With the frequency of this topic of how forecasted weather works, is discussed, further leads to the argument that this function should only be an option such as Smart Cycling. Utilizing forecasted weather is quit difficult, watering based off of forecasted weather can be a risk proposition in certain parts of the country where rainfall can be quite different from 1 location to another within a very small area. Once a watering event is missed or stopped you can't get it back. I'd rather make the savings up on the back end using only real time collected data to make decisions on scheduling. If i'm not mistaken this is the method used during S.W.A.T. accreditation.
I realize that using forecasted weather may work in some parts of the country but in my neck of the woods a 60% chance of precipitation only means about a 5% chance of that precipitation falling at my location. Unless you are using 2 Square Kilometer weather modeling i'll let my rain sensor interrupt a scheduled event if the precipitation actually occurs.
I can think of dozens of other questions for you to answer on how weather forecasting works, but in the end, I believe getting back to the basics of why the system works is most important.
Turf and Landscape Irrigation System Smart Controllers –
"This evaluation will be accomplished by creating a virtual landscape subjected to a
representative climate and to evaluate the ability of individual controllers to adequately and
efficiently irrigate that landscape. The individual zones within the landscape will represent a
range of exposure, soil types and agronomic conditions. As a standard from which to judge the
controller’s performance, a detailed moisture balance calculation will be made for each zone.
The total accumulated deficit over time will be a measure of the adequacy. The accumulated
surplus of applied water over time will be a measure of system efficiency. Water applied
beyond the soil’s ability to absorb it will be characterized as runoff, further degrading the
application efficiency. The study will use ASCE-EWRI data from a representative accredited
weather station. Further the study is not meant to include individualized water management
strategies aimed at producing special physiological affects. If the controller maintains root zone
moistures at the levels specified, the protocol assumes that the crop growth and quality will be
adequate. The moisture balance calculation will assume that the plant materials are functioning
as mature plants. "Source 8th Draft Testing Protocol Rev. 3 – September 2008 © 2008 Irrigation Association
I do not see anything here about watering based off of Weather forcast, only real time data.