11/14/16 Aviation Weather Services AC 00-45H 1-9
• Density Altitude. The recording will include the statement “check density altitude” for any weather reporting point with a field elevation of 2,000 feet (ft) mean sea level (MSL) or above that meets certain temperature criteria.
• En Route Forecast. A summary of appropriate forecast data provided in logical order, e.g., climb out, en route, and descent.
• Winds Aloft. A summary of winds aloft forecast for the route/area.
• Request for PIREPs. When weather conditions within the area or along the route meet requirements for soliciting PIREPs, a request will be included in the recording.
• NOTAMs. Information that affects the route/area may be included as part of the briefing, on a separate channel, or obtained by direct contact with a pilot weather briefer.
• Military Training Activity. A statement is included in the closing announcement to contact a briefer for information on military training activity.
• Closing Announcement.
TIBS services may be reduced during the hours of 1800 to 0600, local time only.
Resumption of full broadcast service is adjusted seasonally to coincide with daylight hours. During the period of reduced broadcast, a recorded statement may indicate when the broadcast will be resumed and to contact Flight Service for weather briefing and other services.
For those pilots already in flight and needing weather information and assistance, the following services are provided by FSSs. They can be accessed over the proper radio frequencies printed in flight information publications.
1.3.4 Hazardous In-flight Weather Advisory Service (HIWAS).
HIWAS is a national program for broadcasting hazardous weather information continuously over selected Navigational Aids (NAVAID). The broadcasts include advisories such as AIRMETs, SIGMETS, Convective SIGMETs, and urgent PIREPs.
These broadcasts are only a summary of the information, and pilots should contact an FSS for detailed information.
The HIWAS broadcast area is defined as the area within 150 NM of HIWAS outlets.
HIWAS broadcasts are not interrupted or delayed, except for emergency situations, when an aircraft requires immediate attention, or for reasonable use of the voice override capability on specific HIWAS outlets in order to use the limited remote communications outlet (RCO) to maintain en route communications. The service is provided 24 hours a day. An announcement is made for no hazardous weather advisories.
Hazardous weather information is recorded if it is occurring within the HIWAS broadcast area. The broadcast includes the following elements:
• A statement of introduction including the appropriate area(s) and a recording time.
11/14/16 Aviation Weather Services AC 00-45H 1-10
• A summary of Convective SIGMETs, SIGMETs, AIRMETs, Urgent PIREPs, Aviation Watch Notification Messages (SAW), Center Weather Advisories, and any other weather, such as isolated thunderstorms that are rapidly developing and increasing in intensity, or low ceilings and visibilities that are becoming widespread, which are considered significant and are not included in a current hazardous weather advisory.
• A request for PIREPs, if applicable.
• A recommendation to contact FSS for additional details concerning hazardous weather.
Once the HIWAS broadcast is updated, an announcement will be made once on all communications/NAVAID frequencies, except emergency and navigational frequencies already dedicated to continuous broadcast services. In the event a HIWAS broadcast area is out of service, an announcement is made on all communications/NAVAID frequencies, except on emergency and navigational frequencies already dedicated to continuous broadcast services.
1.3.5 Flight Information Service-Broadcast (FIS-B).
FIS-B is a ground-based broadcast service provided through the FAA’s Automatic Dependent Surveillance-Broadcast (ADS-B) Services Universal Access Transmitter (UAT) network. The service provides users with a 978 megahertz (MHz)F data link capability when operating within range and line of sight of a transmitting ground station.
FIS-B enables users of properly-equipped aircraft to receive and display a suite of broadcast weather and aeronautical information products.
The following list represents the initial suite of textual and graphical products available through FIS-B and provided free-of-charge. This advisory circular (AC) and the current edition of AC 00-63, Use of Cockpit Displays of Digital Weather and Aeronautical Information, contain detailed information concerning FIS-B meteorological products.
AIM Chapter 3, Airspace; Chapter 4, Air Traffic Control; and Chapter 5, Air Traffic Procedures contain information on Special Use Airspace (SUA), TFR, and NOTAM products.
