Crawfish Tales
A Quarterly Publication of the National Weather Service Lower Mississippi River Forecast Center
Slidell, Louisiana

David Reed, Hydrologist In Charge Vol. 4 No. 2, Winter 2001 Ethan A. Jolly, Editor

Features Web Site Additions & Redesign 24 Hour Operations Test Spring Flood Potential Outlook

From the HIC

2000 was a successful year. The staff at LMRFC made great strides in customer service by expanding or presence on the web and expanding the number of forecasts provided routinely. We are reviewing our data and web products and hope to continue to expand our internet presence. Much of this newsletter is devoted to enhancements made to our website over the past few months.


In 2001, we will continue this trend and provide detailed maps of rainfall over a small areas including major cities in the LMRFC forecast area. We will be working to compare rainfall against climatological normals and let you know more about how the current rainfall conditions compare to normal. We will also be looking into utilizing database technology to provide data in a more efficient and effective manner.



In conjunction with other Southern Region RFCS, we will be implementing a river flood watch program to alert you to potential flooding. For this product, we will use 24 hours of forecasted precipitation instead of the normal 12 hours and highlight areas that are expected to flood due to this rainfall. We will also be looking at rainfall forecasts as much as 72 hours in the future and prepare a flood potential to alert you to more long-range flooding possibilities.


While this is going on, we will continue to maintain a hydromet watch. Our number 1 priority will remain providing timely and accurate forecasts and quality service to our customers and partners. We look forward to continuing to serve you in 2001. Please do not hesitate to call with any questions or needs for additional services.

- Dave Reed

Web Site Additions & Redesign

The LMRFC's web site continues to expand and grow to keep up with our many user's requests. Over the past six months, we have added so many new features and products, that we had to completely redesign the site in order to accommodate these additions. Some of these new additions include forecast hydrographs, graphical extended streamflow prediction, and multi-day rainfall totals. More additions are planned for the near future, so we had to design a site that would be flexible enough to change and grow with needs of our users.


The newly redesigned web site conforms with the National Weather Service's standard which includes links to our parent agencies. The web site also has links to its major areas to the left of every page to make navigation as easy as possible. The major areas of the site are River Forecasts, Precipitation Data, Precipitation Forecasts, Graphical Hydrometeorological Discussion, About Our Office, Advanced Hydrologic Prediction Services, Newsletters, Education Station, and Links. The River Forecasts section has links to all of the points that we forecast, both daily and weekly, including the Mississippi River. The Precipitation Data section has images showing past and current precipitation, a week's archive of daily Stage III (radar & rain gage) and gage only images, 2, 3, 5, &, 7 day Stage III totals, and more. Precipitation Forecasts include 24 hours of future rainfall, flash flood guidance, and drought and hurricane information. The Graphical Hydrometeorological Discussion and Advanced Hydrologic Prediction Services sections are new and will be discussed further in this article. The remaining sections provide useful information to hydrologists, meteorologists, teachers, students, and anyone who is interested in expanding their knowledge of hydrology and river related subjects.


New Site Additions

About four months ago, the LMRFC introduced the Graphical Hydrometeorological Discussion (HMD) to our suite of web products. This product gives a "snapshot" of river and weather conditions for our area. The Graphical HMD will consist of four parts; twenty-four hour rainfall, current river conditions, future rainfall (QPF), and a flood potential map. The current river conditions and the flood potential map will be coming soon. The 24 hour rainfall shows the precipitation estimates from the WSR-88D and gage only data from 12Z to 12Z. Currently, links to the past week's data are available. The Graphical HMD also has a link to our text version of the HMD which we have been producing for several years. In the future, the Graphical HMD may replace the text HMD. The graphical HMD can be found at


Another feature that we have added to our forecast points are hydrographs. Hydrographs contain observed gage readings for the past 5 days, forecast stages for three to five days depending on the forecast point, flood stage, and flood of record. See Fig. 1 for an example of the new feature.


Figure 1: Hydrograph (Pearl River at Pearl River)
US Drought Monitor
Click for larger image

Over the past year, a large emphasis has been placed on providing graphical depictions of cumulative precipitation. In mid December, we enhanced our 6, 12, and 24 hour Stage III page, added a 2, 3, 5, &, 7 day cumulative Stage III page (Fig. 2), and added a 24 hour gage only page. These products are produced with ArcView for consistency and because of ArcView's greater flexibility. Thumbnails (small images) of all products are used as quick reference. Click on the thumbnail for the full sized image. This is one of the best products to determine rainfall amounts for a specific event.

