Nowcasting: Very Short-Term Forecasting with Radar

What is nowcasting and why is it key for agriculture?

Nowcasting is a weather forecasting technique that focuses on the very short term, typically 0 to 6 hours. Unlike traditional forecasts that look days ahead, nowcasting uses real-time observations, especially from weather radars, to anticipate with high precision what will happen in the next minutes or hours. For farmers and fruit growers in Argentina, Chile, and Uruguay, this tool has become indispensable for protecting crops, planning tasks, and making critical decisions.

Weather radar: the heart of nowcasting

Weather radar emits pulses of energy that bounce off water droplets or ice particles in the atmosphere. By measuring the time it takes for them to return and the signal intensity, meteorologists can determine the location, intensity, and movement of precipitation. In South America, the radar network has grown significantly. For example, in Argentina, the National Weather Radar System (SINARAME) has more than 20 radars distributed throughout the country, while Chile has a network operated by the Chilean Meteorological Directorate (DMC) and Uruguay has radars in Treinta y Tres and Colonia.

How does radar nowcasting work?

The process combines several steps:

• Detection: The radar identifies areas of precipitation and their intensity.
• Tracking: Using algorithms, the movement of rain or storm cells is tracked.
• Extrapolation: The future direction of these cells in the next minutes or hours is projected.
• Now: Hyperlocal alerts and forecasts are issued for specific areas.

Thanks to high temporal resolution (updates every 5-10 minutes), nowcasting can anticipate the arrival of a storm at a farm with a very low margin of error.

Practical applications in South American agriculture

Radar nowcasting has a direct impact on agricultural activities:

1. Protection of sensitive crops

In regions such as the Uco Valley (Mendoza, Argentina), Chile's Central Valley, or the citrus zone of Salto (Uruguay), frost and hail are constant threats. Nowcasting allows for activating anti-frost irrigation systems, anti-hail nets, or generating early alerts for producers.

2. Planning of agricultural tasks

Knowing whether it will rain in the coming hours helps decide if it's time to spray, harvest, or sow. For example, in Argentina's Humid Pampas, soybean and corn producers use nowcasting to avoid applying herbicides before imminent rain, which would reduce their effectiveness.

3. Water resource management

In arid zones such as Coquimbo (Chile) or San Juan (Argentina), anticipating precipitation allows for optimizing irrigation and reservoir recharge. Nowcasting models feed early warning systems for flash floods.

Advantages of nowcasting over other forecasts

• Greater local precision: While a traditional forecast gives a probability for a broad region, nowcasting can tell if it will rain at a specific farm.
• Constant updating: It refreshes every few minutes, capturing rapid changes in weather.
• Early alerts: It allows issuing warnings hours in advance for severe events such as storms, hail, or strong winds.
• Ideal complement: It combines with numerical models to extend prediction beyond 6 hours.

Limitations and challenges in the region

Despite its benefits, nowcasting faces challenges in South America:

• Limited coverage: Although the radar network has grown, there are still rural areas without complete coverage, especially in mountainous or remote areas.
• Lack of maintenance: Some radars have technical failures or require periodic calibration.
• Need for training: Producers must learn to interpret radar maps and alerts to make informed decisions.

Institutions such as the National Meteorological Service (SMN) of Argentina, the Chilean Meteorological Directorate (DMC), and the Uruguayan Institute of Meteorology (INUMET) work constantly to improve the infrastructure and dissemination of this data.

Tips for making the most of nowcasting on your farm

• Consult official sources: Use the websites of SMN, DMC, or INUMET, which publish updated radar images.
• Use specialized applications: Platforms like Contingencias offer hyperlocal alerts based on nowcasting for your exact location.
• Integrate with your agricultural calendar: Check nowcasting before scheduling fumigations, irrigations, or harvests.
• Get trained: Participate in workshops or talks on interpreting radar and short-term forecasts.

The future of nowcasting in South America

With the improvement of the radar network and the incorporation of artificial intelligence, nowcasting will become increasingly accurate. Systems that combine radar, satellites, and weather stations to issue automatic alerts to producers' cell phones are already being developed. In a context of climate change, where extreme events are more frequent, having this technology is an invaluable tool for the resilience of the agricultural sector.

In summary, radar nowcasting is not a luxury, but a necessity for farmers in Argentina, Chile, and Uruguay seeking to protect their crops and optimize their resources. Stay informed and take advantage of these tools to make smarter decisions.