Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
1.3 Dissemination of Aviation Weather Products The ultimate users of aviation weather services are pilots and aircraft dispatchers. Maintenance personnel may use the service to keep informed of weather that could cause possible damage to unprotected aircraft.
Pilots contribute to aviation weather services as well as use them. PIREPs help other pilots, dispatchers, briefers and forecasters as an observation of current conditions.
In the interest of safety and in compliance with Title 14, Code of Federal Regulations, all pilots should get a complete weather briefing before each flight. The pilot is responsible for ensuring he/she has all the information needed to make a safe flight.
1.3.1 Weather Briefings Prior to every flight, pilots should gather all information vital to the nature of the flight. This includes an appropriate weather briefing obtained from a specialist at an FSS, AFSS, or via Direct User Access Terminal Service (DUATS).
To provide an appropriate weather briefing, specialists need to know which of the three types of briefings is needed - a standard, abbreviated or outlook. Other helpful information is whether the flight will be conducted VFR or IFR, aircraft identification and type, departure point, estimated time of departure (ETD), flight altitude, route of flight, destination, and estimated time en route (ETE).
This information is recorded in the flight plan system and a note is made regarding the type of weather briefing provided. If necessary, it can be referenced later to file or amend a flight plan.
It is also used when an aircraft is overdue or is reported missing.
1.3.1.1 Standard Briefing A standard briefing provides a complete weather picture and is the most detailed of all briefings.
This type of briefing should be obtained prior to the departure of any flight and should be used during flight planning. A standard briefing provides the following information in sequential order if it is applicable to the route of flight.
1. Adverse Conditions - This includes info rmation about adverse conditions that may influence a decision to cancel or alter the route of flight. Adverse conditions include significant weather such as thunderstorms, aircraft icing, turbulence, wind shear, reduced visibilities and other important items such as airport closings.
2. VFR Flight NOT RECOMMENDED (VNR) - 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 that VFR is not recommended. The pilot can then decide whether or not to continue the flight under VFR, but this advisory should be weighed carefully.
3. Synopsis - The synopsis is an overview of the larger weather picture. Fronts and major weather systems along or near the route of flight and weather which may affect the flight are provided.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
4. Current Conditions - This portion of the briefing contains the current surface weather observations, pilot weather reports (PIREPs), satellite and radar data along the route of flight. If the departure time is more than 2 hours away, current conditions will not be included in the briefing.
5. En Route Forecast - The en route forecast is a summary of the weather forecast for the proposed route of flight.
6. Destination Forecast - The destination forecast is a summary of the expected weather for the destination airport at the estimated time of arrival (ETA).
7. Winds and Temperatures Aloft - Winds and temperatures aloft is a forecast of the winds at specific altitudes along the route of flight. However, the temperature information is provided only on request.
8. NOTAMs - This portion supplies Notice to Airmen (NOTAM) information pertinent to the route of flight which has not been published in the Notice to Airmen publication.
Published NOTAM information is provided during the briefing only when requested.
9. ATC Delays - This is an advisory of any known air traffic control (ATC) delays that may affect the flight.
10. Other Information - At the end of the standard briefing, the specialist will provide the radio frequencies needed to open a flight plan and to contact En Route Flight Advisory Service (EFAS). Any additional information requested is also provided at this time.
1.3.1.2 Abbreviated Briefing An abbreviated briefing is a shortened version of the standard briefing. It should be requested when a departure has been delayed or when specific weather information is needed to update a previous standard briefing. When this is the case, the weather specialist needs to know the time and source of the previous briefing so the necessary weather information will not be omitted inadvertently.
1.3.1.3 Outlook Briefing An outlook briefing should be requested when a planned departure is 6 or more hours away. It provides initial forecast information that is limited in scope due to the timeframe 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. A follow-up standard briefing prior to departure is advisable since an outlook briefing generally only contains information based on weather trends and existing weather in geographical areas at or near the departure airport.
The FSS/AFSS’s purpose is to serve the aviation community. Pilots should not hesitate to ask questions and discuss factors they do not fully understand. The briefing should be considered complete only when the pilot has a clear picture of what weather to expect. Pilots should also make a final weather check immediately before departure if at all possible.
