The Challenge of Convective Forecasting

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The Challenge of Convective Forecasting
ASP/MMM Colloquium July 10-21, 2006
Predictability does not necessarily imply
ability to predict
Introduction/Motivation
Morris Weisman NCAR/MMM
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Numerical prediction of thunderstormshas its
time come?
Weather prediction is the principal reason for
the support which we are given by our fellow
citizens I believe it is time for
convective-storm scientists to apply our
knowledge to this purpose and to subject our
products to its discipline ..The task is not
trivial..
Doug Lilly, Q. J. of the Royal Meteor. Soc., 1990
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Initialized 05 Nov 2005 00 UTC
Composite NEXRAD Radar
Reflectivity forecast
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(tiff)
06 Nov 2005
31 h valid 07 UTC
08 UTC
Reflectivity forecast
Composite NEXRAD Radar
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Evansville Tornado ???
Well, actually from Greg Thompsons Web page
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WRF-ARW Mass Coordinate Core

• Terrain-following hydrostatic pressure vertical
  coordinate
• Arakawa C-grid, two-way interacting nested grids
  (soon)
• 3rd order Runge-Kutta split-explicit time
  differencing
• Conserves mass, momentum, entropy, and scalars
• using flux form prognostic equations
• 5th order upwind or 6th order centered
  differencing
• for advection
• Multiple physics combinations (many converted
  from MM5), Noah and RUC land-surface submodels

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WRF Model Physics

• Plug-compatible interface defined for physics
  modules
• Physics options implemented in WRF
• Microphysics Kessler-type
  (no-ice)
• Lin et al. (graupel included),WSM6
• NCEP Cloud3, Cloud5, Ferrier
• Cumulus Convection New Kain-Fritsch, Grell
  Ensemble
• Betts-Miller-Janjic
• Shortwave Radiation Dudhia (MM5), Goddard,
  GFDL
• Longwave Radiation RRTM, GFDL
• Turbulence Prognostic TKE,
• Smagorinsky, constant diffusion
• PBL MRF, MYJ,
  YSU
• Surface Layer Similarity theory, MYJ
• Land-Surface 5-layer soil model, RUC LSM
• Noah unified LSM, HRLDAS

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Idealized WRF Simulations
PBL LES, Dx 50 m
Density current, Dx 100 m
5 min
10 min
15 min
Mountain wave, Dx 20 km
Baroclinic wave, Dx 100 km
(Chin-Hoh Moeng)
Supercell thunderstorm, Dx 1 km
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WRF Realtime Convective Forecasting
May 1 July 31 4 km 00 UTC -- 36h
2003, 2004, 2005
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00Z 10 June 13Z 11 June 2003
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Real-time WRF 4 km BAMEX Forecast
Initialized 00 UTC 9 June 03
Reflectivity forecast
Composite NEXRAD Radar
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Real-time WRF 4 km BAMEX Forecast
Initialized 00 UTC 10 June 03
Reflectivity forecast
Composite NEXRAD Radar
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Realtime WRF 4 km BAMEX Forecast
Valid 6/12/03 06Z
Composite NEXRAD Radar
30 h Reflectivity Forecast
Correspond
Missed
MCS position
Correspond
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Model Physics in High Resolution NWP
Physics No Mans Land
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What does it take to simulate convection??
How much resolution do we need??
George Bryan NCAR/MMM (Thursday morning)
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0500 UTC 29 April 2005 1 km model reflectivity,
NEXRAD BREF
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Power Spectra for 3 h Precipitation
12Z forecasts, 15-18 Z accum precip, valid 4 June
2002
(From Mike Baldwin and Matt Wandishin, NOAA/NSSL)
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Does microphysics matter at all???
Axel Seifert (DWD), Friday morning
4 km WRF-ARW 12 h reflectivity forecast,
Valid 10 June 2003 12 Z
Column Max Reflectivity (
dBZ
)
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4 km WRF 12 h Precipitation Forecast
Valid 10 June 2003 12 Z
WSM
-
6 Scheme
Lin, et al. Scheme
NCEP Stage 4 Data
Total Precipitation (mm)
(Axel Seifert, 2004)
Reisner
Scheme
SB2004 Scheme
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Cold Pools??
Lin
WSM-6
12 h Surface Theta
Reisner
SB2004
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Are we properly representing the structure and
evolution of the PBL??
Jack Kain (NSSL) PBL observations and
forecasting issues Friday afternoon Bjorn
Stevens (UCLA), PBL theory and parameterization
Monday Morning Fei Chen (NCAR/RAL), Land
surface modeling Monday Afternoon
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YSU
Model
Raob
MYJ
Raob
Model
(Jack Kain, NSSL)
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YSU
Model
Raob
MYJ
Model
Raob
(Jack Kain, NSSL)
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Land Surface Sensitivities
(19 June 2002 IHOP, Stan Trier)
Similar large-scale heterogeneity in OK EDAS is
wetter along the TX dryline
(b) 4-km HRLDAS fields
(a) 40-km EDAS soil fields
dry
wet
Black Contours Surface Mixing Ratio
Colors Surface Volumetric Soil Moisture
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Theoretical Predictability Limits??
Rich Rotunno (NCAR/MMM) Tuesday morning (wk 2)
Lorenz, 1969
Atmos. Energy Spectrum
Predictability Limit for given scale
Error spectrum at given time
Scale (km)
Subsynoptic waves (1200 km) 1.5 days
Convective Systems (300 km) 12 h
Thunderstorms (10 km) 1h
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What can data assimilation offer us??
Chris Snyder, (NCAR/MMM) Fundamentals of data
assimilation, Tuesday morning David Dowell
(NCAR/MMM-RAL) Ensemble Kalman Filters, Wednesday
morning Jenny Sun (NCAR/MMM-RAL) The VDRAS
system, Thursday morning
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IHOP case, June 12, 2002
Three hour forecast (4DVar data assimilation
system, Juanzhen Sun)
Observed reflectivity (KVNX radar)
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EnKF assimilation of KOUN NEXRAD data (50
ensemble members) Dowell et al. 2004
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What is the future for Mesoscale Observations?
Howard Bluestein (OU) Thursday morning (wk 2)
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Sensitivity studies indicate that moisture is the
key observable for improved short range
forecasts of hazardous weather.
WATER VAPOR DIAL LIDAR
REFRACTIVITY
GPS PRECIPITABLE WATER
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POLARIMETRIC RADAR OBSERVATIONS
Particle discrimination
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So, will we ever be able to predict this.
.hours,days in advance???
Lou Wicker (NSSL) Tuesday afternoon (wk 2)
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Hurricane Frances Reflectivity near Landfall
48 h forecast from 4 km WRF valid at 00Z Sept 5
Melbourne Radar
Chris Davis (NCAR/MMM), Wednesday (wk 2)
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Convective storms/systems
Morris Weisman (NCAR/MMM)
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Upscale Growth of Convection
Chris Davis (NCAR/MMM)
Bow echoes
0540 UTC 10 June, 2003
MCV
0600 UTC 10 June, 2003
MCSs
11 June, 2003
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Synoptic and mesoscale influences
Lance Bosart (SUNY), Howard Bluestein (OU), Stan
Trier (NCAR/MMM), Steve Weiss (SPC)
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Colloquium Goals

• What are our current capabilities related to
  convective NWP in the 0-36 h range?

• What are our current limitations? (numerics,
  physics, observations, assimilation
  techniques,computer capacityi.e.,where do we
  need research?)

• What can we hope to achieve? e.g.,
  predictability!!!