# Presentation: 336673

## NAEFS TELECONFERENCEJune 17 2005

## ENSEMBLE PRODUCTS - FUNCTIONALITIES

|  | FUNCTIONALITY | CENTRALLY GENERATED | LOCALLY GENERATED | INTERACTIVE
ACCESS |
| --- | --- | --- | --- | --- |
| 1 | Mean of selected members  Done |  |  |  |
| 2 | Spread of selected members Done  |  |  |  |
| 3 | Median of selected values Sept. 2005 |  |  |  |
| 4 | Lowest value in selected members Sept. 2005 |  |  |  |
| 5 | Highest value in selected members Sept. 2005 |  |  |  |
| 6 | Range between lowest and highest values Sept. 2005 |  |  |  |
| 7 | Univariate exceedance probabilities for a selectable threshold value FY06? |  |  |  |
| 8 | Multivariate (up to 5) exceedance probabilities for a selectable threshold value FY06? |  |  |  |
| 9 | Forecast value associated with selected univariate percentile value Sept. 2005 - FY06? |  |  |  |
| 10 | Tracking center of maxima or minima in a gridded field (eg – low pressure centers) Sept. 2005, Data flow FY06? |  |  |  |
| 11 | Objective grouping of members FY08? |  |  |  |
| 12 | Plot Frequency / Fitted probability density function at selected location/time (lower priority) FY07? |  |  |  |
| 13 | Plot Frequency / Fitted probability density as a function of forecast lead time, at selected location (lower priority) FY07? |  |  |  |

- List of centrally/locally/interactively generated products required by NCEP Service Centers for each functionality are provided in attached tables (eg., *MSLP, Z,T,U,V,RH, etc, at 925,850,700,500, 400, 300, 250, 100, etc hPa)*

***Potentially useful functionalities that need further development:***
- - Mean/Spread/Median/Ranges for amplitude of specific features - Mean/Spread/Median/Ranges for phase of specific features

***Additional basic GUI functionalities:**** *- Ability to manually select/identify members - Ability to weight selected members *Sept. 2005*

## 		Deadline for operational implementation: March 2006
Must decide soon what we will implement
Two centers will generate same basic products in GRIB2 format
Ensures all end-products will be consistent on 2 sides
Bias corrected individual ensemble members
First moment decaying average bias correction (Bo Cui)
Second moment bias correction in 2007?
Bias correct toward each center’s own operational analysis?
Bias correct (all) model variables, OR pressure level GRIB2 data?
Weights for combining ensembles for each member
Normalized weighting, weighting with ridging, BMA???
Different weights for 2 subsets, or each member of MSC ensemble?
Climate percentile forecasts (for each ensemble member)
Parameterized cumulative climate distributions (based on reanalysis, for selected variables)
Algorithm to determine climate percentiles
Bias adjustment to account for systematic difference between operational & reanalysis fields?
End products generated based on basic products will differ:
NCEP
High priority items from NCEP Service Center request list
NDGD uncertainty information
Bias-corrected 10-50-90 percentile forecast value for selected variables
Climate percentile corresponding to 10-50-90 percentile forecast values
Week-2 experimental products?
MSC -Host of products

- Must decide soon what we will implement
- Two centers will generate same basic products in GRIB2 format
- Ensures all end-products will be consistent on 2 sides
- Bias corrected individual ensemble members
- First moment decaying average bias correction (Bo Cui)
- Second moment bias correction in 2007?
- Bias correct toward each center’s own operational analysis?
- Bias correct (all) model variables, OR pressure level GRIB2 data?
- Weights for combining ensembles for each member
- Normalized weighting, weighting with ridging, BMA???
- Different weights for 2 subsets, or each member of MSC ensemble?
- Climate percentile forecasts (for each ensemble member)
- Parameterized cumulative climate distributions (based on reanalysis, for selected variables)
- Algorithm to determine climate percentiles
- Bias adjustment to account for systematic difference between operational & reanalysis fields?
- End products generated based on basic products will differ:
- NCEP
- High priority items from NCEP Service Center request list
- NDGD uncertainty information
- Bias-corrected 10-50-90 percentile forecast value for selected variables
- Climate percentile corresponding to 10-50-90 percentile forecast values
- Week-2 experimental products?
- MSC -Host of products

