Red River Basin Disaster Information Network
OnLine Workshop
March 23, 2000 -- 12:00 Noon CST

Spring Flood Outlook 2000

Featuring

Mark Ewens
National Weather Service, Grand Forks

[Introduction]

Amy Sebring: Good afternoon, and thank you for joining us in the Red River room of the EIIP Virtual Forum.

First, if you see a blue Web address, you can click on it and the referenced Web page should appear in a browser window. After the first one, the browser window may not automatically come to the top, so you may need to bring it forward by clicking on a button at the status bar at the bottom of your screen. Then to return to the chat, you will need to bring your chat window back to the top.

Background information for today's session may be found at http://www.emforum.org/redriver/workshop/wk000323.htm

Almost exactly one year ago, we did an online session with members of the National Weather Service that focused on AHPS, the Advanced Hydrologic Prediction System. The transcript is still available from our Web site under the Workshops link. Today, we are pleased to have Mark Ewens from the NWS Grand Forks office to provide an update on the Spring Flood Outlook, what's new this year, and progress towards implementing AHPS.

Mark previously worked in the Fargo NWS office, and has been with the Grand Forks office since 1995 as Data Acquisition Program Manager, and from what he is going to tell us, it's obvious that there is a lot of data involved! Mark was also one of our first network members, and we are very happy he is taking this opportunity to share with us today. Welcome, Mark. I turn the floor over to you.

[Presentation]

Mark Ewens: Thank you, Amy. Currently the Red River of the North and associated tributaries are enjoying one of the easiest floods in 8 years. Not since the drought years of 1988 --- 1992 have rivers been so low. Only 5 points in the Red Basin --- Fargo, Dilworth MN, Sabin MN, Alvarado and Warren MN reached flood stage.

And as of 7:00 a.m. this morning, no rivers were in flood with only Fargo showing modest rises, this due to the runoff of recent snows. Unless significant snows or intense, widespread convection occurs, the spring of 2000 will be a non-event. And of course, a major storm system is taking aim at the northern plains with some rain and thunderstorms possible.

The National Weather Service (NWS) has just completed a major overhaul of its meteorological services. This Modernization and Associated Restructuring (MAR) has pushed the limits of operational meteorology to new highs. Similarly, the MAR has begun to revamp the way the NWS does its hydrologic operations.

To this end, the cornerstone of the hydrologic MAR is the Advanced Hydrologic Prediction Service or AHPS. AHPS will provide a greater variety of hydrologic information to all users. This information will be especially useful to emergency managers and flood fight planners. A preview of the AHPS can be seen at the next link, where there is also an active example.

http://www.crh.noaa.gov/ncrfc/ahps/index.html

The following is a GIF image generated by a PC application titled SHEFPLOT. We use this program to graphically detail the RFC's forecasts. We use this to make the public flood forecast, and these images will be going on the Grand Forks homepage in the hydro section.

[Slide 1]

AHPS will provide a wealth of information that will allow users to make better informed decisions. For example, had AHPS been in use during the spring of 1997, the inherent error rate of 10% in the models would have been displayed. What would the implications have been for Grand Forks?

The outlook value of 49 feet which became a point of fixation would have had an upper reliability limit of 54 feet (the ultimate crest) and a lower limit of 44 feet. In other words, what was connoted in the outlook verbiage would have been explicitly displayed. It was this variability in flood outlook values that many in Grand Forks missed, even though it was stated. Yet showing something graphically has greater attention getting power than something written.

Other links within the Grand Forks NWS AHPS page [to be located at http://www.crh.noaa.gov/fgf/ahps/ahpsmain.htm] will become active during the next 1 to 2 months. Keep checking back for updates.

After the flood of '97, the NWS promised residents of the Red River Valley AHPS would be implemented soon. Yet due to funding cuts it took longer than originally anticipated. During the 2000 fiscal year cycle, monies for the Red River Basin were originally not available.