• Text: METAR and SPECI;
• Text: PIREP;
• Text: Winds and Temperatures Aloft;
• Text: TAF;
• Text: NOTAM Distant and Flight Data Center;
• Text/Graphic: AIRMET;
• Text/Graphic: SIGMET;
• Text/Graphic: Convective SIGMET;
• Text/Graphic: SUA;
11/14/16 Aviation Weather Services AC 00-45H 1-11
• Text/Graphic: TFR NOTAM; and
• Graphic: Next generation weather radar (NEXRAD) Composite Reflectivity Products (Regional and National).
Users of FIS-B should familiarize themselves with the operational characteristics and limitations of the system, including: system architecture, service environment, product lifecycles, modes of operation, and indications of system failure.
Update intervals are defined as the rate at which the product data is available from the source for transmission. Transmission intervals are defined as the amount of time within which a new or updated product transmission must be completed and/or the rate or repetition interval at which the product is rebroadcast. Table 1-1, FIS-B Over UAT Product Update and Transmission Intervals, provides update and transmission intervals for each product.
Where applicable, FIS-B products include a look-ahead range expressed in nautical miles for three service domains: Airport Surface, Terminal Airspace, and En route/Gulf of Mexico. Table 1-2, Product Parameters for Low/Medium/High Altitude Tier Radios, provides service domain availability and look-ahead ranging for each FIS-B product.
Prior to using this capability, users should familiarize themselves with the operation of FIS-B avionics by referencing the applicable user’s guides. Users should obtain guidance concerning the interpretation of information displayed from the appropriate avionics manufacturer.
Users should report FIS-B malfunctions not attributed to aircraft system failures or covered by active NOTAM via the ADS-B/Traffic Information Services-Broadcast (TIS-B)/FIS-B Problem Report on the following Web site:
http://www.faa.gov/exit/?pageName=this%20form&pgLnk=http%3A%2F%2Fgoo%2Egl %2Fforms%2FisWDKYpYYv. Users may also report malfunctions by submitting FAA Form 8740-5, Safety Improvement Report, via mail, fax, or email to your local Flight District Standards Office (FSDO) Safety Program Manager (SPM).
11/14/16 Aviation Weather Services AC 00-45H 1-12 Table 1-1. FIS-B Over UAT Product Update and Transmission Intervals Product FIS-B Over UAT Service Update Interval1 FIS-B Service Transmission Interval2 AIRMET As available 5 minutes Convective SIGMET As available 5 minutes METARs/SPECIs 1 minute/as available 5 minutes NEXRAD Composite Reflectivity (CONUS) 15 minutes 15 minutes NEXRAD Composite Reflectivity (Regional) 5 minutes 2.5 minutes NOTAMs–D/FDC/TFR As available 10 minutes PIREP As available 10 minutes SIGMET As available 5 minutes Special Use Airspace Status As available 10 minutes TAF/AMEND 8 hours/as available 10 minutes Temperature Aloft 12 hours 10 minutes Winds Aloft 12 hours 10 minutes
1. The Update Interval is the rate at which the product data is available from the source.
2. The Transmission Interval is the amount of time within which a new or updated product transmission must be completed and the rate or repetition interval at which the product is rebroadcast.
11/14/16 Aviation Weather Services AC 00-45H 1-13 Table 1-2. Product Parameters for Low/Medium/High Altitude Tier Radios Product Surface Radios Low Altitude Tier Medium Altitude Tier High Altitude Tier
CONUS NEXRAD
N/A CONUS NEXRAD not provided
CONUS NEXRAD imagery
CONUS NEXRAD imagery Winds & Temps Aloft 500 NM look-ahead range 500 NM look-ahead range 750 NM look-ahead range 1,000 NM look-ahead range METAR 100 NM look-ahead range 250 NM look-ahead range 375 NM look-ahead range CONUS: CONUS Class B & C airport METARs and 500 NM look-ahead range Outside of CONUS:
500 NM look-ahead range TAF 100 NM look-ahead range 250 NM look-ahead range 375 NM look-ahead range CONUS: CONUS Class B & C airport TAFs and 500 NM look-ahead range Outside of CONUS:
500 NM look-ahead range
AIRMET, SIGMET, PIREP and Special Use Airspace/SAA 100 NM look-ahead range.
