Hurricane Ivan over Gulf Sept 2004 Source NOAA Thunderstorms Tornadoes and Hurricanes October 27 28 2010 Definitions Climate Change Changes in climate of the past present or future associated with natural or anthropogenic human factors Global Warming Warming of the 20th and 21st century associated with anthropogenic activities Weather describes whatever is Climate describes the total of all Weather is what happens from Climate tells us what it s usually like happening outdoors in a given place at a given time minute to minute weather occurring over a period of years in a given place in the place where you live can change a lot within a very short time Weather includes daily changes in precipitation barometric pressure temperature and wind conditions in a given location Climate is what you expect weather is what you get Begin in cumulus stage Warm moist air rises cools Water condenses out of air releasing heat Updrafts develop Precipitation occurs when weight of precipitation overcomes updrafts Cloud draws in drier air which evaporates some moisture causes cooling This cool dense air sinks creating downdrafts Downdrafts mark mature thunderstorms Downdrafts and updrafts make the thunderstorm cell Storm may extend to top of tropopause 12 km 1 Why doesn t precipitation fall right as condensation occurs A rush of cold air downdraft usually occurs at onset of precipitation Storms usually dissipate within 15 30 min Updrafts weaken downdrafts dominate Provide summer rainfall for much of the US Cooling of up to 10 C 18 F on hot summer days Strong downdrafts can force more warm air up causing multi cell storms Thunderstorm development time lapse Florida http vimeo com 4806845 Stronger winds aloft than at surface vertical wind shear Tips over top of storm allows for prolonged updrafts longer storm life Hail forms due to strong updrafts falls when heavy enough to overcome updrafts Strong downdrafts called microbursts may occur winds up to 146 kt Dangerous to aviation Microburst 2 How do you think it could be dangerous to aviation Source Wikipedia days per year thunderstorms observed Do you think hail follows the same distribution 3 How are max min different here Why do you think more hail over Rockies Great Plains Lightning occurs to reduce a buildup of positive and negative charges within a cloud charged ice crystals tend to be at top of cloud and charged hailstones at bottom Area of positive charge on ground develops below storm When electrical potential gradient large enough the electrical current flows to surface as lightning Can have cloud to cloud cloud to ground or lightning within a cloud http apollo lsc vsc edu classes met130 notes chapter14 graphics lightning mpg Can heat the air rapidly to 30 000 C 54 000 F This rapid heating causes air to expand and makes a booming sound wave thunder Sound takes 3 sec to go 1 km 5 sec per mile 4 If you see lightning and hear thunder 15 sec later how far away is the lightning 5 km 3 miles away Sometimes thunder is not heard due to the atmosphere bending the sound waves upward 100 people per year die of lightning strikes If about to strike hair stands on end skin tingles hear clicking sounds Source www goldengatephotos com Sept 2003 Carquinez Straits CA After rare influx of moisture from SW Cloud to ground lightning over Las Vegas during SW monsoon season Rapidly rotating winds around intense low pressure center Start as funnel shaped cloud Diameter of 100 600 meters 300 2000 ft Move at 20 40 kt 23 46 mph Last only a few minutes Travel up to 7 km 4 mi Source http www cs uwaterloo ca Most violent event April 3 and 4 1974 148 tornadoes over a 16 hour period Covered 13 states 307 people killed 6000 injured 600 million in damage Trailer park destroyed in Huntsville AL F4 tornado over Parker City IN Source http www april31974 com Tri state tornado event March 18 1925 7 tornadoes across MO IL IN 695 people killed US has most tornadoes of all countries Occur in all states greatest number in Tornado Alley This is area where cool dry air from Canada meets warm moist air from Gulf Source http wximpact40 88 pbworks com Tornado alley susceptible since warm humid air overlain by cool air aloft If strong vertical wind shear occurs and thunderstorms form tornadoes likely Usually occur March July in late afternoon Can pick up people animals appliances railroad cars 220 kt winds max most 125 kt Can pop roofs off collapse houses Bernoulli s principle 5 How can tornadoes pop a roof off a structure Tornadoes around the US http www youtube com watch v 43VoMesUd2Q An intense storm winds over 64 kt 74 mph Generally form in tropics 23 1 2 N S of equator Warm humid areas A tropical aka Easterly wave in atmosphere disrupts usual wind flow In western N Pacific Asia Japan typhoon In Indian Ocean Australia cyclone Today we will use hurricane to refer to all Hurricane and SST Change Webster et al report that the number of category 4 and 5 hurricanes has almost doubled globally over the past three decades Webster et al 2005 Science Hurricanes are natural events and are not linearly related to climate change Climate change by increase SST indeed makes it more possible to have strong hurricane occur Anatomy of a hurricane Convergence at surface brings warm moist air up Divergence aloft and sinking air outside the hurricane clear skies immediately surrounding Ingredients for Hurricane Winds light Deep layer of high humidity warm air Water 80 F Season lasts June November Need converging winds so form in ITCZ Take in heat at ocean surface convert it to kinetic energy as wind Form between 5 and 10 N and S 6 Why don t they form over equator No Coriolis effect at equator to start spin 7 Why do hurricanes move from East to West Begins as tropical disturbance wave Tropical depression winds 20 34 kts closed isobars Tropical storm winds 35 60 kts Hurricane winds 64 kts Hurricane Katrina Source NOAA Atlantic and Pacific Storm tracks 2010 Source Wikipedia Source Washington Post High winds can collapse structures Storm surge High wind driven waves Low pressure in storm center causes sea level to rise up to 0 5 m 1 5 ft Like water up a straw Strong downbursts Heavy sudden rains can cause flooding Katrina damage in Mississippi Source www katrinadestruction com August 21 1992 Hit Louisiana with 120 kt winds 200 000 homes destroyed 30 billion in damage 53 deaths Most deaths in US from hurricane 1900 Galveston TX more than 6 000 died Confused when calm eye hit went out to check things out other