Hydrograph Ensembles Based on a Variety of Quantitative

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) July 12, 2007 River Forecast Ensembles 1

Hydrograph Ensembles Based on a Variety of Quantitative Precipitation Forecasts Outline • • July 12, 2007 Background QPF ensemble Hydrologic models Hydrograph ensemble & interface Examples Uses Future… River Forecast Ensembles 2

Background • 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. July 12, 2007 River Forecast Ensembles 3

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 • • July 12, 2007 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 River Forecast Ensembles 4

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. HPC QPF Ensemble NCRFC Hydrologic Models Hydrograph Ensemble Process is automated so it is not cumbersome or time consuming to generate results. QPF ensemble is scientifically based and spatially consistent. July 12, 2007 River Forecast Ensembles 5

QPF Ensemble • 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 July 12, 2007 River Forecast Ensembles 6

HPC 95% Confidence Interval QPF 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. Given this relationship, they can determine the spread in the current SREF QPFs and estimate the error in the corresponding HPC QPF July 12, 2007 Maximum Absolute Error with 95% Confidence River Forecast Ensembles 7

HPC 95% Confidence Interval QPF Minimum QPF with 95% Confidence HPC QPF - = Maximum QPF with 95% Confidence Maximum Absolute Error with 95% Confidence HPC QPF = July 12, 2007 Maximum Absolute Error with 95% Confidence + River Forecast Ensembles 8

QPF Ensemble 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 July 12, 2007 River Forecast Ensembles 9

RFC Hydrologic Models HPC QPF Ensemble NCRFC Hydrologic Models Hydrograph Ensemble • 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. July 12, 2007 River Forecast Ensembles 10

Hydrograph Ensemble Results Interface Results Map July 12, 2007 Sortable Results Table River Forecast Ensembles 11

Hydrograph Ensemble July 12, 2007 River Forecast Ensembles 12

Ensemble Example La Moine River at Colmar, Illinois June 23 rd, 2007

La Moine River at Colmar, IL June 23 rd, 2007 RFC QPF Radar Estimate July 12, 2007 CLMI 2 HPC Max QPF HPC Min QPF River Forecast Ensembles CLMI 2 14

La Moine River at Colmar, IL June 23 rd, 2007 Crested at 21. 3 ft on June 25 th. July 12, 2007 River Forecast Ensembles 15

La Moine River at Colmar, IL June 23 rd, 2007 Crested at 21. 3 ft on June 25 th. July 12, 2007 River Forecast Ensembles 16

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

Red River of the North at Wahpeton, ND June 2 nd, 2007 WHNN 8 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. July 12, 2007 River Forecast Ensembles 18

Red River of the North at Wahpeton, ND June 2, 2007 Issued May 31 st Issued May 30 th Issued June 1 st River crested at 15. 7 ft on June 3 rd. July 12, 2007 River Forecast Ensembles 19

Ensemble Example Turtle Creek near Austin, Minnesota April 8, 2006

Turtle Creek near Austin, MN April 7, 2006 July 12, 2007 HPC QPF Max QPF Radar Estimate Min QPF River Forecast Ensembles 21

Turtle Creek near Austin, MN April 7, 2006 Crested at 11. 6 ft on April 8 th. July 12, 2007 River Forecast Ensembles 22

So What Can We do With This? • 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. July 12, 2007 River Forecast Ensembles 23

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. July 12, 2007 River Forecast Ensembles 24

Where do we go from here? July 12, 2007 River Forecast Ensembles 25

Verification • 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 July 12, 2007 River Forecast Ensembles 26

Expansion of Service to Other RFC’s • 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. July 12, 2007 River Forecast Ensembles 27

Other Sources of Uncertainty… • • • 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. July 12, 2007 River Forecast Ensembles 28

Summary Since we began incorporating QPF into our hydrologic forecasts in 1994, we have received many requests forecasts based on alternative QPF scenarios. Responding to these requests was cumbersome and time-consuming and resulted in subjective and inconsistent forecasts. July 12, 2007 River Forecast Ensembles 29

Summary NCRFC developed a system to generate and ensemble of hydrologic forecasts based on HPC QPF Old Cumbersome New Automated Time consuming Run via cron Based on SREF Analysis Each ensemble member is spatially consistent Graphical forecasts Subjective/Arbitrary QPF may be spatially inconsistent Verbal forecasts July 12, 2007 River Forecast Ensembles 30

How Do We Access This Great New Resource? • Intranet Link – QPFC interface – http: //intranet. msr. noaa. gov/ – Hydrology Products tab – 24 -48 -60 Hour Ensemble Forecast Summary • Intranet Link – Map. Server interface – http: //intranet. msr. noaa. gov/ – Hydrology Products tab – Interactive Map • Download Adobe SVG Viewer • Programs are started at 13 Z and 16 Z and images are available about 2 hours later. July 12, 2007 River Forecast Ensembles 31