(Use for questions 1-6)
TAF
KSTL 161715Z 161818 16014G20KT P6SM SCT060 SCT120 TEMPO 1823 BKN120 BECMG 2324 19012KT SCT050 BKN120 PROB40 0006 19012G30KT 3SM TSRA OVC030CB BECMG 0607 20010KT -TSRA OVC030CB TEMPO 0813 20010G40KT 2SM +TSRA OVC015CB FM1400 25010KT BKN035 BKN100 PROB40 1518 5SM -TSRA =
1. The forecast conditions at 20Z are?
The KSTL TAF is valid for 24-hours and has four forecast time groups. The 20Z conditions are found in the first forecast time group from 18Z till 23Z, when conditions are forecasted to gradually change. 161818 16014G20KT P6SM SCT060 SCT120 TEMPO 1823 BKN120 BECMG 2324 The forecasted wind, visibility, and weather conditions are constant throughout the time group. The sky condition is predominantly scattered with a temporary (occasional) broken ceiling expected to occur for less than an hour at a time for less than half the time period. The TEMPO time period is 18Z to 23Z.
2. The forecast conditions at 03Z are?
The 03Z forecast falls within the second time group. BECMG 2324 19012KT SCT050 BKN120 PROB40 0006 19012G30KT SM TSRA OVC030CB BECMG 0607 Conditions forecasted during the second time group begin to gradually occur at 23Z and the changes are complete by 0000Z. All ending times of 0000Z in TAF reports are indicated by 24, including TEMPO, PROB40, and forecast valid period ending times. This time group is valid until another gradual change begins to occur at 06Z. During the time group there is a 30% but less than 50% probability (chance) of thunderstorms and rain developing from 00Z till 06Z. So, the forecast at 03Z would also include this chance of precipitation. If the thunderstorms and rain occur, the winds will become more gusty and the visibility and sky conditions will lower.
3. The forecast conditions at 12Z are?
The 12Z conditions are in the third time group. BECMG 0607 20010KT -TSRA OVC030CB TEMPO 0813 20010G40KT 2SM +TSRA OVC015CB FM1400 Conditions in this time group gradually occur between 06Z and 07Z and rapidly end at 1400Z. During the period, thunderstorms and light rain are forecasted to occur but visibility will remain above six miles. Temporarily or occasionally between 08Z and 13Z, which includes the 12Z forecast, those thunderstorms will become more intense with heavy rain, gusty winds and lowering visibility, and sky conditions.
4. What cloud type is forecast at 12Z?
CB. When cumulonimbus clouds are forecasted, the contraction, CB, is appended to the associated cloud layer. Cumulonimbus is the only cloud type forecast in TAF reports.
5. What is the forecast for weather at 1430Z?
NSW. The 1430Z forecast is in the fourth time group valid from 14Z till the end of the TAF valid period of 18Z. FM1400 25010KT BKN035 BKN 100 PROB40 1518 5SM -TSRA Between 14Z and 15Z, no weather appears in the FM group. Each FM group includes all the required elements -- wind, visibility, weather, sky conditions. When weather is omitted from a FM group, it is implied to be not significant to aviation.
6. What are the chances of thunderstorms developing after 15Z?
30% TO LESS THAN 50%. The 15Z forecast is in the fourth time group valid from 1400Z till the end of the TAF valid period at 18Z. FM1400 25010KT BKN035 BKN100 PROB40 1518 5SM -TSRA During this time group, there is a chance of thunderstorms and light rain occurring from 15Z till 18Z. The PROB40 group always indicates a chance of thunderstorms or some other precipitation event occurring along with associated weather conditions. The probability range is 30% up to but not including 50%.
(Use for questions 7-11)
TAF AMD
KSEA 161440Z 161512 23012KT P6SM SCT014 OVC020 TEMPO 1518 5SM -DZ BR BKN012 BECMG 1819 27008KT BKN022 BECMG 2022 30010KT SCT025
BECMG 0405 21012KT OVC015 =
7. The forecast conditions at 16Z are?
The KSEA TAF is an amended report issued at 1440Z and has four time groups. The 16Z forecast is found in the first time group which ends at 18Z, with a gradual change till 19Z. 161512 23012KT P6SM SCT014 OVC020 TEMPO 1518 5SM -DZ BR BKN012 BECMG 1819 During the first time group, conditions are temporarily affected by drizzle and mist between 15Z and 18Z, which includes the 16Z forecast. While drizzle and mist are occurring, the visibility and sky conditions will lower but wind remains constant throughout the time group.
