Weather Services: METARs, TAFs, briefings and flight category

Report versus forecast, and flight categories 0:02:48

A REPORT gives current conditions; a FORECAST predicts future conditions. Flight categories classify conditions by ceiling and visibility.

VFR - ceiling GREATER than 3,000 ft AND visibility GREATER than 5 statute miles.

MARGINAL VFR - ceiling 1,000 to 3,000 ft, visibility 3 to 5 SM.

IFR - ceiling BELOW 1,000 ft or visibility BELOW 3 SM.

Part 107 needs 3 SM minimum, so IFR conditions are always disqualifying.

Forecasts are frequently wrong; they inform a go/no-go decision rather than guaranteeing conditions.

Where to get weather, and the three briefing types 0:04:35

Weather comes from aviationweather.gov, mobile apps, and Flight Service by telephone (1-800-WX-BRIEF), where a live briefer can be questioned.

STANDARD briefing - the most complete; get it the morning of the flight.

ABBREVIATED briefing - a shortened update when you have already had a standard.

OUTLOOK briefing - for flights more than 6 hours in the future.

Surface observations come from AWOS (Automated Weather Observing System) or ASOS (Automated Surface Observing System); for practical purposes they are interchangeable. Human-augmented observations are more precise.

These observations cover a small area but update frequently.

METAR - the Aviation Routine Weather Report 0:07:48

An hourly OBSERVATION of actual conditions at an airport, in a standardised international format. Special issuances (SPECI) appear when conditions change significantly.

The format is international - a METAR reads the same in Spain as in the US.

Station identifiers are four letters. K prefixes the contiguous US, C Canada, L southern Europe (LF France).

Decoding a METAR field by field 0:08:42

Fields appear in a fixed order - station, date/time, wind, visibility, weather, sky condition, temperature/dew point, altimeter, then remarks.

DATE/TIME - two digits day, four digits time, always ZULU.

WIND - three digits direction (TRUE north) plus speed in knots; G marks gusts; VRB means variable.

VISIBILITY - in statute miles; P means greater than.

SKY - CLR/SKC clear, FEW, SCT, BKN, OVC, each followed by height in HUNDREDS of feet (009 = 900 ft).

TEMPERATURE / DEW POINT - degrees Celsius; M prefix means minus.

ALTIMETER - A followed by four digits, inches of mercury (A3003 = 30.03).

REMARKS - RMK. A01 is a non-precipitation-discriminating station; A02 CAN distinguish precipitation type.

SLP - sea level pressure in hectopascals with the leading 10 or 9 omitted; SLP132 = 1013.2, SLP995 = 999.5.

A $ at the end means the station needs MAINTENANCE - treat its data with suspicion.

Other remarks - WSHFT (wind shift, suggesting frontal passage), RAB18 (rain began 18 past the hour), PK WND, PRESFR (pressure falling rapidly), and hourly precipitation totals.

The final T group gives temperature and dew point to a tenth of a degree.

I'm not just reading numbers. I'm making sense of them.0:14:40

The METAR weather code list 0:21:28

Weather is coded as intensity + descriptor + phenomenon.

INTENSITY - minus is light, nothing is moderate, plus is heavy. VC means vicinity.

DESCRIPTORS - SH shower, TS thunderstorm, FZ freezing, BL blowing, DR low drifting, MI shallow, PR partial.

PRECIPITATION - DZ drizzle, RA rain, SN snow, SG snow grains, IC ice crystals, PL ice pellets, GR hail, GS small hail/snow pellets, UP unknown.

OBSCURATION - BR mist, FG fog, FU smoke, VA volcanic ash, DU dust, SA sand, HZ haze.

OTHER - SQ squall, SS sandstorm, DS duststorm.

CLOUD SUFFIXES - CB cumulonimbus, TCU towering cumulus. Both signal thunderstorm activity and matter to you.

LIGHTNING - no qualifier means within 5 miles; VC means 5-10 miles; DSNT means beyond 10 miles. IC is in-cloud, CG is cloud-to-ground.

The instructor notes GR (hail) and BR (mist) come from French - 'grele' and 'brume'.

TAF - Terminal Aerodrome Forecast 0:25:40

A FORECAST for the area within about 5 statute miles of an airport, issued at larger airports only, valid 24 to 30 hours and updated FOUR times daily at 0000, 0600, 1200 and 1800 Zulu.

The header gives issue time, then the VALID PERIOD as from-day/hour to to-day/hour.

FM (from) - a permanent change beginning at that time; everything after replaces what preceded it.

TEMPO - temporary fluctuations expected to last less than an hour within the stated window.

PROB40 - a 40 percent probability of the stated conditions in that window.

AMD means amended - reissued early because conditions changed significantly, so its valid period is shorter.

Same field order and codes as the METAR, so decoding skill transfers directly.

The instructor's practical technique - do not read line by line; scan for the disqualifying keywords (wind, low visibility, mist, rain, CB) and check whether they fall in your operating window.

I'm not going to read each line like I did when I was reading them to you. I'm going to basically just read very quickly through the information and then get what I need out of it.0:26:48

Weather question technique 0:33:49

Exam weather questions supply a METAR or TAF block and ask you to extract one value or classify the conditions.

Flight-category questions - check BOTH ceiling and visibility, and remember only BKN/OVC count as ceiling.

Valid-period questions - the FIRST time group is the ISSUE time; the second is the valid period. Do not confuse them.

Wind questions - answer in TRUE degrees; the answer options usually omit the word 'true'.

Cloud-type questions - the only types forecast in a TAF are CB and TCU.

SPECI marks a special issuance rather than a routine hourly METAR.