ATMS 120 1st Edition Lecture 16 Outline of Last Lecture I Drought worldwide II Drought III Heat waves IV 1995 Chicago heat wave V US drought monitor VI Causes of drought in central US VII Major drought in the US in the last 100 years Outline of Current Lecture I Flood fatalities in US II Flood prone areas in the US III Comparing the 3 types of floods IV Miscellaneous notes Current Lecture I Flooding is the number 1 weather related killer in the United States and the number 2 killer in the world There are 93 deaths per year on a 30 year average There are three main types of flooding Coastal Widespread Flash Coastal flooding is almost always associated with hurricanes These types of floods can be made worse if it occurs during a full moon Widespread flooding is when big river systems overflow such as the Mississippi They are the most costly type of flooding These types of floods are often predictable several days in advance more so than coastal flooding even when associated with hurricanes Flash flooding is the most deadly type of flooding They can be caused by training thunderstorms explained later II Mountainous regions flash flooding is topography induced snow melting in the spring contributes to flooding 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 Northern rivers ice jams in the spring cause floods every spring Flood of the Milennium in 1997 occurred in this region of the US Coastal flooding hurricanes gulf lows and nor easters bring torrential rains crashing waves and storm surges several miles onshore Desert southwest flash flooding from thunderstorms must runoff as it can t be absorbed into the soil very quickly people in these regions are used to very little rain Major river systems drain the eastern half of the country modified by man straightened out dredged and held in with levees have large flat flood plains Basically just about everywhere in the United States is prone to flooding Coastal Flooding Widespread Flooding Flash Flooding Onset When tropical cyclones make landfall Slow with advance warning Rapid with little warning Duration Several days to weeks Weeks to months Couple of hours to a day or two Predictability 1 3 days in advance Very predictable but inevitable Difficult to forecast Coverage Large regions small state Large regions states Localized county Who what is affected Coastal regions can extend far inland too The watersheds of large river systems Small rivers streams urban areas flat open fields Primary causes Slow moving tropical cyclones Persistent weather patterns Slow moving thunderstorms training thunderstorms along stationary front When they typically occur Hurricane season Any time of the year usually a combination of seasons March September thunderstorm season IV Tropical Storm Allison in 2001 is the only tropical cyclone to have its name removed from the name list without achieving hurricane strength Allison provided an entire year s worth of rain to the Houston area in one storm A 500 year flood means that the probability of the flood of this magnitude happening in any year is 1 in 500 Training thunderstorms are one storm following the previous one on the same track Thunderstorms can develop and ride along a stationary front and multiple storms riding the same front are called training thunderstorms