Nowcasting and Short-Term
Weather Prediction: Why Climate
is Not the Only Game in Town
Cliff Mass
University of Washington
Minutes to Hours
Although weather prediction on the scale of days
and climate prediction over decades and longer
are undoubtedly important, only modest
emphasis, outside of severe convective
forecasting, has been given to the periods of
minutes to hours.
The Premise
• Understanding and predicting weather features
on times scales of minutes to hours has the
potential for huge societal benefits—saving lives,
protecting economic assets, improving the quality
of life.
• Recent technological and scientific advances
have opened the door to huge improvements in
short-term diagnosis and prediction as well as
the communication of this information to the
public.
Bottom Line: We need
more emphasis on
NOWCASTING
AMS Nowcasting Definition
A description of current weather and a shortterm forecast varying from minutes to a few
hours; typically shorter than most
operational short-range forecasts.
American Meteorological Society’s Glossary of
Weather and Climate
Some Examples of Why We Need It
Nowcasting and Auto Accidents
More People are Killed or Injured by Auto
Accidents Associated with Roadway Icing,
Fog, and Heavy Rain Than Any Other
Traditional Weather Threat (Floods,
Hurricane, Thunderstorms)
Consider the statistics of accidents occurring
in the presence of rain, sleet, snow and fog,
and on wet, snowy, slushy or icy pavement.
U.S. Weather-Related Accidents
Accidents: 1,561,430 police-reported
weather-related accidents per year
Injuries: 673,000 per year on average
Fatalities: 7400 per year on average
Bottom Line: A quarter of all reported crashes
are weather-related, and the National
Highway Traffic Safety Administration
estimates 57 percent of all weather-related
accidents go unreported.
State-of-the-art
Nowcasting Coupled
With New Data Delivery
Approaches
(smartphones, electronic
message boards) Could
Reduce the Toll of Death,
Injury, and Loss
Heavy Rain Crossing
Roadways
• Many examples of
multi-vehicle crashes
when convective
cells cross roadways.
• Leaving the heavy
precipitation in
daylight often blinds
drivers…and major
accidents occur,
sometimes involving
tens of cars/trucks.
Nowcasting Solution
• Use time extrapolation of intense radar
echoes—perhaps providing 10-15 minutes
warning lead time.
• Use electronic message boards to slow down
the traffic and instruct drivers to leave more
room for cars in front of them.
Multi-vehicle Accidents in Fog and
Dust
Interstate 10 Dust Storm in Arizona
Three died, 22 vehicles
Oct 22, 2009
Nowcasting Approaches
• Dust-lofting algorithms coupled with real-time
observations could predict visibility loss.
• Satellite-based observations of dust and fog.
• Fog diagnosis from highway observations.
• Use of electronic message boards, flow
control, and smartphone warning systems to
get the message out.
Guiding Road Maintenance Crews
• Road maintenance crews need real-time information
to pre-position trucks with deicer and plows.
• This information is often lacking with bad results.
• Example: November 22, 2010—Seattle was thrown
into gridlock when maintenance crews did not realize
severe icing conditions were imminent.
• Obvious from weather observations—cold air was
surging southward and elevated roadways were
covered in slush.
Once the traffic locked up, it was too late—some
people abandoned cars, others took 12 hr to get home.
Probably could have been avoided if real-time weather
data was effectively used.
Construction
• Unexpected weather events cost the
construction industry many millions of dollars
per year (if not billions).
• Some of these losses could be prevented if a
short-term warnings of adverse weather were
readily available.
Local Example: UW Molecular
Engineering Bldg.
Waterproofing goes on one day
Washes off a few hours later
Reapplied the Next Day
How Much Did This Cost?
Wind Energy
The Ramp-Up, Ramp-Down
Problem Costs Millions
• Current automated forecasts have been poor at predicting
steep energy ramps in the short-term
• More effective nowcasting would greatly enhanced wind
energy’s potential.
Predicting Heavy Precipitation Events an Hour in
December
13,
2006:
The
Madison
Advance—Perhaps By Temporally Extrapolating
Radar-- Could Save
LivesStorm
and Property
Valley
One-hour
totals
December 14, 2006
Nearly 1 inch in an hour
Do We Expect Such
Events to Increase
in Frequency or
Intensity Under
Global Warming?
