Chapter 3a

10. Altimeter Setting

-Reported as inches of mercury ("Hg) in a 4 digit number group (A2970) -Always preceded by the letter "A" -Rising or falling pressure may also be denoted in the "Remarks" section as "PRESFR," respectively

5. Wind

-Reported with 5 digits (14021KT) unless speed > 99 knots (in that case reported with 6 digits) -First 3 digits indicate direction the true wind is blowing from in tens of degrees -If wind is variable, reported as "VRB" -Last 2 digits indicate speed of wind in knots (unless the wind is greater than 99 knots, in which case it is indicated by 3 digits) -"G" follows the wind speed if winds are gusting (G26KT) -After "G," the peak gust recorded is provided -If wind direction varies more than 60 degrees and the wind speed is greater than 6 knots, a separate group of numbers, separated by a "V," will indicate the extremes of the wind directions

9. Temperature and Dew Point

-The air temperature and dew point are always given in degrees Celsius (C) of (18/17) -Temperatures below 0 degrees C are preceded by the letter "M" to indicate minus

Information Included in TAF

1. Type of report 2. ICAO station identifier 3. Date and time of origin 4. Valid period dates and times 5. Forecast wind 6. Forecast visibility 7. Forecast significant weather 8.Forecast sky condition 9. Forecast change group 10. PROB30

METAR report information in sequential order:

1. Type of report 2. Station identifier 3. Date and time of report 4. Modifier 5. Wind 6. Visibility 7. Weather 8. Sky condition 9. Temperature and dew point 10. Altimeter setting 11. Zulu time 12. Remarks

DOD

Department of Defense

7. Forecast Significant Weather (TAF)

Weather phenomena are coded in the TAF reports in the same format as the METAR.

Runway Visual Range (RVR)

the distance a pilot can see down the runway in a moving aircraft

3. Date and Time of Origin (TAF)

time and date (081125Z) of TAF origination is given in the six number code with the first two being the date, the last four being the time. Time is always given in UTC as denoted by the Z following the time block

NWS

National Weather Service

Convective Significant Meteorological Information (WST) or Convective SIGMETs

- Issued for severe thunderstorms with surface winds greater than 50 knots, hail at the surface greater than or equal to 3/4 inch in diameter, or tornadoes - Also issued to advise pilots of embedded thunderstorms, lines of thunderstorms, or thunderstorms with heavy or greater precipitation that affect 40% or more of a 3,000 square mile or greater region.

1. Type of Report (TAF)

- can either be a routine forecast (TAF) or an amended forecast (TAF AMD)

2. ICAO Station Identifier (TAF)

- same as that used in a METAR

1. Type of METAR Report:

-2 Types: 1. Routine METAR report that's transmitted on a regular time interval 2. Aviation selected SPECI - a special report that can be given at any time to update the METAR for rapidly changing weather conditions, aircraft mishaps, or other critical information

Terminal Aerodrome Forecasts (TAF)

-A report established for the five statute mile radius around an airport -Usually given for larger airports -Valid fo 24 to 30 hour time period; updated 4 x a day

11. Zulu Time

-A term used in aviation for UTC, which places the entire world on one time standard

8. Sky Condition

-Always reported in the sequence of amount, height, and type or indefinite ceiling/height (vertical visibility) (BKN008 OVC012CB, VV003) -Heights of cloud bases are reported with a 3 digit number in hundreds of feet AGL -Clouds above 12,000 feet are not detected or reported by an automated station -Towering cumulus (TCU) or cumulonimbus (CB) clouds, are reported with their height -Contractions are used to describe the amount of cloud coverage and obscuring phenomena -The amount of sky coverage is reported in eighths of the sky from horizon to horizon

Aviation Routine Weather Report (METAR)

-An observation of current surface weather reported in a standard international format -Issued on a regularly scheduled basis unless significant weather changes have occurred

7. Weather

-Can be broken down into two different categories: qualifiers and weather phenomenon (+TSRA BR) -Qualifiers of intensity, proximity, and the descriptor of the weather are given -Intensity: light (-), moderate ( ), or heavy (+) -Proximity: only depicts weather phenomena that are in the airport vicinity (usually 5-10 miles from airport) -Descriptors: used to describe certain types of precipitation and obscurations

Surface Aviation Weather Observations

-Compilation of elements of the current weather at individual ground stations across the US

4. Modifier

-Denotes that METAR/SPECI came from an automated source of that the report was corrected -If "AUTO" is listed, the report came from an automated source -"AO1": NO precipitation discriminator -"AO2": WITH precipitation discriminator ----both noted in "remarks" section to indicate the type of precipitation sensors employed at the automated station -"COR": identifies a corrected report sent out to replace an earlier report -Ex: METAR KGGG 161753Z COR

3. Date and Time of Report

-Depicted in a six-digit group (161753Z) -First 2 digits are the date -Last 4 digits are time of METAR/SPECI, always given in coordinated universal time (UTC) -"Z" is appended to the end of the time to denote the time is given in Zulu time (UTC) as opposed to local time

2. Station Identifier

-Four-letter code as established by the International Civil Aviation Organization (ICAO) -Unique three-letter identifier is preceded by the letter "K" -Ex: "KGGG," K being the country designation and GGG being the airport identifier -Alaska "PA," Hawaii "PH"