**OPERATIONAL IMPLEMENTATION RELATED ISSUES**

## 2006 is first implementation, will be followed by two others in 07 & 08
No need to be comprehensive with all aspects of our work
Focus on most important elements in procedures
Eg, ignore 2nd moment bias correction if not that important, add later?
Provide climate anomaly forecasts for selected variables now, add others later?
12-hrly output frequency, increase to 6 hrly later?

What codes/procedures need to be shared?
Scheduling requirements for adapting codes from other center?
New situation, never done before

TOC (operational NWP) server: No changes allowed Sept05 – Feb06
NCEP server (prd) available (24/7, reliable)

Implementation scheduling requirements
Codes need to be delivered 45 days prior to planned implementation
Notification to user community about new products: 30 days prior to implementation
Minimum 60-day notification requirement if we change existing files

- No need to be comprehensive with all aspects of our work
- Focus on most important elements in procedures
- Eg, ignore 2nd moment bias correction if not that important, add later?
- Provide climate anomaly forecasts for selected variables now, add others later?
- 12-hrly output frequency, increase to 6 hrly later?
- What codes/procedures need to be shared?
- Scheduling requirements for adapting codes from other center?
- New situation, never done before
- TOC (operational NWP) server: No changes allowed Sept05 – Feb06
- NCEP server (prd) available (24/7, reliable)
- Implementation scheduling requirements
- Codes need to be delivered 45 days prior to planned implementation
- Notification to user community about new products: 30 days prior to implementation
- Minimum 60-day notification requirement if we change existing files

**OPERATIONAL IMPLEMENTATION RELATED ISSUES**

## Tentative implementation schedule:
March 2006	Bias corrected products
NCEP operational web pages (including Carribean & South American products)
“Experimental” status for first 60 days
NAWIPS grids for NCEP service centers
NDGD grids (10-50-90 percentile forecast values)

Febr 2006		Bias correction, weighting algorithms oper. Implemented
Dec 2006		Codes/scripts delivered to NCO
Oct 2006		Codes/algorithms exchanged between MSC-NCEP
Sept 2006		Decision regarding what to implement

- March 2006	Bias corrected products
- NCEP operational web pages (including Carribean & South American products)
- “Experimental” status for first 60 days
- NAWIPS grids for NCEP service centers
- NDGD grids (10-50-90 percentile forecast values)
- Febr 2006		Bias correction, weighting algorithms oper. Implemented
- Dec 2006		Codes/scripts delivered to NCO
- Oct 2006		Codes/algorithms exchanged between MSC-NCEP
- Sept 2006		Decision regarding what to implement

**OPERATIONAL IMPLEMENTATION RELATED ISSUES**

## NDGD FORECAST UNCERTAINTY RECOMMENDATION

- Provide 3 ensemble-based guidance products for inclusion in NDGD:
- 10, 50, and 90 percentile values
- SREF guidance out to day 3
- NAEFS guidance out to 16 days
- Use NDGD grid (5x5 km), with GRIB2 packing, minimal space overhead
- Approach
- Solicit comments on specific proposal from NCEP Service Centers and regions/field
- Use NAWIPS software (available soon?) to generate products
- Work with NAWIPS group to provide algorithm:
- Simple counting of members with linear interpolation now
- Gaussian Kernel method in later implementation
- Factor of 3 increase in disc space
- D. Ruth positively inclined (WG member at NDFD Workshop)

