Development of a convection- resolving
CONUS ensemble system (aka: Warn on
Forecast)
Presented By: Lou Wicker (NSSL)
Contributors
Geoff DiMego (NCEP)
Stan Benjamin (GSD)
Jack Kain (NSSL)
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Potential Attribute(s) of the
Planned Operational WOF System
System Name
Acronym
Areal
Coverage
Horz
Res
Cycle
Freq
Fcst
Length (hr)
Warn on Forecast (v1)
[1 km deterministic mean +
3 km ensemble]
WoF-HRD Sub-CONUS
(high-res
Nest
determin)
3/1
km
15
min
1-3 hr
2
Fcsts/hr
Warn on Forecast (v2)
[~0.5 km deterministic mean +
~1 km ensemble]
WoF-HRE Sub-CONUS
(high-res
Nest
ens)
0.5 /
1 km
5
min
1-3 hr
4
Fcsts/hr
System Data Assimilation or Initialization Technique
System
Attributes
WoF (v1)
EnKF-Hybrid multi-res system having 1 km regional deterministic
mean (uses HREF-RR or regional 3 km for fcst probabilities)
WoF (v2)
EnKF-Hybrid multi-res system having 0.5 km regional
deterministic mean with 1 km regional ensemble. (uses IC/BCs
from the HREF-RR)
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Why System(s) would be
Operational
 Primary stakeholders and requirement drivers
 NWS offices, SPC, WPC, FAA, aviation/transportation, high-impact weather
 What products are the models contributing to?
 SPC short-term outlooks (new watches, MDs, 4-hour tornado fcsts)
 Tornado/severe thunderstorm warnings, FF warn, terminal fcsts?
 What product aspects are you trying to improve with your development
plans?
 WoF will extend severe weather lead times for local offices towards 1 hour
 WoF will produce probabilistic guidance for multiple local weather threats
 WoF could might be helpful in improving flash-flood forecasts
 Top 3 System Performance Strengths
 Convective storms hazards: tornadoes, hail, winds, QPF
 Top 3 System Performance Challenges
 Reduction of model errors to improve analysis and forecast accuracy
 Still unclear whether current observational densities are sufficient for needed
forecast accuracy at convective scales
3
System Evolution
Over the Next 5 Years
 Major forcing factors
 Weather Ready Nation Requirements
 Increased societal awareness of high-impact weather events
 Science and development priorities




Ens. assimilation of conventional and rapid-scan radar and satellite data
Reduction of model error: big need for improved parameterizations
Probabilistic guidance for severe weather
Hazardous event detection platform – collaboration with FACETs program
to provide a seamless multi-scale threat-alert capability
 What are your top challenges to evolving the system(s) to meet
stakeholder requirements?
 HPC for ensemble DA and forecasts for both research and operations.
 QC and data latency (Radar data already has ~5 min latency!)
 MADIS system not designed for RR applications (today ~30 min lat.)
 GOES delivery will need to be improved (today ~15 min lat.)
 Potential opportunities for simplification going forward
 Unify all regional modeling applications with HREF & SREF consolidation,
eventually including rapid refresh, hurricane, fire weather, AQ etc using a
single-dycore HREF. Single ensemble DA including aerosols and even
land-surface. Retain GSI extended to 4D for regional/global DA.
4
Top 3 Things You Need
From the UMAC
1. Consider moving NCEP’s operational atmospheric modeling
systems toward 2 cores (global and regional) by 2020, and
toward a unified core (global+regional) by 2025. In parallel,
simplify the product suite (HREF & SREF consolidation). Both
would improve NCEP’s ability to be agile and innovate.
2. Product suite is currently heavily weighted toward delivery time.
Have user priorities changed since ~2000? Example: Would
having the 00Z “GEFS” first yield a better 00Z HREF a bit later?
Would forecasters “wait” for that improvement? Should relative
priorities of timeliness and accuracy be revaluated?
3. NWP as a science has grown considerably in last 10 years,
particularly for convective-scale NWP. Problem is now “too big”
for any one group to solve alone. Should (and can?) NCEP and
the U.S. weather research community agree to use established
community modeling systems to increase R2O between various
wx groups?
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