# Presentation: 509458

## Hydrograph Ensembles Based on a Variety of Quantitative Precipitation Forecasts

- July 12, 2007

**River Forecast Ensembles**

*Hydrograph Ensembles **Based on a Variety of Quantitative Precipitation Forecasts*

- Presented at the NWS HPM Conference
- NWS Training Center – July 12, 2007
- By Brian Connelly (NCRFC)

## Hydrograph Ensembles Based on a Variety of Quantitative Precipitation Forecasts

- July 12, 2007

**River Forecast Ensembles**

*Hydrograph Ensembles **Based on a Variety of Quantitative Precipitation Forecasts*

- Background
- QPF ensemble
- Hydrologic models
- Hydrograph ensemble & interface
- Examples
- Uses
- Future...

**Outline**

## Background

- July 12, 2007

**River Forecast Ensembles**

- The NCRFC has incorporated both HPC and WFO QPF into it’s QPF process since 1994 with reasonable success.
- Operational hydrologic forecasts include 24 hours of QPF.

## BackgroundProblem...

- July 12, 2007

**River Forecast Ensembles**

- Background*Problem...*

- We have received numerous requests to provide river forecasts based on different QPF scenarios.
- We were able to meet some of these requests by manually manipulating the data
- Cumbersome
- Significant overhead to the forecast process
- Results were subjective and lacked consistency
- Until recently we were only able to convey crest values/dates verbally

**Notes:**
Cumbersome because it is difficult to redraw QPF or even make runtime modifications to the QPF inputs, especially in the winter/spring seasons.
Overhead because it takes a significant amount of time to prepare the QPF simulations and report the results
Subjective because we would often implement QPF modifications that were arbitrary or based on a single WFO’s QPF and not a consensus product
Lacked consistency because we may provide guidance for a WFO based on their modifications, but we wouldn’t necessarily modify the QPF for neighboring basins or conflicting modifications.  As a result the forecasts for points downstream would be the result of inconsistent QPF in the upstream watershed.

## BackgroundSolution...

- July 12, 2007

**River Forecast Ensembles**

- Background*Solution...*

- The NCRFC developed a system that generates hydrograph ensembles based on a variety of QPFs from the HPC and displays them on the NCRFC Intranet website.

**Notes:**
This addresses the “cumbersome”, “overhead”, and “consistency” issues.

## QPF Ensemble

- July 12, 2007

**River Forecast Ensembles**

- Current QPF ensemble has 9 members
- Variety of time durations
- RFC QPF based on HPC and WFO guidance and current conditions.
- 95% Confidence Interval ***Maximum*** QPF based on the Short Range Ensemble Forecast (SREF)
- 95% Confidence Interval ***Minimum*** QPF based on SREF

**Notes:**
We use the term ensemble loosely here.  If we were creating a true ensemble, we would run the model for each member of the SREF and then generate some statistics on the results.  Instead, we are taking the 95% CI max and min QPF and running them through our model.

## HPC 95% Confidence Interval QPF

- July 12, 2007

**River Forecast Ensembles**

- After reviewing many past events, HPC has learned that there is a good correlation between the error in their 6-hour QPF and the corresponding spread in the QPF generated by the SREF.

**Notes:**
HPC used to derive 50% CI QPF but it gave bad results.  It was kind of like us going from old-fashioned outlooks to esp...you never hit the mean.

## HPC 95% Confidence Interval QPF

- July 12, 2007

**River Forecast Ensembles**

**=**

**=**

## QPF Ensemble

- July 12, 2007

**River Forecast Ensembles**

| RFC QPF | 24 hours | 48 hours | 72 hours |
| --- | --- | --- | --- |
| HPC 95% Max QPF | 24 hours | 48 hours | 60 hours |
| HPC 95% Min QPF | 24 hours | 48 hours | 60 hours |

**Notes:**
What about straight NDFD grids?

## RFC Hydrologic Models

- July 12, 2007

**River Forecast Ensembles**

- Use the same hydrologic models we use during the deterministic forecast process, FFG, and ESP.
- Raw model output
- Model states reviewed and adjusted daily
- Currently not generating ensembles for some points where dynamic routing is required.

**Notes:**
Raw model output – Only reflects phenomena that we model, not things like ice jams.  Doesn’t include forecaster value

