Transcript Derechos and Hurricanes: Predictions, Warnings, and Responses Chris Davis and Rebecca Morss NCAR Earth System Laboratory Mesoscale and Microscale Division November 13, 2012 CONFIDENTIAL AND PROPRIETARY Any.

Derechos and Hurricanes: Predictions,
Warnings, and Responses
Chris Davis and Rebecca Morss
NCAR Earth System Laboratory
Mesoscale and Microscale Division
November 13, 2012
CONFIDENTIAL AND PROPRIETARY
Any use of this material without specific permission of UCAR-NCAR is strictly prohibited
Hazards: Prediction, Uncertainty
and Warning
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Derechos
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Damging lines of thunderstorms
Short lead time (0-6 h)
Unquantified uncertainty
No comprehensive warning strategy
Hurricanes
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Approaching derecho
Sandy, near Jamaica
Tropical cyclones
Long lifetime of storm (3-10 days)
Major prediction uncertainties
Detailed but complex warning strategy
500 km
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Components of Hazard Prediction
using Numerical Models
 Dynamical models solve equations of motion given observed
initial conditions
 State-of-the-art model: Weather Research and Forecasting
Model (WRF) represents scales of 1 to 1000 km
 Finite predictability requires probabilistic forecasts
 Sustained (community) effort in model evaluation and
improvement
 Communication of complex scenarios emerging from models
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Derechos: Severe Lines of Thunderstorms
• Damage from straight-line wind
• Long swaths (> 400 km), long duration (> 6 h)
• Wide damage swaths (100-500 km)
• Rapid movement: 20-30 m/s
Earthsky.org
NOAA Storm Prediction Center
Csmonitor.com
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Derechos Occur in Populated Areas
• Affect major metropolitan areas
• One event per year is typical at a given location
• Similar frequency to hurricane landfalls in U.S.
Metropolitan areas
with more than
2,000,000 people
NOAA Storm Prediction Center
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Derechos: Prediction Capability
WRF Forecast From 8 AM EDT 29 June
18 UTC (6 h)
21 UTC (9 h)
00 UTC (12 h)
03 UTC (15 h)
Composite Radar
18 UTC
21 UTC
00 UTC
03 UTC
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Derechos: Wind Swath Prediction
SPC Storm Reports
WRF Forecast
*High resolution forecasts can offer explicit
guidance as to severe weather potential
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Derechos: Forecast Uncertainty
• Model predicted threatening system several
hours in advance
Radar at 11 PM EDT
• Position and/or intensity varied from
forecast to forecast
• How can warnings and responses cope
with this uncertainty?
9 h Forecast
Too far south
7 h Forecast
DC threat
3 h Forecast
Too weak
Forecasts, all valid at 11 PM EDT, produced hourly by NOAA Earth System Research Lab, using WRF
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Derechos Accompany Heat Waves
One-two punch
• Tree damage and power loss from derecho
• Prolonged heat without power creates vulnerability
Derecho Favored
Extreme Heat
June 28, 2012: The day before (The Weather Channel)
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Hurricanes: More than Wind
Sandy, flooding in New Jersey
(www.businessweek.com)
Tuckerton, New Jersey
US Coast Guard via AFP/Getty Images
Aftermath of Sandy, in Ossining,
New York (www.absnews.go.com)
New York subway flooding
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Hurricanes: Evolution of Sandy
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Hurricane Sandy: Environment
• Embedded within larger mid-latitude system
• Anomalous deep easterly flow
• Anomalously warm water
October 28, 2012 sea
surface temperature (oC)
27C
26C
“Tropical core”
October 29, 10 AM EDT
Jet Stream
October 2012 sea surface
temperature anomaly (oC)
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Hurricanes: Size of Sandy
• Maximum wind is not the most important parameter
• Extent of strong winds responsible for waves and storm surge
• Forecasts of storm structure need more evaluation
 In Sandy,
merger with
mid-latitude
weather
system
expanded the
area of strong
winds.
Sandy, 11 AM EDT
October 25
Max wind 105 m.p.h.,
Category 2
Sandy, 5 PM EDT
October 29
Max wind 90 m.p.h.
Category 1
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Hurricanes: Forecast Uncertainty
An ensemble of highresolution forecasts
Forecasts using WRF, grid size of 4 km
• Ensemble is
generated from
small differences in
initial conditions.
• Uncertainty varies
with forecast lead
time.
