SPC Ensemble Applications: Current Status, Recent Developments, and Future Plans David Bright Storm Prediction Center Science Support Branch Norman, OK

SPC Ensemble Applications:SPC Ensemble Applications:Current Status, Recent Developments, Current Status, Recent Developments,

and Future Plansand Future Plans

David Bright

Storm Prediction CenterScience Support Branch

Norman, OK

4th Ensemble User WorkshopTuesday, 13 May 2008

Laurel, MDWhere Americas Climate and Weather Services Begin

Outline: SPC Ensemble Applications

• Current Status– Large-Scale Predictability: GEFS and NAEFS– Mesoscale Guidance: SREF

• Recent Developments– HWT/Spring Experiment Storm-Scale

Ensemble Forecst (SSEF)– Rapid-Refresh Ensemble Forecast

• Ongoing and Future Plans

Application of the GEFS and NAEFS

Day 4 through 8: Severe Weather Outlook Day 3 through 8: Fire Weather Outlook

• Assess the large-scale pattern and its predictability• Anticipate the spectrum of possible high-impact weather• Three Forecast categories:

1) Potential Too Low2) Predictability Too Low3) Outlook An Area

168h Forecast Valid 00 UTC 22 Oct 2007

GEFS Ensemble Mean: 500 mb Height and Vorticity

Application of the GEFSGEFS in NMAP2: Pattern


GEFS Ensemble Spaghetti: 500 mb Height (Single contour at 5760 m)

Application of the GEFSGEFS in NMAP2: Predictability and spread


GEFS Ensemble: Mean 500 mb Height and its Departure from Normal (# of SD)

Application of the GEFSGEFS in NMAP2: Departure from normal


NAEFS Ensemble: 500 mb Mean Height and its Standard Deviation

Application of the NAEFS

NAEFS via WEB: Predictability of the large-scale pattern

Mesoscale Scale

• 90% of products here…so most work in this area

• Build confidence

• Assess range of plausible solutions

Application of the SREF Ensemble • The High Impact Challenge: High impact events often occur on time and space scales below the resolvable resolution of most observing, forecasting (and ensemble) systems

• Key Application Premise: We use knowledge of the environment, unresolved processes, and consider uncertainty, to determine the spectrum of possible hazardous weather, when and where it may occur, and how it may evolve over time

Applications of Mesoscale Applications of Mesoscale Ensemble Guidance at the SPCEnsemble Guidance at the SPC

• Develop specialized guidance for the specific application (severe weather, fire weather, winter weather)

• Design guidance that…– Helps blend deterministic and ensemble approaches– Provide guidance for uncertainty/probabilistic forecasts– Provide guidance that aids (deterministic) confidence– Illustrates a range of plausible scenarios– Allows for diagnostic analysis – is not just a statistical black-box– Probabilities and joint probabilities most commonly applied

SREF Probability of STP Ingredients: Time Trends

48 hr SREF Forecast Valid 21 UTC 7 April 2006

Prob (MLCAPE > 1000 Jkg-1)

X

Prob (6 km Shear > 40 kt)

X

Prob (0-1 km SRH > 100 m2s-2)

X

Prob (MLLCL < 1000 m)

X

Prob (3h conv. Pcpn > 0.01 in)

Shaded Area Prob > 5%

Max 40%




X


X

Prob (0-1 km SRH > 100 m2s-2)

X


X



Max 50%




X


X

Prob (0-1 km SRH > 100 m2s-2)

X


X



Max 50%




X


X

Prob (0-1 km SRH > 100 m2s-2)

X


X



Max 50%

Severe Event of April 7, 2006• SREF severe weather fields increased forecaster

confidence resulting in a “High Risk” outlook• First ever Day 2 outlook High Risk issued by SPC • More than 800 total severe reports

