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Pg. 37 75% of deaths from Natural Disasters are from weather

Wild Weather. Pg. 37 75% of deaths from Natural Disasters are from weather More than EQ, MW, and volcanoes combined WHY??? OVERVIEW (we will be adding a few others but basically) principles of weather thunderstorms wind tornadoes extreme heat and drought. Wild Weather. Pg. 37

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Pg. 37 75% of deaths from Natural Disasters are from weather

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  1. Wild Weather Pg. 37 75% of deaths from Natural Disasters are from weather More than EQ, MW, and volcanoes combined WHY??? OVERVIEW (we will be adding a few others but basically) principles of weather thunderstorms wind tornadoes extreme heat and drought

  2. Wild Weather Pg. 37 PRINCIPLES OF WEATHER Water + Heat (sun) = weather Warm air =more heat energy and more moisture Cool Air = less heat energy and less moisture WATER and WATER VAPOR has huge heat capacity – ND pg. 273 table 10.1 Snickers vs. rice cake absorbs and holds LOTS of heat & transports it around the earth and releases it HEAT - more of sun’s energy absorbed at equator less at poles due to angle earth is tilted Pole vs. equator sun energy AIR MOVEMENTwarmair to poles cool air to equator but things complicate this simplicity often = STORMS

  3. Wild Weather Pg. 37 WHAT CAUSES WEATHER IN THE UNITED STATES?? 1.) Global Wind Patterns Air heated at equator heats, expands and rises. As expands (lowers pressure/density) causes cooling (adiabatic process) total heat stays the same but volume increase causes temperature to drop Cooling air sinks and compresses becoming dense so warms heat at surface warms also. GLOBAL WIND PATTERNS

  4. Wild Weather Pg. 37 ADD BUT WAIT We first need to talk about… THE CORIOLIS EFFECT ***1.) Northern hemisphere -Air currents and ocean currents are deflected to the right 2.) Southern hemisphere -Air currents and ocean currents are deflected to the left

  5. Wild Weather Pg. 37-38 WHAT CAUSES WEATHER IN THE UNITED STATES?? 1.) Global Wind Patterns(continued) Angle of Earth’s tilt causes different amounts of radiation to hit surface at different points. Differential surface heating Produces Cells of global air circulation Hadley - produce deserts Ferrel - occur over continental masses = turbulence and jet stream variation create severe weather conditions Polar – cool air sinks and moves toward equator But remember Coriolis Effect

  6. Wild Weather • Pg. 38 • Jet Stream- area of pressure gradient between • cold polar air and warm subtropical air = lots of • atmospheric disturbance • Occurs in troposphere(up high) hot air=high pressure • cold air=low pressure • THIS IS OPPOSITE BAROMETRIC PRESSURE • Coriolis “bends” the wind to the right/east • MOVES LOTS OF AIR=weather • fast moving air (up to 370 mph) • from 5 to 8 miles high • moves from west to east over North America • position changes due to seasons and turbulence

  7. Wild Weather Pg. 38 3.) Fronts- Air masses have different temperatures so don’t mix, boundary = fronts Air masses in U.S. related to latitude and relationship of ocean/land 3 types of fronts Cold - cold air under warm, warm moved upward = thin band of intense thunderstorms Warm - warm over wedge of cold = gentle gradient = wide spread clouds Occluded - 3 masses warm, cool and cold come together

  8. Wild Weather Pg.38 4.) High and Low pressure zones Barometric Pressure - measured by a column of mercury

  9. Wild Weather Pg. 38 Low Pressure - rising warm air creates low pressure so air rushes in to replace rising air produces counterclockwise surface winds air moving upward cools, water vapor condenses = precipitation (stormy) ADD Two things contribute or can cause rising air 1.) warm air rises 2. divergence aloft creates a vacuum and “sucks” up air from below BOTH cause upward movement of air=low pressure

  10. Wild Weather Pg. 38 Low Pressure (continued) Chicken or the egg? Divergence or warm air? Usually working together Aloft air diverges Has to go some place Warm Air rises Barometer Effect? Air Rushes in from side Low Pressure Air rising Ground

  11. Wild Weather Pg. 38 Low Pressure (continued) Top View Coriolis Effects bends wind to Right (---) Rushing in wind begins to blow from one “arrow” to the next creating circular path-counterclockwise

  12. Wild Weather Pg. 39 Cyclone - winds rotate counterclockwise about a core of air moving upward Northern Hemisphere-counterclockwise Low pressure-air rises ND pg. 281 fig. 10.17 Generally occurs in/downstream of trough of jet- divergence WHY???

  13. Wild Weather Pg. 39 High Pressure - air comes together in upper atmosphere and descends and/or cold air sinks Produces clockwise surface winds ADD Two things can cause air to sink 1.) convergencealoft “crashing” air aloft is forced down 2.) cold air sinks

  14. Wild Weather Pg. 39 High Pressure (continued) Chicken or the egg? Divergence or cold air? Usually work together Air converges aloft and is forced down Cold Air Sinks Barometer Effect? Air hits ground and Rushes out to sides High Pressure Air sinking Ground

  15. Wild Weather Pg. 39 High Pressure (continued) Top View Coriolis Effects bends wind to Right(---) Rushing OUT air begins to bend to right and set up clockwise rotation

  16. Wild Weather Pg. 39 Descending air WARMS as it descends so creates dry windy conditions = no precip. (clear weather) Anticyclone - winds moves clockwise around downward moving air ND pg. 281 fig. 10.17 Generally occurs at ridge of jet- Convergence WHY??

