How does weather forecasting work?

Weather forecasts try to predict what the atmosphere will do in the future, based on the information available now. This is an ongoing challenge for meteorologists: the nature of weather processes is chaotic and not fully understood, and forecasts become less accurate as their time range increases. However, even when their accuracy is not perfect, weather forecasts are useful for construction companies and other businesses with outdoor operations. Knowing what weather to expect in the short term is useful for planning purposes.

Forecasts were originally based on past observation, but modern weather science makes ample use of technology. Large amounts of weather data are collected from multiple sources and processed by supercomputers. The data sources include weather stations, satellites, sea buoys, even airplanes and ships. All weather variables that can be measured are useful when forecasting - air temperature, wind speed, wind direction, relative humidity, atmospheric pressure, etc.

• For example, the wind is strongly influenced by atmospheric pressure differences.
• Wind moves from high-pressure to low-pressure regions, and a larger pressure difference results in stronger winds.
• Based on atmospheric pressure differences and other measured date, meteorologists can estimate the expected wind speed and its prevailing direction.

A sudden drop in atmospheric pressure is a clear warning sign that harsh weather is on the way. Project managers should prepare for windy and rainy conditions if they notice a pressure drop at a construction site. How fast the pressure decreases is also important: a slow drop means the weather will worsen slowly, while a fast drop means the weather with get harsh very quickly.

The calculations involved in modern weather science are impossible for a human within a realistic timeframe. For example, the supercomputers used by the US National Oceanic and Atmospheric Administration (NOAA) can perform 2.8 quadrillion calculations per second.

How accurate are weather forecasts?

There is a misconception that weather forecasts are inaccurate, but meteorology has improved a lot in recent decades. For example, 5-day forecasts from NOAA now have 90% accuracy.

• Time is one of the main factors that limits accuracy: as the timeframe for a weather forecast is increased, accuracy is lost. In the case of NOAA, if the forecast is increased from 5 to 10 days, the accuracy drops to 50%.
• Accuracy also depends on what aspect of the weather you are trying to predict. For example, hurricanes can be forecast several days in advance, but thunderstorms have only been predicted successfully a few hours before they occur.
• Construction companies can use weather forecasts to plan short-term operations. To compensate for the accuracy limitations of forecasts, they can use direct weather monitoring at project sites.

When dealing with hurricanes, predicting the landfall location is key to prevent damage. Modern weather science can calculate landfall locations within 220 miles, five days in advance. For a 24-hour forecast, the accuracy improves to 47 miles.

Applications of weather forecasts

Weather forecasts have management applications in the construction industry. However, they are only useful for short-term planning, as mentioned above. Construction managers cannot plan activities over several weeks or months based on a weather forecast - instead, they must constantly adjust project plans based on the latest forecast available.

In spite of their usefulness, weather forecasts by themselves are not enough to guarantee safety in construction sites. While they provide a general idea of the weather conditions that can be expected, they do not reflect site-specific conditions and sudden changes in the wind:

• Weather forecasts provide no information about gusts, which are the main wind threat in construction projects. If the wind speed starts increasing dangerously, project managers must be ready to stop work based on direct measurements.
• Another limitation of weather forecasts is that they provide general conditions for a region, but they miss small-scale weather effects around construction sites. For example, wind patterns can be disrupted by terrain features, trees, and surrounding buildings.
• Also consider the limitations of weather forecasting: their accuracy has improved significantly in recent decades, but it is not 100%.

A reliable weather monitoring system like WINDCRANE offers a clear snapshot of wind conditions at any project site. Also, if many units are deployed across multiple construction sites, they can be checked simultaneously from a built-in mobile application. To enhance safety, WINDCRANE can send automatic notifications to the project staff when dangerous weather conditions are detected.

WINDCRANE combines a dust-tight and weatherproof enclosure with a long-life battery and cloud-based data storage. This allows the unit to withstand extreme conditions, while making the data available even when there is no direct connectivity.

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