時間：2011-04-18 00:52來源：藍天飛行翻譯 作者：航空 點擊：次
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c. Aerodrome Forecast (TAF). A concise state-ment of the expected meteorological conditions at an airport during a specified period. At most locations, TAFs have a 24 hour forecast period. However, TAFs for some locations have a 30 hour forecast period. These forecast periods may be shorter in the case of an amended TAF. TAFs use the same codes as METAR weather reports. They are scheduled four times daily for 24.hour periods beginning at 0000Z, 0600Z, 1200Z, and 1800Z. Forecast times in the TAF are depicted in two ways. The first is a 6.digit number to indicate a specific point in time, consisting of a two.digit date, two.digit hour, and two.digit minute (such as issuance time or FM). The second is a pair of four.digit numbers separated by a “/” to indicate a beginning and end for a period of time. In this case, each four.digit pair consists of a two.digit date and a two.digit hour. TAFs are issued in the following format: TYPE OF REPORT/ICAO STATION IDENTIFIER/ DATE AND TIME OF ORIGIN/VALID PERIOD DATE AND TIME/FORECAST METEOROLOG-ICAL CONDITIONS NOTE. The “/” above and in the following descriptions are for separation purposes in this publication and do not appear in the actual TAFs. TAF KORD 051130Z 0512/0618 14008KT 5SM BR BKN030 TEMPO 0513/0516 1 1/2SM BR FM051600 16010KT P6SM SKC FM052300 20013G20KT 4SM SHRA OVC020 PROB40 0600/0606 2SM TSRA OVC008CB BECMG 0606/0608 21015KT P6SM NSW SCT040 TAF format observed in the above example: TAF = type of report KORD = ICAO station identifier 051130Z = date and time of origin (issuance time)0512/0618 = valid period date and times 14008KT 5SM BR BKN030 = forecast meteorolo-gical conditions Explanation of TAF elements: 1.Type of Report. There are two types of TAF issuances, a routine forecast issuance (TAF) and an amended forecast (TAF AMD). An amended TAF is issued when the current TAF no longer adequately describes the on-going weather or the forecaster feels the TAF is not representative of the current or expected weather. Corrected (COR) or delayed (RTD) TAFs are identified only in the communica-tions header which precedes the actual forecasts. 2.ICAO Station Identifier. The TAF code uses ICAO 4.letter location identifiers as described in the METAR section. 3.Date and Time of Origin. This element is the date and time the forecast is actually prepared. The format is a two.digit date and four.digit time followed, without a space, by the letter “Z.” 4.Valid Period Date and Time. The UTC valid period of the forecast consists of two four.digit Meteorology 7.1.67 sets, separated by a “/”. The first four.digit set is a two.digit date followed by the two.digit beginning hour, and the second four.digit set is a two.digit date followed by the two.digit ending hour. Although most airports have a 24.hour TAF, a select number of airports have a 30.hour TAF. In the case of an amended forecast, or a forecast which is corrected or delayed, the valid period may be for less than 24 hours. Where an airport or terminal operates on a part.time basis (less than 24 hours/day), the TAFs issued for those locations will have the abbreviated statement “NIL AMD SKED AFT (closing time) Z” added to the end of the forecasts. For the TAFs issued while these locations are closed, the word “NIL” will appear in place of the forecast text. A delayed (RTD) forecast will then be issued for these locations after two complete observations are received. 5. Forecast Meteorological Conditions. This is the body of the TAF. The basic format is: W I ND /V ISIB ILITY/WEAT HER / SKY CONDITION/OPTIONAL DATA (WIND SHEAR)The wind, visibility, and sky condition elements are always included in the initial time group of the forecast. Weather is included only if significant to aviation. If a significant, lasting change in any of the elements is expected during the valid period, a new time period with the changes is included. It should be noted that with the exception of a “FM” group the new time period will include only those elements which are expected to change, i.e., if a lowering of the visibility is expected but the wind is expected to remain the same, the new time period reflecting the lower visibility would not include a forecast wind. The forecast wind would remain the same as in the previous time period. Any temporary conditions expected during a specific time period are included with that time period. The following describes the elements in the above format. (a) Wind. This five (or six) digit group includes the expected wind direction (first 3 digits) and speed (last 2 digits or 3 digits if 100 knots or greater). The contraction “KT” follows to denote the units of wind speed. Wind gusts are noted by the letter “G” appended to the wind speed followed by the highest expected gust. A variable wind direction is noted by “VRB” where the three digit direction usually appears. A calm wind (3 knots or less) is forecast as “00000KT.” EXAMPLE. 18010KT . . . . . wind one eight zero at one zero (wind is blowing from 180). 35012G20KT . . wind three five zero at one two gust two zero. (b) Visibility. The expected prevailing visi-bility up to and including 6 miles is forecast in statute miles, including fractions of miles, followed by “SM” to note the units of measure. Expected visibilities greater than 6 miles are forecast as P6SM (plus six statute miles). EXAMPLE. 1/2SM . visibility one.half 4SM . visibility four P6SM . visibility more than six (c) Weather Phenomena. The expected weather phenomena is coded in TAF reports using the same format, qualifiers, and phenomena contractions as METAR reports (except UP). Obscurations to vision will be forecast whenever the prevailing visibility is forecast to be 6 statute miles or less. If no significant weather is expected to occur during a specific time period in the forecast, the weather phenomena group is omitted for that time period. If, after a time period in which significant weather phenomena has been forecast, a change to a forecast of no significant weather phenomena occurs, the contraction NSW (No Significant Weather) will appear as the weather group in the new time period. (NSW is included only in BECMG or TEMPO groups). NOTE. It is very important that pilots understand that NSW only refers to weather phenomena, i.e., rain, snow, drizzle, etc. Omitted conditions, such as sky conditions, visibility, winds, etc., are carried over from the previous time group. |
