Standard Wx Briefing

Weather Resources - Standard Wx Briefing

You should request a standard briefing any time you are planning a flight and you have not received a previous briefing.  The briefer will automatically provide the following information in the sequence listed, except as noted, when it is applicable to your proposed flight. 

1. Adverse Conditions - Significant meteorological and aeronautical information that might influence the pilot to alter the proposed flight; e.g., hazardous weather conditions, runway closures, NAVAID outages, etc. 

2. VFR Flight Not Recommended - When VFR flight is proposed and sky conditions or visibilities are present or forecast, surface or aloft, that in the briefer’s judgment would make flight under visual flight rules doubtful, the briefer will describe the conditions, affected locations, and use the phrase “VFR flight is not recommended.” This recommendation is advisory in nature. The final decision as to whether the flight can be conducted safely rests solely with the pilot. 

3. Synopsis - A brief statement describing the type, location and movement of weather systems and/or air masses which might affect the proposed flight.

NOTE - These first 3 elements of a briefing may be combined in any order when the briefer believes it will help to more clearly describe conditions.

4. Current Conditions - Reported weather conditions applicable to the flight will be summarized from all available sources; e.g., METARs, PIREPs, RAREPs. This element will be omitted if the proposed time of departure is beyond 2 hours, unless the pilot specifically requests the information. 

5. En Route Forecast - Forecast en route conditions for the proposed route are summarized in logical order; i.e., departure/climbout, en route, and descent. 

6. Destination Forecast - The destination forecast for the planned ETA. Any significant changes within 1 hour before and after the planned arrival are included. 

7. Winds Aloft - Forecast winds aloft will be summarized for the proposed route. The briefer will interpolate wind directions and speeds between levels and stations as necessary to provide expected conditions at planned altitudes. 

8. Notices to Airmen (NOTAMs)--

(a) Available NOTAM (D) information pertinent to the proposed flight.
(b) NOTAM (L) information pertinent to the departure and/or local area, if available, and pertinent FDC NOTAMs within approximately 400 miles of the FSS providing the briefing.

9. ATC Delays - Any known ATC delays and flow control advisories which might affect the proposed flight.

Computer Weather Briefing (from DUAT)

1. Area forecast
· Issued – three times a day for large areas
· Includes a synopsis and general forecast
· Includes a 12-hour specific clouds and weather forecast and a 6-hour categorical outlook
· Synopsis is a brief summary of location and movements of fronts, pressure systems, and circulation patterns

2. Convective SIGMETs
· Issued – any time required, and  updated as required at H+55
· Issued for any of the following:
· Severe thunderstorm due to:
· Surface winds greater than or equal to 50 knots
· Hail at the surface greater than or equal to ¾ inches in diameter
· Tornadoes
· Embedded thunderstorms
· A line of thunderstorms
· Thunderstorms greater than or equal to VIP level 4 affecting 40% or more of an area at least 3000 square miles

3. Center Weather Advisory
· Issued – as required.  Valid for up to two hours.
· Issued to update area forecasts with current conditions that affect ARTCC traffic operations.

4. AIRMETs and SIGMETs
AIRMETs
· Issued – on a scheduled basis every 6 hours.  Also updated and corrected as necessary.  Valid for a 6-hour period.

AIRMETs are significant for light aircraft and include
· AIRMET ZULU for moderate icing
· AIRMET TANGO for moderate turbulence or sustained surface winds of 30 knots or greater
· AIRMET SIERRA for IFR conditions affecting over 50% of the area or extensive mountain obscurement

SIGMETs
· Issued as necessary, and valid for a maximum of 4 hours.
· First issuance is UWS, further issuances are WS.

SIGMETs are significant for all aircraft, and include
· Severe icing not associated with thunderstorms
· Severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms
· Dust storms, sand storms, or volcanic ash lowering surface or in-flight visibilities to below 3 miles
· Volcanic eruption

5. Current surface observation – METAR reports are generally issued every hour by reporting stations.  SPECI reports are unscheduled reports that may be issued due to significant changes in weather or on demand.

