Changes in FScale, Hail and Convective Wind Reports

1
Changes in F-Scale, Hail and Convective Wind
Reports

• Dan McCarthy
• Joe Schaefer
• NOAA/NWS Storm Prediction Center

2
Questions Number of Severe Reports

• Why are there so many?
• Is the increase due to El Nino? La Nina?
• Does the increase have anything to do with global
  warming?

3
Reporting Has Changed

• Training has increased
• More spotters
• NWS
• Media
• EM
• Need for news!
• Cable news revolutionized news
• Weather Channels (TWC, NBC, private)

4
Reporting Has Changed

• There are TWO types of severe
• NWS definition
• ¾ diameter hail or larger
• Convective gusts 50 kt or greater
• Tornado
• WHAT THE PUBLIC PERCEIVES TO BE SEVERE!
• Vivid lightning
• Any kind of damage
• Darkness
• Heavy rain

5
Reporting Has Changed

• Age of Communications and Electronics
• Cellular phones
• Including picture phones
• Hand sized cameras
• Hand sized digital recorders
• With CD rather than tape!

All this technology makes more eyewitnesses!!!
6
Reports have Changed

• SELS days in KC (when we hand plotted reports)
• Did not log
• Tree Damage
• Marble-size Hail
• Wind gusts gt 50 kt unless thunder was reported
  within 30 minutes
• Observers comments before ASOS was installed
• Possible Tornadoes or Funnel Clouds
• Dime size hail became non-severe 2 years ago

7
Convective Winds Hail 1955-2005
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Convective Gusts (kt)
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Storm Data

• In 2005, two special reports
• Downed trees and power lines 5 kt
• Downed trees and power lines 10,000 10 kt
• Local Storm Reports
• Tree limbs down
• Branches down
• Several branches down

Tree Damage?
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Hail Size Distribution
11
Hail Distribution
Penny
Golf Ball
Quarter
Nickel
Grapefruit
Tennis Ball
Tea Cup
Half Dollar
Ping Pong
Hen Egg
Baseball
Softball
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Kansas Experiment
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Tornadoes
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F-Scale Distribution
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Enhanced Fujita (EF) Scale
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National Severe Weather Workshop

• March 1-2-3, 2007
• National Center for Employee Development/Marriott
  in Norman, OK
• Banquet at NWC with tours!!

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Thank You
Questions?