Title: Hydrograph Ensembles Based on a Variety of Quantitative Precipitation Forecasts
1Hydrograph 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)
1
2Hydrograph Ensembles Based on a Variety of
Quantitative Precipitation Forecasts
Outline
- Background
- QPF ensemble
- Hydrologic models
- Hydrograph ensemble interface
- Examples
- Uses
- Future
2
3Background
- The NCRFC has incorporated both HPC and WFO QPF
into its QPF process since 1994 with reasonable
success. - Operational hydrologic forecasts include 24 hours
of QPF.
3
4BackgroundProblem
- 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
4
5BackgroundSolution
- 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.
5
6QPF 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
7HPC 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.
8HPC 95 Confidence Interval QPF
9QPF Ensemble
9
10RFC Hydrologic Models
- 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.
10
11Hydrograph Ensemble Results Interface
12Hydrograph Ensemble
13Ensemble Example
- La Moine River at Colmar, Illinois
- June 23rd, 2007
14La Moine River at Colmar, ILJune 23rd, 2007
15La Moine River at Colmar, ILJune 23rd, 2007
Crested at 21.3 ft on June 25th.
16La Moine River at Colmar, ILJune 23rd, 2007
Crested at 21.3 ft on June 25th.
17Ensemble Example
- Red River of the North at Wahpeton, ND
- June 2nd, 2006
18Red River of the North at Wahpeton, NDJune 2nd,
2007
WHNN8
24-hr max QPF issued June 1st and gage reports
for June 2nd.
Hydrograph ensemble issued June 1st.
River crested at 15.7 ft on June 3rd.
19Red River of the North at Wahpeton, NDJune 2,
2007
Issued May 31st
Issued May 30th
Issued June 1st
River crested at 15.7 ft on June 3rd.
20Ensemble Example
- Turtle Creek near Austin, Minnesota
- April 8, 2006
21Turtle Creek near Austin, MNApril 7, 2006
HPC QPF
Max QPF
Radar Estimate
Min QPF
22Turtle Creek near Austin, MNApril 7, 2006
Crested at 11.6 ft on April 8th.
23So 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.
24So 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.
24
July 12, 2007
River Forecast Ensembles
25Where do we go from here?
26Verification
- 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
27Expansion of Service to Other RFCs
- 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.
28Other 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.
28
29Summary
- 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.
30Summary
NCRFC developed a system to generate and ensemble
of hydrologic forecasts based on HPC QPF
31How 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 MapServer interface
- 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.