Weather forecasts are a combination of surface and upper altitude weather observations. To get the weather observation used to create forecast meteorologists use four types of weather observations, they are:
Surface observations are gathered by either an ASOS (automated surface observing system) or AWOS (automated weather observing system).
AWOS units are operated by the FAA, whereas ASOS units are not usually located on an airport, and are a joint system of the National Weather Service (NWS), FAA, and the
Department of Defense (DOD).
The information is then translated to a surface aviation weather observation (METAR), which are the current weather conditions along with other information for a given airport.
Upper air observations are a combination of pilot reports (PIREPs), Aircraft Meteorological Data Relay and the Meteorological Data Collection.
Four different types of radar systems take radar observations, these are:
NEXRAD (Doppler radar) provides in depth observations of weather.
FAA terminal Doppler weather radar (TDWA), which is at some major airports, it provides serve weather alerts and warnings to ATC.
Radar used to detect precipitation is also the same radar used by ATC to detect aircraft.
Airborne radar is radar equipment mounted to an aircraft to detect heavy precipitation, thunderstorms.
With advanced technology, satellites allow real-time weather information to individuals.
Outlets are serviced by several different agencies such as government, government contracts, and private agencies. The government agencies include the FAA, NOAA (National Oceanic Atmospheric Administration), and NWS (National Weather Service). Their job is to work together to provide different ways to access weather information.
FSS (Flight Service Station):
Is the primary source for obtaining a preflight weather briefing. They are operated 24 hours a day. To get a weather briefing call them on the phone from anywhere in the United States and Puerto Rico.
1-800 WXBRIEF (992-7433)
TIBS (Telephone Information Briefing Service):
TIBS is an automated telephone service provided by the FSS (Flight Service Station) of meteorological and aeronautical information. The automated system provides area and route briefings, airspace procedures, and any special announcements.
Recordings are automatically updated
TIBS phone numbers are listed in the Chart Supplement U.S.
Before every flight pilots are required to gather all information for that flight per FAR Part 91.103. It shows a list of items, you as a pilot should know or have on hand particular to that flight. One of them is getting a weather briefing for your local FSS (Flight Service Station). There are three types of weather briefings, they are:
This type of briefing should all ways be obtained prior to any flight. It provides the most information and best overall picture. The following items are provided in a Standard briefing in order:
Adverse conditions, VFR flight recommendation, Synopsis, Current conditions, En-route forecast, Destination forecast, Winds/Temps aloft, NOTAMS, ATC delays, and any other information to include the frequencies to open a flight plan with FSS or EFAS.
This briefing is a shortened or abbreviated version of a Standard Briefing. It is or should used to get an update on any changes to the standard, if there has been any delays on the departure of the flight.
These briefing should be used to get weather information 6 hours or more from the schedule departure time. An Outlook, is away to get information ahead of time to make any changes to the flight plan such as; route, altitude, or go/no-go.
Weather reports are designed and updated at different times, to show accurate and up to date current weather conditions.
Aviation Routine Weather Report (METAR), is an observation of the current weather conditions at a given time and location i.e. airport.
METAR’s are issued ever 50-55 minutes past the hour, and are valid for one hour or until a new one is released.
KSAN 281451Z 00000KT 10SM BKN200 BKN250 08/04 A3003 RMK AO2 SLP169 T00780039 53005
KSAN - METAR for San Diego International airport
Date and Time - 28 at 1451 Zulu
Wind direction and velocity - Calm
Visibility - 10SM (Statue Miles)
Cloud cover - BKN200, BKN 250 (Clouds are Broken at 20,000 and 25,000ft MSL)
Temperature/Dewpoint - 08⁰C and 04⁰C
Altimeter (A) - 30.03
RMK - Remarks section
AO2 - Automated station with a precipitation sensor
SLP - Sea Level Pressure 1016.9
A more detailed explanation about METARs see: How to understand a METAR
Pilots provide the only real time source of upper altitude weather observations. Pilots can give information regarding turbulence, icing, and cloud heights while inflight. PIREPs are very useful to ATC and FSS around.
It is always encouraged and very easy to give a PIREP when possible to ATC or a FSS.
UA /OV BFL /TM 1407 /FL035 /TP C172 /RM NEG
UA – Routine observation
/OV – location (/OV BFL – over Meadows airport)
/TM – time when the report was received 1407 Zulu
/FL – altitude or Flight Lever (FL 3,500ft)
/TP – Type aircraft (C172 – Cessna 172)
/RM – Remarks (NEG – no additional remarks)
A more detailed explanation about PIREPs see: How to Decode PIREPs
There are different types of forecasts that are used for the preflight. There are, four types of forecasts that pilot’s need to be familiar with. Below we have combined SIGMETS and AIRMETS into the Area Forecast section.
