Forecasts
TW.........Surface Observation 3-hour trend
TAF........Terminal forecast
FD.........Winds Aloft Forecast
UA.........Pilot Reports
SD.........Radar Summaries
FDC........FDC NOTAMS (Facilities)
NO.........NOTAMs-Distant
FA.........Area Forecasts
The Area Forecast is best considered a 'dress rehearsal' in preparation for the big event.
WS.........SIGMETS
Warn all pilots of any weather up to 3000 square miles containing thunderstorms, icing, turbulence, or storms. Valid for four hours and named from November to Yankee except for Sierra and Tango which are reserved for warnings. SIGMETS follow area Forecast format.
WA.........AIRMETS
Conditions dangerous to small aircraft. Every six hours with six-hour outlook for moderate icing, turbulence, winds to 30 kts, less than 3 and ceilings below 1000'. Tango for turbulence, Zulu for icing
CWA........Center Weather Advisories
Conditions within two hours including real time PIREPs.
WST........Convective SIGMETS
Actual and forecast thunderstorms and level four or higher storms covering 40% of area. Numbered and lettered in sequence and area. NONE if no SIGMET 24,795 in 1996.
ATC........Flow Control Advisories
WH.........Hurricane and Tropical Depressions
A
AC.........Severe Weather Convective Outlook
A 24-hour perspective on thunderstorms less than severe.
10% is 'high' probability but when? Twice daily at 700Z and 1500Z valid for 24 hours. Goes with chart issued at 0800Z.
Every weather briefing must, according to the FAA, begin with an adverse weather advisory if such weather exists. There are several levels of such advisories. WHs are Hurricane Advisories, A Severe Weather Watch comes as a Bulletin called
TSNO........At the end of a weather observation to say that the station has no way to detect thunderstorms.
VNR.........VFR not recommended. Advisory appended to other items.
Special Notes
PE for ice pellets is being changed to PL to avoid a word when prefixed with RA for rain.
All VFR visibilities and cloud clearances are listed in FAR 91.155
METAR Sequence
When or SPECI (special weather report) sometimes data is omitted user must know and recognize sequence. Exceptions are RVR (runway visibility range) and SLP (sea level pressure) SPECI remarks will be in plain language.
1. wind information
2. prevailing visibility in statute miles
3. RVR information
4. Cloud layers and description as (FEW, SCT, BKN, OVC) with heights in three digits.
5. temperature and dewpoint in Celsius
6. Altimeter settings are begun with A or Q plus four digits
A2992 means given in inches and hundredths of mercury
Q1013 means hecto Pascals or centimeters of mercury
--RMK begins the remarks section which will include the sea level pressure
-- Always read in the past tense
METAR Sequence Another Way
----where
K first letter of all U. S. three letter identifiers making four letters. Alaska begins with PA, Hawaii with PH
-- when
First METAR time is six digits followed by Z. First two digits are day of month, last four are time of observation. All other times are four digits read in groups of two. From (or between) xx to xx.
----wind
First three digits are wind direction to nearer 10-degrees;. Next digits are wind speed usually in KT (knots) V between wind directions that vary more than 60-degrees and greater than 6 knots. VRB (variable) when less than 6 knots. Peak winds in remarks section with /time past hour of occurrence.
----Visibility
Fractions shown by /.SM (statute miles) follows.
Visual range uses R+runway/hundreds of feet. Letters other than R may be M(below sensor ability) P (above sensor ability) V (variable).
---- Weather
Two letter descriptor followed by two character weather type. Intensity - = light, none = moderate, + = heavy.
---- Clouds
Categorized on eights of the sky. (octas)
SKC = sky clear; FEW 1-2/8; SCT 3-4/8; BKN 5-7/8; PVC 8/8.
VV = vertical visibility; VV/// = indefinite ceiling
----Temperature/dewpoint
Listed in Celsius with / between. M = minus temperatures
---- Altimeter
A2992 if in inches. Q if metric.
ASOS/AWOS
AUTO included unless human makes remarks. Remarks tells number of sensors. CLR means no clouds below 1.
--Usually from airports
--Hourly at 50 minutes after hour
--Specials preceded by S
--Reports (METAR) whenever visibility is less than 6 miles.
--ASOS will more than double weather reporting sites
--ASOS measures weather at touchdown zones
--ASOS detects hourly changes and sends them to weather network
--ASOS weather is available by phone and radio
--ASOS issues special report if visibility is below three miles
--
Demo Sequences
OSM FG VV000
visibility, zero statuted miles; fog; vertical visibility, zero
Demo Sequence
KOAK 091720Z 1818 22020KT 4 SM -SHRA BKN020CB
Interpretation
Oakland, 9th day of month made at 1720 valid 1800 9th to 1800 10th Winds are as 220 degrees at 20KT as direction and velocity, variable winds given as 180V220 or as VRB08 Visibility given as 4 miles prevailing. If greater than 6 miles gives as P6S(statute) Weather given as light showers (-SH) and rain (RA)
Clouds are broken (BKN) at 2000' (020) and cumulonimbus.