PIREP/SUA is N/A 250 NM look-ahead Range 375 NM look-ahead range 500 NM look-ahead range Regional NEXRAD 150 NM look-ahead range 150 NM look-ahead range 200 NM look-ahead range 250 NM look-ahead range NOTAMs–D/FDC/TFR 100 NM look-ahead range 100 NM look-ahead range 100 NM look-ahead range 100 NM look-ahead range Users should obtain guidance concerning the content, format, and symbology of individual FIS-B products from the manufacturer of the avionics equipment used to receive and display them.
1.3.6 Operational Use of FIS-B Products.
FIS-B information may be used by the pilot for the safe conduct of flight and aircraft movement. However, FIS-B does not replace a preflight briefing from an FSS via the phone, a Lockheed Martin Flight Services or DUATS II via the Internet, or dispatch/System Operations Control (SOC) (if applicable). A pilot should be particularly alert and understand the limitations and quality assurance issues associated with individual products. This includes graphical representation of NEXRAD imagery and NOTAMs/TFR.
11/14/16 Aviation Weather Services AC 00-45H 2-1 CHAPTER 2. AVIATION WEATHER PRODUCT POLICY The demand for new and improved aviation weather products continues to grow, and with new products introduced to meet the demand, some confusion has resulted in the aviation community regarding the relationship between regulatory requirements and new weather products.
This chapter will clarify that relationship by providing:
• Policy guidance for using aviation weather products,
• Descriptions of the types of aviation weather information, and
• Categorization of the sources of aviation weather information.
2.1 Use of Aviation Weather Products.
This advisory circular (AC) describes the weather products distributed by the NWS.
Pilots and operators using the Internet to access weather from a third-party vendor should request and/or review an appropriate description of services and provider disclosure. This should include, but is not limited to, the type of weather product (i.e., current weather or forecasted weather), the currency of the product (i.e., product issue and valid times) and the relevance of the product. Pilots and operators should be cautious when using unfamiliar weather products. When in doubt, consult with a Flight Service Specialist.
Note that the FAA does not approve or qualify Internet providers of aviation weather service.
The development of new weather products, coupled with the termination of some legacy textual and graphical products, may create confusion between regulatory requirements and the new products. All flight-related aviation weather decisions must be based on all available pertinent weather products. As every flight is unique and the weather conditions for that flight vary hour-by-hour, day-to-day, multiple weather products may be necessary to meet aviation weather regulatory requirements. Many new weather products have a precautionary use statement displayed that details the proper use or application of the specific product.
2.2 Types of Aviation Weather Information.
The FAA has identified the following three distinct types of weather information that may be needed to conduct aircraft operations: observations, analyses, and forecasts.
2.2.1 Observations.
Observations are raw weather data collected by sensor(s). The observations can either be in situ (i.e., surface or airborne) or remote (i.e., weather radar, satellite, profiler, and lightning).
2.2.2 Analyses.
Analyses of weather information are an enhanced depiction and/or interpretation of observed weather data. Examples of these types of analyses can be seen in paragraph 4.1.1. Another type of analysis is the representation of an atmospheric variable
(e.g., temperature, ceiling height, and visibility) derived from a finite set of irregularly
11/14/16 Aviation Weather Services AC 00-45H 2-2 distributed observations onto a regular grid. See the figures in paragraph 4.2 for examples.
2.2.3 Forecasts.
Forecasts are the predictions of the development and/or movement of weather phenomena based on meteorological observations and various mathematical models.
In-flight weather advisories, including Terminal Aerodrome Forecast (TAF), significant meteorological information (SIGMET), Convective SIGMETs, Airman’s Meteorological Information (AIRMET), Center Weather Advisories (CWA), and Meteorological Impact Statements (MIS) are considered forecast weather information products.
2.3 Categorizing Aviation Weather Sources.
The regulations pertaining to aviation weather reflect that, historically, the Federal Government was the only source of aviation weather information. That is, the FAA and NWS, or their predecessor organizations, were solely responsible for the collection and dissemination of weather data, including forecasts. Thus, the term “approved source(s)” referred exclusively to the Federal Government. The Federal Government is no longer the only source of weather information, due to the growing sophistication of aviation operations and scientific and technological advances.