As good fortune would have it, and with coaxing from the NWS director General (Ret.) Kelly, the Red River was added to the AHPS cycle for FY00. However, the news came too late to implement it immediately. In addition to the external forces delaying its start, the calibration of the models driving AHPS were not complete.

The North Central River Forecast Center (NCRFC) in Chanhassen, Minnesota has been running the primary model, the Sacramento Soil Moisture Model in house during the 2000 spring flood season. Results of these parallel testing will not be available until next year.

During the summer and fall of 1999, a survey of our customers was performed. In it we asked questions such as how soon do you need river forecasts, what venue do you use to obtain them, how would you view the efficacy of probabilistic versus deterministic forecasts.

In order for the NWS in Grand Forks to keep it's promise of AHPS implementation, a scheme to demonstrate the probabilistic forecasting was developed. This scheme of "what if" entailed generating 3 numbers during the spring 2000 outlook.

The first number was what river stages would be if the snow melt was accompanied by 50% of climatological normal precipitation, the second was snowmelt runoff only and the third new number was runoff with 150% of climatological normal. Being as this was such a low snowfall year the full utility of this technique was not realized.

What has been most interesting, however, is how accurate the 3rd outlook number actually was. Just 2 days after the outlook was released, significant rains and snows fell on the basin. In all but 3 locations the rivers reached the outlooked values.

This 3rd number was very well received by city engineers and flood fighters alike. With few exceptions this method was accepted as a natural transition from the traditional outlook method to the new method. Even so, this transition does not grasp the full potential of where AHPS will place river forecasting. For a more detailed view of the Sacramento model and its implications for AHPS go to

http://www.crh.noaa.gov/ncrfc/documents/Papers/SacramentoMethods/SacramentoMethods.htm

To fully appreciate how forecasting is done, lets look at a few examples of data flow from the field to the public. The schematic is very simplified, but this works.

[Slide 2]

In the 'olden days' of teletype and telephones only, data flow to the Weather Service Office in Fargo was a garden hose. In the modernized era, data arrives at the WFO in Grand Forks by the fire hose. The staff at WFO, while larger than just 5 years ago, has many times the duties and data to handle.

Flow of data is exponential to the amount of 'weather' on any given day. So the example of GOES data, Observer generated and manual gage data oversimplifies the amount of information we receive. During flood season, WFO Grand Forks can handle over 2000 individual reports a month.

This is only 64 or so observations (on average) per day, but much of the data comes within a 2 hour time window. At the same time, the hydro meteorologist on duty is busy maintaining a basic weather watch of non-hydrologic automated weather observing sites, a forecast shift, answering the telephone and fulfilling climate requests to the public, police, fire or litigators.

Forecasting the stage of a river then involves more than just ingesting data and allowing a river model to run. There is a tremendous amount of human interaction that occurs. The model generates flows based on how water is routed through channels of a known size, with that flow converted to a stage via a rating curve.

[Slide 3]

As most forecast points have several rating curves, for channel conditions such as ice or no ice, the human forecaster has to decide which rating curve to use. He or she can override the model to produce the best forecast possible.

The forecast interface has the option to generate a coordination message to alert the target WFO of problems or data requests. Finally, the hydrologist can generate a forecast.

The next link has a very detailed description of how forecasts and outlooks are made, how the models operate and verification of previous years. I had planned on using some of the graphs in this paper, but I could not do it justice. It would be better if everyone gets time to look at this. The author, Pat Neuman of the NCRFC has done an outstanding job of describing the task of generating a river forecast.

http://www.crh.noaa.gov/ncrfc/documents/Papers/Outlooks/Outlooks.htm

Well, that's about it. This is a *very brief* overview of current hydrologic operations and a glimpse into its future. Thank you for your attention and now I will be happy to try to answer your questions.

[Question and Answer]

Amy Sebring: Thank you very much for the update Mark. We will take audience comments and questions next. Please indicate you wish to be recognized by sending in a question mark at any time. Then compose your question, have it ready so we can keep the flow moving, but hold it until you are recognized.

