Numerical Simulation and Prediction of Supercell Tornadoes Ming Xue School of Meteorology and Center...
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Transcript of Numerical Simulation and Prediction of Supercell Tornadoes Ming Xue School of Meteorology and Center...
Numerical Simulation and Prediction of Supercell Tornadoes
Ming XueSchool of Meteorology and
Center for Analysis and Prediction of StormsUniversity of Oklahoma
February 2008
Outline of Talk
LES-resolution simulation of supercell tornado
Prediction of real tornados with radar data assimilation
Sensitivity of tornado prediction to microphysics
Tornadogenesis and Tornado Dynamics as Revealed by LES-resolution Numerical
Simulations of Supercell Storm
Numerical Simulation of Supercell Tornado using up to 12.5 m Grid Spacing
Using the Advanced Regional Prediction System (ARPS, Xue et al 2000, 2001, 2003) of CAPS
1977 Del City, OK sounding (~3300 J/kg CAPE) 2000 x 2000 x 83 point uniform resolution covering 50 x 50 km2. x = 25 m, zmin = 20 m, dt = 0.125 s.
x = 12.5 m in a 20 x 20 km subdomain, dt = 0.05 s.
Warmrain microphysics with surface friction at the later stage Simulations up to 5 hours Using 2048 Alpha Processors at Pittsburgh Supercomputing Center 60TB of data generated by one 25m simulation over 30 minutes, output
at 1 second intervals
Sounding for May 20, 1977 Del City, Oklahoma tornadic supercell storm
CAPE=3300CAPE=3300J/kgJ/kg
Full Domain Surface Fields of 50m simulation
t =3 h 44 mint =3 h 44 min
Red – positive Red – positive vertical vorticityvertical vorticity
Near surface vorticity, wind, reflectivity, and temperature perturbation from 25-m run
2 x 2 km2 x 2 km
Vort ~ 2 sVort ~ 2 s-1-1
Movie
Near surface vorticity, wind, reflectivity, and temperature perturbation from 12.5 m grid
1.5 x 1 km1.5 x 1 kmdomaindomain
Vort > 4 sVort > 4 s-1-1
Movie
Near surface vorticity, wind and p' felds- evolution from single to multiple vortices
t=13447 s t=13661s
Vort_max=3.27 /s Vort_max=3.28 /s
Movie of Cloud Water Field25 m, 7.5x7.5km domain, 30 minutes
Movie of Cloud Water Field. dx=25m 7.5x7.5km domain, 30 min.
130m/s
-100mb
>120m/s max >120m/s max surface windssurface winds
>90mb p drop>90mb p drop +60m/s speed +60m/s speed increase in ~2minincrease in ~2min
220min 236min220min 236min
Max sfc wind speedMin. sfc perturb. p220min 236min220min 236min
Maximum surface wind speed and pressure drop in 12.5 m simulation
What is the main source of air parcel and vorticity feeding the tornado?
Trajectory calculations based on 1-s model output
View from SouthView from Southt=13250st=13250sbeginning of beginning of vortex intensificationvortex intensification
z = 3 kmz = 3 km
View from NortheastView from Northeast
3km3km
RFD of1st cell
RFD of2nd cell
Inflowfrom east
Low-level jump flowLow-level jump flow
East West
Diagnostics along Trajectories
Orange portion t=13250-500s – 13250+200s
t=13250sBeginning of low-level spinup
14km14km
X Y Z
8km8km
WVh
Streamwise Vort.Cross-stream Vort.Horizontal Vort.
Vertical Vort.Vertical Vort.Total VortTotal Vort..
13250132501275012750 1345013450
Vorticity components along trajectory
Force along trajectoryForce along trajectory
BuoyancyBuoyancyVert. PgradVert. PgradSum of the twoSum of the two
Perturbation pressurePerturbation pressure-76mb-76mb
55
-5-5
1325013250
~2 m s~2 m s-2-2
+b' due to -p'+b' due to -p'
Forces along trajectory
Can we numerically predict real tornadoes?
May 8th, 2003 OKC tornado
OKC tornado2210-2238 UTC
30 km long path
F4
(Hu 2005; Hu and Xue 2007)
DA cycles on 1-km Grid3DVAR+Cloud Analysis Forecast
2030 UTC 2140 UTC
4 nested grids
Observed v.s. Predicted Z and Vr at 1.45° of the supercell storm
Observation 1 km Forecast
From 2140 to 2240 UTC every 5-min
Reflectivity
Radial velocity
What about the prediction of embedded tornado?
50-m Grid Forecast v.s. Observation
Forecast Low-level Reflectivity Observed Low-level Reflectivity
Movie
43 minute forecast
50-m Grid Forecast v.s. Observation
Forecast Low-level Reflectivity Observed Low-level Reflectivity
Movie
43 minute forecast
43 min. forecast on 100m grid
t=34 min
t=40 min
Sfc vert. vort., and p’ E-W x-sections of vert. vort. and w
A case from CASA 2007 Spring Experiment
CASA – an NSF ERC for Collaborative Adaptive Sensing of Atmosphere
- Low cost, high density, adaptively scanning radars
© KSWO TV
© Patrick Marsh
May 8-9, 2007
A series of low-levelcirculations.
NWS TornadoWarnings: 7:16pm,7:39pm, 8:29pm
7:21pm (0021Z)
8:30pm (0130Z)
9:54pm
10:54pm (0354 Z) Minco Tornado
A Case from 2007 CASA Spring Experiment
dx = 400 m 115-min. prediction of sfc winds, Z (color), and vertical vorticity at 0355 UTC. Both WSR-88D and CASA IP1 data were assimilated very 5 min. for 1 h. The black triangle indicates the location of observed Minco tornado.
0:00Z 0:30Z 1:00Z 1:30Z 2:00Z
0Z Analysis1 hr. spin-up period 1 hr. assimilation window
with 5 min assimilation intervals
Forecast to 0500 UTC
0:00Z 0:30Z 1:00Z 1:30Z 2:00Z
0Z Analysis1 hr. spin-up period 1 hr. assimilation window
with 5 min assimilation intervals
Forecast to 0500 UTC
Predicted sfcVort. max
115-min sfc forecastMinco tornado
Importance and/or Uncertainties of Microphysics?
Daniel Dawson’s Poster Yesterdayusing multi-moment microphysics
Impact of Microphysics on Prediction of Tornadic Supercell Storm
May 3, 1999 Moore – OKC F-5 Tornado Case
Daniel Dawson’s Poster Yesterdayusing multi-moment microphysics
Surface ’gray shading), Z (blue contours), vertical vorticity (color shading), and wind vectors at the time of largest vertical vorticity using 100 m resolution and with MY1 (a) and MY2 (b) schemes.
HP storm LP storm
100 m simulations with MY1 and MY2 schemes
Vis5D visualization of the cloud field (gray surface), and 0.3 s-1 vertical vorticity iso-surface (yellow) from the 100
m simulations using MY1 (left) and MY2 (right) schemes.
MY Single-moment MY two-moment
Greensburg, Kansas Tornado, 5 May 2007
Numerical prediction of tornados - has its time come?
What is the predictability of tornadoes?