Figure 2 : 2, 3, 5, & 7 Day Stage III
US Drought Monitor
Click to go to Stage III Cumulative Page

Lastly, we have added a 24 hour "gage only" product that shows an isohyetal analysis of precipitation according to ground based observations. This can be used either for comparison to Stage III or by itself. All of these products are kept on the site for one week and images are time/date stamped to make it easier for our users to archive. Point your browser to for these and other useful products.

The last major addition is the Ensemble Streamflow Prediction System (ESP) forecasts for Ross Barnett (South MS), Enid (North MS), and Timms Ford (Central TN) Dams. ESP, a component of the Advanced Hydrologic Prediction Services (AHPS), provides the capability of making long-range probabilistic forecasts of streamflow and streamflow related variables. The ESP assumes that past meteorological events are representative of events that may occur in the future. ESP forecasts are produced each Monday and can be found at . Figure 3 is an examples of an ESP forecast.

Figure 3 : ESP: Exceedance Probability
US Drought Monitor
Click for larger image

Future Endeavors

In the near term, we will continue to expand our Precipitation Data section by adding 2, 3, 5, & 7 day gage only data as well as 30, 60, 90 & 180 day precipitation totals for both Stage III and gage only. These values will be compared to precipitation normals. A "zoom" feature will be added to the precipitation maps so the user can examine the data images in more detail.


A map of current and future river conditions would show 24 hours changes in stage and indicate the points currently in flood. The user will zoom within their river system of choice for greater detail, then click on forecast point to get the forecast and hydrograph.


Many of the features and products that we have added have come from suggestions and comments from our users. The purpose of our web site is to get as much beneficial information to our users as possible in a quick and efficient manner. We will continue to aggressively develop and prepare graphical representations of our data to support customers' needs. If you have any suggestions for the LMRFC web site that would benefit you and other users, please email our webmaster at

- Ethan Jolly

24-hour Operations Test

On December 2, the 9-month long test of routine 24-hour operations at all four Southern Region RFCs concluded. During the test, each RFC and Weather Forecast Office in the country completed a log daily on hydrologic forecast activities. Our customers and partners have been surveyed to determine the benefits of routine around-the-clock

operations at the RFC. The evaluation team of NWS personnel and external users and cooperators will review the results and make a report and recommendation to upper level NWS management this Spring. Operations at RFCs across the country may be changed as a result of the findings of this team. Thanks to all cooperators and users that took time to participate in the survey.

Spring Flood Potential Outlook - NEWESGSIL

Each Winter/Spring flood season, the LMRFC prepares and issues a river guidance/outlook product describing the potential and relative magnitude for Spring flooding over our larger basins. This basin-by-basin potential considers any expected snowmelt, river ice conditions, existing soil moisture and streamflow conditions relative to long term averages, available reservoir flood control storages, and future precipitation falling at normal seasonal rates. Also, included in the discussion is any ongoing flooding, the current meterological scenario, and the NWS 30-day and 90-day precipitation and temperature outlooks over the LMRFC area.


Generally, this seasonal product is first issued during mid-February and updated on a biweekly basis through mid-April. Information on flooding potential for LMRFC area basins includes the lower Mississippi River and its tributaries, as well as, all Louisiana and Mississippi coastal


drainages. This flooding outlook is released to the LMRFC area Weather Forecast Offices (WFOs) on Thursdays for their information, then repackaged for dissemination on Fridays to the public. The WFO versions contain flood potential information for local basins within their Hydrologic Service Area. Links to the WFO websites can be found on the LMRFC website at:


The primary objective of this product is to provide flood potential outlooks to our servicing WFOs so they can alert the general public to the likelihood of Spring flooding over their local area basins. For calendar year 2001, the schedule for flood potential outlooks covering the entire LMRFC area is: February 16 , March 9, and April 13. A nationwide outlook is scheduled for March 13, 2001, and will be released during a press conference hosted by the National Weather Service Headquarters.

-Bob Stucky is the U.S. government's official web portal to all federal, state and local government web resources and services.