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    WITH A TRIBUTE TO MOORE IN MAY 13

    TORNADOES....THE RECENT

    OKLAHOMA EXPERIENCE.

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    EVOLUTION OF THETORNADO...

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    When the ground

    warms and the high

    air is cold the warm

    air near the surface

    rises. As it cools, the

    water vapor will

    condense, forming

    clouds

    Formation of a Thunderstorm

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    THREE STAGES :

    1.AN UNSTABLE ATMOSPHERE AND

    VERTICAL UPDRAFTS KEEP

    PRECIPITATION SUSPENDED

    2.ENTRAINMENT OF DRY AIR THAT

    CAUSES COOLER AIR FROM

    EVAPORATION, TRIGGERING

    DOWNDRAFTS AND FALLING

    PRECIPITATION AND GUST FRONTS

    3.WEAKENING UPDRAFTS AND LOSS OF

    THE FUEL SOURCE AFTER 15 TO 30

    MINUTES.

    ORDINARY THUNDERSTORMS

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    Severe Thunderstorms

    Severe thunderstorms produce a minimum of

    3/4 inch hail and/or

    wind gusts of 50 knots and/or

    tornado winds.In ordinary storms, the downdraft and falling precipitation cut off the

    updraft.

    In severe storms, winds aloft push the rain ahead and the updraft is

    not weakened and the storm can continue maturing.

    The single supercell storm shown here maintained its structure forhours

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    Cool downdrafts leaving a mature and dissipating storm may

    offer relief from summer heat, but they may also force

    surrounding, low-level moist air upward.

    Hence, dying storms often trigger new storms, and the

    successive stages may be viewed in the sky.

    Multicell Storms

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    Pre-frontal squall linesidentify major stormstriggered by a cold front thatmay contain several severe

    thunderstorms, somepossibly supercells,extending for more than1000 kilometers.

    This 1989 storm spawned 25tornadoes, the worst killing25 people.

    Pre-frontal Squall Lines

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    An organized collection ofthunderstorms extending across alarge region is a mesoscaleconvective complex (MCC).

    MCC's can regenerate new stormsand last for upwards of 12 hoursand may bring hail, tornadoes,and flash floods.

    They often form beneath a ridgeof high pressure.

    Mesoscal Convective

    Complex

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    Gust front and Microburst

    Turbulent air forms along the

    leading edge of the gust front,

    which can generate tumbling dust

    clouds.

    Such gust fronts and associatedcold dense air often feel like a

    passing cold front, and may cause

    a 1 to 3 mb local rise in pressure,

    called a mesohigh.

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    Shelf Cloud

    When unstable air is prevalent near

    the base of the thunderstorm, the

    warm rising air along the forward

    edge of the gust front is likely togenerate a shelf, or arcus, cloud.

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    Trailing Stratified Clouds

    An extensive region of stratified clouds may follow behind a squall line.

    This figure shows a loop of rising and falling air that supplies the moisture to

    the stratiform clouds and associated light precipitation

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    This is wind shear formation --- the roll cloud.... more later.

    When winds aloft blow in

    one direction and winds

    on the surface blow inanother direction, they

    create a horizontally

    rotating mass of air

    Wind Shear Formation

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    Abrupt geographic change

    from moist to dry dew-pointemperature, called drylineform in western TX, OK, aKS in the spring and summ

    Cool air pushes hot and drair over the warm moist airthe height of the centralplains. Such mixing causelarge scale instabilities and

    the birth of many supercelstorms.

    Dry Line Formation

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    Middle troposphere winds control individual thunderstorms.Dying storm downdrafts spawn new storms so the storm systemmoves rightwards relative to the upper level winds.

    Here upper level winds move storms to the northeast, but downdraftsgenerate new cells to the south, which eventually cuts off moisture tothe old cell.

    Thunderstorm Movement

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    Lightning & Thunder

    Charge differences between the

    thunderstorm and ground can

    cause lightning strokes of

    30,000C, and this rapid heating

    of air will creates an explosive

    shock wave called thunder, which

    requires approximately 3 seconds

    to travel 1 kilometer.

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    Lightning Stroke Development

    Charge layers in the cloud are formed

    by the transfer of positive ions fromwarmer hailstones to colder ice crystals.

