| NATS 101 Lecture 29 Tornadoes |
| What is a Tornado? |
| Tornado - | |
| A violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud | |
| Glossary of Meteorology (Glickman 2000) |
| Slide 3 |
| Tornado
Classification (Classified by Maximum Winds) |
| Slide 5 |
| Intense Tornado, Likely F5 |
| Tornado Debris-No Funnel |
| Waterspouts |
| Weak Tornadoes | |
| Occur over Water |
| Slide 9 |
| Tornado Formation |
| Horizontal wind shear lead to rotation about horizontal axis | |
| Updraft of developing thunderstorm tilts the axis of rotation from horizontal to vertical | |
| Causes thunderstorm to rotate about vertical axis |
| Supercell Thunderstorm |
| Suction Vortices |
| Multiple vortices are frequently observed with tornados | |
| Leads to further localization of tornado damage | |
| More Tornadoes |
| Airborne Debris |
| More Airborne Debris |
| Dissipating-Weak Tornadoes |
| Tornado Weather |
| Strong jet stream | |
| 500 mb trough | |
| Cold, dry air aloft | |
| Warm, moist air at low levels | |
| Sharp boundary between cold, dry air and warm, humid air at surface |
| Slide 18 |
| Where do Tornados Occur? |
| Maximum frequency situated in Central Plains, or so-called ÒTornado AlleyÓ |
| Peak Frequency |
| What Time of Day Do Tornados Occur? |
| Diurnal peak in tornado frequency varies by region Mostly afternoon, early evening |
| Slide 22 |
| Slide 23 |
| Slide 24 |
| Wall Cloud |
| Funnel with Debris |
| Funnel |
| Funnel without Debris |
| Overshooting Top |
| Tornado |
| Tornado Warning |
| Severe Thunderstorm Watch |
| Severe Thunderstorm Warning |
| Tornado Fact |
| Tornadoes occasionally develop where a severe thunderstorm watch or warning is in effect. | |
| Tornado Fact |
| Where are Strongest Winds? |
| Total speed is the sum of the rotational velocity (± 50 kts) and translational velocity (+100 kts) components | |
| Accounts for the asymmetric damage along tornado path |
| Damage Path |
| Tornado Damage |
| Trailer Damage |
| Flying Auto! |
| Damaged Framed Structure |
| House Lifted from Foundation |
| Storm Cellar |
| House Destroyed, but | |
| No Damage in Cellar! | |
| SoÉanother reason why you should store your fine cabernets and pinot noirs in a cellar! |
| Slide 44 |
| Slide 45 |
| Slide 46 |
| Convective Outlooks |
| NOAA Storm Prediction Center issues Day 1-2-3 convective outlooks for the United States | |
| Based on output from NWP models and forecaster experience. |
| Satellite Imagery |
| Doppler Radar |
| Doppler Radial Winds |
| Doppler Radar |
| Doppler can measure wind component into and away from radar | |
| Radar can detect horizontal shear and rotation of supercell thunderstorms |
| Radar Reflectivity |
| Tornados are located in regions where reflectivity shows Òhook echoÓ |
| Supercell with Tornado |
| Tornado occurs in precipitation free region (almost always) | |
| Note that updraft rotates and tilts | |
| Assignment for Next Lecture |
| Topic - Hurricanes | |
| Reading - Ahrens, p293-314 | |
| Problems – | |
| 11.6, 11.9, 11.10, 11.13 , 11.14 , 11.15 | |