The West Gulf River Forecast Center provides hydrologic forecasts for a diverse region covering parts of Texas, Oklahoma, Arkansas and Louisiana. They use precipitation estimates from multiple sensors, hydrologic models, and expert judgment to issue river forecasts. Their focus has expanded beyond routine forecasts to include impact-driven services like custom graphics and briefings to better inform emergency managers and the public. Future improvements include higher resolution modeling and expanded flood inundation mapping to provide more localized streamflow information.

1. Beyond Routine Forecast Services –
NWS West Gulf River Forecast
Center’s Approach to Impact
Decision Support
Gregory Waller
Service Coordination Hydrologist
NWS – West Gulf River Forecast Center

2. NWS Mission
To provide weather, water, and climate data, forecasts and
warnings for the protection of life and property and enhancement
of the national economy.
NWS accomplishes this mission in close collaboration and cooperation
with State, Local, and Other Federal Agencies

3. NWS River Forecast Centers
• 13 Offices (12 CONUS + 1 Alaska/Pacific)
• Hydro-geologic boundaries
– Some modeling of headwaters in Canada/Mexico
(no forecast services)
• Daily Operations
– Data collection and quality
control
– Precipitation and
Hydrologic Forecasts
• Project Activities
– New technologies
– New products

4. The WGRFC Area
Diverse Water Issues
402,000 mi2 total area
87,000 mi2 in MX (Rio Grande headwaters)
320 forecast points, 15 major river systems
Over 65,336 miles of rivers (U.S. only)Snowpack
Water supply
• Hill Country Hydrology
• Flash flood threats
• Rapid river responses
• Cycles of Flood/Drought

5. WGRFC Demographics
• 3 - Top 10 Metro areas in the U.S. (DFW Metro, Houston
Metro, Austin/San Antonio Metro)
• 7 of Top 100 Fastest Growing Counties in the nation*:
Hays, Fort Bend, Comal, Andrews, Montgomery,
Williamson, Kendall
• 5 – Top 20 largest cities in the U.S.
• Approximately 12% of the Texas’ land area is susceptible
to flooding, which makes it the top state for total flood
prone area.
• There are over 6M people who speak Spanish in Texas.
2M people: Spanish is their only language.
• Texas projected to double in population over the next 50
years**
• *U.S. Census Bureau change from 2010 to 2011
• **State of Texas – Office of the Demographer (2015)

6. Now…The Hydrologic Cycle
Courtesy of the USGS Water Science School

7. Hydrologic Forecast Process
1. How much rain will reach the
river?
 Rainfall to Runoff Model
2. How fast will water reach the river
gage?
 Unit Hydrograph
3. What about water from upstream
locations?
 Routing
4. Translating water volume into
water height
 Rating Curves

8. The Meteorology
• Past rainfall
– Hourly
– 4km grid
• Future rainfall
– 6 hourly
– Blend of model and human
– At West Gulf RFC, we routinely use 12 hours of
future rainfall in our hydrologic forecasts (can
extend on rare occasions)

9. What is MPE?
• Multi-sensor Precipitation Estimator
– Inputs
• Radar
• Gauges
• Satellite
– Final multi-sensor precipitation product is better than
any single sensor.
• Goals
– Reduce spatial inaccuracies and bias errors in rainfall
datasets
– Produce a quality precipitation dataset for ingest into
National Weather Service (NWS) hydrologic models

10. Precipitation Best Estimate
• 4km x 4km spatial resolution
• 1 hour temporal resolution
• Human quality control of
data inputs
Gauge
Radar
Satellite
Best Estimate (Multi-
sensor Field)
Satellite

11. Precipitation Forecast/QPF
• 4 km x 4 km spatial resolution
• 6 hour temporal resolution
• 72 hours (12 periods) processed
– RFCs ingest 6-24 hours (1-4 periods)
operationally in hydrologic models
– Additional periods ingested based on
confidence in forecast
Guidance forecast issued by
National Center
Forecaster at RFC makes
adjustments based on local
expertise

12. The Hydro Model
• Community Hydrologic Prediction System
• Hydrologic Model
– Think “more math, less physics”
– Has capability of “plugging in” other models

13. Hydrologic Forecast Process
• A lot of estimates…
– Estimate how much rain gets into the river
• Rainfall to Runoff
– Estimate timing (how fast) of runoff to the river gage
• Unit Hydrograph
– Estimate how fast any upstream water arrives at the
gage
• Routing
– Estimate water flow (we use) into water height (the
public uses)
• Rating
• We can modify any/all of the above