Comment:

Mike Anderson: Nice job, Mark. There is a lot of information in your presentation and Neuman's paper.

Question:

Amy Sebring: Will give folks a moment to think. In the meantime, Mark, does it look like AHPS will be fully implemented by Spring 2001 then?

Mark Ewens: I'm not sure; at present it looks to be on target for then but this is a government agency!

Question:

Kevin Ruud: Mark, how much impact will the new dikes and levees impact upstream of Grand Forks? Is there a way to know?

Mark Ewens: That's a question better answered by a hydrologist but I'm betting it will have an effect as the river widens and deepens just downstream from Grand Forks.

Question:

Paul Bourget: Given the nature of the Red, has there been an interest from your Canadian counterparts in this technology?

Mark Ewens: The Canadians use a probabilistic technique already to make outlooks on the Red. I do not have the URL on hand, but their outlooks are available on the Internet. [See http://www.gov.mb.ca/natres/watres/spring00.html]

Question:

Linwood DeLong: I noticed in a recent issue of the Winnipeg Free Press a short article about a new, high-tech agrometeorology center, which is supposed to improve flood forecasting. Do you know about this? Does it use some brand new techniques?

Mark Ewens: Caught me off guard! No I have not read about it, perhaps someone from the NCRFC might be able to take a stab at it?

Linwood DeLong: Maybe I could fax you a copy of the article, if you would like. You can contact me afterwards.

Mark Ewens: That would be nice.

Mike Anderson: Not aware of this. Maybe someone from the regional office knows?

Question:

Amy Sebring: Yes, we are sorry we do not have the Canadian side with us today; would be happy to follow up on that Linwood. Mark, I am interested in understanding how the changes such as Kevin spoke of are accommodated; are the rating curves revised periodically?

Mark Ewens: Yes, the USGS makes readings frequently to compare how the stage reading at any given time looks against the curve for that flow. They do this as often as possible. They very busy boys and girls in the GS.

Question:

Linwood DeLong: I gather that after the Mississippi flood of 1993 a lot of work went into better data collection. Did this result in any new flood forecasting techniques?

Mark Ewens: To my understanding, yes! Look at the Des Moines project for the AHPS. If you go to the NWS in Grand Forks home page you can get to the Des Moines home page and look at AHPS as it was in the post 93 era. Lots of good information.

Question:

Gus Wruck: What is the concern about Devils Lake? In Manitoba it is of considerable concern if it goes into the Red River?

Mark Ewens: Devils Lake is a closed, hence stagnant basin and the Canadians are concerned that certain micro-organisms will get into the Red then onto Canada, adversely affecting the water supply for them.

Amy Sebring: Please note that there is some info in the Neuman paper specifically on Devils Lake.

Gus Wruck: Is this a fact?

Mark Ewens: It is greatly debated. The fact that Devils Lake is a closed basin is obviously true, but I'm not a microbiologist so I can't answer that.

Question:

Amy Sebring: Mark, why are the numeric forecasts expressed in tenths of a foot? Doesn't that imply a certain level of precision that might be misunderstood? You mentioned a 10% error in the models.

Mark Ewens: Let me clarify please. The errors come from many places the changes in channel size, width and depth as silting occurs, is natural and tough to model. The NCRFC does an outstanding job of forecasting the River with the information they have. Forecasting the Red River is like making a medical diagnosis over the phone. It can be done, but the RFC does it well.

Tenths of a foot forecasts are a part of the model output. There is debate on how to present these forecasts and outlooks to the public when we go fully AHPS. River forecasting is misunderstood as is weather forecasting.

Question:

Amy Sebring: Will there be any follow up surveys on that point, and is the previous survey posted anywhere?

Mark Ewens: There is on going dialogue internally and with external users which will continue for some time as we struggle with the best way to service the public.