    When the negative charge near the

    bottom of the cloud is large enough to

    overcome the air's resistance, a

    stepped leader forms.

    A region of positive ions move from the

    ground toward this charge, which then

    forms a return stroke into the cloud.

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    Nearly 90% of lightning is the negative cloud-to-ground type,

    but positive cloud-to-ground lightning can generate more

    current and more damage.

    Several names, such as forked, bead, ball, and sheet

    lightning describe forms of the flash.

    Distant, unseen lightning is often called heat lightning.

    Types of Lightning

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    Lightning Rods & Fulgurite

    Metal rods that are grounded by wires

    provide a low resistance path for

    lightning into the earth, which is a poor

    conductor.

    The fusion of sand particles into root like tu

    called fulgurite, may result.

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    A rapidly rotating

    column of air oftenevolves through a

    series of stages, from

    dust-whirl, to organizing

    and mature stages, and

    ending with theshrinking and decay

    stages.

    Winds in this southern

    Illinois twister exceeded150 knots.

    Tornado

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    Tornado Occurrence

    Tornadoes from all 50 states of the U.S. add up to more than 1000 tornadoes

    annually, but the highest frequency is observed in tornado alley of the Central

    Plains.

    Nearly 75% of tornadoes form from March to July, and are more likely when warm

    humid air is overlain by cooler dryer air to cause strong vertical lift.

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    The 4 New Tornado Alleys

    Recent research

    shows that there

    are really 4 separate

    tornado alleysTornado alley

    Hoosier alley

    Dixie alley

    Carolina alley

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    How we get from....

    To here:

    Transition...

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    Remember wind shear formation --- the roll cloud -

    Wind Shear initiates rotation...

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    Rising air elevates the roll cloud

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    The first sign that a supercell may form a tornado is rotating clouds at thebase of the storm, which may lower and form a wall cloud, shown in this

    picture.

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    Spinning horizontal vortex tubes created by surface wind shear may be tilted and forin a vertical path by updrafts. This rising, spinning, and often stretching rotating air m

    then turn into a tornado.

    This changes the roll cloud into a vertical formation: A tornado

    Rotation Moved From Horizontal to Vertica

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    And... A tornado is spawned

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    As the tornado moves

    along a path, the circulartornado winds blowingopposite the path of

    movement will have lessspeed.

    For example, if the stormrotational speed is 100knots, and its path is 50

    knots, it will have amaximum wind of 150knots on its forward

    rotation side.

    Tornado Wind Speed

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    A system of tornadoes with smallerwhirls, or suction vortices,

    contained within the tornado iscalled a multi-vortex tornado.

    Damage from tornadoes mayinclude its low pressure centerscausing buildings to explode out

    and the lifting of structures.

    Human protection may be greatest

    in internal and basement rooms ofa house.

    Suction Vortices...

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    Tornadoes from all 50 states of the U.S. add up to more than 1000 tornadoesannually, but the highest frequency is observed in tornado alley of the Central Plains

    Nearly 75% of tornadoes form from March to July, and are more likely when warm

    humid air is overlain by cooler dryer air to cause strong vertical lift.

    Tornado Occurrence

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    Supercell thunderstorms may have many of the features illustrated here, includingmesocyclone of rotating winds formed when horizontal vorticity was tilted upward

    Tornado Breeding Superstorms

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    f

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    Supercell thunderstormdevelopment may create anarea where the updraft andcounterclockwise swirl of

    upper winds converge into arear flank downdraft.

    This downdraft can theninteract with lower level

    inflow winds and spawn atornado.

    Rear Flank Downdraft

    N S ll T d

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    If a pre-existingwall cloud was notpresent, than anytornado formed isnot from asupercell storm.

    These tornadoesare often not asstrong as thoseformed bysupercells.

    Non-Supercell Tornadoes

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    A single Doppler radar unit canuncover many features ofthunderstorm rotation andmovement, but cannot detect windsparallel to the antenna.

    As such, data from two or moreunits might be combined to providea complete view of the storm.

    Doppler lidar (light beam ratherthan microwave beam) provides

    more details on the storm features,and will help measure wind speedsin smaller tornadoes.

