Short-term Forecasting

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Short-term Forecasting and WRF Case Study
Steven J. Goodman, W. Lapenta, K. La Casse, E.
McCaul, and W. Petersen NASA Marshall Space
Flight Center Earth and Planetary Science
Branch Huntsville, Alabama, USA
SPoRT Science Advisory Committee Meeting 21
November 2005
Photo, David Blankenship Guntersville, Alabama
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NWS STIP Solutions (Science and Technology
Infusion Plan)
Theme Service Gap Solution Impact
Severe Weather Specification of pre-storm environment, boundaries, severe WX signatures WRF, DA, ensembles, lightning data, SCAN, higher res. satellite obs. Improved POD, lead-time, FAR, more precise boundary observations
Aviation Weather Timing and location of convection, probabilistic information for DSS WRF, ensembles, DA, hourly updates, NCWF (radar lightning) 50 increase POD, greater operational utility
Weather Research and Forecast, WRF Data
Assimilation, DA
Additional Forecast Interests CI - convective
initiation Ti - First lightning (35 dbZ at -15C,
glaciation) Tp Peak flash rate a VIL (Mass) Tf
- Final lightning
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Flash Rate Coupled to Mass in the Mixed Phase
Region Cecil et al., Mon. Wea. Rev. 2005 (from
TRMM Observations)
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Lightning Connection to Thunderstorm Updraft,
Storm Growth and Decay

• Total Lightning responds to updraft velocity
  and concentration, phase, type of hydrometeors,
  integrated flux of particles
• WX Radar responds to concentration, size,
  phase, and type of hydrometeors- integrated over
  small volumes
• Microwave Radiometer responds to
  concentration, size, phase, and type of
  hydrometeors integrated over depth of storm (85
  GHz ice scattering)
• VIS / IR cloud top height and temperature,
  texture, optical depth

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WWRP/Tom Keenan
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Enhanced Thunder 19 July 2005 2000Z 2012Z
SPC Experimental Product
NCEP SPC/Schaefer
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SPC Experimental Product
- Pr (CPTP) gt 1 x Pr (PCPN) gt .01
Uncalibrated probability of lightning
F15 SREF 3-hr COMBINED PROBABILITY OF LIGHTNING
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North Alabama Nowcasting Short-term Forecasting
Test Bed
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WRF Thunderstorm and Lightning Forecasts10
December 2004
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WRF Configuration10 December 2004 Case Study

• 4km horizontal resolution
• 37 vertical levels
• Dynamics and physics
• Eulerian mass core
• Dudhia SW radiation
• RRTM LW radiation
• YSU PBL scheme
• Noah LSM
• WSM 6-class microphysics scheme
• Explicit convection
• 24h forecast initialized at 00 UTC 10 December
  2004 with AWIP212 NCEP EDAS analysis
• Eta 3-h forecasts used for LBCs

Cloud cover 18h forecast valid at 18 UTC 10 Dec.
2004
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Observed Thunderstorm Precipitation and
Lightning10 December 2004, 1700-2125 UTC KHTX
NEXRAD, LMA, NLDN
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WRF Surface Based CAPE 18h fcst valid 18 UTC Dec
10
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WRF Sounding 800 J/kg CAPE
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MIPS Sounding 761 J/kg CAPE

• Low level lapse rates and low freezing level
  efficient for converting CAPE to kinetic energy
• Surface T15C, Td10C
• Max w 19 m/s

UAH MIPS, Kevin Knupp
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WRF 3h Precipitation 18h fcst valid 18 UTC Dec 10
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WRF 3h Precipitation 21h fcst valid 21 UTC Dec 10
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WRF 3h Precipitation 21h fcst valid 21 UTC Dec 10
Question Any lightning, when was it, What was
WRF reflectivity at -15 C?
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WRF Reflectivity (dBZ)at -15 C (4.0 km) 1200 UTC
forecast valid at 1850 UTC 10 Dec. 2004
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x1 Reflectivity (dBZ), Temperature (C), and
Pressure (hPa) 1200 UTC forecast valid at 1850
UTC 10 Dec. 2004
Max dBZlt 40 dBZ
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x2 Reflectivity (dBZ), Temperature (C), and
Pressure (hPa) 6h 50m forecast valid at 1850 UTC
10 Dec. 2004
Max dBZ50 dBZ
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Ground-truth Report of Dime-Size Hail Owens
Crossroads, Alabama
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10 December Hail Case ARMOR collected data! First
time ZDR used on television!

• Cold upper-low
• GOES 2057 J/kg CAPE in a layer about 7.5 km deep
• GOES sounding too warm and moist near surface,
  likely cloud contaminated
• Dime to quarter-sized hail reported in SE
  Madison county and in S. Tennessee

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ARMOR 1.3 degree PPI scan at 1755 UTC on 10 Dec.
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Particle Identification
Reflectivity dBZ
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At 1755 IC fl. rate 3/minute in southern
cell No ICs in northern cell at 1755 No CGs in
either cell for 20 minutes centered on 1755 Only
3 CGs detected for duration of storms
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LMA Observed Flashes Precede Hail Report
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RAMS Configuration

• 500 m horizontal resolution
• Height, Dz is variable, from 250 m at bottom to
  750 m at 20 km height
• Domain 75 km x 75 km x 24.5 km
• Time, Dt 4 s, five acoustic steps between
• Smagorinsky subgrid mixing scheme
• 5-class precipitating hydrometeors
• Rain, snow, aggregates, graupel, hail
• Initialized with 3K warm bubble, radius12 km at
  z0
• 120 min simulation, initiation effects dominate
  until t60 min

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RAMS Configuration
Graupel

• 500 m horizontal resolution
• Height, Dz is variable, from 250 m at bottom to
  750 m at 20 km height
• Domain 75 km x 75 km x 24.5 km
• Time, Dt 4 s, five acoustic steps between
• Smagorinsky subgrid mixing scheme
• 5-class precipitating hydrometeors
• Rain, snow, aggregates, graupel, hail
• Initialized with 3K warm bubble, radius12 km at
  z0
• 120 min simulation, initiation effects dominate
  until t60 min

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RAMS Configuration
Hail

• 500 m horizontal resolution
• Height, Dz is variable, from 250 m at bottom to
  750 m at 20 km height
• Domain 75 km x 75 km x 24.5 km
• Time, Dt 4 s, five acoustic steps between
• Smagorinsky subgrid mixing scheme
• 5-class precipitating hydrometeors
• Rain, snow, aggregates, graupel, hail
• Initialized with 3K warm bubble, radius12 km at
  z0
• 120 min simulation, initiation effects dominate
  until t60 min

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WRF Thunderstorm and Lightning Forecasts1 May
2004
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1h WRF forecast valid at 01 UTC 1 May 2004 using
MODIS SSTs
A
B
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Cross-section of reflectivity on sigma levels 1h
WRF forecast valid at 01 UTC 1 May 2004
A
B
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LIS Ground Truth - Florida 1May 2004 (Day 122)
0303 UTC
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NLDN Observed Lightning, 1 May 2004
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WRF Thunderstorm and Lightning ForecastsMotivati
ons to study the 1-3 May 2004 Florida Cases

• High resolution 2 km WRF database
• Validation of convective processes with TRMM LIS
  and ancillary data sets
• Examine the Warn on Forecast framework for
  lightning threat WRF-Nowcaster-LMA