الارصاد الجوية - التنبؤات القصيرة الامد - التنبؤات الطويلة الأمد .. الحاسبات تعمل

Meteorology - Short-term forecasts - Long-term forecasts .. Computers work

Meteorology

Weather forecasting has been a matter of guesswork for many years, without solid scientific foundations, but the use of computers and satellites in this field has greatly increased the accuracy of forecasting and its longevity.

Short-term forecasts

Weather forecasting requires monitoring a wide area of ​​the atmosphere surrounding the area in question and tracking the change in weather conditions and the movement of air masses in it, so that the weather observer can analyze these variables to predict what the weather conditions will be like in the near future.

Weather conditions are monitored by special stations or ships equipped with radar and ground measuring devices or carried in balloons or rockets, which measure temperature, atmospheric pressure, humidity, wind speed and direction, visibility and cloud distribution. These measurements are recorded every three, six or twelve hours and transmitted wirelessly to a central receiving station, where all this information is transferred to paper or magnetic tapes, then entered into an electronic computer, which analyzes it and prepares a chart of surface atmospheric pressure showing points with the same atmospheric pressure. The computer may output the results of its analysis to an incremental plotter, equipped with a ruler in a holder that moves in two perpendicular directions over a flat surface on which a sheet of paper is fixed. The computer can move the ruler in steps that do not exceed a small fraction of a millimeter, right or left, forward or backward, thus achieving any required linear drawing.

The incremental plotter is used to draw equal air pressure lines on geographical maps of various altitudes. This provides the weather observer with detailed three-dimensional maps every three hours that enable him to predict the movement of the wind and the occurrence of precipitation such as rain, hail, snow or fog. This system is not by nature prepared to predict weather conditions on a narrow local scale, due to the vast area it covers. However, the rapid preparation of these maps by computer allows the weather observer sufficient time to combine the available data and take into account the special local conditions.

Long-term forecasts

The aforementioned system allows weather forecasting with acceptable accuracy for a period not exceeding thirty-six hours, because the weather observer can track any pattern of weather conditions that may form, such as an anticyclone, for example, and predict its changes for a period not exceeding thirty-six hours, after which the forecasts become unreliable.

Weather conditions can be forecasted for a longer period by comparing current conditions with similar conditions that prevailed in the past. For this purpose, the computer is used to quickly search through its stored records.

(The context diagram that explains the method of selecting past records that match the present weather conditions).

Information about weather conditions for a period that may extend to a week is entered into the computer by means of punched cards. Let us assume, for example, that three cards have been prepared, indicated by the numbers 1, 2 and 3, representing the weather conditions for the past three days.

The computer searches its records for weather conditions similar to those contained in card No. 1, and may find six similar cases, indicated by the letters (1) to (F), each of which has lists of weather conditions for the days or months preceding and following it. The computer then searches among these six cases for those whose weather conditions on the following day are similar to those contained in card No. 2. These may be cases “1”, “H”, and “F”, for example. The computer then searches among these three cases for those whose weather conditions on the third day are similar to those contained in card No. This may be case (H), for example. The computer examines the list of this case to determine the weather conditions for the days following the third day, and then prints this information to be used in the long-term forecast.