"Nice weather, isn't it?" - Traditionally, this phrase was considered the most appropriate beginning of any small talk. But not this year. And not for the residents of St. Petersburg. This summer, the Northern capital and the adjacent territories were flooded in such a way that nothing but anger or, at best, a sarcastic grin, was not to be expected from the Petersburgers in response to such an entry. And what curses did not fall on the heads of the poor weather forecasters, who dared to promise the North-West region a "dry, hot, dry summer" in late spring! But is the fault of professional weather forecasters really that great? How accurately and for how long can it be predicted in principle?
Rain, rain, rain …
There is no place on our planet where it would not rain. Yes, yes, even over the Sahara Desert, which is rightfully considered the driest place on Earth, sometimes dark rain clouds thicken. As recently as the beginning of May of this year, a real tropical downpour fell over that part of the Great Desert that belongs to Morocco. The tourists are lucky …
The Indian city of Cherrapunji is considered the wettest place in the world, where an average of about 12 thousand millimeters of precipitation falls per year (for comparison: in St. Petersburg - an average of 660 millimeters). But local residents, who have adapted to such difficult conditions, and even learned to grow bridges from the rapidly growing roots of a rubber tree, do not need meteorological observations. A simple calendar is enough for them: from March to October - continuous rains, from November to February - dry.
The citizens of the state of Uganda, in eastern Africa, do not need forecasters either: for two-thirds of the year, rain falls on their heads with an inevitable thunderstorm. But the inhabitants of another African state, Botswana, on the contrary, are accustomed to a dry and arid climate. Rain in Botswana is such a rare and precious phenomenon that the word “pula” (“rain”) is not only said here to greet, but also is called their national currency.
However, if you ignore both the extremely arid and 100% humid places of the planet, weather predictions are in great demand.
But the quality of this product, unfortunately, does not always satisfy the consumer. Especially in the countries of that climatic zone, where there is a significant difference between the seasons and where people are used to cold snowy winters, clear and warm summers and - so be it! - changeable and rainy off-season.
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Here, the attitude towards weather forecasters can be very serious, up to legal responsibility. For example, in the 17th century in Great Britain the "law on rain" was passed, according to which one poor fellow was even executed for an incorrect prediction.
Seagulls walk on the sand …
The history of weather forecasting goes back to time immemorial. Our wise ancestors, who did not have any meteorological instruments, predicted the weather by wind and clouds, by the state of plants and the behavior of animals. Elderly people used “barometers and hygrometers” for head vasospasm and bone aches. In difficult cases, it was possible to turn to the oracle, who for a modest payment communicated the will of the deity on duty responsible for the weather.
Over the centuries, a huge layer of folk signs was formed, which made it possible to predict the weather for the coming days with dignified accuracy and sometimes with quite sufficient fidelity, which is not always achievable in our time - for the coming season.
Reddish morning dawn - cloudy and most likely rain.
Bees are reluctant to crawl out of the entrance and are lazy with collecting nectar - as if it will rain, and even with a thunderstorm. Chickens bury themselves in the dust - soon to be bad weather.
And the famous sailor's "Seagulls walk on the sand, promise the sailor longing"? Or vice versa: "If the seagull sits in the water, wait for good weather."
Unfortunately, all this is gradually forgotten. People are accustomed to trusting instruments and computer modeling of atmospheric processes more than their own perception of the world around them and the signs of nature.
Does the computer know better?
Yes, that's how it happens now - by means of computer modeling. Data from weather stations on air flows, wind direction, atmospheric pressure, temperature, air humidity, etc. Are entered into the computer. With the help of one of the three main currently existing weather forecasting programs (the so-called hydrodynamic models of the atmosphere), this data is processed, and the computer produces a short-term or long-term forecast.
A hydrodynamic model of the atmosphere is a very expensive and complex program. Even a supercomputer with colossal computing power and speed spends several hours of processor time on each forecast. Therefore, the owners of the program provide consumers (meteorological services of various countries, commercial organizations) not with access to the model itself, but the results of calculations based on it - meteorological maps for the area of interest for different heights and at different times.
The most informative, that is, having the largest coverage of predictions (almost the entire globe), is the American numerical model GFS (Global Forecast System). GFS calculations are based on data from the United States National Atmospheric and Oceanic Research Administration. However, experts believe that this program is not sufficiently adapted for Russia, since it does not take into account the possible thickness of the snow cover.
Results closer to our conditions are provided by the Finnish meteorological service Foreca and the British meteorological bureau MetOffice.
A word in defense of the hydrometeorological center
All these calculations - both short-term and long-term - are united by the following. They are produced automatically, without human intervention. Their results are published by numerous Internet resources, and the people's anger in the event of an unreliable forecast falls on the heads of living forecasters.
Meanwhile, the automatic forecasts of Internet sites are one thing, and the forecasts of our hydrometeorological center are quite another. It is in the hydrometeorological center that people are necessarily involved in forecasting. The results obtained with the help of one or another, albeit the most modern and recognized computer program, are necessarily subject to "visual control". Forecasters collect all data and calculation results, up-to-date information from weather stations and once again recalculate the forecast for each region.
And despite the fact that the modern hydrometeorological center does not have enough data from the high-mountainous Pamir and Tien Shan weather stations, which it freely used in the Soviet era, its short-term, for the next 1-3 days, predictions are 15-20% more accurate than forecasts from the numerical computer modeling.
As for the longer term, the forecast for 5-10 days, no one will be able to make it better yet - neither people nor a computer program. The state of the atmosphere can change too quickly and unpredictably during this time, experts of the hydrometeorological center say. Here, the reliability remains at the level of the predictions of the ancient oracle - 20-30%. What can we say about more long-term forecasts …
In general, dear reader, if you are going to the dacha for the weekend, then feel free to trust the predictions of the hydrometeorological center. If you are going on a week-long hike, then, in spite of the rosy forecast, just in case, take with you “means of protection from the rain” (as our Finnish neighbors delicately call raincoats and rubber boots).
Well, you can find out what summer will be in the spring without asking anyone, but simply throwing a coin. In this case, the probability of guessing correctly will still be 50%, and not 20%, as predicted …