Progressive Management - Superstorm Encyclopedia: Tornadoes, Severe Thunderstorms, Hurricanes, Tropical Storms, Typhoons, Cyclones--Meteorology, Forecasts, Safety and Preparedness, History, Disaster Health Problems

U.S. Government, National Weather Service(NWS), National Oceanic and Atmospheric Administration (NOAA),National Hurricane Center (NHC), Federal Emergency ManagementAgency (FEMA), Centers for Disease Control (CDC)

Smashwords Edition

Copyright 2011 Progressive Management

Questions? Suggestions? Comments? Concerns?Please contact the publisher directly at

Remember, the book retailer can't answer yourquestions, but we can!

* * * * * * * * * * *

Smashwords Edition, License Notes

This ebook is licensed for your personalenjoyment only. This ebook may not be re-sold or given away toother people. If you would like to share this book with anotherperson, please purchase an additional copy for each person youshare it with. If you're reading this book and did not purchase it,or it was not purchased for your use only, then you should returnto Smashwords.com and purchase your own copy. Thank you forrespecting the hard work of this author.

* * * * * * * * * * *

This is a privately authored news service andeducational publication of Progressive Management. Our publicationssynthesize official government information with original material -they are not produced by the federal government. They are designedto provide a convenient user-friendly reference work to uniformlypresent authoritative knowledge that can be rapidly read, reviewed,or searched. Vast archives of important data that might otherwiseremain inaccessible are available for instant review no matterwhere you are. This e-book format makes a great reference work andeducational tool. There is no other reference book that is asconvenient, comprehensive, thoroughly researched, and portable -everything you need to know, from renowned experts you trust. Forover a quarter of a century, our news, educational, technical,scientific, and medical publications have made unique and valuablereferences accessible to all people. Our e-books put knowledge atyour fingertips, and an expert in your pocket!

TORNADO CONTENTS

* * * * * * * * * * * *

* * * * * * * * * * * *

Tornadoes were, for most, dark and mysteriousmenaces of unfathomable power, fast-striking monsters from the skycapable of sudden and unpredictable acts of death anddevastation.

* * * * * * * * * * * *

Tornado Basics

What is a tornado?

A tornado is a narrow, violently rotatingcolumn of air that extends from the base of a thunderstorm to theground. Because wind is invisible, you can't always see a tornado.A visible sign of the tornado, a condensation funnel made up ofwater droplets, sometimes forms and may or may not touch the groundduring the tornado lifecycle. Dust and debris in the rotatingcolumn also make a tornado visible and confirm its presence.(Condensation funnel - A funnel-shaped cloud associated withrotation and consisting of condensed water droplets (as opposed tosmoke, dust, debris, etc.)

What is known?

Tornadoes are the most violent of allatmospheric storms.

There are two types of tornadoes: those thatcome from a supercell thunderstorm, and those that do not.

Tornadoes that form from a supercellthunderstorm are the most common, and often the most dangerous. Asupercell is a long-lived (greater than 1 hour) and highlyorganized storm feeding off an updraft (a rising current of air)that is tilted and rotating. This rotating updraft - as large as 10miles in diameter and up to 50,000 feet tall - can be present asmuch as 20 to 60 minutes before a tornado forms. Scientists callthis rotation a mesocyclone when it is detected by Doppler radar.The tornado is a very small extension of this larger rotation. Mostlarge and violent tornadoes come from supercells.

SUPERCELL - A thunderstorm with apersistent rotating updraft. Supercells are rare, but areresponsible for a remarkably high percentage of severe weatherevents - especially tornadoes , extremely large hail and damagingstraight-line winds. They frequently travel to the right of themain environmental winds (i.e., they are right movers). Radarcharacteristics often (but not always) include a hook or pendant,bounded weak echo region (BWER), V-notch, mesocyclone, andsometimes a TVS. Visual characteristics often include a rain-freebase (with or without a wall cloud), tail cloud, flanking line,overshooting top, and back-sheared anvil, all of which normally areobserved in or near the right rear or southwest part of the storm.Storms exhibiting these characteristics often are called classicsupercells; however HP storms and LP storms also are supercellvarieties.

UPDRAFT - A small-scalecurrent of rising air. If the air is sufficiently moist, then themoisture condenses to become a cumulus cloud or an individual towerof a towering cumulus or Cb.

UPDRAFT - A small-scalecurrent of rising air. If the air is sufficiently moist, then themoisture condenses to become a cumulus cloud or an individual towerof a towering cumulus or Cb.

GUSTNADO - [Slang], gustfront tornado. A small tornado, usually weak and short-lived, thatoccurs along the gust front of a thunderstorm. Often it is visibleonly as a debris cloud or dust whirl near the ground. Gustnadoesare not associated with storm-scale rotation (i.e. mesocyclones );they are more likely to be associated visually with a shelf cloudthan with a wall cloud.

LANDSPOUT - [Slang], atornado that does not arise from organized storm-scale rotation andtherefore is not associated with a wall cloud (visually) or amesocyclone (on radar). Landspouts typically are observed beneathCbs or towering cumulus clouds (often as no more than a dustwhirl), and essentially are the land-based equivalents ofwaterspouts.

Visualizing Updraft Rotation in Supercell andNon-Supercell Thunderstorms

To visualize the horizontal spinning effectcaused by wind shear, roll a pencil along a table top with the palmof your hand. Now put it between your hands, tilt your handsvertically and slide your right hand away from you. You have justcreated a miniature rotating updraft! To illustrate the waynon-supercell tornadoes are formed, put a pencil between yourhands, and place your hands perpendicular to a table (the tablerepresents the ground, your hands represent wind coming fromdifferent directions at ground level, and the pencil is a parcel ofair that gets caught and starts spinning). The spinning at thesurface is drawn into the updraft of a developing or maturethunderstorm and is stretched into a tornado.

SHEAR - Variation in wind speed(speed shear) and/or direction (directional shear) over a shortdistance. Shear usually refers to vertical wind shear, i.e., thechange in wind with height, but the term also is used in Dopplerradar to describe changes in radial velocity over short horizontaldistances.

DOWNDRAFT - A small-scalecolumn of air that rapidly sinks toward the ground, usuallyaccompanied by precipitation as in a shower or thunderstorm. Adownburst is the result of a strong downdraft.

More Ideas About Supercell Tornadogenesis

Scientists are actively trying to prove ordisprove a number of tornadogenesis hypotheses. It is complicatedscience that draws on information from observations, theory, andmathematical and physical models. These are some basic ideas (basicto a scientist, that is) about the processes that might causetornadoes to form from supercells:

Dynamic Pipe Effect

Development of a tornado begins whenhorizontal winds coming together from different directions arestrong 3-4 km above the ground and weak or absent near the ground.The result is that rotation first increases aloft. The youngtornado will build downward by something called the dynamic pipeeffect (DPE): air can not enter through the sides of this belt ofrotating air, but can pass through its ends like a pipe. Thepartial vacuum created within the pipe draws weakly rotating air upinto the pipe's lower end. This causes the air to spin faster andeventually become part of the pipe. New sections on the rotatingpipe form at lower and lower altitudes through this same processuntil the pipe (tornado) is in contact with the ground.