Surface Observations

-Provide local weather conditions and other relevant information for a specific airport -Information includes the type of report, station identifier, date and time, modifier (as required), wind, visibility, runway visual range (RVR), weather phenomena, sky condition, temperature/dew point, altimeter reading, and applicable remarks

12. Remarks

-Remarks section always begins with the letters "RMK" -May or may not appear in this section of the METAR -Information contained in this section may include wind data, variable visibility, beginning and ending times of particular phenomenon, pressure info, and various other info deemed necessary

Aviation Weather Reports

-designed to give accurate depictions of current weather conditions

6. Visibility

-the prevailing visibility (3/4 SM) is reported in a statute miles as denoted by the letters "SM" -Reported in both miles and fractions of miles -At times, RVR is reported following the prevailing visibility -When RVR is reported, it is shown with an R, then the runway number followed by a slant, then the visual range in feet -Ex: R17L/1400Ft: Visual range of 1,400 feet on runway 17 left

10. PROB30 (TAF)

A given percentage that describes the probability of thunderstorms and precipitation occurring in the coming hours. This forecast is not used for the first 6 hours of the 24-hour forecast.

AIRMET

Airman's Meteorological Information

ASOS

Automated Surface Observing Systems

AWOS

Automated Weather Observing Systems

FA

Aviation Area Forecast

FAA

Federal Aviation Administration

9. Forecast Change Group (TAF)

For any significant weather change forecast to occur during the TAF time period, the expected conditions and time period are included in this group. This information may be shown as from (FM), and temporary (TEMPO). "FM" is used when a rapid and significant change, usually within an hour, is expected. "TEMPO" is used for temporary fluctuations of weather, expected to last less than 1 hour.

6. Forecast Visibility (TAF)

Given in statute miles and may be in whole numbers or fractions. If the forecast is greater than six miles, it is coded as "P6SM."

8. Forecast Sky Condition (TAF)

Given in the same format as the METAR. Only CB clouds are forecast in this portion of the TAF report as opposed to CBs and towering cumulus in the METAR.

Example: METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

Routine METAR for Gregg County Airport for the 16th day of the month at 1753Z automated source. Winds are 140 at 21 knots gusting to 26. Visibility is 3/4 statute mile. Thunderstorms with heavy rain and mist. Ceiling is broken at 800 feet, overcast at 1,200 feet with cumulonimbus clouds. Temperature 18 degrees C and dew point 17 degrees C. Barometric pressure is 29.70 "Hg and falling rapidly.

Example: TAF KPIR 111130Z 1112/1212 TEMPO 1112/1114 5SM BR FM1500 16015G25KT P6SM SCT040 BKN250 FM120000 14012KT P6SM BKN080 OVC150 PROB30 1200/1204 3SM TSRA BKN030CB FM120400 1408KT P6SM SCT040 OVC080 TEMPO 1204/1208 3SM TSRA OVC030CB

Routine TAF for Pierre, South Dakota...on the 11th day of the month, at 1130Z...valid for 24 hours from 1200Z on the 11th to 1200Z on the 12th...wind from 150° at 12 knots... visibility greater than 6 SM...broken clouds at 9,000 feet... temporarily, between 1200Z and 1400Z, visibility 5 SM in mist...from 1500Z winds from 160° at 15 knots, gusting to 25 knots visibility greater than 6 SM...clouds scattered at 4,000 feet and broken at 25,000 feet...from 0000Z wind from 140° at 12 knots...visibility greater than 6 SM...clouds broken at 8,000 feet, overcast at 15,000 feet...between 0000Z and 0400Z, there is 30 percent probability of visibility 3 SM...thunderstorm with moderate rain showers...clouds broken at 3,000 feet with cumulonimbus clouds...from 0400Z...winds from 140° at 8 knots...visibility greater than 6 miles...clouds at 4,000 scattered and overcast at 8,000... temporarily between 0400Z and 0800Z...visibility 3 miles... thunderstorms with moderate rain showers...clouds overcast at 3,000 feet with cumulonimbus clouds...end of report (=).

RVR

Runway Visual Range

SIGMET

Significant Meteorological Information

TAF

Terminal Aerodrome Forecast

4. Valid Period Dates and Times (TAF)

The TAF valid period (0812/0912) follows the date/time of forecast origin group. Scheduled 24 and 30 hour TAFs are issued four times per day, at 0000, 0600, 1200, and 1800Z. The first two digits (08) are the day of the month for the start of the TAF. The next two digits (12) are the starting hour (UTC). 09 is the day of the month for the end of the TAF, and the last two digits (12) are the ending hour (UTC) of the valid period. A forecast period that begins at midnight UTC is annotated as 00. If the end time of a valid period is at midnight UTC, it is annotated as 24. For example, a 00Z TAF issued on the 9th of the month and valid for 24 hours would have a valid period of 0900/0924.

5. Forecast Wind (TAF)

The wind direction and speed forecast are coded in a five-digit number group. An example would be 15011KT. The first three digits indicate the direction of the wind in reference to true north. The last two digits state the wind speed in knots appended with "KT." Like the METAR, winds greater that 99 knots are given in three digits.

FB

The winds and temperatures aloft forecast