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The Nature of Storms

Dive into the dynamic world of thunderstorms and severe weather to understand their formation, types, and impact. Discover the science behind lightning, tornadoes, and the Enhanced Fujita Scale.

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The Nature of Storms

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  1. The Nature of Storms

  2. Lesson 7 Thunderstorms and Severe Weather

  3. Think About It… During which months do we get the most damaging thunderstorms here in the Piedmont?

  4. Focus Question… How do the major types of thunderstorms form?

  5. 1. Average Number of Thunderstorm Days Annually… Florida is #1!!

  6. 2. Cause of Thunderstorms… • Warm air rises over a mountain • Temperature difference b/tw land & sea • Fronts See next several slides for details, if desired!

  7. Types of Thunderstorms… • Air Mass - Mountain • Where… within one air mass over a mountain • Why… warm air rises over a mountain, forming storm clouds! • When… midafternoon http://web.mst.edu/~rogersda/umrcourses/ge301/press&siever12.3.png

  8. Types of Thunderstorms… • Air Mass - Sea-Breeze • Where… coastal areas, esp. tropics/subtropics • Why… temperature differences between land and sea create convection cells and updrafts • When… summer http://apollo.lsc.vsc.edu/~wintelsw/MET1010LOL/web/notes/chapter11/ts_ingredients4summary.html

  9. http://apollo.lsc.vsc.edu/classes/met130/notes/chapter11/graphics/cf_xsect.jpghttp://apollo.lsc.vsc.edu/classes/met130/notes/chapter11/graphics/cf_xsect.jpg Types of Thunderstorms… • Frontal - Cold • Where… at the leading edge of a cold front • Why… cold air pushes warm air rapidly up at the steep cold-front boundary • When… anytime a cold front moves in!

  10. Types of Thunderstorms… • Frontal – Warm • Where… at the leading edge of a warm front • Why… warm air mass slides up over a cold air mass creating clouds • When… if a warm front moves in with enough moisture and instability http://www.atmoz.org/img/warm-front.png

  11. 3. Thunderstorms in the Piedmont… Which types of thunderstorms do we experience here in the Piedmont? • Frontal (warm and cold) • Local Air Mass (in the summer) http://www2.journalnow.com/mgmedia/image/0/354/118602/severe-storms-cause-damage-across-region/

  12. Stages of Development of a Thunderstorm… http://chiefio.wordpress.com/2010/12/28/ignore-the-day-at-your-peril/

  13. NSSL – Q&A Thunderstorms… • The National Severe Storm Laboratory is in Norman, OK. • http://www.nssl.noaa.gov/primer/tstorm/tst_detecting.html

  14. Severe Thunderstorms anvil Rain Free Base Precipitation http://ed101.bu.edu/StudentDoc/Archives/ED101fa06/mattwall/Extreme%20Weather.htm

  15. 4. Lightning… 4. What is lightning? • A giant spark of static electricity How does a lightning bolt form? • A ‘-’ channel of air from a cloud (stepped leader) connects with a ‘+’ channel on the ground (return stroke). http://i.imwx.com/web/multimedia/images/blog/stepped_lightning2.jpg

  16. How Lightning Forms … http://www.erh.noaa.gov/bgm/preparedness/swaw/ny/images/Light1.gif

  17. Lightning… What causes thunder? • Super-heated air expanding and contracting How hot is lightning? • 30,000 degrees Celsius http://www.eoearth.org/files/119701_119800/119773/Step5.jpg http://www.srh.noaa.gov/jetstream/lightning/images/lightning8.jpg

  18. http://www.barransclass.com/phys1090/circus/JenkinsD/JenkinsD.htmlhttp://www.barransclass.com/phys1090/circus/JenkinsD/JenkinsD.html Lightning Damage… The damage that lightning can do… • 7500 forest fires/year • 300 injuries/ 93 deaths/year • Property damage Lightning-struck trees on the Blue Ridge Parkway http://www.sciencephoto.com/images/download_lo_res.html?id=670034119

  19. 5. Lightning Q&A and Safety… http://www.srh.noaa.gov/jetstream/lightning/lightning_faq.htm#10 “When lightning roars, go indoors!”

  20. Think About It… Where is the safest place to be during a tornado?

  21. Hail

  22. 1. Tornadoes (Formation of…) • change in wind direction & speed creates horizontal rotation. • Strong updrafts tilt rotating air to vertical position. • Tornado forms within rotating winds. http://www.weatherwizkids.com/tornado_formation.jpg

  23. Tornado Alley The Midwest! 2. A supercell is a giant, self-sustaining storm that can spawn tornados. (A cP air mass from Canada meets a mT air mass from the Gulf of Mexico) 3. Tornado Alley is in the midwest. 4. Most tornadoes occur in May. http://midwestweather.net/archives/tornadoclimatology.htm

  24. TornadoAlley… (Accuweather, 6/8/13)

  25. 5. The Enhanced Fujita Scale… • This scale is used to classify a tornado AFTER the tornado has passed by looking at the damage and effects of the tornado. • EF0 to EF5

  26. The Enhanced Fujita Scale…EF0 or EF1 - Least dangerous - % of all tornados… • 80 - Path… • up to 3 miles - Wind Speed… • 60-115 mph - Duration… • 1 – 10 minutes Dr. Theodore Fujita http://0.tqn.com/d/weather/1/0/i/C/-/-/fujita2s_600.jpg

