All planes that take off need weather information

Weather affects flying in many ways. Different types of fog, rain, and snowfall affect visibility, which can deteriorate very quickly under conditions of thick snowfall, for example. Icy conditions can challenge aviation with ice formation on the plane itself and on runways, for example. Wind conditions are also very significant from the point of view of aviation.

Clouds pose challenges - especially cumulonimbus clouds and thunderclouds. These clouds also contain electric charges which can damage the sensitive electrical instruments of aircraft. “Pilots fly around cumulonimbus clouds even if they have to fly long distances to do so”, says Jorma Tikkamäki of the Finnish Meteorological Institute who works as a weather observer at Helsinki-Vantaa Airport.

“Planes used in commercial aviation are so well-equipped nowadays, that they can take off in almost any kind of weather”, Tikkamäki observes. Weather information nevertheless continues to be essential also for commercial pilots, affecting matters such as the planning of flight routes and the selection of auxiliary airfields. The economics of flying, which are affected by factors such as high-altitude wind conditions, are also considered in flight planning. Securing flight safety is nevertheless the most important goal in flight planning and flight weather services.

The most important goal is ensuring flight safety.

The versatile flight weather services of the Finnish Meteorological Institute make it possible to prepare for weather phenomena that affect flying. Flight weather reports mainly comprise Meteorological Terminal Air Report (METAR) observations of flight weather as well as Terminal Aerodrome Forecasts (TAF), and warnings. In addition, an extensive selection of different types of weather maps and other products are available.

Flight weather observations at airports are made either automatically or manually. Terminal Aerodrome Forecasts, meanwhile, are made by meteorologists utilising weather models of different types as well as more recent flight weather observations. In addition, pilots have access to space weather reports on disturbances caused by space weather, on which more information is available on our website.

Fogs and precipitation of different types affect visibility at airports. Picture: Kim Frisk

The important role of observations in flight weather

An observer from the Finnish Meteorological Institute arriving at Helsinki-Vantaa Airport in the morning is immediately given a comprehensive overview of the events of the night: what the previous night's weather was like, how the instruments taking measurements have worked, and what kind of weather is to be expected based on the forecasts. When the person on the night shift leaves, it is the turn of the next observer to create the important flight weather observations and to ensure for their part that pilots are given current and precise information on the weather in the airport area.

Information on observations is needed on factors such as wind, visibility, clouds, temperature, humidity, air pressure, and various weather phenomena. This observational information is used by all pilots landing at the airport and taking off from there, as well as other airport actors.

Although observations are also made automatically, and various instruments can be used to measure weather phenomena accurately, on-site flight weather observers continue to play a significant role. “Two eyes know how to interpret details better. The worse the weather conditions get, the more important the role of an observer becomes”, Tikkamäki points out.

In addition to making observations on the coverage of the cloud layer and on visibility, for example, an observer also follows and monitors automatic observations in case of errors and suspicious results.

Pilots interpreting the observations need to keep in mind that point-specific observations hardly ever represent the weather of an entire area and detailed generalisations cannot be made of regional weather on their basis. The primary purpose of METAR notifications is to describe prevailing weather conditions at an airfield. Another important observation is that the weather can change very quickly, in which case the observer reacts to the situation by drafting a so-called SPECIAL weather bulletin according to precise internationally agreed publication criteria.

A challenge facing the making of observations involves situations in which visibility is poor, which means that the observer must be especially vigilant at night. Spotlights are the only illumination used in the weather tower to help the observer's eyes accommodate to darkness. Picture: Nicholas Kujala

Flight weather is typically forecast only about 24 hours in advance

Flight weather forecasts differ significantly from the so-called general weather forecasts which are shown on television, for instance. The focus in standard weather forecasts is on temperature, cloudiness, and the location of precipitation, while flight weather forecasts there is a greater focus on the three-dimensional structures of the atmosphere and these phenomena. Important information for pilots also includes the altitudes of the upper and lower limits of clouds and what types of cloud are involved, where the jet streams move, and at what altitudes turbulence and ice formation occur, for example.

Flight weather forecasting is largely so-called nowcasting, which means that the TAF forecasts are made for a maximum of 24 hours in advance. Weather observations have a significant role at the beginning of the forecast, but toward the end, various weather models are emphasised.

A meteorologist forecasting flight weather has the task of producing the best possible vision for the coming weather to keep weather phenomena from taking any aviator by surprise. This works by combining the meteorologist's own experience and professional skills, as well as weather models of different kinds.

Aviation weather information is available to all

Flight weather services are freely available on the flight weather pages of the Finnish Meteorological Institute. In addition to flight weather observations, forecasts, and warnings, the service also offers various satellite and radar images as well as forecasts on wind, overall cloudiness, and precipitation areas. The page also offers the possibility to put a planned flight path on a map which can be used to list flight weather observations and forecasts that are relevant to the route.

Pilots also need a diverse understanding of meteorology if they are to understand flight weather information. Meteorology studies are an important part of the training of all pilots, both commercial and amateur.

“Meteorology takes on great importance especially for small planes”, Tikkamäki notes, adding that contrary to aircraft used in commercial aviation, small planes actually only fly in good weather.

In 2020 the Finnish Government extended the sole right given to the Finnish Meteorological Institute to provide legally mandated flight weather services to all airports in Finland that meet the definition set by the Aviation Act. The task entails great responsibility, because without weather information, air traffic would practically come to a complete standstill.

“Meteorology is of vital importance for aviation. Each plane that takes off needs weather information”, emphasises Jorma Tikkamäki when asked about the significance of meteorology for aviation.