Meteorology is based on the observation of gases in the atmosphere, their changes in state and movement. To make a weather forecast, you need to measure the pressure, read the temperature, estimate the humidity, and study the wind.
How to interpret the weather?
The lower the needle goes (and therefore the lower the atmospheric pressure), the worse the weather: rain, cold, grey, clouds, etc. And the higher the needle rises (the higher the atmospheric pressure), the temperature, sunshine and pleasant climate will be milder.
On weather maps, wind direction and speed are represented by special symbols. The wind direction is indicated by an arrow pointing from the direction the wind is blowing towards the center of the small circle representing the measurement site.
Atmospheric pressure varies slightly depending on the weather. It is a little lower when the weather is cloudy or rainy (depression), and a little higher when the weather is fine (anticyclone or anticyclone).
| Wind direction / Barometer | North |
|---|---|
| & gt; 1020 hPa | Beautiful, with a tendency to haze and fog. Cool temperatures. |
| From 1013 to 1020 hPa | Quite handsome. Showers in the mountains. It’s cold. |
| From 1006 to 1013 hPa | Snow or sleet. It’s cold. |
| < 1006 hPa | Snow and strong wind in some places. It’s cold. |
What is the role of meteorology? Meteorology is a science that aims to study atmospheric phenomena such as clouds, precipitation or wind in order to understand their formation and development based on measured parameters such as pressure, temperature and humidity.
Why is the weather nice when the pressure is high? This is because the air rises to a low point, the warm moist air mass cools, which in turn leads to frequent clouds and precipitation. On the other hand, in the high pressure zone, the air flows downwards. … In areas of high pressure, the weather is usually fine.
How to read air pressure?
But to achieve this precisely, it is ideal to equip yourself with a barometer, thermometer, hygrometer, anemometer or weather station that combines these functions. Measuring atmospheric pressure, temperature, humidity and wind speed is the key to realistic forecasts!
| Wind direction / Barometer | North | East / North East |
|---|---|---|
| From 1006 to 1013 hPa | Showers or thunderstorms. Mild temperatures. | Stormy rains. Mild temperatures. |
| Rain and wind. Mild temperatures. | Stormy rain with little wind. Harsh and wet weather. |
This atmospheric pressure is measured in pascals or even in bars. At ocean level and without any particular meteorological phenomenon (anticyclone, depression), the atmospheric pressure is 101,325 pascals (1,013.25 hectopascals), which corresponds to one bar.
How to set the barometer? Adjust the position of the needle on your barometer. Look for the small adjustment screw that is usually found on the back of the device. Use a small screwdriver to turn the adjustment screw to place the needle on the scale corresponding to the spot’s actual barometric pressure.
How do I know if the barometer is working? The needle only moves if the atmospheric pressure changes. If you doubt its operation, try a simple demonstration: place the device in a transparent plastic bag inflated with air, press it lightly: the needle moves.
What is the value of the pressure? The standard unit defined in the International System is the pascal (symbol Pa). The pressure of a pascal corresponds to the force of a newton acting on a surface of one square meter: 1 Pa = 1 N/m2 = 1 kg m – 1 s – 2.
How to read a marine weather chart?
The Météo France coastal bulletin is still structured according to the same scheme. Describes the general state of air masses with large-scale trend information. Next come the wind, sea, weather and visibility forecasts for the navigation area in question.
Marine weather analysis On the frontological map and the pressure fields, the centers of action (changes of anticyclones, depressions), the zones of strong wind and calm wind, the disturbances will be identified. The situation at the limit of anticyclones, very noticeable in summer, is favorable to navigation.
Coastal cruising VHF is most often used to receive weather reports.
How to read the weather? The weather reports are pessimistic, admitted Didier Robert-Lacroix. “If the risk of precipitation is 30% at noon and 70% at 5 p.m., we will opt for the worst case. Therefore, the forecast for the whole afternoon will be 70% chance of showers (with a cloud icon illustrating this).
How to read a Torricelli barometer? – If you have a Torricelli barometer, turn it on and wait for the mercury to rise. Then slide the capillary until the mercury indicates the day’s value.
How do I know if I can go out to sea? The number to dial is 3201 (paid access). At sea, sea time is available mainly on radio, via VHF, on medium wave such as France Inter and France Info, via SSB requiring certain 12:17 equipment or via satellite (IMARSAT broadcast: covered all oceans).
| To oblige | Surname | Wind in km/h |
|---|---|---|
| 1 | The breeze is very light | 2 to 6 |
| 2 | A light breeze | 7 to 11 |
| 3 | A light breeze | 13 to 19 |
| 4 | A nice breeze | 20 to 30 |
How to read the wind map?
The wind force is calculated in km/h. The arrow indicates the direction of the wind. The first number (in white) indicates the expected average wind speed (over 10 minutes). When the current wind speed exceeds the average wind speed by 10 to 15 knots (1 knot = 1852 km/h), it is called a “gust”.
The axis, which represents the longest line, indicates the direction from which the wind comes and in which direction the wind goes. The points that are these lines (small or large) or triangles placed on a pole indicate the wind speed at the nodes.
Reading an isobaric chart If the center of the depression passes to the south of the observer, the latter sees the wind turning from southeast to east then to northeast. If it passes to the north, the wind turns from south to south-west, then to north-west (very often in Brittany).
The following terms are used for public (terrestrial) forecasts:
- Easy (0 to 9 km/h)
- Moderate (10 to 40 km/h)
- Strong / windy (41 to 60 km/h)
- Very strong / rush (61 to 90 km/h)
- Very strong / storm force (more than 91 km/h)
- Hurricane force (more than 115 km/h)
| Station | Bordeaux |
|---|---|
| Frequency (MHz) | 127,000 |
| language | French |
| Airfields included | Bordeaux, Toulouse, Tarbes, Biarritz, Marseille, Nice, Paris Orly, Paris CDG, Lille, Pau, Tours |