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Terminology of weather forecasts
Weather and climate forecasts and their inherent limitations
Forecasts Terminology of weather forecasts
Terminology of weather forecasts
Classification of the timing of meteorological forecasts 1.
Current weather forecast Description of the current weather and forecast of meteorological parameters for a period of 0 to 2 hours.
2. Ultra short term weather forecast Forecast of meteorological parameters for a period of up to 12 hours.
3. Short term weather forecast Forecast of meteorological parameters for the period from 12 to 72 hours. (3 days)
4. Medium term weather forecast Forecast of meteorological parameters for the period from 72 (3 days) to 240 hours. (10 days)
5. Weather forecast with extended term Forecast meteorological parameters for the period from 10 to 30 days, usually averaged and expressed in the form of deviations from the climatic variables for the period 6.
Long term forecast a forecast for the period from 30 days to 2 years 6.1 Monthly outlooks Description of averaged weather parameters expressed in the form of deviations (anomalies) from climate values for that month (not necessarily for the upcoming month) 6.2 3 months or 90 daily outlooks Description of averaged weather parameters expressed as a deviation from climate values for that 90 of the circadian period (not necessarily for the upcoming 90 the daily period) 6.3 Seasonal outlooks Description of averaged weather parameters expressed as a deviation from climate values for that season 7.
Climate forecasting For a period of more than 2 years 7.1 Forecasting climate variability Description of expected climate parameters associated with changes in interannual, decadal and intrasecual climate anomalies 7.2 Climate forecasting Description of the future climate taking into account the influence of natural and anthropogenic factors
Notes: a) In some countries, long term forecasts are considered climate products;
b) The season is roughly defined as: winter December/January/February, spring March/ April/May, etc. in the Northern Hemisphere.
In the tropical zone, the seasons may have different durations; approximate forecasts may be made covering several months.
(From the Manual on the Global Data Processing System. WMO No. 485)
Terminology used in general purpose short term weather forecasts and storm warnings (in accordance with the Guidance Document RD 52.27.724-2009 "Manual on general purpose short term weather forecasts")
The following meteorological values (elements)are indicated in short term general purpose weather forecasts: clouds, precipitation, wind direction and speed, minimum air temperature at night and maximum temperature during the day (in C), as well as weather phenomena.
In the table.
1-5 the terms used in forecasts for various meteorological quantities (elements), weather phenomena and their corresponding quantitative characteristics are given.
To take into account the specifics of the expected synoptic process and/or the influence of regional features of the territory for which the forecast is made, if the predicted meteorological values and weather phenomena in certain parts of the territory will differ significantly, they are carried out by detailing the forecast, using additional gradations.
To distinguish individual parts of the territory, use the characteristics of the geographical location (west, south, northern half, central areas, right bank, coastal areas, suburbs, etc.), as well as terrain features (low places, lowlands, valleys, foothills, passes, mountains, etc.).
Detailing the forecast by territory or point using additional gradation and the terms "in certain areas" or "in places" is allowed, as a rule, if there is an influence (impact) of atmospheric processes (phenomena) of mesometeorological scale: - heavy precipitation, thunderstorms, hail, squall associated with the development of intense convection; - fogs and air temperatures (including frosts in the air and on the ground) caused by the influence of terrain features or radiation factors (the influx of solar radiation into the atmosphere and on the Earth's surface, its absorption, scattering, reflection, own radiation of the earth's surface and atmosphere).
In order to take into account the influence of radiation factors, it is allowed to detail the forecast of air temperature using additional gradation and the terms "when clearing", "when clouds flow".
The use of the terms "in places" or "in certain areas (points)" in the weather forecast implies that the expected weather phenomenon or the value of a meteorological magnitude will be confirmed by the observation data of no more than 50% of the meteorological observation units located in the territory for which the forecast is made.
The terms used in cloud forecasts are Clear, clear weather, low cloud, low cloud weather, light cloud cover, sunny weather - Up to 3 points of medium and/or lower tier cloud cover or any amount of upper tier cloud cover Variable (changing) cloud cover From 1-3 to 4-7 points of the lower and/or middle tier Cloudy with clarifications, cloudy weather with clarifications 4-7 points of clouds of the lower and/or middle tier or a combination of clouds of the middle and lower tier with a total of up to 7 points Cloudy, cloudy weather, significant cloudiness, cloudy, cloudy weather 8-10 points of clouds of the lower tier or dense, non illuminating forms of clouds of the middle tier If a significant change in the amount of clouds is expected during half a day, it is allowed to use two characteristics from the terminology given in table 1, and also apply the words "decrease" or "increase".
