Mississippi Delta MSEA Volume 2, Issue 2, Page 3

MISSISSIPPI DELTA

REPORTER

WEATHER FORECASTING AND THE TIMING OF AGRICHEMICAL APPLICATIONS

A key input and contribution to the Mississippi Delta MSEA project from the Soil and Water Research Unit in Baton Rouge, LA deals with the evaluation of using the National Weather Service (NWS) Daily and 7-Day Forecasts in scheduling agrichemical applications to farmland in the Deep Hollow Lake watershed. Agrichemical applications for the Beasley Lake watershed, and perhaps for the Thighman Lake watershed, will follow normal practices, while for the Deep Hollow Lake watershed agrichemical application timing will be adjusted based upon the probability of rainfall in the Daily and 7-Day Forecasts issued by the NWS for the watershed area in the state of MS. The 7-Day Forecast includes the probabilities of rainfall in the 12-hr. a.m. and p.m. periods, and over the 24-hr period of each day (plus other forecast data such as Min/Max Temperatures, Cloud Cover, Wind Speed, etc.) and a climatological 30-yr. mean probability of rain (called "CLIMO") centered on Day 4 of the 7-Day period. See the example 7-Day forecast for the Jackson, MS area (below), which was obtained via Internet on 24 June 1996 from the Southern Regional Climate Center (SRCC) computer system Home Page on the World-Wide-Web (http://www.srcc.lsu.edu/). A Text Only version of the forecast information can be obtained via computer and modem from the SRCC computer system.

To evaluate any reduction in the risk or potential of agrichemical losses in runoff during rainfall events that occur soon after application, scheduled applications in the Deep Hollow Lake watershed may be advanced or delayed from the normal or desired timing (i.e., the applications in the Beasley Lake watershed) based upon rainfall forecasts. Measured agrichemical losses will be compared for the Beasley Lake and Deep Hollow Lake watersheds. As an example use of the weather forecasts to schedule agrichemical applications on the Deep Hollow Lake watershed: if the 7-Day Forecast indicates a high probability of rain within 24 hr before or after the scheduled application, the date to apply agrichemicals could either be advanced or delayed depending upon the chemicals involved, soil moisture conditions, and stage of crop growth. In general, it is preferable to apply the agrichemicals after a rainfall vent, if and when the forecast shows a decreasing chance of rain with each passing day. Since the 7-Day Forecast is available from the NWS each day (about 6:00 a.m.), the application advisory can be modified as the proposed date nears. The Soil and Water Research Unit at Baton Rouge, in cooperation with the SRCC at LSU, is providing (via fax) the Daily and the 7-Day Forecasts to the on-site scientist's and management staff for the Mississippi Delta MSEA project. The Daily and 7-Day Forecasts will be posted in the future to a new World-Wide-Web (WWW) Home Page being created for the Mississippi Delta MSEA project by the Baton Rouge Unit. The forecast information will be faxed to those managers or farmers who do not access to Internet and the WWW, or do not have computer equipment to access the SRCC system via modem. The 7-Day Forecasts obtained daily will also be entered onto a Weekly Table for display (see the Example table shown below). This table will also be included on the Home Page and/or faxed to project personnel, as needed. The tabular display of the 7-Day Forecasts provides a means for all project personnel to quickly observe how consistent the forecast is for a given date up to a week ahead of time (e.g., the date for the next proposed agrichemical application). This type of information may also aid the project managers in adjusting the application date for the Deep Hollow Lake watershed.

The 7-Day Medium Range Forecast (MRF) is a computer model derived statistical forecast with local weather factor inputs on a daily basis, plus other statistical factors based on previous weather patterns for the area/region. The 7-Day Forecast product was Beta Tested for several years by the NWS in the major climate regions of the USA before it was released for public access and use in 1992. A detailed technical description of the forecast product is provided in the Technical Procedures Bulletin No. 411 from the NWS. The forecast data for the Jackson, MS area is available since early 1994 from computer achieves at the SRCC, and these data are being used to analyze and determine the threshold forecast rainfall probabilities for which significant rainfall events consistently occurred in the North West region of MS. These threshold probabilities will be used to aid project managers and farmers in scheduling agrichemical applications in the Deep Hollow Lake watershed in an attempt to avoid the occurrences of significant rainfall events soon after agrichemical applications. There are other NWS supplemental forecasts available that may have utility in the management and scheduling of agrichemical applications in the MSEA project watersheds, and these will be explored with cooperators from the SRCC at LSU. A tour for the project personnel, and perhaps the farmers from the Deep Hollow Lake watershed, to visit the SRCC staff and facilities at LSU is being planned during the 1996 season. A demonstration and training session will be conducted during this tour on computer Internet access to the Daily and 7-Day Forecasts for the Jackson, MS and/or other nearby locations in MS where the experimental watersheds are located.

Dr. J. L. Fouss, Agricultural Engineer
USDA-ARS-Soil & Water Management

P. O Box 25071
University Station
Baton Rouge, LA
70894-5071
Phone: 504-388-1082
Fax: 504-388-4883
Email: jfouss@gumbo.bae.lsu.edu