# Presentation: 562689

## SPC Ensemble Applications:Current Status, Recent Developments, and Future Plans  

**David Bright**
**(Steve Weiss, Russ Schneider, Gregg Grosshans, Jason Levit)**
*`*
***Storm Prediction Center***
*Science Support Branch*
*Norman, OK*
**4****th**** Ensemble User Workshop**
- Tuesday, 13 May 2008
- Laurel, MD

*Where Americas Climate and Weather Services Begin*

## Outline: SPC Ensemble Applications

**Current Status**
- Large-Scale Predictability: GEFS and NAEFS
- Mesoscale Guidance: Extensive SREF Usage
- Enhanced WEB guidance since last workshop
**Recent Developments and Future Plans**
- Rapid-Refresh Ensemble Forecast (RREF)
- HWT/Spring Experiment Storm-Scale Ensemble Forecst (SSEF)

## GEFS/NAEFS Application

**GEFS/NAEFS Application**

**GEFS in NMAP2: Large-Scale *****Pattern***

**GEFS in NMAP2: *****Predictability & spread***

**GEFS in NMAP2: *****Departure from normal***

**WEB Based: *****Predictability & pattern***

**168 Hour Forecasts **
**Valid 00Z 22 Oct 2007 **

## Application of the GEFS and NAEFS

**Day 4 through 8: *****Severe Weather Outlook***

**Day 3 through 8: *****Fire Weather Outlook***

-  **Use GEFS, NAEFS, and deterministic models to **
**  ****assess the large-scale pattern and its predictability**
** ****Anticipate the spectrum of possible high-impact weather**
** ****Three Forecast categories: **
**1) Potential Too Low**
**2) Predictability Too Low**
**3) Delineate Area**

- (Have become* operational *outlooks since the last Ensemble User Workshop)

## Mesoscale SREF Guidance

- SPC products are weighted toward the shorter time ranges
- 75% of all products valid within the next 24 hr period
- Product suite is both deterministic and probabilistic
- Use the SREF to assess a range of plausible high-impact environments
- The SREF aids creation of probabilistic forecasts and improves the confidence of deterministic forecasts
- High-Impact events often occur on scales below the resolvable resolution of the SREF

## Application of the SREF Ensemble 

- 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

**Notes:**
Ignoring all possible error sources in fcstg and observing systems (i.e., perfect measurements and models!), high impact events still occur at time and space scales below the resolvable resolution of most obs and fcstg systems.  Thus...

## Applications of Mesoscale Ensemble 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 & joint probabilities
-     used extensively

**Notes:**
The approach we’ve taken in developing ensemble guidance as well as the operational implementation of ensembles.

## 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%

## SREF Probability of STP Ingredients: Time Trends

_***36 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 50%

## SREF Probability of STP Ingredients: Time Trends

_***24 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 50%

## SREF Probability of STP Ingredients: Time Trends

_***12 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 50%

## Severe Event of April 7, 2006

- SREF environmental guidance increased forecaster confidence leading to a “High Risk” Day 2 outlook
- This was the _*first*_ Day 2 High Risk ever issued by SPC
- Impact: More than 800 total severe reports
- 3 killer tornadoes and 10 deaths

## SPC SREF Webpage for Mesoscale High-Impact Applications

**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

## SPC SREF Webpage for Mesoscale Applications is Popular

**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**

## Improvements to the SREF calibrated thunderstorm guidance

Calibrated SREF convective mode guidance:
Probability of > 1 tornado

Development of a Rapid Refresh Ensemble System (RREF)
Based on weighted, time-lagged RUC forecasts
Seeking ensemble guidance on convective initiation 
Initial operational storm scale ensembles may require scaled, time lagged members

Storm Scale Ensemble Forecast (SSEF) 
Experimental forecast for the SPC/NSSL HWT Spring Experiment

- Calibrated SREF convective mode guidance:
- Probability of _>_ 1 tornado
- Development of a Rapid Refresh Ensemble System (RREF)
- Based on weighted, time-lagged RUC forecasts
- Seeking ensemble guidance on convective initiation
- Initial operational storm scale ensembles may require scaled, time lagged members
- Storm Scale Ensemble Forecast (SSEF)
- Experimental forecast for the SPC/NSSL HWT Spring Experiment

**Recent Developments and  ****Future Plans**

**RREF: Calibrated Hourly Thunderstorm Probability**

- One Hour Thunderstorm Forecast
- F004: Valid 22 UTC 9 May 2008

**RREF: Calibrated Hourly Thunderstorm Probability**

- One Hour Thunderstorm Forecast
- F004: Valid 22 UTC 9 May 2008

## Experimental Storm Scale Ensemble Forecast (SSEF)

- 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**

## Experimental Storm Scale Ensemble Forecast (SSEF)

**Experimental Storm Scale Ensemble Forecast (SSEF)**

- Radar and no
- radar data
- assimilation

- Eight perturbed initial conditions

- WRF-ARW with mixed physics

## Convective Mode: Supercell Detection

**2 km AGL**

**5 km AGL**

**Convective Mode: Supercell Detection**

- Besides 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 2008
- UH _>_ 50 _**+**_** 25 mi**

## Probability Updraft Helicity > 50 m2/s2

- Radar BREF 0142 UTC 22 Apr 2008

## Probability Updraft Helicity > 50 m2/s2

**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**

## 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

- 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 2008

**Probability Linear Mode Exceeding 200 miles**

- Squall Line Detection

- F026: Valid 02 UTC 18 Apr 2008

- Squall Line Detection

**Probability Linear Mode Exceeding 200 miles**

- F028: Valid 04 UTC 18 Apr 2008

## Linear Convective Mode: Impacts

**Linear Convective Mode: Impacts**

- Aviation impacts ~ 01 UTC
- 18 April 2008

**Image provided by Jon Racy**

**Direct Severe Guidance from SSEF**

**Probability of Severe Thunderstorms based on “synthetic reports”**

**Direct Severe Guidance from SSEF**

**Probability of Severe Thunderstorms based on “synthetic reports”**

- _Actual Reports_
- Red: Tornado
- Blue: Wind
- Green: Hail

**Direct Severe Guidance from SSEF**

**Probability of Severe Thunderstorms based on “synthetic reports”**

**Direct Severe Guidance from SSEF**

**Probability of Severe Thunderstorms based on “synthetic reports”**

- _Actual Reports_
- Red: Tornado
- Blue: Wind
- Green: Hail

## Summary: Ensemble Applications at the SPC

- Ensemble usage continues to expand at the SPC
- Developing additional calibrated fields, particularly from the SREF (e.g., tornado; hail/wind)
- Steadily moving toward higher temporal and spatial scales
- Hourly SREF output (through F024) would be useful for convective initiation guidance, convective watch, and aviation support
- RREF and SSEF efforts ongoing
- Expanding the role of NAEFS in the extended outlook process