Weather sign
Weather signs are visible and palpable changes in cloud cover, wind and other weather characteristics, which point to imminent weather changes and thus enable a short-term and local weather forecast . The weather signs supplement weather forecasts where forecasts are either imprecise (for example in remote areas for which no high-resolution weather models are available) and for mountains where the weather is already much more changeable than on the flatlands. Accordingly, interpreting weather signs is an important skill of mountain guides and other people who work in weather-dependent professions.
The reliable interpretation of weather signs requires a lot of experience. In some situations, however, you cannot rely on weather signs, for example when you are on the east side of a mountain range and approaching a bad weather front from the west.
Cloud cover
Clouds make the water content and the movement of air masses directly observable and are therefore among the most important weather signs. Some weather signs can be assigned to the warm, others to the cold fronts. A cold front leads to a rapid and marked deterioration in the weather, with heavy, but short, precipitation. There is also a threat of gusts of wind and storms at the front. Warm fronts can be recognized by a thickening, sinking cloud cover and lead to mild, but longer precipitation.
It should be noted that weather fronts move relatively quickly - cold fronts at around 30 to 40 km / h, warm fronts around half as fast. If a cold front is visible on the horizon from a mountain, there are only a few hours left to seek protection. However, weather fronts as well as high and low pressure areas are predicted very reliably by weather forecasts. This makes weather signs that indicate small-scale phenomena such as rain showers and thunderstorms all the more important.
| Signs | Weather change | image |
|---|---|---|
| Cirrostratus clouds create a halo around the sun or moon | Indicates humid air at high altitudes. Slow weather deterioration can herald a warm front. | |
| Increasing, downward shifting clouds Type of cloud changes: Cirri → Cirrocumulus → Cirrostratus → Altostratus |
Warm front or occlusion likely within the next 12 to 24 hours. | |
| Cloud flags on the leeward side of mountain peaks | The air is very humid. Precipitation is to be expected within the next one to four days. If they get smaller, this indicates an improvement in the weather. |
Matterhorn with a clear cloud flag
|
| Gaps in the cloud cover close, a " wall of clouds " approaches Cloud type : larger and denser cumulus and cumulonimbus clouds |
Cold front . Passing thunderstorms possible. | |
| Cumulus clouds that stay small ( Cumulus humilis ) | Stable, good weather conditions, in case they dissolve again towards evening. Mountain hikers / mountaineers often experience this cloud as suddenly emerging fog, which makes orientation difficult. | |
| Widening cumulus clouds ( Cumulus congestus ) that grow up to form towers ( Cumulus castellanus ) and eventually lead to a thundercloud ( Cumulonimbus ) | There is a risk of fixed thermal thunderstorms and rain showers in the next few hours or during the day. Because of the threats ( lightning , precipitation, gusts of wind and flash floods ), these clouds must be constantly monitored if one is far away from a place of refuge. Note: Clouds that have sharp, clear boundaries will continue to swell. Clouds that dissolve at the edges need less attention. |
|
| Fixed lenticularis clouds ("foehn fish"), lee waves | Warm foehn weather. If they fray or ripples form at the edges, the weather worsens. | |
| Clouds in several layers | Bad weather signs; early sign of a cold front. | |
| Foehn wall : The wind builds up the humid air on the windward side and leads to dense clouds and heavy rainfall there. The mountains hold back the bad weather, so to speak. This leads to a sharply defined wall of clouds directly above the mountains. Above it is blue sky, the so-called foehn window. | When the clear sky over the hair dryer window disappears and the clouds slosh over the mountain: Very significant weather deterioration in the next few hours. The foehn wall is of course only recognizable if you are on the side of the mountains facing away from the wind. | |
| Closed fog cover in the lowlands (inversion position, "sea of fog ") | A lowering of the fog cover often indicates an influx of cold, dry air, which continues to promise nice weather. However, an increase in the fog indicates an approaching low and thus worse weather | |
| contrails | If contrails dissolve quickly, this indicates dry air and stable weather conditions, and long-standing contrails indicate a slow deterioration in the weather. |
,_Graz,_%C3%96sterreich,_23._Oktober_2010.jpg)
Other weather signs
Distant view from the Stanserhorn
Sunset on Lake Starnberg
wind
Strong freshening of the wind or change of wind direction indicates rather worse weather. Wind gusts before thunderstorms and rain showers are particularly striking. Steady, weak wind is a sign of good weather.
Distant view
If the distance visibility improves, this means weather stabilization and drier air. Conversely, poor visibility means deterioration in the weather. Very good visibility with wind is often a foehn situation, the end of the foehn comes with a significant deterioration in the weather.
temperature
In a stable, good weather situation, the night brings a steady cooling. A lack of cooling can indicate a warm front. Mild, muggy mornings indicate changeable weather.
Dawn and Dusk
In Europe, where the weather is mostly determined by westerly winds, the dawn is a fairly reliable sign of bad weather, while the sunset is a sign of good weather.
plants and animals
Some wild animals and plants change their behavior or their appearance before bad weather. Since they are continuously dependent on weather conditions, they are particularly sensitive. Before bad weather, for example, mountain game descends and plants close their flowers. Because of their low body mass, insects are very dependent on good weather. The activity of insects can be indirectly observed by other insect-eating animals, for example swallows during the day and bats at night .
See also
literature
- Günther D. Roth: The FSVO meteorology . BLV Buchverlag, 2017, ISBN 978-3-8354-1688-8 .
swell
- K. Winkler, H.-P. Brehm, J. Haltmeier: Mountain Sports Summer: Technology / Tactics / Safety . Swiss Alpine Club SAC, 2010, ISBN 978-3-85902-342-0 .
- Steven M. Cox and Kris Fulsaas (Editors): Mountaineering: The Freedom of the Hills . The Mountaineers, 2009, ISBN 978-0-89886-828-9 .
- ^ Joe Rao: Weather Fronts: Definition & Facts. August 20, 2013, accessed May 13, 2018 .