8. The forecast conditions at 20Z are?
The 20Z forecast falls right at the beginning of the third time group which indicates a gradual change in winds and sky conditions. This change is forecast to be completed by 22Z. BECMG 1819 27008KT BKN022 BECMG 2022 30010KT SCT025 BECMG 0405 Until 22Z, we can only state that the winds and sky conditions are gradually changing from those in the second time group (18Z to 20Z) to those in the third time group (20Z to 04Z). Visibility and weather forecasts have not changed from the initial time group and therefore are omitted from the second and third time groups.
9. The forecast conditions at 08Z are?
The fourth time group from 04Z till the end of the forecast valid period at 12Z includes the 08Z forecast. BECMG 0405 21012KT OVC015 A gradual change in winds and sky conditions is forecasted to occur between 04Z and 05Z. The visibility and weather conditions are omitted because they are forecasted to remain the same as those forecasted in the initial time group.
10. How many hours is this forecast valid for?
21 HOURS. Since this is an amended TAF report, it is valid for less than the normal 24-hours. The amendment was issued at 1440Z and is valid from 15Z till 12Z, or 21 hours. Note, origin time and valid period are given as date/time groups. KSEA 161440Z 161512 The 16 indicates this TAF report was prepared on and is valid for the sixteenth day of the month.
11. How long will drizzle occur?
LESS THAN 1 1/2 HOURS. Drizzle is forecasted as part of the TEMPO group from 154Z till 18Z. The TEMPO group is used when conditions are expected to last for generally less than an hour at a time and are expected to occur during less than half the TEMPO time period. This TEMPO time period is three hours. So, the drizzle can be expected to occur during less than half the three hour time period, or less than 1 1/2 hours.
(Use for questions 12-16)
TAF
KJAX 161735Z 161818 32007KT P6SM BKN250 BECMG 1920 34007KT SCT035 BKN250 BECMG 2324 00000KT BKN035 BECMG 0708 10010KT 3SM BR BKN025
TEMPO 0813 1 1/2SM BR PROB40 1113 TSRA FM1300 20012KT P6SM SCT025 BKN250 TEMPO 1316 BKN025 BECMG 1617 19010KT SCT030 BKN250 =
12. The forecast conditions at 21Z are?
The KJAX TAF is valid for 24-hours and has six time groups. The 21Z forecast falls within the second time group. BECMG 1920 34007KT SCT035 BKN250 BECMG 2324 The conditions in this group gradually begin at 19Z and end gradually between 23Z and 0000Z. The only conditions changing from the initial time group (18Z till 19Z) are winds and sky conditions. Since visibility and weather are not changing, those items are omitted in the second time group.
13. The forecast conditions at 00Z are?
In this case, the 00Z forecast is the ending BECMG time. BECMG 2324 00000KT BKN035 BECMG 0708 Therefore, after 00Z conditions are no longer gradually changing, but have changed. The third time group will remain valid until the next gradual change beginning at 07Z. Again, visibility and weather have not changed and are omitted in this time group.
14. The forecast conditions at 11Z are?
The 11Z forecast is in the fourth time group, after 07Z till 1300Z. BECMG 0708 10010KT 3SM BR BKN025 TEMPO 0813 1 1/2SM BR PROB40 1113 TSRA FM1300 This time group includes a TEMPO group from 08Z till 13Z and a PROB40 group from 11Z till 13Z, which both apply to the 11Z forecast. Visibility during this time group is forecasted to lower due to mist with temporary periods of IFR visibility in mist. Then beginning at 11Z, there is a chance of thunderstorms and moderate rain developing until 13Z. The forecasted winds and sky conditions remain constant throughout the time group.
15. Describe the surface winds at 03Z?
CALM. The 03Z winds forecast is found in the third time group from 23Z till 07Z. This BECMG group is forecasting the winds to be 00000KT, which is the METAR/TAF way of encoding calm winds.
16. What event is forecast to occur after 13Z?
WARM FRONTAL PASSAGE. The FM indicator is used when a rapid change of prevailing conditions is expected. Typically, a rapid change of conditions is associated with a synoptic feature passing through the terminal area. The trend of the KJAX TAF is consistent with warm frontal passage. Ahead of the front winds are out of the east, visibility is reduced due to mist, and a lower broken ceiling develops, BECMG 0708 10010KT 3SM BR BKN025 As the front approaches, visibility lowers to IFR in mist and the chance of thunderstorm activity increases, TEMPO 0813 1 1/2SM BR PROB40 1113 TSRA After 1300Z every prevailing condition is forecasted to change rapidly, the winds shift to the southwest, visibility becomes more than six miles, the threat of thunderstorms diminishes, and the sky becomes scattered occasionally broken.
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