– 3 killer tornadoes and 10 deaths

http://www.spc.noaa.gov/exper/sref/

SPC SREF Webpage for Mesoscale High-Impact Applications

http://w1.spc.woc.noaa.gov/exper/sref/frames.php?run=case_2007060703

Case study support added for WFOs

http://www.spc.noaa.gov/exper/sref/

SPC SREF Webpage for Mesoscale Applications is Popular

SPC SREF Webpage for Mesoscale Applications: Plumes

Click on forecast hour for dSREF/dt depiction(Courtesy of Steve Listema and Steven Zubrick, WFO Sterling)

SPC SREF Webpage for Mesoscale Applications: dSREF/dt

SPC SREF Webpage for Mesoscale Applications: dSREF/dt

• Decomposition of severe:– Probability of > 1 tornado

• Improved calibrated thunderstorm

• Rapid Refresh Ensemble System (RREF)– Based on time-lagged RUC– Guidance for convective initiation (and initial

operational storm scale ensembles will likely require scaled time lagging

Recent SREF Developments and Plans

RREF: Calibrated Hourly Thunderstorm Probability

RREF: Calibrated Hourly Thunderstorm Probability

Storm Scale

Future Applications: Explicit High Impact Ensembles

• NOAA Hazardous Weather Testbed (HWT)• HWT Spring Experiment

Focused on experimental high-res WRF forecasts since 2004 (dx ~2-4 km)• Convection allowing ensemble forecasts (2007-2009) to address uncertainty

10 WRF members 4 km grid length over 3/4 CONUS Major contributions from: SPC, NSSL, OU/CAPS, EMC, NCAR

• Evaluate the ability of convection allowing ensembles to predict: Convective mode (i.e., type of severe wx) Magnitude of severe type (e.g., peak wind) Aviation impacts (e.g., convective lines/tops) QPF/Excessive precipitation Year 1 Objective (2007): Assess the role of physics vs. initial condition uncertainty at high resolution

2003 Spring Experiment

2 km AGL

5 km AGL

Convective Mode: Supercell DetectionBesides simulated reflectivity, need a quantitative tool for supercell detection

and strength in deterministic and ensemble forecasts

Probability Updraft Helicity > 50 m2/s2

Supercell Detection

F026: Valid 02 UTC 22 Apr 2008UH > 50 + 25 mi


Radar BREF 0142 UTC 22 Apr 2008


View of the left split looking south from Norman, OK (0145 UTC 22 Apr 2008)

(Numerous large hail reports up to 2.25”)

Jack Hales

Convective Mode: Linear Detection

• Determine contiguous areas exceeding 35 dbZ

• Estimate mean length-to-width ratio of the contiguous area; search for ratios > 5:1

• Flag grid point if the length exceeds:– 50 miles– 100 miles– 200 miles

Probability Linear Mode Exceeding 200 miles

Squall Line Detection F024: Valid 00 UTC 18 Apr 2008Linear mode + 25 miles


Squall Line Detection F026: Valid 02 UTC 18 Apr 2008Linear mode + 25 miles

Squall Line Detection


F028: Valid 04 UTC 18 Apr 2008Linear mode + 25 miles

Base Reflectivity 0140 UTC 18 April 2008

Radar Reflectivity Valid 02 UTC 15 May 2007

Linear Convective Mode: Impacts

Direct Severe Guidance from SSEFProbability of Severe Thunderstorms based on “synthetic reports”




Summary: Ensemble Applications in High Impact Forecasting

• Ensemble approach to forecasting has many similarities to the deterministic approach– Ingredients based inputs– Diagnostic and parameter evaluation

• Ensembles contribute appropriate levels of confidence to the forecast process– Ability to view diagnostics and impacts in probability space

• Calibration of ensemble output can remove systematic biases and improve the spread

• Ensemble techniques scale to the problem of interest (weeks, days, or hours)

Documents

SPC Ensemble Applications: Current Status, Recent Developments, and Future Plans David Bright Storm Prediction Center Science Support Branch Norman, OK