Since all three types of weather information defined in paragraph 2.2 are not available from all sources of aviation weather information, the FAA has categorized the sources as follows: Federal Government and commercial weather information providers.
2.3.1 Federal Government.
The FAA and NWS collect weather observations. The NWS analyzes the observations and produces forecasts, including in-flight aviation weather advisories (e.g., SIGMETs).
The FAA and NWS disseminate meteorological observations, analyses, and forecast products through a variety of systems. The Federal Government is the only approval authority for sources of weather observations (e.g., contract towers and airport operators).
Commercial weather information providers contracted by the FAA to provide weather observations (e.g., contract towers, Lockheed Martin, Direct User Access Terminal System (DUATS II)) are included in the Federal Government category of approved sources by virtue of maintaining required technical and quality assurance standards under FAA and NWS oversight.
2.3.2 Commercial Weather Information Providers.
Commercial weather information providers are a major source of weather products for the aviation community. In general, they produce proprietary weather products based on NWS information with formatting and layout modifications, but no material changes to the weather information itself. This is also referred to as “repackaging.”
In other cases, commercial providers produce forecasts, analyses, and other proprietary weather products which may substantially differ from the information contained in NWS-produced products. Operators who desire to use products prepared by a commercial weather provider, as opposed to using products that are simply repackaged, may require
11/14/16 Aviation Weather Services AC 00-45H 2-3 FAA approval. This approval is granted under the provisions in Operations Specification (OpSpec) paragraph A010. Please provide which services and products you are contemplating using, to include the appropriate description of the service. This should include, but is not limited to:
• The type of weather product (e.g., current weather or forecast weather);
• The currency of the product (i.e., product issue and valid times); and
• The relevance of the product.
Pilots and operators should be cautious when using unfamiliar products, or products not supported by FAA/NWS technical specifications.
11/14/16 Aviation Weather Services AC 00-45H 3-1 CHAPTER 3. OBSERVATIONS The first of three distinct types of weather (meteorological) information is observations.
Observations are weather data collected by one or more sensors, and are the basic information upon which forecasts and advisories are made in support of a wide range of weather-sensitive activities within the public and private sectors, including aviation. Chapter 3 describes and discusses surface observations, aircraft observations, radar observations, and satellite observations (e.g., imagery).
3.1 Aviation Routine Weather Reports (METAR) and Special Weather Reports (SPECI).
Surface weather observations are fundamental to all meteorological services. Aviators typically view surface observations through METARs and SPECIs. Although the METAR/SPECI code is used worldwide, there are some code differences among countries. Each country is allowed to make modifications to the code for use in their particular country, as long as they notify the International Civil Aviation Organization (ICAO). These paragraphs will focus on the METAR/SPECI code as used in the United States.
3.1.1 Aviation Routine Weather Report (METAR).
The METAR report has been adopted by the United States to provide surface observations in support of aviation for the terminal. A METAR report includes the airport identifier, time of observation, wind, visibility, Runway Visual Range (RVR), present weather phenomena, sky conditions, temperature, dewpoint, and altimeter setting.
Excluding the airport identifier and the time of observation, this information is collectively referred to as the “body” of the report. Coded and/or plain language information elaborating on data in the body may be appended to the end of the METAR as “remarks.” The contents of the remarks section varies with the type of reporting station. At some designated stations, the METAR may be abridged to include only a few of the mentioned elements.
3.1.2 Special Weather Report (SPECI).
A SPECI is an unscheduled report taken when any of the criteria given in Table 3-1, SPECI Criteria, are observed during the period between hourly reports. SPECIs contain all data elements found in a METAR. All SPECIs are issued as soon as possible when relevant criteria are observed.
Whenever SPECI criteria are met at the time of the routine METAR, a METAR is issued.
11/14/16 Aviation Weather Services AC 00-45H 3-2 Table 3-1. SPECI Criteria 1 Wind Shift Wind direction changes by 45 degrees or more, in less than 15 minutes and the wind speed is 10 knots or more throughout the wind shift.
