Updated: Dec 8, 2020
Weather Reports Lesson by wifiCFI
Service Outlets (PHAK C13)
Flight Service Station (FSS):
The FSS is the primary source for preflight weather information.
A preflight weather briefing from an FSS can be obtained 24 hours a day by calling 1-800-WX BRIEF from anywhere in the United States and Puerto Rico.
Telephone numbers for FSS can be found in the Chart Supplement U.S. (formerly Airport/Facility Directory) or in the United States Government section of the telephone book.
The FSS also provides in-flight weather briefing services and weather advisories to flights within the FSS area of responsibility.
Weather Briefings (PHAK C13)
A standard briefing provides the most complete information and a more complete weather picture.
This type of briefing should be obtained prior to the departure of any flight and should be used during flight planning.
Contents of a Standard Briefing:
This includes information about adverse conditions that may influence a decision to cancel or alter the route of flight.
Adverse conditions include significant weather, such as thunderstorms or aircraft icing, or other important items such as airport closings.
VFR Flight Not Recommended:
If the weather for the route of flight is below VFR minimums, or if it is doubtful the flight could be made under VFR conditions due to the forecast weather, the briefer may state “VFR flight not recommended.”
It is the pilot’s decision whether or not to continue the flight under VFR, but this advisory should be weighed carefully.
An overview of the larger weather picture.
Fronts and major weather systems that affect the general area are provided.
The current ceilings, visibility, winds, and temperatures.
If the departure time is more than 2 hours away, current conditions are not included in the briefing.
A summary of the weather forecast for the proposed route of flight.
A summary of the expected weather for the destination airport at the estimated time of arrival (ETA).
Forecast Winds and Temperatures Aloft:
A forecast of the winds at specific altitudes for the route of flight.
The forecast temperature information aloft is provided only upon request.
Notices to Airmen (NOTAMs):
Information pertinent to the route of flight that has not been published in the NOTAM publication.
Published NOTAM information is provided during the briefing only when requested.
An abbreviated briefing is a shortened version of the standard briefing.
It should be requested when a departure has been delayed or when weather information is needed to update the previous briefing.
An outlook briefing should be requested when a planned departure is 6 hours or more away.
It provides initial forecast information that is limited in scope due to the time frame of the planned flight.
This type of briefing is a good source of flight planning information that can influence decisions regarding route of flight, altitude, and ultimately the go/no-go decision.
Should be followed up with a Standard Briefing prior to the flight.
Service Outlets (PHAK C13)
Hazardous In-Flight Weather Advisory Service (HIWAS):
Hazardous Inflight Weather Advisory Service (HIWAS), available in the 48 conterminous states, is an automated continuous broadcast of hazardous weather information over selected VOR navigational aids (NAVAIDs).
The broadcasts include advisories such as AIRMETS, SIGMETS, convective SIGMETS, and urgent PIREPs.
The broadcasts are automatically updated as changes occur.
Weather Reports and Charts (PHAK C13) (AVW.GOV)
Aviation Routine Weather Report (METAR):
A METAR is an observation of current surface weather reported in a standard international format.
Decoding the METAR:
KOGD = Station Identifier
091753Z = Time and date of the report
VRB05KT = Wind direction and velocity
10SM = Visibilty
CLR = Sky condition
09/M02 = Temperature/Dewpoint
RMK = Remarks
A02 = Automated Station Type 2 (precipitation descriminator)
SLP257 = Sea Level Pressure of 1025.7
T00941022 = Specific Temperature/Dewpoint of 9.4 and -2.2
Which sky coverages count as “ceilings?”
PIREPs provide valuable information regarding the conditions as they actually exist in the air, which cannot be gathered from any other source.
Pilots can confirm the height of bases and tops of clouds, locations of wind shear and turbulence, and the location of inflight icing.
If the ceiling is below 5,000 feet, or visibility is at or below five miles, ATC facilities are required to solicit PIREPs from pilots in the area.