Winds and Temperatures Aloft
TAF (Terminal Aerodrome Forecast):
TAF (Terminal Aerodrome Forecast) are weather reports for a five statute mile radius usually around a larger airport. TAF’s are updated four times a day, 0000Z, 0600Z, 1200Z, and 1800Z. They are issued for 24 hour or 30-hour periods.
KONT 281739Z 2818/2924 VRB04KT P6SM BKN200 FM282100 20008KT P6SM SCT050 BKN150 FM282300 26014G22KT P6SM BKN040 FM290600 26009KT 2SM RA OVC009 FM291200 25006KT P6SM -SHRA SCT025 BKN035 FM291900 25010KT 6SM SHRA SCT015 BKN025 FM292300 25010KT P6SM VCSH SCT025 BKN040
Area Forecast (FA):
Area Forecasts cover a large area of several states and covers general weather conditions, visual meteorological conditions (VMC). Area Forecast are issued three times a day and a valid for 18 hours.
AIRMET, SIGMET, Convective SIGMET are inflight weather advisories that have detailed information on potential hazardous weather to inflight aircraft. These advisories are in conjunction with the Area Forecast.
AIRMETs (WA) are issued every six hours, they include surface winds of 30 knots or greater, ceilings less than 1,000 feet and visibility less than 3 miles. AIRMETs are broken down into three categories:
Sierra – IFR and mountain obstructions.
Tango – Turbulence, low-level wind shear, strong surface winds.
Zulu – Icing, freezing levels.
Synopsis gives a detailed summary of the location, movement and types of weather pressure systems, fronts, and circulation patterns.
SIGMETs (WS) are unscheduled weather forecasts valid for four hours. If a SIGMET is for a hurricane or typhoon than the SIGMET is valid for six hours. These reports are for severe or extreme turbulence or CAT (clear air turbulence) not associated with thunderstorms, dust storms, and volcanic ash.
Convective SIGMETs are issued at 55 minutes past the hour and are valid for 2 hours. Convective SIGMETs cover the areas of the lower 48 states not including Alaska and Hawaii.
They are broken up into three areas of the U.S.:
They are numbered from 1-99 starting at time 00Z. These reports are for tornadoes, hail of 2 inches or greater in diameter, wind gusts up to 65 knots.
(Convective SIGMET number 14 in the E-eastern region on the U.S.)
Winds and Temperatures aloft (FB):
Winds and Temperature aloft (FB) forecast is for wind and temperature forecasts for specific areas of the U.S., Hawaii and Alaska. They are issued twice a day at 0000Z and 1200Z.
No wind or temperature is forecasted from the surface to but not including 3,000 feet.
For winds and Temperature from 3000 – FL240 (24,000 feet) it is read as is.
SAC at 6000ft the wind/temp is 2125-01
(210⁰ at 25 knots -01⁰C)
For winds greater than 99 knots but less than 199 knots or above 30,000 feet, it has to be converted with the equation:
-50, +100 to the first 4 numbers. The last two numbers are always the temperature in negative Celsius.
SAN at 30000 the wind/temp is 216645
50 – 21 = 29 becomes 290⁰
then 66 + 100 = 166 knots
Therefore, the wind is 290⁰ at 166 knots -45⁰C
If the forecast indicates ‘9900’ than the winds are calm or less than 5 knots or light and variable.
Weather charts are used to show the overall view of the U.S. current or forecast weather. These charts show fronts and major weather systems as the move across the counter. There are three types of charts used, they are:
Surface Analysis Chart
Weather Depiction Chart
Surface Analysis Charts:
This charts show the current surface weather such as high and low pressure, fronts, temperature, dew point, wind direction and speed, etc. These three charts are issued every three hours and cover the lower 48 states.
Weather Depiction Charts:
They show the surface conditions derived from the METARs. These charts are issued every three hours starting at 0100Z. Weather depiction charts also shows areas of IFR, VFR, and MVFR (Marginal VFR) along with fronts, troughs, and squall lines.
IFR – Ceiling less than 1,000 feet with visibility less than 3 miles.
VFR – Ceiling greater than 3,000 feet or clear skies with visibility more than 5 miles.
MVFR – Ceilings 1,000 – 3,000 feet with visibility 3 – 5 miles.
These can be seen in two different ways, one is low-level form the surface up to FL240 (24,000 feet) and the other is high-level from FL250 – FL630 (25,000 - 63,000 feet). The low-level Prognostic chart is the primary chart to help brief the VFR pilots.
They are issued four times a day 0000Z, 0600Z, 1200Z and 1800Z. The Prognostic Charts are used to show freezing levels, turbulence, and low cloud ceilings or restricted visibly by area of MVFR and or IFR conditions.
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