A woman drowned
in her basement
and dozens of cars
lost.
Recreation
• Should I head out on my bicycle?
NO!!!
Short-Term Warning For Severe
Convection
• Obvious and profound benefit.
• The one area in which nowcasting in the U.S.
is well-developed and often effective.
Current Status of Nowcasting
• National Weather Service: not much emphasis
except for convective storms
– 6-hr basic forecast cycle
– Bias towards forecast consistency even when there
is a suggestion that reality is going elsewhere.
– For significant weather NWS sometimes releases
special statements.
– Not unusual for short-term forecast and observed
weather to be inconsistent.
Forecast Released at 8:41 AM Sept 18, 2010
Reality: Sunny Warm Morning
Zone Forecast
Infrequently, a short-term forecast
is provided
Gridded Forecasts Every Three Hours,
Updated Every 6 hr, Modified If Necessary
The Weather Channel
WeatherChannel’s TruPoint (0-6 hr)
• TruPoint uses weather radar, satellite, a
lightning detection network, weather
prediction models, surface sensors and
observations to derive the current weather
conditions.
• Temperature, wind, humidity, precipitation,
visibility, and cloud cover are updated several
times each hour for points every 1.5 miles
across the country.
Short-Term Objective Forecast
• Start with NWS model output (RUC) as a "first
guess."
• Statistically combines with geographical data,
conventional surface observations, satellite data,
Doppler radar, and lightning data to produce the
forecast.
• Apples quality-control procedures to ensure a
sensible weather report/forecast
Local TV Stations
Morning, noon, dinnertime, and
late night updates
Radar Temporal Extrapolation: The
Predominant Automated
Nowcasting Technology
NCAR (RAL) AutoNowcaster
The Key Ingredients For NextGeneration Nowcasting Are Now
Available
Ingredients
• The Communication Revolution
• The Weather Data Revolution
• New Generation of Data Assimilation and
Modeling Systems
• Nowcasting Testbeds
The Communication Revolution
• Until recently, a major problem for nowcasting
was the inability to get weather information
rapidly to users…quickly enough for decision
making.
• But that has all changed now.
First, PCs Connected to the Internet
Hardwired, WIFI, or 3G
Today Smartphones Offer a Powerful,
Portable Platform for Viewing Weather
Information, Forecasts, and Warnings
Smartphones are Ideal!
• Lots of bandwidth
• They know where they are, so forecast
information can be tailored to the user
• Substantial computational capacity.
And other real-time delivery
approaches now exist
The Weather Data Revolution
• Exponential increase in surface and upper air
data has given us a highly detailed view of the
conditions at the surface over land.
• Extraordinary number of new surface
networks, from highway departments and air
quality agencies, to utility companies and local
governments.
• Plus amateurs with good weather stations on
the internet.
Example:
The Pacific
Northwest
Based on 72
different
networks
3000-4000
observations
per hour over
WA and OR
And much more..
• ACARS and TAMDAR data from aircraft flying
in and out of airports.
Remote Sensing Mesoscale
Revolution
• U.S. Doppler radars soon to include dualpolarization. Provides precipitation-type
information.
• Global hyperspectral soundings—radiosonde
vertical resolution every 15 km globally.
• Global COSMIC soundings using GPS delay
information.
• And many, many more.
New Generation of Data
Assimilation and Modeling Systems
• Can we effectively combine observations with
high-resolution models?
• Can we produce a physically consistent
description of the atmosphere with short-term
predictions every hour?
• Can we do this, considering the uncertainties in
the observations and imperfections in the
modeling systems?
National Weather Service Rapid
Update Cycle (RUC) System
•Hourly
•13 km grid
spacing
•Includes
virtually all
mesoscale
data sources.
•18 h forecasts
•MAP model
•3DVAR
assimilation
Replacement This Year: Rapid Refresh (RR)
•Uses WRF
ARW
Model
•Larger
domain
•Also 13-km
•3DVAR
High-Resolution Rapid Refresh
(HRRR)
•3-km
•3DVAR
But can we do high-resolution data
assimilation more effectively?
Can we get beyond deterministic
data assimilation?
