions They are short and distinctive There are only 21 letters used no Q U X Y Z Names alternate between male and female The Greek alphabet is only used if they run out of names this happened in 2005 Name retiring is only done if the storm was particularly devastating such that using this name in the future would be insensitive or when a certain hurricane was studied a lot Each year they usually go through about 10 names on average stop at J V Thunderstorms develop across northern Africa and develop into tropical disturbances once they hit the Atlantic Ocean There is a trigger mechanism that helps get the storm started off in an easterly wave Something must trigger the air to rise and turn into a storm These easterly waves trigger the development of hurricanes The trade winds or easterlies push the storms to the west and northward Once they hit the point in between the easterlies and the westerly winds that we in the United States experience the storm sits and spins until getting fully picked up by the westerlies sending the storm track northbound VI Key features of a hurricane Very deep central pressure found within the eye Most intense part of the hurricane is found in the eyewall a small area Heavy bands of rain called spiral rainbands create the diameter of the storms Pressure in the eye is extremely low The fastest winds and greatest storm surge occurs in the eyewall which is located right outside the eye of the storm The right hand side of a hurricane in the northern hemisphere is the most dangerous