PIREPs are easy to file and a standard reporting form outlines the manner in which they should be filed.
UA/OV GGG 090025/TM 1450/FL 060/TP C182/SK 080 OVC/WX FV04SM RA/TA 05/WV 270030KT/TB LGT/RM HVY RAIN
There are 4 important elements that should be included when giving a PIREP.
Cloud bases and ceilings
Terminal Aerodrome Forecasts (TAF):
A TAF is a report established for the five statute mile radius around an airport. TAF reports are usually given for larger airports.
Each TAF is valid for a 24 or 30-hour time period and is updated four times a day at 0000Z, 0600Z, 1200Z, and 1800Z.
The TAF utilizes the same descriptors and abbreviations as used in the METAR report.
Decode the following Terminal Aerodrome Forecasts (TAF) Example:
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
AIRMETs (WAs) are examples of inflight weather advisories that are issued every 6 hours with intermediate updates issued as needed for a particular area forecast region.
The information contained in an AIRMET is of operational interest to all aircraft, but the weather section concerns phenomena considered potentially hazardous to light aircraft and aircraft with limited operational capabilities.
Types of AIRMETs:
IFR Conditions and Mountain Obscuration
SIGMETs (WSs) are inflight advisories concerning non-convective weather that is potentially hazardous to all aircraft.
They report weather forecasts that include:
Severe icing not associated with thunderstorms
Severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms
Dust storms or sandstorms that lower surface or in-flight visibilities to below three miles,
SIGMETs are unscheduled forecasts that are valid for 4 hours unless the SIGMET relates to a hurricane, in which case it is valid for 6 hours.
A Convective SIGMET (WST) is an inflight weather advisory issued for hazardous convective weather that affects the safety of every flight.
Convective SIGMETs are issued for severe thunderstorms with:
Surface winds greater than 50 knots
Hail at the surface greater than or equal to ¾ inch in diameter
They are also issued to advise pilots of:
Lines of thunderstorms
Thunderstorms with heavy or greater precipitation that affect 40 percent or more of a 3,000 square mile or greater region.
Each report is issued at 55 minutes past the hour, but special Convective SIGMETs can be issued during the interim for any reason.
Each forecast is valid for 2 hours.
Winds and Temperatures Aloft:
Winds and temperatures aloft forecasts (FB) provide wind and temperature forecasts for specific locations throughout the United States.
The forecasts are made twice a day based on the radiosonde upper air observations taken at 0000Z and 1200Z.
Winds and Temperatures Aloft Example: 731960
What is the wind direction, velocity, and temperature for STL at 39,000ft?
Break the report into 3 parts and perform the following math calculations:
73 - 50 = 230 Wind Direction
19 + 100 = 119 knot Wind Velocity
Make the last 2 numbers negative:
Surface Analysis Chart:
What is a trough?
An elongated area of low pressure.
What are isobars?
Lines of equal pressure.
What does it mean when isobars are close together?
High winds in that area.
Why are some pressure markings bold and underlined while others are not?
To indicate the highest or lowest pressure in the area.
The readings that indicate the high and low pressure systems.
Low Level Prognostic Chart:
The low-level chart is is a forecast of aviation weather hazards, primarily intended to be used as a guidance product for briefing the VFR pilot.
The forecast domain covers the 48 contiguous states, southern Canada and the coastal waters for altitudes below 24,000 ft.
Low altitude Significant Weather charts are issued four times daily and are valid at fixed times: 0000, 0600, 1200, and 1800 UTC.
Each chart is divided on the left and right into 12 and 24 hour forecast intervals.
Turbulence Chart: (symbology below chart)
Icing Chart: (symbology below chart)
Radar Summary Chart: (symbology below chart)
Indicate areas of precipitation, not cloud coverage.
Indicate cloud coverage, not areas of precipitation.
FAA Sources Used for this Lesson
Pilot’s Handbook of Aeronautical Knowledge (PHAK) Chapter 13