The term Marine Meteorology describes the part of Meteorology focusing on the weather conditions that prevail in an area and can affect a boat or a ship. In our days, weather information is provided by innumerable sources, with the internet being the most common among these sources.
However, for someone, either an amateur or professional working at sea, apart from the forecasts issued on a daily basis by official bodies (e.g. Hellenic National Meteorological Service) or by other bodies through websites (e.g. meteo.gr), top priority should be the understanding of some visual stimuli – signs in the sky that warn us about upcoming weather conditions. Additionally, anyone interested should be able to quickly and easily search for weather observations that will help them better understand any upcoming weather changes.
The Greek sky. Photo from a fighter jet Files: Paralos Events & Design
Signs in the sky
Clouds are always a relatively reliable method of identifying weather conditions expecting to prevail from the next few minutes to a few hours ahead. There are 10 main types of clouds and several subcategories. Our purpose is not to learn to recognize all species, but mostly those that can warn us in a relatively accurate manner before any weather change. The most important are the following:
Cumulonimbus
The “King” of clouds, the most impressive cloud in the atmosphere with a height higher than Mount Everest and often extreme weather conditions. It is the famous storm cloud, which a seafarer can easily spot when looking at it from a distance, because it looks like a giant mushroom (see photo 1).
This cloud causes the famous thunderstorms, i.e. sudden weather change with strong winds, temperature drop, torrential rain along with lightning and less often hail or even tornadoes or water spouts. In our country these clouds are formed from mid-spring to mid-autumn, due to thermal instability while the rest of the months relate to cold fronts. In summer, they rarely form above the sea, however when we observe huge cloud towers rising in the afternoon over an area with land, north and west, it is advised to observe them closely, as in some cases they can move over the sea. When a Cumulonimbus is formed just above us, we can understand it as time goes by, as the base of the cloud will become darker. This means that the cloud grows in height and can develop a thunderstorm.
Photo 1: Cumulonimbus from far away in maturation. in the area of Ilia (photo by N. Mazarakis)
Cirrus
Cirrus (photo 2) is the cobwebs we often see in the sky. They are located high, in over 8000 meters and consist of ice crystals, without of course causing any weather phenomena. When we observe the Cirrus from autumn to spring on the western horizon and the wind that blows in our area is directed south, then it is very likely that the weather will change in the next 8-24 hours, since the Cirrus are the first clouds that an observer will notice before the arrival of a warm or cold front.
Photo 2
Cirrostratus
Cirrostratus (photo 3) are clouds that cover the entire sky and are translucent in sunlight or moonlight. Sometimes a luminous circle called halo forms around the sun or the moon. When we see Cirrostratus in the sky and southern winds blow, it is very likely that it will start to rain in the next 2-6 hours.
Photo 3: Cirrostratus above the island of Kea (photo by N. Mazarakis)
Shelf Cloud
This is the greatest fear for every sailor. It is perhaps the most characteristic cloud (photo 4) that warns us of a sharp change in wind intensity. Behind this cloud, the winds can reach for a few minutes even 60 knots, while the rain is torrential. These clouds are associated with strong thunderstorms and precede the beginning of the thunderstorm. If we see this cloud in the sky, we must act swiftly to protect ourselves from the abrupt change of the weather conditions.
Photo 4: Shelf Cloud over Attica (source: meteo.gr)
Network of meteorological stations
In recent years, the National Observatory of Athens has developed an extremely dense network of meteorological stations which provides live weather conditions prevailing in the area of the station. These stations are available on the page https://www.meteo.gr/Gmap.cfm where the user can be transferred to the station page and see the weather conditions live, by clicking on a station. Many of these stations are located on islands and even in or very close to the port or marina, such as Ios, Lefkada and Mykonos.
Lightning activity recording network
Nowadays, an excellent network for recording lightning activity has been developed, where every internet user can see where exactly a thunderstorm is taking place, with one click. By clicking on the following link http://el.blitzortung.org/live_dynamic_maps3.php?map=14 we can see the lightnings that have fallen in an area in the last 2 hours live. The white color (picture 5) shows the lightnings that are marked now, while the red ones show the ones that I marked two hours ago. In this way, we are able to understand the direction of a storm.
Photo 5
Weather forecast
Weather forecast in recent years has made great progress in terms of accuracy. The spread of the internet use has given the opportunity for dozens of sites that deal with weather forecast to be developed. However, we must be very careful when choosing such a site and always prefer those managed by official bodies or institutes, where professional meteorologists work.
Photo 6: Photograph, Dimitris Simeonoglou – Naxos 2020
Thanks
We would like to warmly thank Dr. Nikos Mazarakis, who provided us with the above information and photographic material