APPENDIX D

WEATHER FORECASTS

STUDENT HANDOUT

TERMINAL LEARNING OBJECTIVE: Acting as an aviator and given an IFR or VFR flight mission and available weather information, the student will plan the flight for weather considerations in accordance with (IAW) AR 95-1 andFM 1-230.

SAFETY CONSIDERATIONS: None.

TRAINING RISK ASSESSMENT CODE: L.

ENVIRONMENTAL CONSIDERATIONS: None.

ENABLING LEARNING OBJECTIVE: Given pertinent information about a aviation terminal forecast, the student will identify and interpret the information contained in the forecast IAW FM 1-230.

1. Aviation Terminal Forecast (TAF).

a. Definition. AnAviation Terminal Forecast (TAF) is a concise statement of the expected meteorological conditions at an airport during a specified period (usually 24 hours).

(1) Issued by the National Weather Service for a defined area.

(2) Prepared one-half hour prior to scheduled transmission times.

(3) Scheduled for transmission four times daily 0000Z, 0600Z, 1200Z, and 1800Z (every 6 hours).

(4) Each TAF valid for 24 hours.

b. TAF report elements. (Use the TAF on page D-2 for KMGM as an example for bullets 1 – 5.)

(1) Type of report. (TAF) or Amended report (TAF AMD)

(2) ICAO station identifier. (KMGM)

(3) Date and time of origin. (9th day of the month, transmitted at 1750Z.)

(4) Valid forecast date and time. (Valid on the 9th day at 1800Z until the next day at 1800Z – valid for 24 hours.)

(5) Forecast meteorological conditions. Expected conditions read in METAR format.

c. Forecast change indicators are used when either a rapid, gradual, or temporary change is expected in some or all of the forecast conditions.

(1) From group—-FM is used when a rapid change, usually occurring in less than one hour, in prevailing conditions is expected.

 KMGM……….FM2030 30015G25KT 2SM BKN030 – “After two-zero-three-zero zulu, winds from three-zero-zero at one-five knots gusting to two-five knots, visibility two miles, ceiling zero-three-zero broken.”

(2) Becoming group—-BECMG is used when a gradual change is expected over a longer period of time, usually two hours.

 KTCL...... BECMG 1315 20010KT P6SM SKC – “Gradual change between 1300Z and 1500Z, winds two-zero-zero at ten knots, visibility greater than six miles, skies clear”

(3) Temporary group-—TEMPO is used for any conditions in wind, visibility, weather, or sky conditions which are expected to last for less than one hour at a time, and are expected to occur during less than half the time period.

KDHN……….TEMPO 1214 06010KT 1 SM +SHRA OVC010--“Occasional conditions between1200Z and 1400Z, winds zero-six-zero at ten knots, visibility one with heavy rain showers, ceiling one thousand broken.”

d. Probability forecast.

(1) PROB30 or PROB40 is used when the occurrence of thunderstorms or precipitation is in the 30 percent to less than 50 percent range.

(2) PROB30 or PROB40 will not be shown during the first six hours of a forecast.

  • KMGM……….PROB40 2224 30010KT 2SM SHRA OVC010 – “Forty-percent probability between 2200Z and 2400Z, winds three-zero-zero at ten knots, visibility two miles, rain showers, ceiling one thousand overcast.”

NOTE: Qualifiers and weather phenomena are the same as the METAR report.

(1)P6SM – visibility greater than 6SM. Military TAFs show visibility in meters rather than statute miles. “9999” on a military TAF means more than 6 SM.

(2)NSW – No significant weather expected

(3)CB only cloud type shown in TAF

(4)Wind Shear – WS010/18040

(5)QNH 3020 INS – Forecasted altimeter setting (Used only in military TAFS and foreign countries.)

TAF

KMGM 091750Z 091818Z 22020KT 5SM HZFU SCT010 BKN250

FM 2030 30015G25KT 2SM BKN030

PROB40 2224 30010KT 2SM SHRA OVC010

FM 0300 28010KT 2SM TSRA BKN250

FM 1200 27005KT 4SM FG OVC008

KPNS 091755Z 091818 16008KT 5SM FGHZ SCT030 BKN040

FM 2200 16010KT 4SM FG SCT020 BKN030

FM 0300 19010KT 7SM BKN040

TEMPO 0709 00000KT 5SM BKN008

FM 1200 19010KT 6SM OVC040

KTCL 091753Z 091818 22020KT 3SM –SHRA BKN020

FM 2030 24010KT WS015/30045KT 3SM SHRA OVC015

FM 2300 22010KT 5SM –SHRA BKN020 OVC040

FM 1000 22010KT 5SM –SHRA OVC020

BECMG 1315 20010KT P6SM SKC

KBHM 091750Z 091818 13020KT 6SM BKN030

FM 2100 15015KT 5SM FG SCT020 BKN030

FM 2400 14010KT 7SM BKN040CB

FM 1000 15005KT 7SM CLR

KANB 091755Z 091818 26015KT 4SM –SHRA SCT030 BKN050

FM 2300 24015G25KT 2SM +SHRA OVC040

BECMG 2401 24010KT 5SM –SHRA OVC050

FM 1000 27005KT 7SM SCT030 BKN050 OVC080

KATL 091752Z 091818 03005KT 10SM SCT030 SCT060

FM 2030 03015KT 6SM –SHRA BKN030

FM 0200 00000KT 2SM FG OVC020

FM 1000 04010KT 3SM HZ SCT030 OVC050

KDHN 091754Z 091818 00000KT 1/2SM FG VV003

BECMG 2022 02005KT 2SM FGHZ

FM 0100 03010KT 3SM –SHRA SCT008 BKN020

FM 1000 06015KT 4SM RA OVC020

TEMPO 1214 06010KT 1SM +SHRA OVC010

FM 1500 09010KT 5SM BKN010 BKN030 OVC060

ENABLING LEARNING OBJECTIVE: Given pertinent information about the winds aloft forecast chart, the student will identify and interpret levels, direction of winds, speed, and temperature IAW FM 1-230.

2. Winds Aloft Forecast Chart.

a. Computer prepared and issued by the National Meteorological Center (NMC) at Suitland, Maryland.

b. Data issued to both civil and military weather stations.

c. Valid for 12 hours.

d. Forecast levels.

(1) Dependent on stations’ elevation, but usually for 6, 9, 12, 18, 24, 30, 34, and 39. Thousand-foot levels.

(2) Through 12,000 feet the levels are MSL altitude; 18,000 feet and above are pressure altitude.

e. Direction of wind.

(1) Referenced to true north,to the nearest 10.

(2)The number by the wind arrow

is the middle digit of the wind direction.

f. Speed.

(1) Indicated by using arrowswith flags (the same as on surface weather charts).

(2) Less than 5 knots (99 – lightand variable).

g. Temperature.

(1) In degrees Celsius, given by anumber next to the station circle.

(2) Below zero temperatures preceded by minus.

Wind 240 at 25 knots Wind 040 at 15 knots

Temperature 3 (C) Temperature 3 below zero (C)


D-1