December 3, 2020 Meeting

The third meeting of the 2020-2021 year was held virtually via Google Meet. Our guest speaker was Greg Waller of the National Weather Service West Gulf River Forecast Center.

Meeting Minutes

Call to Order
The third meeting of the 2020-2021 AMS/NWA chapter occurred on December 3, 2020 virtually via Google Meet. The meeting was called to order at 7:02pm by President Eric Carpenter.

Recording Secretary Joanne Culin took note of the number present. In total, there were 14 attendees.

Minutes Approval
Given the virtual format of the meeting, we did not cover minutes from the previous meeting.

New Business
Eric Carpenter discussed our usual sock drive fundraiser, but it will be changed this year. Grace Place is asking for ponchos and thermal underwear. The drive will run through mid-January and Eric will send an email. David Cox gave a treasury report with $452.29 in the treasury. No dues are being collected during this virtual format. Joanne Culin then introduced the speaker, Greg Waller. Greg Waller is the Service Coordination Hydrologist for the National Weather Service West Gulf River Forecast Center (WGRFC). After working for a private firm in Houston for 2 years performing mostly marine and tropical forecasting, Greg joined the National Weather Service (NWS) in May 1994, working in operational meteorology, at the NWS Offices in Columbus GA, Houston/Galveston, TX, and San Angelo, TX. In December 2000, Greg transferred to the West Gulf River Forecast Center, where he has served the last 20 years first as a hydrologist, then Senior Hydrometeorological Analysis and Support Forecaster (HAS), and finally as Service Coordination Hydrologist. Greg’s duties are to serve as a liaison and lead the coordination efforts of the RFC into the future.

He gave an overview of the WGRFC service area. In total, it covers 402,000 square miles with 87,000 square miles of that in Mexico where the Rio Grande headwaters are. They have 320 forecast points and 15 major river systems. He spoke in general terms about RFC in the NWS. There are 13 RFCs with 12 being in the CONUS and one in the Alaska region. Daily operations include data collection and quality control along with precipitation and hydrologic forecasts. In addition projects can include developing new technologies or new products. WGRFC service area covers two of the top ten metro areas in the United States (DFW and Houston), with San Antonio ranking at 24 and Austin at 29. They have four of the top ten fastest growing counties in the nation. There are also almost seven million people who speak Spanish in Texas and two million of which Spanish is their only language. This presents a communication challenge for conveying flooding information and they utilize the NWS Spanish language group. Texas is projected to double in population over the next 50 years. In addition, when working with international partners, they have to convert units into metric units when briefing Mexico.

Greg discussed what goes into a river forecast. Forecasters look at rain that has fallen, the rainfall forecast, soil conditions and lake releases and forecaster knowledge. All of this is combined to create a river forecast and, if needed, a flood warning. He spoke of the hydrologic process and some of the tools and techniques used. Forecasters want to know how much rain will reach the river and use a rainfall to runoff model to understand this. Then they want to know how fast water will reach the river gage and use unit hydrographs for this, and want to know about water from upstream locations and translate water volume into water height using rating curves. He also talked about how weather forecast offices are the RFC voice amplifiers and are a critical piece in giving river forecast information.

Greg discussed what MPE (Multi-sensor Precipitation Estimator) was, which is a method to reduce spatial inaccuracies and bias errors in rainfall datasets and help produce quality data to ingest into hydrologic models. It uses radar, gauges and satellite data. He discussed the hydro model used, which is called CHPS(Community Hydrologic Prediction System). Taking rainfall analysis from precipitation estimates(MPE) and rainfall forecasts, putting them into hydrologic modeling which forecasters can adjust model parameters in real time leads to a river forecast that is issued to the public. He also discussed the use of hydrographs. Forecasters calibrate their own models for their own basins and land use changes dictate that this be performed about every five years.

Greg then spoke about the coordination challenges with an international boundary. WGRFC is one of the few entities in the National Weather Service that coordinates with an international entity. The preferred method of coordination is through the State Department between the NWS and Conagua. Greg then spoke about coordinating with Mexico for Hurricane Hanna, which basically had a three day lead time before landfall. The rainfall forecast shifted from South Texas to over Mexico from Wednesday to Friday. There was a large area that ended up with over 20 inches of rain for the month. Because of this, there was needed coordination on some of the Mexican reservoirs and their operations. The NWS does not make decisions on reservoir operations. When doing forecasts, Mexico does not have radar so they have to rely on satellites and gauges. Water is so critical there that Mexico wanted to hold as much rain in the reservoirs as possible. This presents a problem when there is 20 inches of rain that falls in that area! The NWS routinely meets with the International Boundary Water Commission(IBWC) at least once a year. WGRFC sends email briefings to IBWC for situational awareness and IBWC passes on information on specifics of reservoirs in Mexico. Despite the need to go through the State Department(or the IBWC), the NWS does get daily updates emailed directly from Conagua. Greg spoke about the diversions installed on the Mexican side to redirect water.

In conclusion, Hanna brought torrential rain and flooding across the area(which was driven by rainfall and local runoff and not reservoir releases). Coordination began early between the NWS and IBWC, which was valuable. Even though WGRFC has taken steps to improve modeling across northern Mexico since Hurricane Alex in 2010, there is still tons of value in forecaster knowledge.

The meeting concluded around 8:30pm.

Minutes were submitted by Joanne Culin, Recording Secretary.

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