Betting on Rain? The Accuracy and Reliability of Precipitation Forecasts

For you sports junkies out there, if I could prove to you that I can correctly predict winners and losers with 80% accuracy, would you use my advice in Las Vegas? I don’t gamble, but according to this article on sports forecasting that summarized the results of professional research, the best methods provided only 54% accuracy. Yet, even with what one might think is an accuracy not much better than a coin flip, hypothetical bets using this model would have provided 16% returns.

Now, what if I told you that professional weather forecasts can correctly predict whether rain will fall on your specific field within the next three days 80% of the time and with almost 70% accuracy out to nine days? Considering how many risks we take on things that are less predictable than the weather, whether it be the stock market, horses, or sports, I posit that there is untapped potential in the proper use of weather forecasts to increase efficiency or productivity, and ultimately improve margins. In the case of useful rainfall predictions, there is potential to reduce risk of over-watering or mistiming a rain-sensitive product application or a host of other operations that can affect yield or operational efficiency.

Like my last article where I used independent forecast accuracy assessment from ForecastWatch to demonstrate that location-specific temperature forecasts are skillful out to around 10 days into the future, this month we use their service to demonstrate the accuracy of rainfall predictions. The data discussed here is based on an average of many different weather service providers’ daily nine-day forecasts collected each day for about 750 U.S. locations during January through November of 2017. These are not “area” forecasts where a successful forecast only means rain fell in a larger area. Rather, these are point-to-point comparisons.

For the forecasts to be considered skillful, they have to be better than forecasts created using the “persistence” technique. A persistence forecast is one that assumes the conditions occurring at the time of the forecast will continue through the forecast period. So, if it is raining at the time of the forecast, a nine-day forecast would assume that each of the subsequent nine days would have rain. Such a forecast requires no special knowledge or skill to create.

The graph below shows the average percentage of correct precipitation forecasts for all of the weather services as a function of lead time in days compared to the persistence forecasts. Indeed, the forecast services are around 80% accurate for the first three days and tail off to just under 70% by day nine, and for all days, the forecasts are better than persistence. You might be surprised, though, that the persistence forecasts are 60-70% accurate as well. This is because precipitation events are relatively infrequent when you consider the entire U.S. over nearly a full year, occurring only about 30% of the total time. These overall accuracy numbers include all of the cases where no rain was forecast nor occurred. If you simply forecast dry conditions every day for all the locations, you would still be correct almost 70% of the time.

US-Daily-Percent-Correct-Precipitation-Forecasts

Thus, the value of precipitation forecasts are in those situations where rain is possible. We can use different metrics that focus more on the more difficult, non-dry events that cannot rely on random guessing and still do well. In the following graph, the solid lines show such a metric called the Equitable Threat Score (ETS) for the average of the providers (solid blue) versus persistence (solid red). Perfect forecasts have a value of 1.0, and 0.0 means no skill. Professional service providers on average provide much more skillful forecasts than persistence. In other words, you would do much better betting on one of these forecasts rather than basing future actions only on how much rain has fallen.

US-Daily-Precipitation-Forecast-Skill

For example, rather than irrigating only because you are approaching an inferred deficit of available water content computed from current and past evapotranspiration estimates, rain, and irrigation activities, you can choose to hold off based on a forecast of rain in the next few days, and more often than not this will be the correct decision. This would be important for crops that are sensitive to over-watering, such as soybeans in their vegetative stage where too much moisture can lead to disease as well as yield reductions.

Now, there is one more dashed line on the skill graph that depicts a metric called the Brier Skill Score (BSS). Like ETS, a perfect BSS is 1.0. However, BSS is a measure of how reliable the probability forecasts are. For perfectly reliable (BSS = 1.0) probability forecasts, the number of rainfall occurrences for a large set of forecasts having the same probability are equal. In other words, rain actually fell for 20% of all the forecasts having a 20% chance of rain. Likewise, rain occurs 80% of time for all forecasts of an 80% chance of rain.

Having reliable probabilities means decision support tools can use objective cost-loss modeling to achieve an appropriate level of risk applicable to the potential savings or gains. We are now reaching a point where some providers are able to provide objective, reliable, and calibrated probability forecasts that will enable cost-loss optimization in automated decision support tools. Because of the discrete nature of rainfall, especially in showery situations, there will be times the forecast misses, just like a sports bookie. But a disciplined approach based on objective probabilistic rainfall forecasts will yield more wins than losses, and the agtech community needs to increase reliance on near-term weather forecasts that are professionally generated and designed for agronomic decision making.

Topics:

Leave a Reply

Data Management Stories
Data ManagementDigital Farming: Keep It Simple Analytics
May 15, 2018
In previous articles, I tried to lay out some logical components and processes that enable digital farming to get inside Read More
NOAA-Snow-Depth-Analysis-April-15
Data ManagementRebounding Spring for 2018 Planting: Cold April Weather Finally Gives Way to Promising May Forecast
May 14, 2018
This month, I am taking a break from discussing weather technology or opining on how to better apply weather and Read More
Steve-Pitstick
Data ManagementHow Industrial AI Can Maximize the Potential of Agriculture’s Planting Season
May 10, 2018
I go to great lengths to speak with growers and meet with them in the field. For those of us Read More
Big Data
AmericasUSDA, AgGateway Join Forces on Data Standards
May 1, 2018
AgGateway and USDA have forged an agreement to work together on data projects to benefit American farmers in the transition Read More
Trending Articles
Ernie-Chappell-Screenshot
EventsEFC Systems Sponsorship Demonstrates Commitment to Continuing Education for Retail Dealerships
May 16, 2018
Enterprise software manufacturer EFC Systems, scholarship sponsor of the inaugural PrecisionAg® Professional Accelerator professional development conference this June in Brookings, Read More
Dr Brian Arnall Oklahoma State Paul Schrimpf
Excellence AwardsPrecisionAg Awards Of Excellence Nominations Accepted Through May 18
May 14, 2018
Nominate an outstanding individual for one of four PrecisionAg Awards of Excellence. Recipients will be honored at a special ceremony during the 2018 InfoAg Conference in July. Read More
EventsMeister Media Debuts Growing Innovations
May 10, 2018
As a service provider, you and your grower customers probably can agree on this much: While innovation abounds in agriculture, Read More
UCANR_booth_Food_IT_forum
EventsForum Calling All Innovators of Agriculture Technology
May 2, 2018
The challenges that come with feeding the world continue to grow. Luckily, so do advances in information technology that are Read More
Farm-Storm-Clouds-Photo-Eden-Hills
Data ManagementThe Precipitation Problem in Agriculture
April 17, 2018
Precipitation is arguably the most important agricultural weather parameter, yet it is the most difficult variable to precisely measure. For Read More
SDSU-drone
Business ManagementInside the Key Strategies For Selling Precision Ag Services
April 13, 2018
In its earliest manifestation, the motive for developing precision agriculture service was entirely pure. Agronomists knew that crops were responding Read More
Latest News
Imagery/SensingBREAKING: Mavrx Swallowed Up by Israeli Imagery Provide…
May 17, 2018
Taranis, an Israel-based provider of high-resolution agriculture aerial imagery and deep learning, today announced the acquisition of all Mavrx assets, one Read More
PrecisionAg Professional Accelerator
EventsWhat’s Stopping You From Maximizing Your Precision Prog…
May 16, 2018
Day 2 of the PrecisionAg® Professional Accelerator will challenge you to evaluate and improve your approach to customer value and Read More
Raven-screenshot
EventsRaven Focused on Retail Education with Top Gun Training…
May 16, 2018
It’s no secret that the demand for precision ag technology is growing. As the world population increases, so does the Read More
Ernie-Chappell-Screenshot
EventsEFC Systems Sponsorship Demonstrates Commitment to Cont…
May 16, 2018
Enterprise software manufacturer EFC Systems, scholarship sponsor of the inaugural PrecisionAg® Professional Accelerator professional development conference this June in Brookings, Read More
Industry NewsPinnacle Joins Crowded E-Commerce Segment With My Pinna…
May 16, 2018
Pinnacle announced today the launch of its new website along with a new interactive grower-customer portal, My Pinnacle. The No.6-ranked Read More
Veris Soil EC
Sensors/IoTUsing Electrical Conductivity (EC) Sensors in Precision…
May 16, 2018
The measurement of soil EC is widely used in agriculture. However, there is still confusion around the meaning of the Read More
Corn Field Sunset
Industry NewsRaven Announces DOT Joint Development Agreement
May 16, 2018
Raven Industries announced today it will be utilizing its precision agriculture technologies to power the autonomous farming solutions of the Read More
Field-Equipment
Sensors/IoTTop 6 Digital Transformation Trends in Agriculture
May 15, 2018
In recent years, technology in agriculture, also known as AgTech has rapidly changed the industry, writes Daniel Newman on Forbes.com. Read More
Data ManagementDigital Farming: Keep It Simple Analytics
May 15, 2018
In previous articles, I tried to lay out some logical components and processes that enable digital farming to get inside Read More
NOAA-Snow-Depth-Analysis-April-15
Data ManagementRebounding Spring for 2018 Planting: Cold April Weather…
May 14, 2018
This month, I am taking a break from discussing weather technology or opining on how to better apply weather and Read More
Dr Brian Arnall Oklahoma State Paul Schrimpf
Excellence AwardsPrecisionAg Awards Of Excellence Nominations Accepted T…
May 14, 2018
Nominate an outstanding individual for one of four PrecisionAg Awards of Excellence. Recipients will be honored at a special ceremony during the 2018 InfoAg Conference in July. Read More
Ag Retailer and Growers with tablet WinField United
Industry NewsCommoditAg Announces Enhanced E-Commerce Platform
May 11, 2018
CommoditAg launches CommoditAg LIVE, described as “an enhanced ecommerce platform providing more benefits to growers, and a superior customer experience”. According Read More
Industry NewsTrimble Adds Crop Health Imagery, Work Orders Features …
May 10, 2018
Trimble announced today that it has added Crop Health Imagery and Work Orders features to its Trimble Ag Software. The Read More
Parkland College Student Training
AmericasBushel Garners $7 Million Private Investment Round
May 10, 2018
Bushel today announced a $7 million private investment round to accelerate its patent-pending digital platform for the grain industry. The Read More
Steve-Pitstick
Data ManagementHow Industrial AI Can Maximize the Potential of Agricul…
May 10, 2018
I go to great lengths to speak with growers and meet with them in the field. For those of us Read More
EventsMeister Media Debuts Growing Innovations
May 10, 2018
As a service provider, you and your grower customers probably can agree on this much: While innovation abounds in agriculture, Read More
Farmers Edge Truck
AmericasFarmers Edge, Raven Announce Collaboration Agreement
May 9, 2018
Raven Industries and Farmers Edge announced today a marketing and collaboration agreement. The two companies are working together to develop Read More
Canton-Fair
AsiaChina’s Canton Fair Sheds Light on Agricultural T…
May 7, 2018
Last month I visited China to learn more about agriculture by attending the largest import and export fairs — the Read More