warn on forecast case studies: progress report february 2012

Warn on Forecast Workshop 8-9 February 2012

Warn on Forecast Case Studies:

Progress Report February 2012

• Contributors• Dusty Wheatley (NSSL/CIMMS) • Nusrat Yussouf (NSSL/CIMMS) • Dan Dawson (NSSL/CIMMS)• Ted Mansell (NSSL)• Corey Potvin (NRC PostDoc)• Robin Tanamachi (CAPS/OU)

•Thomas Jones (NSSL/CIMMS)•Mike Coniglio (NSSL)•Adam Clark (NSSL/CIMMS)•James Corriea (SPC)•Terra Thompson (NSSL/OU)

Lou Wicker (NSSL)


PurposeTo test storm-scale NWP in a

variety of severe weather situations• Two basic classes of events

• isolated cells• mesoscale convective systems

• Basic questions to be answered:• core sets of observations needed• accuracy needed of background analysis for

convective scale forecasts• analysis versus prediction• predictability (0-1, 0-3, 0-6 hours?)


Cases• Isolated Cells

• Tornadic supercells • 8 May 2003 OKC F4 tornado• 4 May 2007 Greensburg KS EF5 tornado• 27 April 2011 MS/AL/TN superoutbreak• 10 May 2010 Central OK outbreak

• Downburst• 14 June 2011 Norman macroburst

• Mesoscale convective systems• 4 July 2004 IN/OH/KY derecho (BAMEX)• 14 June 2010 W TX tornado / flash flood (VORTEX2)


May 8, 2003 Oklahoma City Tornadic Supercell

Damage Path of OKC Tornado

Hu and Xue (2007)

HPC Synoptic Scale Surface Analyses at 18:00 UTC

KOUN Radar Observations at 22:10 UTC

Nusrat Yussouf


8 May 2003: Multiscale experiment EnKF used at multiple scales

Mesoscale Ensemble• 45 member WRF mesoscale ensemble at 18 km horizontal grid spacing over CONUS initialized from GFS • 3 day cycling with assimilation of routinely available observations from

metar, marine, radiosondes and ACARS using DART system• Physics options used: MYJ, Thompson, Kain-Fritsch, Noah, Dudhia and RRTM

Storm-scale Ensemble• 45 member storm-scale ensemble nested down from the 45 member mesoscale ensemble data system• 2-km horizontal grid spacing, 225 x 180 x 50 grid points• Assimilates KTLX radar radial velocity and reflectivity observations every 3-min

for a one-hour period

T - 3 days 8 May

Nusrat Yussouf


Reflectivity, Vorticity and Horizontal Winds at 1 km AGL

KTL

X Re

flect

ivity

at 2

2:01

UTC

Fina

l Ana

lyse

s at 2

2:00

UTC

30 m

in F

orec

ast a

t 22:

30

UTC

15 m

in F

orec

ast a

t 22:

15

UTC

Ensemble Member #9

Vorticity contours: 0.005 to 0.01 by 0.001

KTL

X Re

flect

ivity

at 2

2:16

KTL

X Re

flect

ivity

at 2

2:31

UTC

Nusrat Yussouf

mesocyclonemesocyclone


Probability of Vorticity During 45-min Forecast Period

22:00 – 22:45 UTC

Observed damage track and times

~22:06

~22:38

≥ 0.003 s-1 at 1 km

≥ 0.005 s-1 at 3 km

Probability (%)

~22:38

Observed damage track and times

~22:06

~22:38

Nusrat Yussouf


Greensburg KS (2007)• EnKF analysis and prediction of the significant tornadic storm on 5 May 2007 storm near Greensburg, KS

• Single radar retrieval using DDC Vr & dBz

• Homogeneous initial environment

• Examined sensitivity to low-level wind profile and (to a lesser extent) microphysics

Dan Dawson


Probabilistic Vorticity Forecast (All 9 experiments)

Background VAD Profile (UTC) Used 0130 0200 0230

60 min forecasts

45 min forecasts

Dan Dawson

Experiment 1: 1900-2000 UTC initialization


27 April 2011 Tornado Outbreak:EnKF Radar DA and Ensemble Forecasts

45-member WRF-ARW ensembles (Δx=3 km) initialized from Rapid- Refresh model (Δx=13 km) at two times (1900 and 2100 UTC)

