|David Reed, Hydrologist In Charge||Vol. 8 No. 2, Winter 2005||Ethan A. Jolly, Editor|
|Forecasting The Mighty Mississippi River||Spring Flood Outlook||DOC's Bronze Medal|
|From the HIC|
As we start the new year, I want to take a look back at some of the major accomplishments the LMRFC has made in 2004. We rose to the challenge with critical forecasts of major and record flooding during several periods this year. Spring flooding occurred over the LMRFC area and this was followed by a very active tropical season. The LMRFC area was largely spared the worst of the flooding from the tropical events but we still had some records broken in the French Broad River Basin due to heavy rainfall from Hurricane Francis. In addition to meeting operational requirements,the LMRFC implemented AHPS services at 27 locations in the Tennessee Valley and we were able to recalibrate our forecast model at over 20 locations to support this effort. Two LMRFC staff members received special recognition this year. Development and Operations
Hydrologist Bob Stucky received the prestigious Max Kohler Award for outstanding service to the people of the Lower Mississippi Valley. Senior Hydrologist Eric Jones was part of a group that received a NOAA Bronze Medal for implementing a backup computer system for RFCs. Congratulations to those two and congratulations to the entire LMRFC staff for their efforts and successes in 2004.
We expect a busy and successful year in 2005. We always like to hear from our customers about their needs. Please do not hesitate to call or email us and let us know how we are doing or if there are other services you need.
|Forecasting The mighty Mississippi River|
The Mississippi River is the longest and largest, in average annual water volume, of any river in North America, flowing 2,340 river miles from its source at Lake Itasca in the Minnesota North Woods to the Gulf of Mexico. The Mississippi Basin measures 1.84 million square miles, covering approximately 40% of the continental United States and covers about one-eighth of the North America Continent. Of the world’s largest rivers, the Mississippi ranks third in length, second in watershed area, and fifth in average annual discharge.
The Lower Mississippi River Forecast Center (LMRFC) is responsible for preparing and issuing river forecasts for 21 locations along the mainstems of the Ohio and Mississippi Rivers. Mainstem forecast products issued include daily 5-day forecasts, weekly 28-day forecasts, and seasonal spring flood outlooks. Preparation and issuance of these forecasts requires extensive coordination with upstream River Forecast Centers (RFC), the United States Army Corps of Engineers (USACE), the Tennessee Valley Authority (TVA), and six National Weather Service (NWS) Weather Forecast Offices (WFO).
Daily, 5-day stage forecasts are issued for 18 stations from Smithland Dam tailwater on the Ohio River to Cairo, IL, and on the Mississippi River from Cape Girardeau, MO, to New Orleans, LA. These forecasts are normally disseminated by 9:30AM in the NEWRVAORN product. Forecasts for three additional flood-only sites are included when stages are expected to reach flood stage or higher.
Each Wednesday, an extended 28-day forecast is issued for the Ohio River at Cairo and 15 locations on the Mississippi River in the NEWESPORN product. Seasonal Spring Flood Outlooks issued in the NEWESGORN product, are used to qualitatively discuss the potential for river flooding within the Mississippi Valley.
For simplicity, DWOPER is modeled as four mainstem Ohio/Mississippi segments: the Upper segment begins as described in the above section and ends at Memphis, TN; the Middle segment runs from Memphis to Vicksburg, MS; and the Lower from Vicksburg to the Gulf of Mexico. A stand-alone fourth segment runs from Red River Landing, LA, to West Pointe a la Hache, LA, and is used for forecasting hurricane surges as they propagate upstream along the lower reaches of the Mississippi (see Fig.1).
The upstream DWOPER boundary conditions are the observed and forecasted streamflows at Smithland Lock and Dam, Chester, and at Kentucky and Barkley Dams Provided by the Ohio RFC (OHRFC) and North Central RFC (NCRFC) respectively. Observed discharges and projected releases for Barkley and Kentucky Dams are provided by the Tennessee Valley Authority (TVA).