METAR reports contain the following elements
· Type of report
· METAR – routine report
· SPECI – unscheduled report
· AMD – amended report
· COR – corrected report
· Station designator – ICAO designator
· Time of report, UTC – two digit date, four digit time
· Wind – three digits of direction, two or three-digit speed.  Gusty conditions are identified by the letter G followed by the peak gust value
· Visibility – statute miles, or P6SM for greater than 6 miles
· Weather and obstructions to visibility
 

Precipitation intensity descriptors + Heavy - Light (none) Moderate Proximity modifier VC  In the vicinity - between 5 and 10 miles of center of runway complex Obstructions to visibility FG – fog (visibility less than 5/8 mile) BR – mist (visibility 5/8 mile or greater) FU – smoke HZ – haze PY – spray SA – sand DU – dust VA – volcanic ash Precipitation RA – rain DZ – drizzle SN – snow SG – snow grains GR – hail (greater than ¼ inch) GS – small hail or snow pellets PE – ice pellets IC – ice crystals

Descriptors TS – thunderstorm SH – shower(s) FZ – freezing BL – blowing DR – drifting MI – shallow BC – patches Other SQ – squall DS – dust storm FC – funnel cloud, tornado or waterspout SS – sand storm PO – dust or sand swirls Sky condition - Reported in amount/height/type format: SKC – sky clear FEW – less than 1/8 coverage SCT – scattered (1/8 to 4/8 coverage) BKN – broken (5/8 to 7/8 coverage) OVC – overcast (8/8 coverage) Height – three digits giving cloud base height in hundreds of feet Type is optional, and only reported for cumulonimbus (CB) or towering cumulus (TCU)

Temperature and dewpoint - each is a two-digit Celsius number, preceded by M for negative values

Altimeter setting – four-digit number preceded by A

6. Pilot reports (PIREPs) - Pilot reports are preceded by the abbreviation UA, followed by any of the following:
/OV – location, usually specified by radial and distance from a VOR or airport
/TM – time, 4 digits UTC
/FL – altitude or flight level.  DURC is during climb, DURD is during descent
/TP – type of aircraft
/SK – cloud layers: (may not have all info)
Height of cloud base in hundreds of feet MSL
Cloud cover symbol – SCT, BKN, OVC, etc.
Height of cloud tops in hundreds of feet MSL
/WX – weather: visibility or other weather phenomena
/TA – temperature, degrees Celsius (negative with preceding minus sign)
/WV – wind direction and speed in six digits
/TB – turbulence: NEG, LGT, MDT, SEV, EXTREME, with comments
/IC – icing conditions: NEG, LGT, MDT, SEV with type (RIME, CLR, etc)
/RM – remarks

7. Radar summaries - Location and time of report

Radar code
· PPINE – equipment normal, no echoes
· PPIOM – equipment inoperative or out of service for maintenance
· PPINA – not available for some other reason
· ROBEPS – radar operating below performance standards
· ARNO – azimuth/range indicator inoperative
· RHINO – range-height indicator mode inoperative – height information not available

Or echo pattern 
· LN – a line of precipitation echoes at least 30 miles long, at least five times as long as wide, and at least 30% coverage within the line
· FINE LN – a clear air echo representing a strong temperature/moisture boundary such as an advancing dry cold front
· AREA – a group of echoes of similar type and not classified as a line
· SPRL BAND AREA – an area of precipitation associated with a hurricane that takes on a spiral band configuration around the center
· CELL – a single isolated convective echo such as a rain shower
· LYR – an elevated layer of stratiform precipitation not reaching the ground

Type, intensity and intensity trend of weather
· T – thunderstorms
· RW – rain showers
· - - light
· (none) – moderate
· + - Heavy
· ++ - very heavy
· X – intense
· XX – extreme
· U – unknown
· /+ - increasing
· /- - decreasing
· /NC – no change
· /NEW – new echo

Azimuth and range from station of points that define the pattern
Dimension of echo pattern
Pattern movement
Maximum top and location
Remarks – plain language explanations, optional
Digital section – used to prepare the report, contains no useful information for pilots

8. Terminal forecasts – TAF format - are issued four times a day (at 0000Z, 0600Z, 1200Z and 1800Z) and are valid for a 24-hour period.  They contain the following elements:

Type – routine forecast (TAF) or amended forecast (TAF AMD)
Location – ICAO designator
Issuance date and time – 6 digits, two date digits and four time digits, UTC
Valid period – 6 digits: two date digits, two two-digit hour fields for start and end hours of period
Forecast

The forecast field is in similar format as the METAR format – wind, visibility, weather, and sky conditions.