Data from 4 radars assimilated every 3 min for 1 hKBMX, KDGX, KGWX, KHTXadditive noise only source of ensemble spread

Ensemble forecasts produced after radar DA

19Z 20Z 21Z 22Z 23Z

21Z 22Z 23Z

RadarDA

Experiment 2: 2100-2200 UTC initialization KDGX

KGWX

KHTX

KBMX

observedtornadotracks

ensembleforecast

ensembleforecast

RadarDA

David Dowell


Two Ensemble Forecasts:initialized at different times, valid at same time

Ensemble-Based Probabilities of Rotating Updrafts2200-2300 UTC 27 April 2011

2-3 h forecastinitialized at 2000 UTC

0-1 h forecastinitialized at 2200 UTC

northern swath of high probability changed

relatively little

southern swath moved significantly based on

recent radar data and/or RR mesoscale analysis

David Dowell


0-1 h ForecastEnsemble Member 1

2-5 km AGL Max Updraft Helicity2200-2300 UTC

observedcomposite reflectivity

NSSL/Q2 Mosaic3D2200 UTC

observedtornadotracks

model maintains long-livedstorms initialized in

Tuscaloosa County andCullman/Blount County

David Dowell


• Measured wind gusts > 36 m/s (130 km/hr)• Wind-driven golf ball or larger hail• 33,000 residents without power for over a day• Residential damage took > 4 months to repair

http://www.srh.noaa.gov/oun/?n=events-20110614

dBZ 0030 UTCDownburst

June 14 Macroburst

Lou Wicker

http://www.srh.noaa.gov/oun/?n=events-20110614


2245 Vis

Mesoscale Environment

Weak elevated convection

ongoing for hours

Cold Front

CAPE~200

CAPE~2200LCL~730 mb

deep convection initiates ~2330 UTC

CAPE~3200LCL~730 mb

Lou Wicker

Moderate shear


Model Analysis vs Radar Obs at 0010 UTC

35 min of radar DA8 radar volumes

KOUNLocation

Lou Wicker


20 minute Ensemble Forecasts of Svr Wind (0030 UTC)

Verification Wind PlotVectors: Wind speed > 10 m/s

Color: 20 m/s < wind speed < 40 m/s

EnsemblePrediction

for SVR SFCWINDS

Ensemble Forecast Output ofSevere Wind ProbabilityVectorsWind speed > 20 m/s Color at least 33% of members have 25 m/s < wind speed < 40 m/s

Lou Wicker

3DVAR SFC WIND FIELD


The 4-5 July 2003 MCS event

2130 UTC

0200 UTC0030 UTC

2300 UTC

- Observed during BAMEX

- Produced 100+ wind reportsacross Indiana and Ohio

- Contributed to record floodingacross north-central Indiana

- Not captured in NWP models of the day (including the WRF model)

Dusty Wheatley


From Davis et al. 2005

Satellite imagery from 4 July 2003

Outflow boundary

Gravity wave

4 July 2003 MCS

Sensitivity to previous convection

Depicts movementof two earlier systems

Dusty Wheatley


EnKF analyses at 2300 UTC

OBS

• 1.5-km AGL simulated reflectivity• 2-m temperature (deg C)• 10-m winds (full barb = 10 ms-1)

Radar DA only

Sub-hourly surface data

Better cold pool analysis

Radar + Sfc DA

Surface data DA needed on storm-scale grid

Dusty Wheatley

Warn on Forecast Workshop 8-9 February 2012Dusty Wheatley

Simulated reflectivity from sample members at 0030 UTC 5 July


EnKF analyses of 2-m temperature

With the assimilation of sub-hourly surface data, the mesoscale cold pool is better developed at the last analysis time (2300 UTC) and subsequent forecast times.