  17. Wild Weather Pg. 38 GENERAL RULES Warm air rises Cold air sink land = dry ocean = moist TEMP? SUMMER -land is warmer WHY?? RAIN and Storms? WHY?? Warm air rises OR divergence aloft Low pressure Cold air sinks OR convergence High pressure HEAVY RAIN Land Ocean

  18. Wild Weather Pg. 38 GENERAL RULES Warm air rises Cold air sink land = dry ocean = moist TEMP? WINTER –ocean is warmer WHY?? RAIN and Storms? WHY? Cold air sinks OR convergence High pressure Warm air rises OR divergence aloft Low pressure Light RAIN Land Ocean

  19. Wild Weather • Pg.39 • MIDLATITUDECYCLONES - (air mass rotating • counterclockwise around a low pressure core) • Produce most severe weather in U.S.-WHY??? • Three Scales of cyclones • 1) LARGESTJet stream weather system – • cold front behind warm front = thunderstorms • over large area DO FIRST ND pg. 281 fig. 10.17 • 2) Smaller localized can produce thunderstorms • over smaller area • 3) Tornado - smaller radius rotation of • wind (higher speed winds)

  20. Wild Weather • Pg. 40 • 6. Focus on THUNDERSTORMS • HOW DO THEY WORK? • warm moist air absorbs heat so less dense and • rises (hot summer afternoons) • as rises cools and water vapor condenses into • clouds (as water condenses releases heat so • rise even higher) • ice and water becomes heavy updraft can’t • support so falls (precipitation) creating downdrafts • that pull in cool air

  21. Wild Weather • Pg. 40 • 6. Focus on THUNDERSTORMS • HOW DO THEY WORK • 4. updrafts and downdrafts occur in thunderstorm • violent thunderstorm move ice up and down and • create hail • once downdraft pulls in a lot of cool air overwhelms updraft of warm air (no new moisture moved upward) and thunderstorm begins to die out • 6. SUMMARY another summary

  22. Wild Weather Pg. 40 MOST OCCUR WHERE? 1. Florida and inland as tropical moist air moves off of Gulf WHY??? 2. Mountains of western U.S. Moist Gulf air contact dry desert air - moisture moves up (mountains help force upward) and you get a thunderstorm WHY???? Moist Air Forced aloft by low pressure Over land Moist Air Forced aloft Florida warm Mountains Ocean cool

  23. Wild Weather Pg. 40 WHAT TYPE OF WEATHER DO THEY BRING? 1. heavy rain - floods (TEXAS 22 INCHES IN 2 3/4 HOURS!!) and mass wasting Why Texas? - location next to Gulf, air flow onto land over low-lying coastal plain is moved up over highland created by a fault system (warm air moved upward=precip) Moist Gulf Air sent aloft Texas highlands Low-lying coastal plains fault

  24. Wild Weather • Pg. 41 • flash floods in desert especially (S. Utah canyons) • WHY? • low vegetation • hard surfaces • thin soils • topography-narrow passages • 3. hail - nasty on crops - Texas again and Oklahoma (need colder air in interior for ice to form) largest 17 in diameter!! • 4. lightning - starts forest fires and direct strikes cause deaths

  25. Wild Weather Pg. 41 Lightning - a spectacular show in the atmosphere Electric current seeks to balance areas with excess charges cloud to cloud OR cloud to earth Bottom of thundercloud builds negative charge (due to colliding and shattering of supercooled water drops)-not very well understood The negative build up induces a positive build up on the ground directly below. ND Pg. 323 fig. 11.27 Diagram Awesome site describing process

  26. Wild Weather Pg. 41 Anatomy of Lightning: step leaders -Negative charge heads toward ground, when close positive charges moves upward and they connect and see flash. Animation Thunder results from high temp of lightning flash (up to 55,000 degrees F) heats air and expands explosively

  27. Wild Weather • Pg. 41 • winds – • SURFACE WINDS ALWAYS BLOW FROM • HIGH TO LOW PRESSURE • straight-line (derecho) • rotating (tornado)- a little different than H to L • straight-line wind up to 100 mph • tornado wind speed up to 310 mph • Small but deadly Low Pressure WIND WIND WIND High Pressure

  28. Wild Weather Pg. 42 WHAT MAKES A TORNADO?? (3 things) 1.) humidwarm air from Gulf >75 degree F moves north 2.) meeting fast >50 mph cold dry air 3.) jet stream winds >150 mph 4.) single cell vs. super cell system ND pg. 326 fig. 11.30 When these air masses meet warm air is lifted upward, strong updraft is sheared and spun by fast-moving cold air and twisted at upper levels by jet = tornado ND pg. 326 fig. 11.29 Courtesy NOAA

  29. Wild Weather Low Pressure High Pressure Pg. 42 HOW DO THEY (TORNADOES) DESTROY? pressure differences - very low pressure in center, pressure inside a building is much higher - when pressure outside drops instantly - buildings explode. Utah-can occur but rare. WHY?? SLC =1 fatality Kentucky/Indiana case Onset is rapid: very little warning. First siren warning at 1:49am. Second at 1:59am tornado struck at 2:01am. F3(force3) category. 158mph-206mph winds

  30. Wild Weather ADD ON Tornadoes are classified based on wind speed and resultant damage Fujita Scale Here is a BIGGIE

  31. Wild Weather Pg. 42 WHERE DO THEY OCCUR? Good Old Okalahoma-WHY? Can happen in Utah – uncommon-WHY VIDEO????

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