8/9/2019 Tracking a twister

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By Phil Geib and Adam Zoll | TRIBUNE GRAPHICS

Tracking a twister

Recording a tornado

How data will be used

Skilling storm chase

UNMANNED AERIAL SYSTEM (UAS)

STICKNETS (24)

What the name means:Verification of the Originsof Rotation in TornadoesExperiment

Size: 120 scientists andcrew using more than 40vehicles are expected totake part.

Cost: $11.9 million, fundedby the National ScienceFoundation and NationalOceanic and AtmosphericAdministration

Project duration:First phase: May 10-June 13, 2009Current phase: May 1-June 15

Objective: By surrounding supercellstorms and emerging tornadoes andrecording conditions using mobileradar, weather balloons and othertools, scientists hope to answer thefollowing questions:

How, when and why do tornadoesform?

Why are some tornadoes violentand long-lasting while others areweak and short-lived?

What is the structure oftornadoes?

How strong are winds near theground and how do they causedamage?

How can tornado forecasting beimproved?

TORNADO PODS (18)

Cluster ofinstruments thatmeasure:

Wind speedand direction

PrecipitationWater dropsize, distributionand velocity

Tornado podteam quicklysets them upabout 1 mileahead of thestorm in one ortwo rows withpods about 100yards apart. The more pods hit, thebetter the results.

Instrumentsmounted totripods to collectvarious data asthe stormapproaches,including:

Wind speed Barometric

pressure Precipitation Temperature Relative

humidity

Twelve-vehicle team drives innorth-south and east-west patternsaround the storm. Trucks aremounted with sensors to record thefollowing: Time and position of vehicle

via GPS radarAir temperature and pressure Relative humidityWind direction and speed

MESONET (12)

RADAR (10)

Ten radar-mounted trucks including three 13-ton Doppler OnWheels trucks (above) operateat various distances from thestorm and are synchronized andcoordinated to produce three-dimensional maps. Data collectedincludes:Wind speed and direction Precipitation (rain and hail)

Torn

adopa

th

Doppler image of June 5, 2009, tornadoin Wyoming taken by Vortex2

WEATHER BALLOONS(10-20)

Four teams launchhydrogen-filled bal-loons with instrumentsthat relay informationto team vehicles. Theballoons are tracked byradar and record:

Temperature Relative humidityWind

Balloons are deployed atvarious points aroundthe storm.

Radiosonde(measuring device)

2 MILES

A remote-controlled plane is available foruse in parts of the study area. It has a6-foot wingspan, is tethered to amobile mesonet vehicle and hasinstruments to collect readingsfrom around the storm.

Study area Most favorable area for storm intercepts

Tornado sitesreported in 2009

SOURCES: Josh Wurman, Vortex2 radar team leader; NOAA

Predicting tornadoes has long been an inexact science experts say 70 percent of tornado warnings are false alarms. But over the next

several weeks a team of experts will travel throughout the Midwest and Plains states in an unprecedented effort to learn more about

how these storms form and how they can better be predicted.

The Vortex project

Team leaders for the project monitor regional weather reportsbefore deciding which locations may be ripe for tornadoformation. Last year teams drove 12,000 miles in five weekschasing storms.

1-2 miles awayfrom tornado

5-8 miles away

15 miles away

A pair of teams in cars trails the storm and

photographs the following: Cloud formations to help produce mapsshowing patterns on the backside of tornadosystems.Ground-level damage from the storm.Chartered aircraft also may be used.

DAMAGE SURVEY AND PHOTOGRAMMETRY

Sticknet team sets them up 45minutes ahead of the storm in one ortwo rows, with sticknets about a halfmile apart.

MESONET, RADAR AND TORNADO POD PHOTOS COURTESY OF JOSH WURMAN;UAS PHOTO COURTESY SCOTTMILLERMODELS.COM

U.S. TORNADOES

Monthly average for 2007-09

U.S. TORNADO DEATHS

100

200

300

DNOSAJJMAMFJ

1009082007

81

21

126

16*

* As of Wednesday

In a tornadic storm, colder,denser air creates a down-draft while warmer air rises.

By measuring temperature, precipitation, wind and humiditywithin and around a storm, scientists can better understandhow different pockets of air interact to form a tornado.

Scientists will be paying particular attention to a feature calledthe rear flank downdraft and its role in spawning twisters.

WGNs chief meteorologist Tom Skilling is out chasing a storm.Watch Skillings live reports from the field and find out aboutthe latest weather technology tonight on WGN News at 9.

More talkMore Weather Week talk withGreg Jarrett and his team onWGN Radio 720, 5 - 9 a.m.

TomorrowIn the Chicago Tribune and onWGN-TV: The art and scienceof weather prediction.