Tornado May2010

8/12/2019 Tornado May2010

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WITH A TRIBUTE TO MOORE IN MAY 13

TORNADOES....THE RECENT

OKLAHOMA EXPERIENCE.



EVOLUTION OF THETORNADO...



• 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



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



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



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



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



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



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.



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.



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



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



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



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



Lightning & Thunder

Charge differences between the

thunderstorm and ground can

cause lightning strokes of

30,000°C, and this rapid heating

of air will creates an explosive

shock wave called thunder, which

requires approximately 3 seconds

to travel 1 kilometer.



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.



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



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.



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



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.



The 4 “New Tornado Alleys”

Recent research

shows that there

are really 4 separate

tornado alleys… Tornado alley

Hoosier alley

Dixie alley

Carolina alley



How we get from....

• To here:

Transition...



Remember wind shear formation --- the ‘roll cloud’ -

Wind Shear initiates rotation...



Rising air elevates the roll cloud



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.





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



And... A tornado is spawned



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



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...



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





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

Tornado Breeding Superstorms



f



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



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



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



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



Fast Scan of Radar 3May99



Fast Scan of Radar 3May99

Moore 1999 (from space)



Moore 1999 (from space)

1 May 2010



1 May 2010

Waterspout



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???



Just how bad is this tornado???

Fujita Tornado Scale




Comparing Beaufort Fujita and Mach Scales



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

F – scale: 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




The Fujita scale isdesigned to show the windspeed.

Damage assessment was

derived after the fact… thisled to a few problems.


The Enhanced Fujita Scale



The Enhanced Fujita scale isa damage assessmentscale that is related to windspeed.

Damage assessment drivesthe calculation andassignment of the ‘EF’number.

The Enhanced Fujita Scale

EF has 28 Damage Indicators



Residences

Commercial/reta

structures

Schools

Professional build

Metal

buildings/canopie

Towers/poles

Vegetation

g

Each indicator has “Degrees Of Damage



DOD Damage Description EXP LB UB

1 Threshold of visible damage 63 53 80

2 Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 79 63 97

3 Broken glass in doors and windows 96 79 114

4Uplift of roof deck and loss of significant 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




4Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors

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







Each indicator has Degrees Of Damage

DOD Damage Description Framed House EXP LB UB

“Degrees Of Damage”



DOD Damage Description – Framed House EXP LB UB



3Broken glass in doors and windows 96 79 114

4Uplift of roof deck and loss of significant roof covering material (>20%); collapse of

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







Expected wind 97 mph

F to EF Conversion



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



•BEFORE…

10 May 2008

Picher, OK



10 May 2008

Picher, OK



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





















































Lone Grove Tornado



Lone Grove Tornado



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.



Lone Grove „hook‟



?? Lone Grove Tornado ??



Lone Grove Tornado Path



Lone Grove



Power line hazards



Trailer Damage



DOD Damage Description – Framed House EXP LB UB


2 Loss of roof covering material (<20%) gutters and/or awning; loss of vinyl or metal siding 79 63 97

“Degrees Of Damage”





4Uplift of roof deck and loss of significant roof covering material (>20%); collapse of

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







All walls collapsed

Expected wind 170 mph

Frame House



Frame House Damage



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



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 Ark – 1 dead



1May2010 Ark



1May2010 Ark



1May2010 Ark



1May2010 Ark



20 minutes vs 60 Seconds?



• 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 15

minutes ahead of time, deaths decreased.

However, lead times greater than 15 minutes seemed to increase

fatalities compared with no warning.

> 15 Minute Warning



"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



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…



In the event our luck does run out please put me



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...



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]












Tornado May2010

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