For example: In the morning it is cloudy, in the afternoon the cloud cover increases to significant.
Terms used in precipitation forecasts
Weather forecasts and storm warnings use terms that characterize the fact of the absence or presence of precipitation, if there is precipitation - their type (phase state), amount, duration (recommended, but not mandatory).
The terms and corresponding quantitative values for liquid and mixed precipitation are given in Table.
2a, for solid precipitation in Table 2b.
Table 2a
The term Quantity of precipitation, mm/12 h
No precipitation, dry weather -
Light rain, light rain, drizzle, drizzling precipitation, light precipitation 0,0-2
Rain, rainy weather, precipitation, sleet, rain with snow; snow turning into rain; rain turning into snow 3-14
Heavy rain, heavy rain (downpour), heavy precipitation, heavy sleet, heavy rain with snow, heavy snow with rain
The same is true for mudslide prone areas
The same is true for the Black Sea coast of the Caucasus 15-49
15-29 30-79
Very heavy rain, very heavy precipitation (very heavy sleet, very heavy rain with snow, very heavy snow with rain)
The same is true for mudslide prone areas
The same is true for the Black Sea coast of the Caucasus
Heavy downpour (heavy downpours)
The same is true for the Black Sea coast of the Caucasus ≥ 50
≥30 ≥80
≥30 mm for a period of ≤ 1 h
≥50 mm for a period of ≤ 1 h
Table 2b Term Quantity of precipitation, mm/12 h
No precipitation, dry weather -
Light snow, light snow 0,0-1
Snow, snowfall 2-5
Heavy snow, heavy snowfall 6-19
Very heavy snow, very heavy snowfall ≥ 20
For a more detailed description of the expected distribution of precipitation over the territory, it is recommended to use additional (usually neighboring) gradations of precipitation in the forecast, it is also allowed to use the terms "in certain areas" and "in places".
For example: In the second half of the day, thunderstorms are expected in the region, sometimes heavy downpours.
To characterize the type of precipitation (liquid, solid, mixed), the terms "rain", "snow", "precipitation"are used.
The term "precipitation" can be used only with the mandatory addition of one of the terms given in Table 3.
Table 3 The term Characteristics of mixed precipitation
Rain and snow Rain and snow at the same time, but rain prevails
Sleet Snow and rain at the same time, but snow prevails; melting snow
Snow turning into rain Snow is expected first, and then rain
Rain turning into snow Rain is expected first, and then snow
Snow with rain (rain with snow) Alternation of snow and rain with a predominance of snow (rain)
For qualitative characteristics of the duration of precipitation, it is recommended to use the terms given in Table 4.
Table 4, the term Total duration of precipitation, hour
Short term rain (snow, rain with snow, snow with rain, sleet), snow (sleet) with charges <3
Rain (snow, sleet, rain with snow, snow with rain), prolonged rain (snow, sleet, rain with snow, snow with rain), sometimes snow, sleet, rain with snow, snow with rain) >3
If the forecasts indicate "light clouds" or "low cloud weather", then the term "no precipitation" is allowed not to be used.
The terms used in wind forecasts In weather forecasts and storm warnings indicate the direction and speed of the wind.
It is allowed to use the details of the forecast of wind characteristics (direction, speed) for parts of the territory.
The wind direction is indicated in the quarters of the horizon (from where the wind blows): northeast, south, southwest, etc.).
If a change in the wind direction is expected within two adjacent quarters of the horizon during half a day, then two adjacent quarters are indicated; if a change in the wind direction is expected by more than two quarters of the horizon, then the term "with transition"is used.
For example: 1. The wind is south easterly, southerly.
2.The wind is southerly with a transition to the north west.
Weather forecasts and storm warnings indicate the maximum wind speed with gusts in meters per second (hereinafter referred to as the maximum wind speed) or the maximum average wind speed if gusts are not expected.
Note: The maximum average wind speed is the highest average wind speed that is expected at any 10 minute time interval during the duration of the forecast period or storm warning.
In weather forecasts and storm warnings, the wind speed is indicated in gradations with an interval of no more than 5 m/s.
When there is a weak wind (speed < 5 m/s), it is allowed not to indicate the direction or use the term "weak, variable directions".
If the wind speed is expected to change significantly during half a day, then the indication of these changes is formulated using the terms "weakening" or "strengthening" with the addition of a characteristic of the time of day.