2300 UTC 4 Jul 30 min fcst 60 min fcst 90 min fcst

Radar DA only

Inc. sub-hourlysurface DA

Dusty Wheatley


June 14, 2010 west-TX VORTEX2 event

6-h QPEs ending 00Z 15 June 2010

NSSL Q2

Stage IVx LBB

2. Flash flood:

- HP supercell with weakly tornadic mesocyclone along gust front/pre-existing boundary intersection

- Severe wind gusts (34 – 37 m s-1 measured by VORTEX2) and strong cold pool (ΔT 15 - 18 K)

1. Severe weather: x LBB

x LBB

6”+ max 3”+ max

100 km100 km

1937 UTC

Focus area

Mike Coniglio


Initial mesoscale assimilation tests: Final analysis valid 18 UTCEnKF mean RUC analysis

RMSD = 1.90ME = 0.19

RMSD = 2.35ME = 0.47

2-m T

2-m Td

RMSD = 1.70ME = 0.51

RMSD = 2.10ME = 0.54

EnKF mean reduces analysis errors vs. RUCBut moist bias remains (MYJ PBL scheme)

Mike Coniglio


1 Hour Radar Assimilation Experiments: Final analysis valid 19Z

Mike Coniglio


Total 3-h accumulated precipitation 19-22 UTCNMQ QPE (color shading) and ensemble raw

probabilities > 10 mm (contours)

1-radar 4-radars

More backbuilding, slowereastward movement, butstill too far east overall

Little to no backbuilding, convection moves too fast to east

Accumulation too low in most runsMike Coniglio


GOES Cloud Property Assimilation using WRF-DART

• Initial Implementation: convert NASA Langley retrieval algorithm cloud properties into proxy WRF state variables

• Use Cloud Top Pressure (CTP) and Cloud Base Pressure (CBP) to determine 3-D location of cloud

• Create QCLOUD, QICE, QGRAUPEL, QRAIN, Relative Humidity

• Proxy columns on GOES horizontal grid with ~50 hPA vertical resolution

Thomas Jones


GOES Visible & CTP/CBP2045 UTC

• Convection initiating ahead of dryline in OK• Low-level clouds present in eastern OK

Cirrus Outflow

Low-level cloudsCTP ~200 hPa

CTP ~800 hPa

DevelopingConvection

Thomas Jones


WRF-DART Characteristics• WRF-DARTWRF-DART

– ARW, version 3.2.1 – EnKF assimilation using 36 members– Use 15 km CONUS and 3 km one-way nested grid

domains– Mesoscale assimilation window from 1200 UTC – 2100

UTC 10 May• 1 hour intervals

– Nested grid assimilation 1800 – 2100 UTC• 15 minute intervals

• Create 2 runs:– One assimilating derived cloud and humidity

variables (CLD)– One with variables set to evaluate-mode only

(NOCLD)

15 km Domain

3 km Domain

Thomas Jones


QCLOUD Differences2045 UTC

RED = CLD Greater BLUE – NOCLD Greater

Large areas of differences at 900 and 850 hPa

Magnitude ~ 0.1 g kg-1

Greatest differences near developing cumulus and in low-level clouds fields further east

Interesting wave-like pattern in QCLOUD differences at 850 hPa

Differences at 700 hPa and above have limited coverage

Only significant differences occur along dryline

Also see differences in model IWP (black shading)

Hard to ascertain physical significance of these differences

Thomas Jones


1 hour reflectivity forecast

• Probability of simulated reflectivity > 25 dBZ changes between NOCLD and CLD ensembles

• Neither shows much skill relative to the other

Thomas Jones


Summary• Two supercell cases: SS-NWP can predict the track

of the strongest rotation with some accuracy in 0-1 hour time frame.

• Using tornado proxy for track - less skill with genesis/decay

• Microphysical parameterization strongly impacts the forecast at these scales.

• Need to test cases from environments with more marginal tornado parameters

• Initial macroburst forecast is promising


Summary• Mesoscale convective systems

– accurate depiction of mesoscale environment critical

– Multi-radar improved QPF predictions

• Satellite case

– Takes 2 hours of assimilation of cloud properties to start making a difference

– GOES-R should reduce this time by providing 5 – 10 minute resolution data.

– Results likely very sensitive to microphysics


Take Aways..• Prediction of isolated severe convection shows promise

– MCS’s appears to have more challenges

• Everything matters?

– success with isolated cells: getting the (enough) details right over a small area?

– MCS problem may require getting the details right over a much larger area...

• Its the boundary layer....