1.3.2 Direct Use Access Terminal Service (DUATS/DUAT) The Direct User Access Terminal Service, which is funded by the FAA, allows any pilot with a current medical certificate to access weather information and file a flight plan via computer.
Two methods of access are available to connect with DUATS. The first is on the Internet AC 00-45F, CHG 2 Section 1: Aviation Weather Service Program Page 1-7
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) through Computer Sciences Corporation (CSC) at http://www.duats.com or Data Transformation Corporation at http://www.duat.com. The second method requires a modem and a communications program supplied by a DUATS provider. To access the weather information and file a flight plan by this method, pilots use a toll free telephone number to connect the user’s computer directly to the DUATS computer. The current vendors of DUATS service and the associated phone numbers are listed in Chapter 7 of the Aeronautical Information Manual (AIM).
1.3.3 Aviation Digital Data Service (ADDS) The Aviation Digital Data Service (ADDS) provides the aviation community with text, digital and graphical forecasts, analyses, and observations of aviation-related weather variables. ADDS is a joint effort of NOAA Forecast Systems Laboratory (FSL), NCAR Research Applications Laboratory (RAL), and the AWC.
1.3.4 Telephone Information Briefing Service (TIBS) The Telephone Information Briefing Service (TIBS) is a service prepared and disseminated by selected Automated Flight Service Stations. It provides continuous telephone recordings of meteorological and aeronautical information. Specifically, TIBS provides area and route briefings, as well as airspace procedures and special announcements, if applicable. It is designed to be a preliminary briefing tool and is not intended to replace a standard briefing from a flight service specialist. The TIBS service is available 24 hours a day and is updated when conditions change, but it can only be accessed by a TOUCH-TONE phone. The phone numbers for the TIBS service are listed in the Airport/Facility Directory (A/FD).
TIBS should also contain, but is not limited to: surface observations, TAFs, and winds/ temperatures aloft forecasts.
Each AFSS provides at least four route and/or area briefings. As a minimum, area briefings encompass a 50 NM radius. Pilots have access to NOTAM data through: Area or route briefings, on separate channels that are designated specifically for NOTAMs, or by access to a briefer.
Separate channels are designated for each route, area, local meteorological/aeronautical information, special event, airspace procedures, etc.
The order and content of the TIBS recording is as follows:
1. Introduction. Includes the preparation time and the route and/or the area of coverage.
The service area may be configured to meet the individual facility’s needs.
2. Adverse Conditions. A summary of Convective SIGMETs, SIGMETs, AIRMETs, Center Weather Advisories, Alert Severe Weather Watch Bulletins, and any other available information that may adversely affect flight in the route/area.
3. VNR Statement. Included when current or forecast conditions, surface or aloft, would make the flight under visual flight rules doubtful.
4. Synopsis. A brief statement describing t he type, location, and movement of weather systems and/or air masses that might affect the route or the area. This element may be combined with adverse conditions and/or the VNR element, in any order, when it will help to more clearly describe conditions.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5. Current Conditions. A summary of current weather conditions over the route/area.
PIREPs are included on conditions reported aloft and a summary of observed radar echoes. Specific departure/destination observation may also be included.
6. Density Altitude. The statement “check density altitude” will be included for any weather reporting point with a field elevation of 2,000 feet MSL or above that meets certain temperature criteria.
7. En Route Forecast. A summary of appropriate forecast data provided in logical order,
i.e., climb out, en route, and descent.
8. Winds Aloft. A summary of winds aloft forecast for the route/area as interpolate d from forecast data for the local and/or the adjacent reporting locations for levels through 12,000 feet. The broadcast should include the levels from 3,000 to 12,000 feet, but usually includes at least two forecast levels above the surface.
9. 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.
10. NOTAM 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.
11. Military Training Activity. A statement is included in the closing announcement to contact a briefer for information on military training activity.
12. Closing Announcement.
TIBS services may be reduced during the hours of 1800-0600 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 flight service stations. They can be accessed over the proper radio frequencies printed in flight information publications.
1.3.5 Hazardous Inflight Weather Advisory Service (HIWAS) HIWAS is a national program for broadcasting hazardous weather information continuously over selected navigational aids (NAVAIDs). 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/AFSS or En Route Flight Advisory Service (EFAS) 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.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Hazardous weather information is recorded if it is occurring within the HIWAS broadcast area.