For example: A southerly wind of 3-8 m / s with an increase in the afternoon to 20 m/s (i.e. the maximum wind speed with gusts will reach 15-20 m / s).
When predicting a squall, the wind direction is not indicated.
It is recommended to use the terms "squally wind strengthening up to.... m/s" or "squall up to ... m/s" with an indication of the maximum wind speed.
For example: during a thunderstorm, a heavy wind gain of up to 20-25 m/s (or a squall of up to 25 m/s).
In weather forecasts, in addition to the quantitative value of wind speed, a qualitative characteristic of it can be used in accordance with Table 5.
Table 5 Qualitative characteristics of wind speed Wind speed range, m/s
Weak 0-5
Moderate 6-14
Strong 15-24
Very strong 25-32
Hurricane 33 and more
If the predicted wind speed interval can be characterized by two qualitative characteristics, then the characteristic for the upper limit of the interval is used.
For example: a wind with a projected speed of 12-17 m / s has the qualitative characteristic "strong", since 17 m/s is included in the speed range of 15-24 m/s.
Terms used in weather forecasts Weather forecasts should include the following of the expected weather events: precipitation (rain, snow), thunderstorm, hail, squall, fog, ice, frost, sticking (deposition) of wet snow on wires (wires) and trees (trees), snow, blizzard, dust (sand) storm, as well as ice on the roads and snow drifts on the roads.
In weather forecasts, the term "strong", and for precipitation "very strong" is used if it is expected that the phenomenon will reach the OYA criteria in intensity.
In other cases, the characteristics of the intensity of phenomena ("weak" or "moderate"), with the exception of the intensity of precipitation, are not allowed to be specified.
When predicting a squall, the maximum wind speed is indicated.
In weather forecasts, if necessary, the terms "strengthening", "weakening", "termination" are used, indicating the time of day.
The terms used in air temperature forecasts In weather forecasts indicate the minimum air temperature at night and the maximum air temperature during the day, or the change in air temperature during an abnormal course of 5 or more in half a day.
The expected minimum and maximum air temperature is indicated by gradations in the interval for point 2, and for the territory – 5.
In forecasts of air temperature for a point or for a separate part of the territory, it is allowed to indicate the air temperature in one number (for a point – using the preposition "about", and for a part of the territory using the preposition "to").
In the first case, we mean the middle of the predicted temperature range for the point, in the second case, its maximum value for the specified part of the territory.
For example: 1. Temperatures of up to 20 were forecast for the west of the territory.
This means that a temperature of 15...20 is expected.
2. The air temperature in the city is predicted to be about 20°.
This means that the temperature in the city is expected to be 19 ... 21°
If the expected temperature distribution over the territory does not fit into the interval equal to 5, then it is recommended to apply additional temperature gradations, using a detailed temperature forecast for parts of the territory.
At the same time, the forecast should indicate the areas where these air temperature deviations are expected (or the conditions under which they will be noted, for example ," when clearing").
For example: The temperature at night is 1...6, when it clears (or in northern areas) to -2.
If an abnormal course of air temperature is expected, then its highest (lowest) value is indicated with an indication of the time period of the day when it is predicted.
For example: The temperature in the evening is -10...-12°, by the morning the temperature rises to -2°.
When using the terms "increase" ("warming") or "decrease" ("cooling"), " strengthening ("weakening") frost (heat)" the predicted temperature value can be indicated by a single number with the preposition "to".
If during the period of active vegetation of agricultural crops or harvesting, values below 0 fall into the predicted air temperature range, then negative air temperature values are indicated in the weather forecast with the addition of the term "frost".
The term "frost" is also used if temperatures below 0 are expected on the soil surface.
For example: 1. If the expected air temperature at night is from -2 to +3, the temperature forecast is formulated as follows: the temperature is 0...3°, in places (in the east, in the north, in low places) frosts are up to -2°.
2. When the expected air temperature is from 0 to 5° and the soil temperature is below 0°, the forecast is formulated as follows: the temperature is 0...5°, in places (in the east, in the north, in low places) on the ground freezing to -2°.
If the value of the maximum (minimum) temperature is expected in the OJ gradations, then the term "severe heat" ("severe frost") is used in the forecast.
Definitions
Dangerous meteorological phenomena (S): natural processes and phenomena occurring in the atmosphere and/or near the Earth's surface, which, by their intensity (strength), scale of distribution and duration, have or may have a damaging effect on people, farm animals and plants, economic objects and the environment.