• Uncertainty is
highly case
dependent
Figures courtesy of Ryan Torn,
University at Albany, SUNY
stronger
weaker
Ensemble of
forecasts from
early on Oct. 24
Ensemble of
forecasts from
late on Oct. 25
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Summary of Hazard Prediction
 Weather prediction models (WRF) can realistically simulate
hazards
o Derechos: probable occurrence but not exact time/place
o Hurricanes: Useful track guidance out to 5 days, maybe more
o Hurricanes: Less skill for intensity/structure
 Still important systematic errors to be reduced
 Uncertainty is inherent and must be better represented
 Models are not linked well to hazard prediction
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Hurricane Sandy: Messages Matter
“The combination of an
extremely dangerous storm
surge and the tide will cause
normally dry areas near the
coast to be flooded by rising
waters.” (National Hurricane
Center)
“There are people who
panic and evacuate and
there are people who have
been by the ocean for a
long time and they're
unfazed by it.” (Coney
Island resident)
“Perfect storm”
“Frankenstorm”
“Superstorm”
“This is the most
catastrophic event that
we have faced and
been able to plan for in
any of our lifetimes.”
(Connecticut Governor
Dan Malloy)
“Please listen to what your state and
local officials are saying. When they
tell you to evacuate, you need to
evacuate.” (President Barack Obama)
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Predictions, Warnings, and Responses
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Motivation
Fill gaps among forecast and warning information,
people’s decisions, and desired outcomes
Research
Foci
• How are weather forecasts and warnings received,
interpreted, and used in decisions?
• How do people perceive hazardous weather risks?
• How can we improve communication of weather
forecasts and warnings?
Research
Approach
Use social science & interdisciplinary theories and
methods, integrated with weather prediction
knowledge
Capacity
Building
Build the weather-society community: Workshops,
online discussion board, etc.
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System of Weather Communication
Who?
What?
Approaching Hazardous
Weather Event
Generation
Value
Forecasters
Media
Public
Officials
Dissemination
Forecast and
warning
information
Use
in decisions
Perception
Interpretation
Public Audiences
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Message Interpretations and Uses
 Protective decisions involve many
interacting factors, including:
• People’s characteristics,
situations, experiences, etc.
• People’s evaluations of risk
→ What will conditions and
impacts will be for them?
credit: UCAR, Carlye Calvin
• Amount of advance warning
(“lead time”) and uncertainty
 Different people interpret forecast
and warning messages differently
credit: UCAR
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Hurricane Rita: Evacuation Decisions
In the future, if authorities recommended evacuation
due to the following conditions, would you evacuate?
 Most people
respond to the
hurricane
“category”
But it doesn’t tell
the whole story
about impacts
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Hurricane Ike: Public Responses to
Warning Messages
Large Category 2 storm, 20+ foot storm surge predicted
 Local National Weather Service office: “Persons not heeding
evacuation orders … will [may] face certain death.”
For ~70% of respondents who heard statement
 Did it affect your decision to prepare or
evacuate? How?
~30% said yes
 What was your opinion of this statement?
~40% positive: “scared you to death”
~40% negative: “overblown”, “rude”
Many didn’t adequately prepare for flooding
 “I never dreamed of 7 feet of water”
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Testing Experimental Hurricane
Messages with the Public
All respondents received “cone of
uncertainty”, with or without center line
Some respondents also received:
 There is a 55% chance that the eye
of the hurricane will make landfall in
Miami-Dade County.
 There will be storm surge of 4 feet or
higher along coastal areas, reaching
as much as a mile or more inland.
 This storm surge will be extremely
violent, destructive, and deadly. If …
you stay in the area, you may die.
Essential services … may not be
available for several weeks or longer.
 If you live in an area at risk from
storm surge or flooding, evacuation
is the most effective way to protect
yourself and your family.
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Testing Hurricane Messages
Message: This storm surge will be extremely violent, destructive, and deadly.
If … you stay in the area, you may die. Essential services … may not be
available for several weeks or longer.
 Likelihood of
evacuation: 7.4 → 8.6
 Damages will be
devastating: 2.4 → 2.9
 Information is
overblown: 4.9 → 5.4
 Source is reliable:
5.9 → 5.5
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Extreme Weather in the Climate and
Vulnerability Context
Integrating
weather risk
communication
and vulnerability
approaches
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Summary
 Improving forecasts and warnings – and
communication – can help prevent extreme
weather events from becoming disasters
 Some key steps:
• Improving communication of
uncertainty (e.g., scenarios)
• Improving high-resolution
predictions of impacts
• Understanding how different
messages influence responses
UCAR, David Hosansky
credit: UCAR
 Amid the growing complexity of
how information is communicated
 Requires a combination of expertise
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