## NDGD FORECAST UNCERTAINTY - DOWNSCALING

- Ensemble uncertainty information
- Sent on NDGD grid for convenience (if no big overhead)
- Valid on model grids (32km for regional, 110 km for global ensemble)
- How to bridge gap between model and NDGD grids?
- Anomaly uncertainty information – proposed methodology
- Establish reanalysis climatology
- In progress for global (NAEFS), methods can be transferred to regional reanalysis
- Bias correct ensemble forecasts (wrt operational analysis)
- Take 10-50-90 percentile values from bias corrected ensemble
- (For establishing anomaly forecasts, adjust 10-50-90 percentile values to look like re-analysis)
- Check climatological percentile corresponding to 10-50-90 forecast percentiles
- Provide climatological percentiles corresponding to 10-50-90 percentile forecast values as second set of guidance products

## BACKGROUND

## PRODUCT GENERATION STATUS, May 2005

- Toolbox being worked on
- Predictability group (EMC, Service Center ensemble focal points) transfers algorithm/software to NAWIPS developers
- More sophisticated algorithms need to be worked on
- Pdf manipulation tools, clustering
- Automatic product generation
- List of requests from Service Centers for both global/regional ensembles collected
- Currently being prioritized
- NCO will generate products (Larry Sager), based on NAWIPS tools
- First set of NAEFS products (March 2006) based on global requests
- Coordinate SREF products for Winter Desk
- Web display of selected fields, including those for WMO Regions 3-4
- On-demand (additional) product generation
- Under purview of Service Center Focal points
- Interactive product generation
- Not available for all products yet
- Hardware (speed) limitations for some functionalities

## ENSEMBLE-BASED PRODUCTS FOR NDGD

- National Digital Forecast Database (NDFD)
- Official NWS forecast, prepared by WFO offices (central guidance, coordination)
- 5x5 (2.5x2.5) km grid, out to 7 days
- Selected parameters (~15)
- Available in digital format, query tools, etc
- No (minimal) provision for information on forecast uncertainty
- Recommendations from an NDFD workshop, Salt Lake City, 2003
- Interactive Forecast Preparation System (IFPS) offers tools to work with NDFD grids (forecasters can manipulate gridded data, etc)
- National Digital Guidance Database (NDGD)
- For posting numerical guidance products same way as NDFD
- New system, possibility to complement NDFD with forecast uncertainty info
- Based on global (NAEFS) and regional ensemble forecasts
- What forecast uncertainty info to post in NDGD?

## NDGD FORECAST UNCERTAINTY REQUIREMENTS

- Compact (conveys uncertainty without posting all members)
- Add minimal new info
- Current disc, telecommunication, etc limitations
- Simple to understand and use by both trained and novice users
- Expand existing lines of work
- Informative without additional knowledge, tools, that are not yet available
- Solid & scientifically based
- Can fit parametric pdf
- Allows to derive any univariate info
- Additional tools needed to use this feature
- Room for expansion
- Can easily be enhanced without major shift in direction
- More sophisticated methods can be added
- Possibly use Gaussian Kernel method of D. Unger

## NDGD FORECAST UNCERTAINTY ALTERNATIVES

- Current status (in NDFD):
- Expected value (mean, median, or mode??) of distribution only
- Scenario 1 – Add 1 variable
- Add spread to expected value (1 additional grid)
- Workshop WG felt that was not enough info
- Recommended adding 2 pieces of info
- Scenario 2 – Add 2 variables
- Add info on spread on 2 sides of mean/median/mode
- 10/90 or 20-80 percentile values
- Preferred as opposed to variance (spread) info that is more abstract
- NDFD Workshop recommendation

## NDGD FORECAST UNCERTAINTY QUESTIONS

- Use mean, mode, or median in NDGD?
- Mean – Expected value
- Can fall around minimum in pdf
- Requires additional info (what percentile it corresponds with)
- Mode – Most likely event
- Appealing heuristically (well defined meaning)
- Requires additional info (what percentile it corresponds with)
- Use in future when multiple modes can be considered?
- Median – 50 percentile
- Heuristic meaning (half below, half above)
- Consistent with 10/90 (or 20/80) percentile approach
- Verifies similarly to ensemble mean
- No need for additional info
- Used by HPC in PQPF context
- Use 10/90 OR 20/80 percentile?
- 10/90 is more inclusive (covering explicitly 80% of forecast distribution)