    Doppler Radar

    NEXRAD Wi d A l i

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    NEXt Generation WeatherRADar (NEXRAD)Uses Doppler measurementsto detect winds

    moving toward (green)moving away (blue)

    Which shows areas ofrotation and strong shear.

    NEXRAD Wind Analysis

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    Fast Scan of Radar 3May99

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    Fast Scan of Radar 3May99

    Moore 1999 (from space)

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    Moore 1999 (from space)

    1 May 2010

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    1 May 2010

    Waterspout

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    Warm, shallow coastal water isoften home to waterspouts,which are simply a tornadoover water

    The waterspout does not drawwater into its core, but is acondensed cloud of vapor.

    A waterspout may, however, liftswirling spray from the wateras it touches the water surface.

    Waterspout

    Just how bad is this tornado???

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    Just how bad is this tornado???

    Fujita Tornado Scale

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    Fujita Tornado Scale

    Comparing Beaufort Fujita and Mach Scales

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    1 2 3 4 5 6 7 8 9 10 11 120Beaufort Scale

    1 2 3 4 5 6 7 8 90 10 11 12Fujita Scale

    0.6 1.0

    Mach Scale

    B1 B3B5

    B7 B9

    B11

    F0F1

    F2

    F3

    F4

    F5

    F12M1.0

    M0.6

    M0.7

    M0.8

    B17

    Beaufort: V = 1.870B3/2 mph

    Fscale: V = 14.1(F+2)3/2 mphMach scale: V = (742 +1.3)M mph

    These scales have wind speeddefined first, impacts/damage

    were assigned to wind speeds.

    Comparing Beaufort, Fujita, and Mach Scales

    Fujita Tornado Scale

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    The Fujita scale isdesigned to show the windspeed.

    Damage assessment was

    derived after the fact thisled to a few problems.

    Fujita Tornado Scale

    The Enhanced Fujita Scale

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    The Enhanced Fujita scale isa damage assessmentscalethat is related to windspeed.

    Damage assessment drivesthe calculation andassignment of the EFnumber.

    The Enhanced Fujita Scale

    EF has 28 Damage Indicators

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    Residences

    Commercial/reta

    structures

    Schools

    Professional build

    Metal

    buildings/canopie

    Towers/poles

    Vegetation

    g

    Each indicator has Degrees Of Damage

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    DOD Damage Description EXP LB UB

    1 Threshold of visible damage 63 53 80

    2 Loss of roof covering material (20%); collapse of chimney; garage doors

    collapse inward or outward; failure of porch or carport 97 81 116

    5 Entire house shifts off foundation 121 103 141

    6 Large sections of roof structure removed; most walls remain standing 122 104 142

    7 exterior walls collapsed 132 113 153

    8 Most walls collapsed except small interior rooms. 152 127 178

    9 All walls collapsed 170 142 198

    10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220

    Example DODs for a Framed House DI (FR12 or DI2)

    Note some consecutive DODs have larger overlap than others

    DOD Damage Description EXP LB UB

    1 Threshold of visible damage 63 53 80

    2 Loss of roof covering material (20%); collapse of chimney; garage doors

    collapse inward or outward; failure of porch or carport 97 81 116

    5 Entire house shifts off foundation 121 103 141

    6 Large sections of roof structure removed; most walls remain standing 122 104 142

    7 exterior walls collapsed 132 113 153

    8 Most walls collapsed except small interior rooms. 152 127 178

    9 All walls collapsed 170 142 198

    10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220

    Each indicator has Degrees Of Damage

    DOD Damage Description Framed House EXP LB UB

    Degrees Of Damage

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    DOD Damage DescriptionFramed House EXP LB UB

    1 Threshold of visible damage 63 53 80

    2 Loss of roof covering material (20%); collapse of

    chimney; garage doors collapse inward or outward; failure of porch or carport97 81 116

    5 Entire house shifts off foundation 121 103 141

    6 Large sections of roof structure removed; most walls remain standing 122 104 142

    7 exterior walls collapsed 132 113 153

    8 Most walls collapsed except small interior rooms. 152 127 178

    9 All walls collapsed 170 142 198

    10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220

    Expected wind 97 mph

    F to EF Conversion

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    F Scale Wind Speed EF-Scale Wind Speed

