Term
| To convert from true to magnetic wind: |
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Definition
1. Add westerly variation to true direction
2. Subtract easterly variation from true direction. |
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Term
| To convert from magnetic to true direction: |
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Definition
1. Add easterly variation to magnetic direction.
2. Subtract Westerly variation from magnetic direction. |
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Term
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Definition
| The horizontal speed of air past a given point. |
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Term
| How wind speed is determined |
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Definition
| Averaging the speed to the nearest whole knot over a 2-minute period. |
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Term
Beaufort Scale
Calm; smoke rises vertically. |
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Definition
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Term
Beaufort Scale
Direction of wind shown by smoke drift, not by wind vanes. |
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Definition
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Term
Beaufort Scale
Wind felt on face; leaves rustle; vanes moved by wind. |
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Definition
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Term
Beaufort Scale
Leaves and small twigs in constant motion; wind extends light flag. |
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Definition
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Term
Beaufort Scale
Raises dust, loose paper; small branches moved. |
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Definition
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Term
Beaufort Scale
Small trees in leaf begin to sway; crested wavelets form on inland waters. |
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Definition
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Term
Beaufort Scale
Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. |
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Definition
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Term
Beaufort Scale
Whole trees in motion; inconvenience felt walking against the wind. |
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Definition
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Term
Beaufort Scale
Breaks twigs off trees; impedes progress. |
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Definition
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Term
Beaufort Scale
Slight structural damage occurs. |
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Definition
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Term
Beaufort Scale
Trees uprooted; considerable damage occurs. |
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Definition
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Term
Beaufort Scale
Violent Storm - Widespread damage. |
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Definition
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Term
Beaufort Scale
Hurricane - Widespread damage. |
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Definition
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Term
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Definition
| Rapid fluctuations in wind speed with a variation of 10 KT or more between peaks and lulls. |
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Term
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Definition
| Maximum instantaneous speed observed. |
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Term
| Two conditions of variable wind direction |
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Definition
1. Direction is variable and the wind speed is 6 knots or less
2. Direction varies by more than 60 degrees or more AND wind speed is greater than 6 KT. |
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Term
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Definition
| A change in wind direction of 45 degrees or more over a less than 15 minute period with sustained wind speeds of 10 KT or more. |
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Term
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Definition
| A sudden increase in average wind speed of at least 16 KT and sustained at 22 KT or more and lasting for at least one minute. |
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Term
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Definition
| Highest instantaneous speed recorded that is greater than 25 KT since the last routine METAR. |
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Term
2-1
Wind is measured as a vector that includes direction and speed, and is termed______________. |
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Definition
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Term
2-2
What is the term for the absence of apparent motion of the air? |
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Definition
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Term
2-3
Where should wind speed and direction be measured? |
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Definition
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Term
2-4
What is considered to be wind direction? |
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Definition
| The direction from which the wind is blowing. |
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Term
2-5
How shall wind direction be determined? |
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Definition
| By averaging the observed direction over a 2-minute interval when direct-reading dials are used. |
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Term
2-6
In which observations shall wind direction be reported? |
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Definition
| All except single element SPECIs. |
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Term
2-7
In what unit shall direction be reported? |
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Definition
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Term
2-8
To what direction shall wind be reported? |
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Definition
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Term
2-9
How many digits shall wind direction use? |
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Definition
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Term
2-10
What shall always be the last digit of wind direction? |
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Definition
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Term
2-11
What wind direction shall be reported as VRB? |
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Definition
| If the speed is 6 knots or less and a direction cannot be determined. |
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Term
2-12
How is an estimated wind speed or direction indicated on the transmitted report? |
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Definition
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Term
2-13
List ways to estimate wind direction if the wind direction indicator is inoperable. |
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Definition
Observing the wind cone or tee
Movement of twigs, leaves, smoke, etc.
