Crawfish Tales

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

All future issues of the LMRFC’s Crawfish Tales will only be posted to our web site.
Please send Dave Reed an email at with the subject “Newsletter
Reminder” to receive a reminder email when our latest issue becomes available online.

David Reed, Hydrologist In Charge Vol. 8 No. 3, Spring 2005 Ethan A. Jolly, Editor

Features Geographic Information Systems at the LMRFC 2005 Hurricane Season

From the HIC

The Spring Flood Season is over and we are about to enter the hurricane season. With hurricane season comes the threat of inland flooding from tropical systems. We have provided a review of this danger in this newsletter.

LMRFC continues to take advantage of emerging technologies to provide products and services. This issue highlights the work LMRFC is doing in the area of Geographic Information Systems (GIS). GIS is used to create almost all the images on our web site and provides a widely used format to share data with other users of GIS.

To help reduce costs and labor in preparing the newsletter, this will be the final newsletter mailed out to our partners. For the upcoming Summer 2005 issue, we will post the newsletter online and send an email to those interested to alert you of the newsletter availability.

We always like to hear form our customers about their needs. Please do not hesitate to call us and let us know how we are doing or if there are other services you will need.

- Dave Reed

Forecasting The mighty Mississippi River

The Lower Mississippi River Forecast Center (LMRFC) relies heavily on Geographic Information Systems (GIS) to complement our mission of saving lives and reducing property damages. The LMRFC utilizes the many capabilities of a GIS platform along with associated applications to automate graphic production, derive initial soil parameters for model calibration, generate status maps, provide flood information, create graphics for use in presentations and posters, etc. The multi-functionality of GIS provides the capability of generating easy to read graphics that convey a wealth of geospatial information for many of LMRFC’s services and products.

Figure 1: Example of a Precipitation Graphic Generated Using GIS
Central Tennessee and Northern Alabama
Click for larger image

Operational Use of GIS
The objective at the LMRFC is to make the process of generating GIS graphics as proficient as possible by automating the processes of graphic production. Scripts run daily at specified times and ingest required data, such as precipitation, and create various overlays on LMRFC base maps (Figure 1). Using this approach, we are able to automatically generate over 5000 graphics daily using GIS. These automated processes allow the hydrometeorologists to strengthen their focus on precipitation analyses, quality control of river and rainfall data, and on river and flood forecasting.

Some specific GIS products available from the LMRFC include river status maps showing flooding conditions, precipitation totals (both past and future), flash flood guidance, significant flood outlooks, and more. The web link to the LMRFC river status map is


For all river forecast locations, flood status symbols are color coded to show if a river location is below or above flood stage. The status map is updated twice each hour. Over 4500 precipitation products are generated daily and include forecasted precipitation out to 72 hours in the future, all past precipitation in hourly, daily, month-to-date, and year-to-date increments, as well as, percent of normal precipitation. The flash flood guidance graphic depicts the amount of rainfall required over a particular area, within a specified time, to produce flash flooding. The Significant Flood Outlook graphic displays a generalized area of significant flooding that either has significant flooding already in progress or is forecasted to occur within the next five days. All of these graphics are generated daily and posted to the LMRFC website.

GIS is also used at the LMRFC to derive initial sets of soil moisture parameters for the purpose of basin calibration and hydrologic model improvements. In addition, GIS is capable of generating and displaying many useful basin calibration datasets; including, soil types, long term precipitation averages, evaporation, forest type and cover, and many others.

Another use of GIS at the LMRFC is general map production for papers, posters, and presentations (Figure 2). These maps can graphically display locations of river and rain gages, the LMRFC area of responsibility, areal and point precipitation, and other information for use by emergency managers, academia, Weather Forecast Offices, external agencies, etc. GIS graphics assist many of our users with easier visualization and interpretation of important data and messages.

Figure 2: Example of a Map Used in a PowerPoint Demonstration
Central Tennessee and Northern Alabama
Click for larger image

GIS at the LMRFC has evolved into an integral part of our everyday operations. It is a necessary tool for easily conveying large amounts of geospatial data to the user as either a web graphic or for the purpose of instructional presentation. GIS at the National Weather Service, Lower Mississippi River Forecast Center has become an invaluable tool in meeting our mission of reducing the loss of life and property.

- Kai Roth

Spring Flood Outlook

The 2005 Atlantic Hurricane season is fast approaching. The season begins June 1st and runs through November 30. In 2004, an unusually high number of hurricanes and tropical storms affected the United States, underscoring the need for hurricane hazard awareness and preparation. The primary weather hazards associated with tropical cyclones are high winds, storm surge, tornadoes, and inland flooding. Of these dangers, more people have lost their lives over the last 30 years due to inland flooding than from any other hazard associated with landfalling tropical cyclones. Over the past three decades, inland flooding has accounted for 59% of the U.S. tropical cyclone deaths. Of these deaths, 42% are car-related, due to drowning or unsuccessful attempts to abandon vehicles. Additionally, 78% of children killed by tropical cyclones drowned in inland floods.

Inland flooding, also known as freshwater flooding, is especially dangerous as it can occur several hundred miles inland from here the storm made landfall and often occurs after a storm has moved inland and weakened. All tropical cyclones are capable of

producing widespread heavy rains that can result in dangerous inland flooding, including flash, urban, and river floods. Slow moving tropical cyclones that drift slowly or stall often produce the heaviest rains and some of the worst inland flooding has been from weaker tropical storms rather than intense hurricanes. Additional factors that may promote inland flooding during tropical cyclones are orographic effects, antecedent soil moisture, and increased urbanization.

During a tropical storm or hurricane be aware of the danger of inland flooding. If inland flooding is eminent, monitor NOAA Weather Radio, television, or emergency broadcast stations for information. When advised to evacuate, do so immediately. Move to a safe area where access will not be cut off by rising water. Never drive through flooded roadways.

- Connie Clarstrom

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