2 Visibility Surface visibility, as reported in the body of the report, decreases to less than, or if below, increases to equal to or exceeding:
• 3 miles
• 2 miles
• 1 mile
• The lowest standard instrument approach procedure minimum as published in the National Ocean Service (NOS) U.S. Instrument Procedures. If none published, use ½ mile 3 Runway Visual Range (RVR) The highest value from the designated RVR runway decreases to less than, or if below, increases to equal to or exceeding 2,400 feet during the preceding 10 minutes. U.S. military stations may not report a SPECI based on RVR.
4 Tornado, Funnel Cloud, or Waterspout • • Is observed Disappears from sight, or ends 5 Thunderstorm
•
• Begins (a SPECI is not is currently reported) Ends required to report the beginning of a new thunderstorm if one 6 Precipitation
•
•
• Hail begins or ends Freezing precipitation begins, ends or changes intensity Ice pellets begin, end or change intensity 7 Squalls When a squall occurs.
8 Ceiling The ceiling (rounded to reportable values) forms or dissipates below, decreases to less than, or if below, increases to equal to or exceeding:
• 3,000 feet
• 1,500 feet
• 1,000 feet
• 500 feet
• The lowest standard instrument approach procedure minimum as published in the National Ocean Service (NOS) U.S. Instrument Procedures. If none published, use 200 feet.
9 Sky Condition A layer of clouds or obscurations aloft is present below 1,000 feet and no layer aloft reported below 1,000 feet in the preceding METAR or SPECI. was 10 Volcanic Eruption When an eruption is first noted.
11 Aircraft Mishap Upon notification of an aircraft mishap, unless there has been an intervening observation.
12 Miscellaneous Any other meteorological situation designated by the responsible agency of opinion of the observer, is critical. which, in the The information in Table 3-1 can be found in the Federal Meteorological Handbook No. 1 (FMH-1), Section 2.5.2, Aviation Selected Special Weather Report (SPECI).
11/14/16 Aviation Weather Services AC 00-45H 3-3
3.1.3 General Types of Observations.
There are three general types of surface observations:
• Manual Observation. Weather observations done by a human weather observer who is certified by the NWS or the FAA.
• Automated Observation. Automated observations are derived from instruments and algorithms without human input or oversight. In the United States, there are two main kinds of automated observing systems: the automated surface observing system (ASOS) and the Automated Weather Observing System (AWOS). Detailed information on ASOS and AWOS can be found in the Aeronautical Information Manual (AIM), Chapter 7, Safety of Flight, Section 1, Meteorology. Automated METARs and SPECIs contain AUTO in the report (see paragraph 3.1.5.4).
• Augmented Observation. At select airports in the United States, the automated observing system will have input and oversight by human weather observers or tower controllers certified in weather observing. These are referred to as augmented stations. Human observers report weather elements that are beyond the capabilities of the automated system and/or are deemed operationally significant. The weather elements observed and reported by the human observer vary, depending on the selected airport. AUTO is not used in augmented reports.
Whereas manual stations were most common prior to the mid-1990s in the United States, the vast majority of today’s METARs and SPECIs are from fully-automated stations.
3.1.4 Recency of Observed Elements at Automated Stations.
For those elements that the human observer evaluates using spatial averaging techniques
(e.g., sky cover and visibility), the automated station substitutes time averaging of sensor data. Therefore, in an automated observation, sky condition is an evaluation of sensor data gathered during the 30-minute period ending at the actual time of the observation.
All other elements are based on sensor data that is within 10 minutes or less of the actual time of the observation.
11/14/16 Aviation Weather Services AC 00-45H 3-4
3.1.5 Format.
Figure 3-1. METAR/SPECI Coding Format
A U.S. METAR/SPECI has two major sections: the body (consisting of a maximum of 11 groups) and the remarks (consisting of 2 categories). When an element does not occur, or cannot be observed, the corresponding group is omitted from that particular report.
3.1.5.1 Type of Report.
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132 The type of report, METAR or SPECI, precedes the body of all reports, but may not be shown or displayed on all aviation weather Web sites.
3.1.5.2 Station Identifier.
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132 The station identifier, in ICAO format, is included in all reports to identify the station to which the coded report applies.
The ICAO airport code is a four-letter alphanumeric code designating each airport around the world. The ICAO codes are used for flight planning by pilots and airline operation departments. These codes are not the same as the International Air Transport Association (IATA) codes encountered by the general public used for reservations, baggage handling, and in airline timetables.