By facing into the wind in an unsheltered area. |
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Term
2-14
What shall never be used in estimating surface wind direction? |
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Definition
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Term
2-15
When will the observer need to convert the true reading to magnetic? |
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Definition
| When reporting wind direction to an aircraft. |
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Term
2-16
When will the observer need to convert a magnetic reading to true? |
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Definition
| When a magnetic compass is used to estimate wind direction. |
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Term
2-17
After obtaining the local variation from an aeronautical chart, how shall the variation be added to convert from true to magnetic wind? |
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Definition
| Add westerly variation to or subtract easterly variation from true direction. |
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Term
2-18
After obtaining the local variation from an aeronautical chart, how shall the variation be added to convert from magnetic to true direction? |
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Definition
| Add easterly variation to or subtract westerly variation from magnetic direction. |
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Term
2-19
What is the definition of wind speed? |
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Definition
| The horizontal speed of air past a given point. |
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Term
2-20
In gusty winds or squalls, when should the average wind speed not be determined? |
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Definition
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Term
2-21
How shall speed be determined? |
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Definition
| By averaging the speed to the nearest whole knot over a two-minute period. |
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Term
2-22
How shall wind speed be determined where direct-reading dials or recorders are used? |
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Definition
| By averaging the observed values. |
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Term
| 2-23 In what unit is wind speed always reported in surface observations? |
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Definition
| In whole knots, using two digits or three when necessary. |
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Term
2-24
When shall the wind be reported as calm? |
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Definition
| When no motion of the air is detected |
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Term
2-25
How is a calm wind coded? |
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Definition
| With five zeroes: 00000KT |
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Term
2-26
How is a calm wind recorded on the MF1M-10C? |
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Definition
| Three zeroes are recorded in Column 3 Wind direction, two zeroes are recorded in column 4 Wind speed, and the KT is not recorded. |
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Term
2-27
What is the definition of a gust? |
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Definition
| Rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. |
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Term
2-28
What shall be recorded as the speed of the gust? |
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Definition
| The maximum instantaneous speed observed. |
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Term
2-29
If occurring within what window of time relative to the observation shall a gust be reported in the body of the observation? |
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Definition
| When detected within 10 minutes prior to an observation that includes wind. |
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Term
2-30
How shall the transmitted coded group end for a wind observation? |
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Definition
| With the letters KT to indicate the unit of measurement is in knots. |
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Term
2-31
Where is the unit of measurement for wind recorded on the MF1M-10C? |
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Definition
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Term
2-32
Where is the letter "G" recorded on the MF1M-10C? |
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Definition
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Term
2-33
When recording estimated wind data, what information shall be annotated in column 65? |
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Definition
| That wind data is estimated and the reason for the estimation. |
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Term
2-34
Of the four elements to be recorded -- wind direction, speed, gusts and shifts -- which shall not be determined at all stations? |
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Definition
| All of the above shall be determined at all stations. |
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Term
| 2-35 List the two conditions under which the wind direction shall be considered to be variable. |
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Definition
| 1. During the two-minute evaluation period, the wind speed is 6 knots or less and the direction varies so it cannot be determined. 2. During the two-minute evaluation period, it varies or fluctuates by 60 degrees or more when the average wind speed is greater than 6 knots. |
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Term
2-36
When the direction is variable and the wind speed is 6 knots or less, how shall the wind direction be coded? |
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Definition
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Term
2-37
When a light and variable wind is recorded of 6 knots or less, how shall the extremes of variability be recorded in column 6? |
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Definition
| Under this condition, the extremes of variation are never recorded. |
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Term
2-38
When does an observer record a variable wind group in column 6? |
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Definition
| If the wind direction varies by 60 degrees or more and wind speed is greater than 6 knots during the two-minute evaluation period. |
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Term
2-39
How is a variable wind group coded? |
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Definition
| The extreme values are coded using three digits for each direction, in a clockwise direction with a V separating the two extreme values. |
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Term
2-40
Define the indication of a wind shift. |
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Definition
| A change in wind direction of 45 degrees of more over a less than 15 minute period with sustained wind speeds of 10 knots or more. |
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Term
2-41
In the Northern Hemisphere, a wind shift is associated with gusty winds shifting in a clockwise or counter-clockwise manner? |
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Definition
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Term
2-42
A wind shift is associated with a rapid rise or drop in both dew point and temperature? |
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Definition
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Term
2-43
A wind shift is associated with a rapid rise or drop in pressure? |
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Definition
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Term
2-44
In summer, a wind shift is associated with what conditions? |
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Definition
| lightning, thunder, heavy rain and hail. |
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Term
2-45
In winter, a wind shift is associated with what conditions? |
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Definition
| Frequent rain or snow showers. |
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Term
2-46
Where and when shall a wind shift be reported if one occurs? |
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Definition
| Always, and in the remarks section of a METAR/SPECI report. |
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Term
2-47
What type of observation shall be taken immediately after a wind shift occurrence? |
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Definition
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Term
| 2-48 What shall be included in a report regarding a wind shift? |
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Definition
| The wind shift and the time it occurred. |
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Term
2-49
What is regarded as the time of occurrence for a wind shift? |
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Definition
| The time the shift began. |
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Term
2-50
When are only the minutes required in the remarks of a report when a wind shift has occurred? |
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Definition
| When the hour can be inferred from the body of the report. |
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Term
2-51
When the shift is believed to be associated with a frontal passage, what shall be reported in the remarks section immediately after the time the shift began? |
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Definition
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Term
2-52
A SPECI containing a wind shift is NOT given long-line dissemination. How shall the wind data be given long-line transmission? |
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Definition
| It shall be included in the remarks section of the next transmitted report. |
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Term
2-53
How shall a wind shift associated with a frontal passage occurring at 17 minutes after the hour be reported in the remarks? |
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Definition
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Term
2-54
In what column of the MF1M-10C shall squalls be reported? |
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Definition
| Column 9 (Present Weather) |
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Term
2-55
What is the given definition of a squall? |
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Definition
| A sudden increase in average wind speed of at least 16 knots and sustained at 22 knots or more and lasting for at least one minute. |
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Term
2-56
The difference between gust and squall is ____________. |
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Definition
| The duration and intensity of the increase. |
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Term
2-57
For a squall to be reported, when shall they have occurred? |
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Definition
| Within ten minutes prior to the time of observation. |
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Term
2-58
What is the given definition of peak wind speed? |
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Definition
| The maximum instantaneous wind speed recorded that exceeds 25 knots since the last routine METAR. |
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Term
2-59
Which stations record peak wind data? |
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Definition
| Only designated stations, equipped with an instantaneous wind speed recorder. |
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Term
| 2-60 How is peak wind data determined by observers? |
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Definition
| By evaluating the wind speed recorder record. |
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