KPHL 1550Z 2400T 7SM BKN009 OVC020 18/16 A3005
Interpretation
Philadelphia, PA 1550Z observation winds 270 degrees at 7 knots, visibility 7 statute miles, the ceiling is 900 broken with an overcast cloud deck at 2000 feet, temperature is 18 degrees centigrade, dew point 16 degrees centigrade, altimeter 30.05 inches
KLAX 1550Z 2100T 1/2SM R14/3500V5500FT FG OVC 003 14/14 A3018
Interpretation
Los Angeles, CA 1550Z observation, winds 210 degrees at 8 knots, visibility 1/2 mile (statute), runway 14 runway visual range (RVR) is 3500 feet variable to 5500 feet in fog. The ceiling is 300 feet overcast,
temperature 14 degrees centigrade, dew point 14 degrees centigrade, altimeter 30.18
KACY 1545Z 00000KT 11/4SM -SHSN BKNOO6 OVC010 MO3/M03 A2942 RMK SB30
Interpretation
Atlantic City, NJ 1545Z observation, winds calm, visibility 1 and 1/4 statute miles in light snow showers, the ceiling is 600 feet broken with an overcast cloud deck at 1000 feet, temperature is minus 3 degrees centigrade, dewpoint is minus 3 degrees centigrade, the altimeter is 29.42, and remarks indicate that the snow began falling at 1530Z.
KBUF 1549Z 35015G2T 1/4SM BLSN R31/1200FT VV003 01/M01 A3OI3
Interpretation
Buffalo, NY 1549Z Observation, winds are 330 degrees at 15 knots gusting to 27 knots with 1/4 mile )statute) visibility, runway 31 runway visual Range (RVR) is only 1200 feet, and the ceiling is indefinite 300 feet,
temperature is 1 degree centigrade, dew point is minus 1 degree centigrade and the altimeter is 30.13
KBOS 1549Z 1501T6SM -RASN SCT004 BKN009 VOC015 02/M01 A2949 RMK PRESFR
Interpretation
Boston, Mass. 1549Z observation, winds from 150 degrees at 12 knots, visibility 6 statute miles in mixed light rain and snow, scattered clouds at 400 feet, a broken ceiling at 900 feet and an overcast deck at 1500 feet, temperature is 2 degrees centigrade, dewpoint is minimum 1 degree centigrade, the altimeter is 29.49 and
remarks indicate that the pressure is falling rapidly.
KBWI 1550Z S0900T 3/4SM R10/3800FT -FZDZ PE 008OVC M01/M01 A2992
Interpretation
Baltimore, MD 1550Z Observation, winds directly out of the East (090 degrees) at 8 knots, with only 3/4's of a statute miles visibility, runway 10 has a runway visual range (RVR) of only 3800 feet in light freezing drizzle and ice pellets, with a ceiling of only 800 feet, temperature is minus 1 degree centigrade, a dew point of minus 1 degree centigrade and the altimeter is 29.90
METAR HIAD 081055 A 21019G2T 1/2SM RO4/3000FT-SN BR SCT011 OVC015 O1/O3 A2945 RMK SLP045
Interpretation
METAR - hourly report
HIAD - ICAO location indicator
081055 - Issuance time:" ALL times in UTC as a two digit date and a four digit time.
A - ??
21019G2T - three digit true north direction, nearest 10 degrees or VRB (variable); gusts to 27 knots.
1/2SM prevailing visibility in statute miles
R04/3000FT - runway number and visual range in feet
-SN BR - Light snow and mist (French)
SCT 011 - Scattered clouds at 1100'
OVC015 - Overcast 1500'
temperature 1° Celsius, dewpoint 3° Celsius
A2945 - Altimeter 29.45 inches of barometric pressure
RMK - remarks SLP045 - Sea level pressure 3045
KPHL 1550z 2400T 7SM BKN009 OVC020 18/16 A3005
Interpretation
Philadelphia, PA 1550Z observation. Winds 240 degrees at 7 knots, visibility 7 statute miles, the ceiling is 900 feet broken with an overcast cloud deck at 2000 feet, temperature 18 degrees centigrade, dewpoint 16 degrees centigrade, altimeter 30.05 inches of mercury.
KLAX 1550Z 2100T 1/2SM R14/3500V5500FT FG OVC003 14/14 A3018
Interpretation
Los Angeles, CA 1550Z observation, winds 210 degrees at 8 knots, visibility 1/2 statute mile, runway 14 runway visual range (RVR) is 3500 feet variable to 5500 feet in fog, the ceiling is 300 feet overcast, temperature is 14 degrees centigrade, dewpoint 14 degrees centigrade, altimeter 30.18 inches of mercury.
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