The broadcast includes the following elements:
1. A statement of introduction including the appropriate area(s) and a recording time.
2. A summary of Convective SIGMETs, SIGMETs, AIRMET s, Urgent PIREPs, Aviation Watch Notification Messages, 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.
3. A request for PIREPs, if applicable.
4. A recommendation to contact AFSS/FSS/FLIGHT WATCH 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, EFAS, 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, EFAS, and navigational frequencies already dedicated to continuous broadcast services.
1.3.6 En Route Flight Advisory Service (EFAS) The purpose of EFAS, radio call “FLIGHT WATCH” (FW), is to provide en route aircraft with timely and pertinent weather data tailored to a specific altitude and route using the most current available sources of aviation meteorological information.
EFAS specialists tailor en route flight advisories to the phase of flight that begins after climb out and ends with descent to land. Current weather and terminal forecast at the airport of first intended landing and/or the alternate airport is provided on request. When conditions dictate, EFAS specialists provide information on weather for alternate routes and/or altitudes to assist the pilot in the avoidance of hazardous flight conditions. The pilot is advised to contact the adjacent flight watch facility when adverse weather conditions along the intended route extend beyond the Flight Watch Area (FWA).
EFAS is NOT used for routine in-flight services; e.g., flight plan filing, position reporting, or full route (pre-flight) briefings. If a request for information is received that is not within the scope of EFAS, the pilot is advised of the appropriate AFSS/FSS to contact.
EFAS specialists suggest route or destination changes to avoid areas of weather that in the judgment of the specialists constitutes a threat to safe flight.
EFAS is provided on 122.0 MHz to aircraft below FL180. An assigned discrete frequency is used to provide EFAS to aircraft at FL180 and above. This frequency can also be used for communications with aircraft below FL180 when communication coverage permits. Aircraft AC 00-45F, CHG 2 Section 1: Aviation Weather Service Program Page 1-10
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) operating at FL 180 or above that contact FW on frequency 122.0 MHz are advised to change to the discrete frequency for EFAS.
1.3.7 Automatic Dependent Surveillance – Broadcast (ADS-B) Automatic Dependent Surveillance–Broadcast (ADS-B ) is a surveillance system combining the advanced technologies of satellite positioning, aircraft avionics, and ground based transceivers.
ADS-B equipped aircraft automatically broadcast their identification, current position, altitude, and velocity information approximately once per second. This continuous broadcast of flight data, improves aircraft position accuracy beyond the capabilities of current NAS radar/transponder based surveillance systems.
In the United States, two different data links have been adopted for use with ADS −B: 1090 MHz Extended Squitter (1090ES) and the 978 MHz, Universal Access Transceiver (UAT). The 1090ES link is intended for aircraft that primarily operate at FL240 and above, whereas the UAT link is intended for use by aircraft that primar ily operate at lower altitudes. From a pilot’s standpoint, the two links operate similarly and support ADS −B and Traffic Information Services- Broadcast (TIS-B). The UAT link will provide additional weather and other aeronautical information through the Flight Information Service − Broadcast (FIS-B).
1.3.7.1 Flight Information Service – Broadcast (FIS-B) FIS-B provides certain aviation weather and other aeronautical information to aircraft equipped with an appropriate cockpit display. Reception of FIS-B services can be expected within a ground station coverage volume when line-of-sight geometry is maintained between the aircraft and ground station. NAS-wide service availability is targeted for 2013 and is currently available within certain regions.
1.3.7.1.1 FIS-B Products FIS-B provides the following textual and graphi cal aviation weather and aeronautical products free-of-charge. A detailed description of these products can be found within this Advisory Circular and the Aeronautical Information Manual (AIM).
Textual
• Aviation Routine Weather Reports (METARs) and Aviation Selected Special Weather Reports (SPECIs)
• Pilot Weather Reports (PIREPS)
• Terminal Aerodrome Forecasts (TAFs) and their amendments
• Winds and Temperatures Aloft
Graphical
• WSR-88D (NEXRAD) Weather Radar CONUS and regional-scale composite reflectivity mosaic products
Text/Graphical Overlay
• Notice to Airmen (NOTAM) Distant and Flight Data Center
• Airmen’s Meteorological Information (AIRMET)
• Significant Meteorological Information (SIGMET)
• Convective SIGMET
• Status of Special Use Airspace (SUA);
• Temporary Flight Restriction (TFR) NOTAMS
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) AC 00-45F, CHG 2 Section 1: Aviation Weather Service Program Page 1-12 Subject to FAA approval, additional products may be offered by the service provider in the future which may incur a usage fee.