– much of forecast error can be traced (we think) to errors in boundary layer structure of humidity and temperature

– all phases of convective evolution (initiation, intensification, decay) are impacted by these errors (even tornadogenesis?)


Thanks Questions?


Verification

TimingVerification with Tornado reports

Model proxy Tornado

Members shifted and focused more north than observed with minimal members co-located with TOR

Obs cell density axes (30 min)

Spatial location

UH

CA

# members

# storms - # storms verified

Establishing metrics of success

Which DA verifies best?Percent severe Percent model severe

25 50 75 100%Being storm specific next hour

A. No threat now

B. Tornado threat in 30 min

C. Decaying threat (storm ongoing)

• Explicit forecast of which storms will be severe and which won’t

A

C

B

Storm Severe Storm


Microphysical ParameterizationDevelopment

(T. Mansell, D. Dawson, Y. Jung, M. Xue)

• Development of 3-moment microphysical scheme suitable for deep convection

• Testing of 3-moment scheme within EnKF framework

• Verification of microphysical parameterizations– using dual-polarization radar data

– forward operator from Y. Jung and M. Xue

– collaboration with CAPS


Observations 8 May 2003 22:10 (tornadogenesis)

22 minute ensemble mean forecastwith multi-moment microphysics

valid 22:10

22 minute ensemble mean forecastwith single-moment microphysics

valid 22:10

Microphysical Sensitivity


Microphysical SensitivityGreensburg KS Forecasts

Single vs. Two Moment Microphysics

Single Two


GOES Cloud Property Assimilation• GOAL: Provide model analysis information on the location

and vertical distribution of clouds• Need high spatial and temporal resolution data• 1 km, 30 minute cloud property retrievals available from

GOES-13 data– Uses NASA Langley retrieval algorithm – Products include:

• Cloud top pressure (CTP)• Cloud base pressure (CBP)• Cloud liquid water path (CLWP)• Cloud ice water path (CIWP)• Cloud phase

• These variables are not suitable for direct assimilation into WRF-DART– Must convert to something it understands


Observation Diagnostics • QCLOUD

– No difference in bias or RMSE between 18-2000 UTC

– Some reduction in bias and RMSE after 2000 UTC

• Reduction increases with time• Max reduction ~0.05 g kg-1

RH Differences small at all times Posterior bias and RMSE at 2100 are

smaller by ~0.5%

Sample size ~800 Q* data points assimilated at each

time interval Total possible: ~1300

~300 for RH Saw-tooth pattern a result lower sample

size at interpolated times (00, 30)


QCloud and RH Data at 2045 UTC

• Where low clouds exist, RH=100% assimilated• Above 850 hPa, few clouds resulting in QCLOUD = 0 being assimilated

VARIABLE NTOTAL NASSIM %ASSIMQCLOUD 205482 187042 91.0QICE 205482 190796 92.8QRAIN 205482 190380 92.6QGRAUP 205482 196392 92.6RH 37189 22357 60.1TOTAL 859117 780967 90.9

1800 – 2100 UTC

Sample size

50

QCloud data

RH data

Thomas Jones


Cross Sections

• Small differences in location of QCLOUD peaks– 5-10 km offset

• Magnitude of IWP also differs

QCLOUD IWP


Issues/Challenges to Explore

• Case-specific challenges/questions:– Event has multiple convective modes and a strong cold pool. Can Δ=3 km simulations

produce a strong cold pool while still restraining its eastward propagation, as was observed?

2011 CAPS 4-km runs

TTU SND 1732

Currently trying experiment with MYNN Bnd LYR scheme

Environment from MYNN (MYJ) run from 2011 CAPS ensemble one of the best (worst) fits to observed soundings (see poster for more info).

Low-level moist bias in the warm sector- will multiple PBL/land-surface schemes help? Only using MYJ currently.

EnKF mean T, Td 1800

Mike Coniglio



Lou Wicker



EnsemblePrediction

for SVR SFCWINDS


3DVARSFC

WINDFIELD


Verification: Surface Winds Derived from 3DVAR Analysis

Three-radar wind synthesisKTLX, KOUN, TDWR

0010 UTC

Poorretrieval of winds nearsouthernboundary

Gust FrontfromDownburst0020 UTC

0030 UTC

Lou Wicker

warn on forecast case studies: progress report february 2012

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