  27. The Enhanced Fujita Scale…EF2 or EF3 - % of all tornados… • 19 - Path… • 15+ miles - Wind Speed… • 110 - 165 mph - Duration… • 20+ minutes

  28. 5c. The Enhanced Fujita Scale…EF4 or EF5 - Most dangerous!! - % of all tornados… 1 (Thankfully!) - Path… 50+ miles Wind Speed… 200+ mph Duration… 1+ hours http://thedailycap.com/alabama-tornado-2011

  29. Tornado Safety… • Move to a pre-designated shelter – to a basement if possible. • Move to an interior room/hall, lowest floor, under sturdy furniture. (A bath tub is safest!) • Stay away from windows. • Get out of vehicles! • Don’t try to outrun a tornado. • If outside, lie flat in a ditch or depression. • Abandon a mobile home for a shelter.

  30. Lesson 8 Tropical Storms & Hurricanes

  31. Think About It… From which direction do the hurricanes which hit our east coast come?

  32. Focus Question… How does a hurricane form?

  33. Tropical Cyclones… • A tropical cyclone can be described as a… • Large, rotating, low pressure storm 2. We call these storms… • hurricanes 3. Tropical cyclones derive energy from… • Warm, tropical oceans http://www.nhc.noaa.gov/HAW2/english/history.shtml

  34. Tropical Cyclones… • Which direction do tropical cyclones turn in the northern hemisphere? • Counterclockwise • It is a low pressure system! • Remember the Coriolis effect? Fran, 1996, Cape Fear, NC Name was retired!

  35. Tropical Cyclones… • As a hurricane strengthens, what do the following components do? • Air pressure in eyewall– decreases • Surface wind speeds – increase

  36. http://www.srh.noaa.gov/shv/?n=hurricane_rita Tropical Cyclones… 6. Tropical cyclones in the N. Hemisphere move steadily towards… • the west! 7. Which wind system moves across the USA and usually guides hurricanes out into the Atlantic Ocean? • the prevailing westerlies Hurricane Rita – 2005, 3rd lowest pressure in Atlantic (897 mb), hit as cat. 3

  37. 8. Development of a Tropical Cyclone… Tropical Disturbance – a weak, low-pressure system – group of thunderstorms collect

  38. http://www.uvs-model.com/WFE%20on%20tropical%20cyclone%20(Hurricane).htmhttp://www.uvs-model.com/WFE%20on%20tropical%20cyclone%20(Hurricane).htm Development of a Tropical Cyclone… Tropical Depression – a disturbance begins to rotate around the center of low pressure Katrina as a tropical depression

  39. http://www.weatherstockphotography.com/ Development of a Tropical Cyclone… Tropical Storm – a depression is labeled a storm when the wind speeds reach 39 mph. Tropical Storm Dalila, July 2007

  40. http://www.weatherstockphotography.com/ Development of a Tropical Cyclone… Tropical Hurricane – pressure drops and the wind speeds reach 74 mph Dean 2007 Katrina 2005 Ivan2006

  41. Hurricane History… • http://www.nhc.noaa.gov/HAW2/english/history.shtml#galveston

  42. http://apollo.lsc.vsc.edu/classes/met130/notes/chapter15/vertical_circ.htmlhttp://apollo.lsc.vsc.edu/classes/met130/notes/chapter15/vertical_circ.html 9. Anatomy of a Hurricane…

  43. Classifying Hurricanes… The Saffir-Simpson Scale 1. 4 characteristics of a hurricane described… • Wind speed – how high? • Air pressure – how low? • Potential for damage – how much?! • Storm surge • http://www.nhc.noaa.gov/sshws_table.shtml?large

  44. Classifying Hurricanes… 2. The Saffir-Simpson Scale… Categories 1 – 5 Category that does the most damage – 5 Wind speed of a cat 5? > 155 mph Three most powerful storms to hit USA? • Florida Keys, 1935 • Camille, 1969 • Andrew, 1992 http://www.nhc.noaa.gov/pastint.shtml

  45. Classifying Hurricanes… 3. A hurricane runs out of energy When it moves over land or cold water http://backyard.weatherbug.com/profiles/blogs/the-south-central-texas-445

  46. Hurricane Hazards… 1. The strongest winds in a hurricane are in the… • eye wall http://www.med.navy.mil/sites/nmcp/localarea/Weather/PublishingImages/def1.gif

  47. Hurricane Hazards… 2. What is a storm surge? When hurricane force winds drive a mound of ocean water towards coastal areas http://www.chathamemergency.org/images/storm%20surge%202.png

  48. Storm Surge… • 9 of every 10 people who die in a hurricane are killed by the storm surge. • You should EVACUATE so you don’t get killed by the storm surge!

  49. Hurricane Hazards… 3. What hurricane hazard is caused by great amounts of rain? • floods Flooding from Hurricane Fran http://pubs.usgs.gov/of/1996/of96-499/text/PHOTOS.html

  50. Hurricane Hazards… 4. Which agency is responsible for tracking and forecasting hurricanes? • The National Hurricane Center in Miami, FL (FIU Campus) (NOAA)

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