Along the Middle and Lower Mississippi, other significant inflows/outflows include: 1) flows from the Arkansas-Red Basin RFC(ABRFC) for Pine Bluff, AR, on the Arkansas River, 2) Arkansas River discharges at Lock and Dam 2, AR, operated by the USACE Little Rock District (SWL), and 3) the Old River Outflow Control Structure near Simmesport, LA, operated by the USACE, New Orleans District (MVN). Throughout the Ohio/Mississippi complex, runoff from contributing mainstem local area basins and routed flows from smaller tributaries are computed using the NWS Sacramento Soil Moisture Accounting Model (SAC-SMA). The SAC-SMA computed flows are input as additional runoff and lateral inflows to the DWOPER system.
DWOPER output serves as a basis for forecasts on the Mississippi River. Empirical stage-to-stage relationships also provide valuable guidance to forecasted stages. Hydrologists forecasting the Mississippi River must utilize the strengths of DWOPER and the empirical manual techniques to prepare the best forecasts possible.
However, forecasting the Mississippi River during observed or predicted flooding conditions requires a significant increase in the amount of inter/intra-agency coordination. When the Ohio River at Cairo rises above its 40 foot flood stage, the USACE LRD takes over regulation of Barkley and Kentucky Dams requiring close coordination with LRD and TVA. The LMRFC mainstem forecaster must also increase coordination with OHRFC and NCRFC forecasters on upstream handoff forecasts. In addition to LRD, close coordination with the USACE District Offices at Memphis, Vicksburg, and New Orleans is necessary for effective coordination of crest forecasts.
Prior to release of official Ohio/Mississippi River forecasts, the mainstem forecaster must again coordinate with the LRD and reach a consensus on the 5-day forecast and projected crest at Cairo. If any changes to handoff flows or dam releases are received, a new DWOPER run is made and the coordination process with LRD is repeated. All upstream RFC boundary data is passed to LRD for use in their dynamic model. Following consensus, the official Ohio/Mississippi River forecast is released to the public.
During major flood events when the stage crest at Cairo is expected to reach or exceed 50 feet, the USACE begins detailed flood fight planning and invokes daily conference calls between the USACE Mississippi Valley Division, OHRFC, NCRFC, the Hydrometeorological Prediction Center in Camp Springs, MD, and the LMRFC. Other agencies requiring close coordination of changing river conditions are the Lower Ohio and Mississippi River Committee, a conglomerate of barge and towing companies; and, the US Coast Guard, the regulatory authority over all Mississippi River traffic.
The primary focus for close coordination of mainstem river and flood forecasting is to produce the best possible forecast for the benefit of the general public. Because mainstem forecasting has a direct impact on our Nation’s economy, close inter/intra-agency coordination is essential for producing the best possible set of NWS river and flood forecasts along the mainstems of the Ohio and Mississippi.
|Spring Flood Outlook||Department of Commerce's Bronze Medal|
Several times during the winter and spring, Spring Flood Outlooks are issued. LMRFC has already issued some for 2005. Below are the remaining dates for LMRFC to issue Spring Flood Outlooks.
LMRFC Outlook Release Dates:
Senior Hydrologist Eric Jones was part of a team that received the Department of Commerce’s Bronze Medal for implementing an off-site backup computer system for RFCs. The Arkansas-Red Basins RFC in Tulsa served as the team leader for this development effort. Representatives from each RFC in Southern Region then performed testing and implemented it at each RFC. The system consists of a personal computer connected to the Internet through a high speed connection. Day-to-day model information is stored on a secure server which can be accessed through this computer over any high-speed Internet connection. Once model runs are made and forecasts prepared, the same Internet line can be used to transmit the products over the NWS communications circuits and finally to our customers and partners. Congratulations to Eric and the entire team for their efforts and a much deserved award.