Ensemble Kalman Filter (EnKF)
Effort at the UW (Greg Hakim and
C. Mass)
• High-resolution WRF ensembles (36 and 4km)
• 60 members
• Three-hour cycle
• Multiple Data Sources
– Multi-networks at the surface
– ACARS and satellite winds
– Radiosondes
Mesoscale Covariances: A Big
EnKF Benefit over 3DVAR
12 Z January 24, 2004
Camano Island Radar
|V950|-qr covariance
Currently Under Rapid
Development and Real-Time
Testing at the UW
Lots to improve and test!
•
•
•
•
Bias correction
Vertical localization
Evaluate other resolutions
Hybrid approaches with temporal nudging,
4DVAR, or other methods to reduce temporal
shocks and discontinuities.
Nowcasting Testbeds
Olympic Nowcasting:
The Last Few Olympic Games Have
Been Used to Test Prototype
Nowcasting Systems
• Major, multi-national nowcasting efforts at the
Sydney, Vancouver, and Beijing Olympics.
• Tested radar temporal extrapolation, radarmodel hybrid extrapolation, ultra-high
resolution prediction initialized with massive
observation data enhancement, and other
approaches.
The Beijing 2008 Forecast
Demonstration Project
• Systems from China, Australia,
Canada, and the United States.
• Mix of radar echo extrapolation
methods, numerical models,
techniques that blended numerical
model and extrapolation methods,
and systems incorporating
forecaster input.
• Focus on the skill of convective
forecasts.
Our Department Has Been
Developing a Range of Nowcasting
Tools
I90 Route View
Sends emails to appropriate officials!
Also sends out emails!
And soon… Seattle SnowWatch
A
Nowcasting
Test Using
My Blog
People Want This!
Nowcasting Done on 11 January
Second Snow Nowcasting Exp.
The Vision
Component 1: Complete the
Nowcasting Engine
Mesoscale
Data from
Heterogeneous
Networks
Hybrid
EnKF/Variation
al
Data
Assimilation/S
hort-term
HighResolution
Forecasting
System
Mesoscale
Analyses
Bias
Removal
Short-Term
(1-6 hr)
Forecasts
4D “Datacube”
0-6 hr
Component II: A Revised National
Weather Service Forecast Office
• Less emphasis on human forecast intervention
beyond 24-h
• At least one forecaster dedicated to
nowcasting in each office. Hourly gridded
updates of all basic fields (hourly time
resolution) out to 6 hr.
• Starts with Component 1 and perfects it.
• Hourly nowcasting discussion.
Component III: New Generation
of Nowcasting Applications for
Specific Needs
• Rainwatch and WindWatch and current
nowcasting apps are simple prototypes of
what can be done.
• Drawing on the real-time gridded information
of component I and raw observations,
produce real-time, nowcasting guidance for a
wide range of societal needs.
Component III
• Develop range of Smartphone based
nowcasting apps.
– Provides weather information relevant to your
location:
• Some examples:
WeatherProtector
WEATHER
PROTECTOR
Tells you whether heavy
precipitation, winds, or other
weather issue are approaching
your position.
BikeWeatherGuard
BikeWeather
Guard
•Using a map interface,
input your planned
route and when you
want to travel.
•Tells you whether you
should delay your trip,
or perhaps leave a few
minutes early, to stay
dry.
AvalancheGuard
•Tracks your route in the
mountains
AvalancheGuard
•Knowing the slopes
around and ahead of
you and the current
snow conditions, warns
you if you moving into a
dangerous situation.
•Tells you which way to
turn.
GardenKeeper
GardenKeeper
• Using calibrated radarbased precipitation data,
tells you when watering is
necessary at your location
(considering water
demands of your plants
and evapotranspiration
based on recent weather)
• Warns when freezing
conditions are imminent
during the winter.
MayorGuard
ORDER
SALT
NOW!!!
•When snow or ice is
imminent, tells the
mayor what to do.
•Provides information
on best prices and
nearest suppliers.
There has never been as big a gap
between what weather forecasters
know and what they communicate
to the public.
And society has never
had so powerful an
ability to adapt and
avoid dangerous
weather.
The END
Each providing a
sounding as they
land and take off.
Use flow control to limit the number of cars
entering the roadways near convective cells