Question:

Tricia Wachtendorf: Was the move toward probabilistic forecasting on the US side already in the plan for the future in 1997 or did the push begin as a result of the 1997 flood?

Mark Ewens: It's been in the works for some time. 97 helped make it a front burner issue and was all but promised in the post 97 event. But monies are becoming tighter and technology is changing at a rapid pace. We want to do the best we can with what we have. And I think the RFC has done an outstanding job with the tools and technologies they have at their disposal.

Question:

Amy Sebring: Do you know if your office is planning any workshops in the region to explain the use of the new AHPS system when it is fully implemented?

Mark Ewens: There will be a tremendous amount of media workshop type attention give to this when it does come about especially as it will be a "new technology" that promises to do for river forecasting and outlooking what the Doppler radars and satellites have done for operational meteorology.

Question:

Amy Sebring: In hurricane track forecasting, we use a program that plots the forecast against a background of average forecast error, and after Hurricane Brett last year, I think we should also include a background of maximum forecast error as well. I noticed from the report you cited earlier that this average absolute forecast error has already been calculated for the Red. Do you think it would help users of the information to see a forecast or outlook in that context?

Mark Ewens: This is to some extent the "good" part of probabilistic forecasting. It shows many "what if" scenarios that, theoretically, make decisions better.

Question:

Amy Sebring: Mark, the AHPS system uses maps where do you or will you get the maps for the Red?

Mark Ewens: I'm not sure. I think they are based on the GIS data perhaps someone from the RFC can pipe in here. There is a lot of detailed data available to users and forecasters.

Amy Sebring: Mike, or perhaps Wendy, do you know?

Wendy Pearson: The mapping capabilities for AHPS inundation maps are still in the planning phases even for the sites on the Red and the other locations that are scheduled to get AHPS type services in the next few years.

If there are agencies that have GIS data for the Red please contact the Office of Hydrology in NWS Headquarters in Washington to coordinate the best data usage possible. Thanks.

Amy Sebring: Thanks Wendy. I hope this is something that some of our members can help you with perhaps.

Comment:

Gus Wruck: While we are talking about flooding at this point, here in Manitoba at the provincial Emergency Management meeting this AM we were concerned about fires, the earliest ever.

Question:

Amy Sebring: Gus I am glad you mentioned that; are we possibly looking at drought conditions this year Mark?

Mark Ewens: Boy, am I glad you asked that one! We are technically in a meteorological drought, at least the early stages in much of but not all of the Red River basin. We are still very, very much saturated in the upper 6 feet, so we are NOT in a hydrologic drought. River base flows are still near or exceeding daily record flows for many sites. Lots of good information is available on the current met conditions and river conditions from our home page.

Comment:

Wendy Pearson: This is also another great feature of future AHPS that will be able to assist water managers with low flow conditions as well as in high flow.

Question:

Amy Sebring: We have seen a national drought outlook this year for the first time I believe. As warranted, will these outlooks also be used at the regional level?

Mark Ewens: The one main index, the Palmer index is calculated regionally and on a county group level.

Comment:

Linwood DeLong: I had a lot of trouble with my computer and so I missed part of the presentation. I hope that you can post your homepage URL somewhere.

Mark Ewens: http://www.crh.noaa.gov/fgf/index.html

Amy Sebring: Some of the links mentioned today are on the background page also, Linwood. I will add the Des Moines link after, since I don't think I included it.

[Closing]

Amy Sebring: Thank you very much, Mark, for a fine job, and thank you to all our participants today. A transcript will be posted later, and we will notify you via mailing list when it is available.

Please keep us posted on further developments Mark so we can help get the word out.

Mark Ewens: Will do!

Amy Sebring: Before we officially adjourn, are there any announcements from anyone? Any events going on we should know about? I understand there will be a conference in Winnipeg on water resources and climate change in May and when the announcement is out, we will pass it on.

Amy Sebring: We are adjourned.

Mark Ewens: Thank you all for your attention.