Severe Weather: Future, Present, Past

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Severe WeatherFuture, Present, Past

• Deke Arndt
• Associate State Climatologist
• Oklahoma Climatological Survey

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My Role Today
Climate Change SPOOOOKY!
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Climate Change Scenarios

• THE GOOD NEWS

• THE BAD NEWS

• Theres a lot of time between now and future
  projections

• Theres a lot of time between now and future
  projections

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Climate Change Severe Weather

• Trapp, Diffenbaugh, Brooks, Baldwin, Robinson,
  and Pal (2007). Changes in severe t-storm
  environment frequency during 21st century caused
  by anthropogenically enhanced global radiative
  forcing, Proc. of National Academy of Sciences.
• One of many downscaling and add value studies
  in the wake of climate change projections
• Designed to offer more intelligence than 1.6C
  warmer and 3 in. more rain in an average year
• We live our lives in the rhythm of days, studies
  like these take broad-brush projections and ask
  how will these affect our days?

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First of all a definition!

• Severe Thunderstorm has a specific meaning
• 50 knot (58 mph) winds
• 3/4 (nickel) or larger hail
• A tornado

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Ingredients for Severe Storms
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Severe Weather Late 21st Century
Summer
Spring
1-2 more severe weather potential days in
southern plains.
1-3 more severe weather potential days in
eastern 2/3 of U.S.
Potential Severe Weather Days (versus now)
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Ingredients for Severe Storms
Trapp et al. projections for south-central U.S.
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Summer in south-central U.S.

• Summer Implication Here

• For Tropical Cyclone Development

• Higher instability (due to increased low-level
  moisture)
• Even less wind shear than our typical low shear
  summers
• Typically far from any boundaries (mired in a
  large air mass)

• Very high low-level moisture (usually achieved by
  being over warm water)
• Very light wind shear
• A large, homogenous airmass from which to draw
  (after initial development)

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August 2007 Tropical Storm Erin

• Lets stop talking about future projections

Arndt, Basara, McPherson, Illston, McManus,
Demko The Overland Reintensification of Tropical
Storm Erin Bulletin of the American
Meteorological Society. In review.
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Tropical Storm Erin
Tropical Storm Erin Aug 18-19, 2007
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Before Erin WET Summer 2007

• Jun 07 Wettest on record (since 1895) for OK.
• Jun-Jul rain record / near-record across central
  OK.
• Consecutive days of precip at OKC
• Old record 14 days (spring 37) New record 20
  days (Jun. 13 Jul. 2, 07)

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Days of river flooding Jun-Jul 07
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Washita R. Near Chickasha
Photo by Laura Martin, Oklahoma Mesonet
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Why is This Important?

• Despite a relatively dry early August 2007, the
  soil profile remained quite wet (especially for
  summer)
• Evaporation was enhanced
• Vegetation was actively pumping moisture into the
  lower atmosphere.

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Erins Storm Track
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Erins Offshore Life
From R.D. Knabb (2007). Tropical Storm
Erin Tropical Cyclone Report. National Hurricane
Center
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What Erin Encountered in OK

• Relatively High Instability
• Relatively Low shear
• Abundant Low-Level Moisture
• The nearest boundary was in South Dakota

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What Happened
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How Erin was Seen in Real-Time
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How Erin was Seen in Real-Time
Erin at her strongest 223 am (2 hrs before
eye developed). Winds and pressure contours
from the Okla. Mesonet
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Erins Rainfall Superlatives
Tropical Cyclones are prolific rainmakers!
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More Erin Rainfall Superlatives
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Near Chickasha
Photo by Laura Martin, Oklahoma Mesonet
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A Few Concluding Remarks

• There is no evidence that T.S. Erin was driven
  by, or influenced by, climate change
• It was a uniquely rare event
• We saw similar things this year (2008) with Fay
  (central FL)

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Can Mitigation (risk mgmt) save lives?

• Lessons Learned

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May 3, 1999
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May 3, 1999 Tornadoes
NOAA Photo Library
NOAA Photo Library
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May 3, 1999 Tornadoes
NOAA Photo Library
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May 3, 1999 Tornadoes
NOAA Photo Library
NOAA Photo Library
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May 3, 1999 Tornadoes
NOAA Photo Library
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Encouraging mitigation

• In the aftermath, FEMA mitigation money set aside
  to incentivize construction of safe rooms or
  underground shelters
• Safe room is a reinforced-concrete room in the
  interior of a home.
• Existing construction or new construction

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Encouraging Mitigation

• Rooms must be built to FEMA specs (published U
  North Texas).
• Inspected by FEMA official or local EM
• Up to 2000 reimbursement to homeowner (after
  construction)
• Safe rooms built in about 75 school districts
• District provided 25 match (incl. in-kind)

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Do Safe Rooms Work?
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Do Safe Rooms Work?
Photo provided by Oklahoma Department of
Emergency Management
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Thanks!

• Deke Arndt
• darndt_at_ou.edu
• 405-325-3076

Photo by Ken Meyers, OCS