    F0 45-78 EF0 65-85

    F1 79-117 EF1 86-109

    F2 118-161 EF2 110-137

    F3 162-209 EF3 138-167

    F4 210-261 EF4 168-199

    F5 262-317 EF5 200-234Wind speeds in mph, 3-second gust

    F to EF Conversion

    Picher, OK

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    BEFORE

    10 May 2008

    Picher, OK

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    10 May 2008

    Picher, OK

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    Population (year 2000): 1,640.Estimated population in July 2006: 1,633 (-0.4% change)

    Males: 800 (48.8%)Females: 840 (51.2%)

    Ottawa CountyMedian resident age: 36.8 yearsOklahoma median age: 35.5 years

    Zip codes: 74360.Approximately 60% of houses are abandoned.

    Vital Statistics

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    Lone Grove Tornado

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    Lone Grove Tornado

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    EF4 Tornado

    First violent February tornado since 1950

    Killed 8, Injured 46

    Part of complex that hit OKC and Edmond

    6 reported tornadoes in OK that day.

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    Lone Grove hook

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    ?? Lone Grove Tornado ??

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    Lone Grove Tornado Path

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    Lone Grove

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    Power line hazards

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    Trailer Damage

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    DOD Damage DescriptionFramed House EXP LB UB

    1 Threshold of visible damage 63 53 80

    2 Loss of roof covering material (

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    2 Loss of roof covering material (20%); collapse of

    chimney; garage doors collapse inward or outward; failure of porch or carport97 81 116

    5 Entire house shifts off foundation 121 103 141

    6 Large sections of roof structure removed; most walls remain standing 122 104 142

    7 exterior walls collapsed 132 113 153

    8 Most walls collapsed except small interior rooms. 152 127 178

    9 All walls collapsed 170 142 198

    10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220

    All walls collapsed

    Expected wind 170 mph

    Frame House

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    Frame House Damage

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    An EF-4 tornado, with winds estimated by the National WeatService at 180 mph to 185 mph

    2009 2008 2007 2006 3Year

    Monthly Tornado Deaths

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    preliminary Actual Actual Actual Average

    Jan 10 84 21 47 51Feb 44 147 52 12 70

    Mar 33 so far 129 170 150 149

    Apr 189 167 245 200

    May 461 252 139 284

    Jun 294 128 120 181

    Jul 93 69 71 77

    Aug 101 75 80 85

    Sep 111 52 84 82

    Oct 21 86 76 61

    Nov 15 7 42 21

    Dec 46 19 40 36

    Tot 1691 1098 1106 1297

    1May2010 Ark1 dead

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    1May2010 Ark

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    1May2010 Ark

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    1May2010 Ark

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    1May2010 Ark

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    20 minutes vs 60 Seconds?

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    Data analysis of 18,000 tornadoes between 1986 and 2002. On average advanced warning reduced expected injuries by abou

    32 percent. Overall, when people were notified of a tornado up to about 15minutes ahead of time, deaths decreased.

    However, lead times greater than 15 minutes seemed to increase

    fatalities compared with no warning.

    > 15 Minute Warning

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    "There is anecdotal evidence that came out of the

    tornadoes in Oklahoma and Missouri in February. Out

    of the 23 fatalities, eight were people in cars. I don't

    know if those people were trying to outrun the storm,

    or if they just happened to be in their cars."

    > 15 Minute Warning

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    When people don't know what to do in a dangeroussituation, many times they do the wrong thing. I am

    surprised the authors didn't take that approach. It is

    almost like they are saying that advance warning is a

    bad thing, when in reality it is a GREAT thing; it's justthat people are not well educated enough to know how

    to respond.

    WE NEED TO FIX THIS!

    It may be a busy season

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    In the event our luck does run out please put me

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    In the event our luck does run out, please put me

    down for as much warning as possible.

    I have things to do...

    Thank You...

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    Thank You...

    Chuck Stewart MD EMDM

    Professor of Emergency Medicine,

    University of Oklahoma

    email [email protected]

    [email protected]

    Cell - 918-344-4557

    Work - 918-660-3828

    2E24 Schusterman Center4502 E. 41st Street

    Moore 1999

    mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]
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