The Critical Role of Accurate Weather Data in UAV Missions Lee Nelson

Unmanned aircraft are becoming an increasingly important part of defense strategies; helping military personnel respond to a greater demand for improved surveillance and attack operations. These sophisticated unmanned aerial vehicles (UAVs) offer enhanced flexibility, speed, intelligence and a reduced risk of loss of life. The most notorious UAV is the General Atomics Predator, which first was responsible for reconnaissance missions. It later launched missiles at targets in Afghanistan, Iraq and regions of Pakistan. But without a pilot on-board, the success of UAV flights depends heavily on accurate information and reporting.

One crucial type of data for UAV flights is real-time weather information. This information is especially important during take-off and landing, with 84 percent of Predator mishaps occurring during the landing process, according to a large supplier of unmanned aircraft. Real-time weather data is typically gathered from a quick-deployment automatic weather station to support operations. As pilots and military personnel coordinate UAV flights, having information on wind speed and direction, barometric pressure, cloud coverage, thunderstorms and visibility may mean the difference between an effective landing or take-off, and a failed one.

A Closer Look at UAV Operations

As many news sources have recently reported, government intelligence sources consider these UAVs to be one of their most effective weapons against Al Qaeda. The demand for UAVs is increasing, according to the Department of Defense (DOD). In 2003, when the United States invaded Iraq, the DOD planned to increase its UAV inventory to about 350 by 2010, however this number has already been achieved. The Army has about 250 Shadow UAVs, followed by the Air Force with about 110 Predators and 30 Reapers. Small UAVs, sizing only a few feet, are also an effective tool in battlefield surveillance platforms.

Strategic UAVs are often operated remotely with pilots manning the controls in Nevada while the aircraft is based in the Middle East. These pilots rely on accurate information and real-time data to accomplish successful missions. As the New York Times recently noted, Predators and the Air Force’s Reapers are now flying 34 surveillance patrols each day in Iraq and Afghanistan, up from 12 in 2006. They are also transmitting 16,000 hours of video each month, some of it directly to troops on the ground.

The UAV technology is advancing rapidly but is yet to be perfected, however, as Air Force officials acknowledge that more than a third of their unmanned Predator spy planes have crashed. Of these Predator crashes, 55 were lost because of weather conditions, equipment failure or operator errors. With price tags averaging around $4.5 million for the 27-foot Predator, maintaining these valuable pieces of equipment is important in achieving our national defense objectives.

Weather: Direct Impact on UAVs

As with traditional defense aviation, accurate and timely weather data allows UAV pilots to make informed decisions. However, UAVs are more susceptible to weather conditions, according to a 2005 report from the United States Government Accountability Office (GAO). According to the GAO, weather and environmental constraints, including dust and sand storms, limit UAV operations. For example, Marine Corps UAVs have been kept from performing certain missions as a result of dust storms. Having accurate weather reporting enables ground personnel to make the best decisions for UAV flights.

UAV pilots use accurate weather information to plan and execute effective fuel management, diversions and alternate route planning. Information on wind speed and direction, cloud ceiling, visibility, precipitation, humidity and temperature is crucial for flight plan preparation and execution. Many unmanned aircraft often fly at lower altitudes, causing them to be directly affected by the weather.

Effective communication between military personnel in the field and back home can be the key to a successful UAV mission. It is important to use technology that is designed specifically to meet the demands of defense communication in the field, which means equipment that is rugged, versatile and easily assembled in a variety of defense situations. Although situations may vary based on the time of year, region and purpose of the mission, there are a few basic principals of weather measurement to keep in mind for each phase of a UAV flight.


During a UAV take-off it is essential that pilots have accurate, on-demand reporting of wind-speed and direction, atmospheric pressure, humidity and visibility in the take-off area. Additionally, reporting of cloud cover and precipitation can help pilots determine if conditions are favorable for a safe take-off. Depending on the climate, extreme weather during take-off conditions, such as rain, snow and dust storms can inhibit the course of a UAV. Real-time weather data acts as the eyes and ears of a pilot responsible for a plane remotely.


As mentioned, many UAVs often fly at lower altitudes, so they are directly affected by the weather. Accurate information about such phenomena as precipitation, cloud height and depth, and humidity can help pilots make decisions about route planning and alterations, as well as fuel management. Unlike traditional aircraft, a pilot for a UAV cannot glance out the window to check the condition of the plane during flight. A common problem for UAVs, especially during longer flights, is ice accumulation on the wings and body of the vehicle. Pilots and weather officers can use real-time reporting as well as model forecast data to determine the safety of a UAV based on current and future weather conditions.

Safe Landing

In preparation for a landing, pilots need accurate information on wind speed and direction (especially runway cross-winds), atmospheric pressure, temperature and humidity (used to calculate density altitude), and precipitation in the landing area. Hazardous weather conditions, such as freezing rain and thunderstorms, may be detrimental to a UAV landing if pilots are misinformed. Thunderstorm data measured by tactical lightning detectors indicate the presence of lightning strikes in the area. With accurate weather reporting, weather officers and pilots can determine which approach can be used, and even in some cases whether an approach should be attempted or an alternate landing base is required.

Accurate Weather Information a Best Practice

Similar to the best practices of traditional defense aviation, accurate and real-time weather information is mission critical. Whether a UAV mission is tactical and centered on information-gathering, or defense and attack initiatives or a strategic reconnaissance mission, UAVs’ role in the Department of Defense is increasing. As the demand for UAVs grows, so will the need for on-demand weather information, such as wind speed and direction, ceiling, visibility, atmospheric pressure, and present weather (i.e. rain, snow, thunderstorms, etc.). This crucial weather intelligence will improve UAV safety in take-off, flight and landing, and assist defense missions in achieving objectives.

About the Author:

Lee Nelson is New Applications Manager for the Vaisala Defense Segment. He is a retired United States Air Force Weather Officer. He can be reached at [email protected]. Vaisala is a global leader in environmental and industrial measurement. Building on more than 70 years of experience, Vaisala contributes to a better quality of life by providing a comprehensive range of innovative observation and measurement products and services for meteorology, weather critical operations and controlled environments. Headquartered in Finland, Vaisala employs over 1200 professionals worldwide and is listed on the NASDAQ OMX Helsinki.

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