14. Soil Accounting Model
Output
5cm
10cm
20cm
50cm
100cm
Fractional Water Content
at Depth
RDHM SacHT
Output

15. The Result – Our Model

16. Precipitation estimates and
forecasts merged into
continuous dataset
Precipitation dataset ingested
into hydrologic model.
Forecasters adjust model
parameters in real time
River forecast issued to
public
Rainfall
Analysis
Hydrologic
Modeling
Forecast
West Gulf River Forecast Center

17. River Forecast Center
Website Features
HEADER: Shows worst current
forecasted flood occurring in the
area – Tabs cycle through
rainfall and a quick briefing
written daily by hydrologist and
meteorologist
THE MAP: Squares represent
points which forecasts are
available for, triangles are
reservoirs
HYDROGRAPH: Click on any
site to see 3 days of observed
levels and 5 days of forecasted
levels (if a forecast is available)

18. Hydrograph Basics
LOCATION: Of the gage the
forecast is made, AT means the
gage is in the limits of the
town/city, NEAR or NR means
that town/city has the closest
post office
STAGE VS FLOW:
Hydrologists, models, reservoirs
work in flow. Emergency
managers, media, general
public work in
stage…sometimes
What is flow or a cubic foot per
second?
A basketball is roughly
a cubic foot, so
20,000cfs is 20,000
basketballs of water
passing the gage
every second.
The USGS measures the flow
and the stage at every gage
and provides a rating curve
linking the two units.
OBSERVED: Last 3 days of
observations from USGS with
the latest observation noted
FORECAST: 5 Day forecast for
site that is updated every 6
hours

19. ACTION
Impact: Water is over the banks and into the flood plain, but not a
threat to structures or roadways. Some action may be required
such as moving farm equipment or increasing awareness
MINOR
Impact: Typically water is impacting areas inside of flood plain which
can vary by location. Some low water crossings covered by water,
agricultural flooding, water approaching public areas (parks, sidewalks
etc.). Areas frequently flooded can expect to be impacted
MODERATE
Impact: Water now reaching areas only impacted by significant rain
events. Structures can be inundated, several roads covered with
water, water may cut off certain areas, widespread agricultural flooding
MAJOR
Impact: Water is near the highest its ever been representing rare
flooding and significant widespread impacts. Most roads will be
covered by water in the area cutting off if not completely flooding
subdivisions, rivers can be several miles wide in areas. Homes and
structures underwater, bridges inundated and in danger of being hit by
debris. Impacts may be greater than ever experienced.
BELOW CRITERIA
Impact: Water is within the banks of the river with no impacts to
the surrounding area. Flow speeds may still be high during rainfall
or releases which could impact recreational activities

20. So…How Does an Event Unfold
(hopefully)
• We see a heavy rain event on the horizon…

21. The Event
• We coordinate…
– Confidence
– Amounts
– Graphics

22. The Event
• Forecast on a forecast
• Coordinate some more…
Past Rainfall
Future Rainfall

23. What Changed in 2015…
• WGRFC Management overhaul
– New paradigm  Relevant, Reliable, Responsive
• IDSS – Impact Decision Support Services
– Be the “water” expert
– Supplemental graphics
• Don’t lose sight on required duties

24. WGRFC and IDSS – 2015-2016
•Special images
•Event specific
•Can be used for FB posts or tweets
•Not GIS based
•Would like to have GIS skills/shift
•Work creep  Graphicasts
•Graphicasts added to existing workload
• No additional bodies
•Displayed on web but can also be
“special image”

25. WGRFC and IDSS - 2015
Why create these special images?
"Out of everything that was briefed on
the call that is the most valuable piece of
information“ TX State SOC Manager
These special images were
identified as a “Best
Practice” and will now be
shared among our NWS
offices.

26. Upstream HECRAS Boundary
Downstream Boundary
Total Water – New Model
Efforts

27. The Future
• The National Water Center
• University of Alabama
• Bring federal water partners together…

28. The Change in Texas
102,000 NHDPlus reach catchments for Texas
Average area 7.1 km2
Average reach length 3 km
The Future…
NHDPlus reach catchment
Uniquely labeled across nation
• 15 Forecast Groups
– 320 Forecast Locations
– Almost 600 Modeled Watersheds
Now…

30. Another Tool in the Toolbox
• Will be able to provide streamflow information at
“intermediate” points
• Higher resolution grids
• Expansion of flood inundation
• Requires verification and validation
• Operational this year (2016)
• http://water.noaa.gov/map
• Expect full capability with 5 to 10 years

31. Questions/Comments?
Gregory Waller
Service Coordination Hydrologist
NWS West Gulf River Forecast Center
greg.waller@noaa.gov