## Hydrograph Ensemble Results Interface

- Results Map

- Sortable Results Table

- July 12, 2007

**River Forecast Ensembles**

**Notes:**
Discuss different ensemle sets via the tabs

## Hydrograph Ensemble

- July 12, 2007

**River Forecast Ensembles**

**Notes:**
Discuss different ensemle sets via the tabs

## Ensemble Example

- La Moine River at Colmar, Illinois
- June 23rd, 2007

## La Moine River at Colmar, ILJune 23rd, 2007

- July 12, 2007

**River Forecast Ensembles**

## La Moine River at Colmar, ILJune 23rd, 2007

- July 12, 2007

**River Forecast Ensembles**

- La Moine River at Colmar, ILJune 23rd, 2007

*Crested at 21.3 ft on June 25**th**.*

## La Moine River at Colmar, ILJune 23rd, 2007

- July 12, 2007

**River Forecast Ensembles**

*Crested at 21.3 ft on June 25**th**.*

## Ensemble Example

- Red River of the North at Wahpeton, ND
- June 2nd, 2006

## Red River of the North at Wahpeton, NDJune 2nd, 2007

- July 12, 2007

**River Forecast Ensembles**

*24-hr max QPF issued June 1**st** and gage reports for June 2**nd**.*

*Hydrograph ensemble issued June 1**st**.*

*River crested at 15.7 ft on June 3**rd**.*

- WHNN8

## Red River of the North at Wahpeton, NDJune 2, 2007

- July 12, 2007

**River Forecast Ensembles**

*Issued May 30**th** *

*Issued June 1**st** *

*Issued May 31**st** *

*River crested at 15.7 ft on June 3**rd**.*

## Ensemble Example

- Turtle Creek near Austin, Minnesota
- April 8, 2006

## Turtle Creek near Austin, MNApril 7, 2006

- July 12, 2007

**River Forecast Ensembles**

- HPC
- QPF

- Radar
- Estimate

- Max
- QPF

- Min
- QPF

## Turtle Creek near Austin, MNApril 7, 2006

- July 12, 2007

**River Forecast Ensembles**

*Crested at 11.6 ft on April 8**th**.*

## So What Can We do With This?

- July 12, 2007

**River Forecast Ensembles**

- Provide forecasters with insight into how QPF affects hydrologic forecasts.
- Demonstrate the inherent uncertainty in hydrologic forecasts due to QPF.
- Help prioritize work.
- Provide customers with initial guidance for “what-if” scenarios.
- Provide initial guidance later in the day if actual precipitation deviates from operational QPF.

**Notes:**
THESE ARE NOT FORECASTS

THEY COULD ISSUE TEXT-TYPE FORECASTS, NOT NUMBERS, BASED ON THIS INFO, BUT SHOULD CONTACT RFC FOR UPDATED FORECASTS.

## So What Can We do With This? (continued)

- July 12, 2007

**River Forecast Ensembles**

- So What Can We do With This? *(continued)*

- Assess staffing requirements at the WFO and RFC.
- RFC can use results as guidance when creating the Flood Outlook Product.
- Guidance for writing hydrology section of HWO or ESF products.
- RFC can view ensembles while forecasting.

**Notes:**
THESE ARE NOT FORECASTS

THEY COULD ISSUE TEXT-TYPE FORECASTS, NOT NUMBERS, BASED ON THIS INFO, BUT SHOULD CONTACT RFC FOR UPDATED FORECASTS.

## Where do we go from here?

- July 12, 2007

**River Forecast Ensembles**

## Verification

- July 12, 2007

**River Forecast Ensembles**

- NCRFC is archiving results at all forecast points for later analysis.
- Look at verification as a function of
- QPF type
- QPF duration
- Drainage area
- Geographic area

## Expansion of Service to Other RFC’s

- July 12, 2007

**River Forecast Ensembles**

- Mississippi River Basin from Aitkin, MN to New Orleans, LA.
- Requested by the USACE Mississippi Valley Division.
- A PDD has been submitted to make this a public experimental product.

## Other Sources of Uncertainty...

- July 12, 2007

**River Forecast Ensembles**

- Precipitation forecast ensemble
- Air temperature forecast ensemble
- Initial soil moisture states
- Initial snowpack states
- Snowmelt rates

***The NWS Hydrology Laboratory is developing a forecast system to prepare short term probabilistic forecasts, but this is not yet available for general use.***

## Summary

- July 12, 2007

**River Forecast Ensembles**

- Since we began incorporating QPF into our hydrologic forecasts in 1994, we have received many requests for forecasts based on alternative QPF scenarios.
- Responding to these requests was cumbersome and time-consuming and resulted in subjective and inconsistent forecasts.

## Summary

- July 12, 2007

**River Forecast Ensembles**

| Old | New |
| --- | --- |
| Cumbersome | Automated |
| Time consuming | Run via cron |
| Subjective/Arbitrary | Based on SREF Analysis |
| QPF may be spatially inconsistent | Each ensemble member is spatially consistent |
| Verbal forecasts | Graphical forecasts |

- NCRFC developed a system to generate and ensemble of hydrologic forecasts based on HPC QPF

## How Do We Access This Great New Resource?

- July 12, 2007

**River Forecast Ensembles**

- Intranet Link – QPFC interface
- _[http://intranet.msr.noaa.gov/](http://intranet.msr.noaa.gov/)_
*Hydrology Products *tab
*24-48-60 Hour Ensemble Forecast Summary*
- Intranet Link – MapServer interface
- _[http://intranet.msr.noaa.gov/](http://intranet.msr.noaa.gov/)_
*Hydrology Products *tab
*Interactive Map*
- Download Adobe SVG Viewer
- Programs are started at 13Z and 16Z and images are available about 2 hours later.