There are usually multiple forecast fields during the forecast period for changes during the period: 
· FMHHmm  - changes in weather beginning at time HHmm 
· BECMGHHhh – gradual changes in weather during the period HH00Z to hh00Z

There can be temporary conditions and probability forecasts within the forecast blocks:
· PROBxx HHhh – xx percent probability (30% to 50% range) between the hours of HH00Z to hh00Z of weather phenomena
· TEMPO HHhh – temporary occurrence between HH00Z and hh00Z of weather phenomena

9. Winds Aloft Forecast - Winds aloft forecasts are issued twice daily, and are valid for specific time intervals specified in the report.  Winds and temperatures are forecast for 3000, 6000, 9000, and 12,000 feet, and for flight levels 180, 240, 300, 340, and 390.  Winds are not available within 1500 feet of the station.  Temperature is not available at the 3000-foot level or within 2500 feet of the station. 

A wind/temperature group is a 6-digit encoding:
· Two digits for true wind direction (add a zero to get degrees)
· Two digits for wind speed in knots.  For winds in excess of 100 knots, 50 is added to the direction code.  For winds in excess of 199 knots, 199 knots is used.
· Two digits for temperature in degrees Celsius.  For altitudes at and below FL 240, temperatures are prefaced with a positive (+) or negative (-) indication.  Temperatures above FL240 are negative.

10. Notices to Airmen (NOTAMs) - are items of time-critical information that are either temporary or not known with sufficient advance notice to publish in the normal charts or publications.  The AIM contains a thorough abbreviation decoding table. 

There are three NOTAM categories:
· Local NOTAMs, or NOTAM (L) items include data related to airports such as airport closures, airport lighting outages and closed taxiways.
· Distant NOTAMs, or NOTAM (D) items are issued for navigational facilities that are part of the national airspace system and public use airports listed in airport and facility directories.
· FDC NOTAMs are issued by the National Flight Data Center and contain data on amendments to instrument approach procedures and other aeronautical chart data.  FDC NOTAMs are also issued for temporary flight restrictions based on natural disasters, presidential functions, etc.

Weather Charts

Surface Analysis Charts

Issued – every three hours.

Features
· Valid time
· Isobars
· Pressure systems
· Fronts
· Troughs and ridges
· Station information

Usage – good for getting detailed information on pressure systems, fronts, and overview of winds, temperatures and dew points.

Weather Depiction Chart

Issued – every three hours beginning at 01Z. Valid at the time of the plotted data.

Features
· Station surface observations – sky cover, cloud height and ceiling, weather, obstructions to vision, and visibility
· Analysis – regions of IFR, MVFR, and VFR 

Usage – good for a first-pass view of areas of favorable and adverse weather.

Radar Summary Chart

Issued – every hour at H+35 from available data.  Available 16 or 24 hours a day.

Features
· Echo type
· Intensity and intensity trend
· Echo configuration and coverage
· Echo heights
· Echo movement
· Severe weather watch areas

Usage – good for identifying areas and movement of precipitation and thunderstorms.  It does not necessarily identify areas of adverse weather and reduced visibilities.  Pay careful attention to radar sites that are not available (marked as NA)

Significant Weather Prognostic Charts (progs)

Issued – four times daily with 12- and 24-hour forecasts based on 00Z, 06Z, 12Z and 18Z synoptic data.

Features
· Four-panel chart with 12- and 24-hour forecasts for significant weather from the surface to 400 MB (about 24,000 feet) and for the surface.

Usage – used for outlook purposes.  Use to get a general picture of the weather conditions that are in the relatively distant future.

Winds and Temperatures Aloft Charts

Issued – daily for 12-hour progs valid at 12Z and 00Z.

Features
· For altitudes 6000, 9000, 12,000, 18,000, 24,000, 30,000,  34,000 and 39,000 feet MSL
· Shows wind direction and speed
· Shows temperature aloft

Composite Moisture Stability Chart

Issued – twice daily with valid times of 12Z and 00Z.

Features
· Four-panel chart – Stability Panel, Freezing Level panel, Precipitatable Water panel, Average Relative Humidity panel

Usage – most useful panel is lifted index panel. The top number is the lifted index, and the bottom number is the K-index.  The more negative the lifted index or the higher the K-index, the higher the chance for thunderstorms. The freezing level panel is also interesting for avoiding icing in IFR flight.