1.3.7.1.2 Operational Use of FIS-B Products FIS-B products are intended to enhance the user’s situational awareness and enable more efficient use of ATC/FSS/AOCC services. The in formation provided by FIS-B is advisory in nature and should not be used in lieu of individual pre-flight, in-flight, weather, or flight planning briefings provided by ATC/FSS/AOCC services.
Specific guidance on the operational use of Flight Information Services can be found in Chapter 7, Safety of Flight of the AIM.
Guidance concerning the content, format, and symbology of individual FIS-B products should be obtained from the manufacturer of the avionics equipment used to receive and display them.
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 2 AVIATION WEATHER PRODUCT CLASSIFICATION AND 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 the new weather products.
This section will clarify that relationship by providing:
• classification of the weather products and policy guidance in their use,
• descriptions of the types of aviation weather information, and
• categorization of the sources of aviation weather information.
2.1 Classification of Aviation Weather Products The FAA has developed two classifications of aviation weather products: primary weather products, and supplementary weather products. The classifications are meant to eliminate confusion by differentiating between weather products that may be used to meet regulatory requirements and other weather products that may only be used to improve situational awareness.
All flight-related, aviation weather decisions must be based on the primary weather products.
Supplementary weather products augment the primary products by providing additional weather information, but may not be used as stand-alone products to meet aviation weather regulatory requirements or without the relevant primary products. When discrepancies exist between primary and supplementary products pertaining to the same weather phenomena, pilots must base flight-related decisions on the primary weather product. Furthermore, multiple primary products may be necessary to meet all aviation weather regulatory requirements.
Aviation weather products produced by the federal government (NWS) are primary products unless designated as a supplementary product by the FAA. In addition, the FAA may choose to restrict certain weather products to specific types of usage or classes of user. Any limitations imposed by the FAA on the use of a product will appear in the product label.
2.1.1 Primary Weather Product Classification A primary weather product is an aviation weather product that meets all of the regulatory requirements and safety needs for use in making weather-related flight decisions.
Note: Sections 3 through 8 of this Advisory Circular are considered Primary Weather Products.
2.1.2 Supplementary Weather Product Classification A supplementary weather product is an aviation weather product that may be used for enhanced situational awareness. A supplementary weather product must only be used in conjunction with one or more primary weather products. In addition, the FAA may further restrict the use of the supplementary weather products through limitations described in the product label.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Note: Section 9 of this Advisory Circular contains information on Supplementary Weather Products.
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 some type of sensor(s). The observations can either be in situ (e.g. surface or airborne) or remote (e.g. weather radar, satellite, profiler, and lightning).
2.2.2 Analysis Analyses of weather information are an enhanced depiction and/or interpretation of observed weather data.
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 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 its 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 2.3 are not available from all sources of aviation weather information, the FAA has categorized the sources as follows:
federal government, Enhanced Weather Information System (EWINS), 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).
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Commercial weather information providers contracted by the FAA to provide weather observations (e.g., contract towers) 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 Enhanced Weather Information System (EWINS) EWINS is an FAA-approved proprietary system for tracking, evaluating, reporting, and forecasting the presence or absence of adverse weather phenomena. EWINS is authorized to produce flight movement forecasts, adverse weather phenomena forecasts, and other meteorological advisories.
To receive FAA approval, EWINS-approved source must have sufficient procedures, personnel, and communications and data processing equipment to effectively obtain, analyze, and disseminate aeronautical weather data. For a full explanation of the requirements for EWINS approval, see the Air Transportation Operations Inspector’s Handbook, Order 8400.10, volume 3, chapter 7, section 5. An EWINS-approved source may produce weather analyses and forecasts based on meteorological observations provided by the federal government. Approval to use EWINS weather products is issued on a case by case basis and is currently only applicable to FAR part 121 and 135 certificate holders, who may either act as their own EWINS or contract those services from a separate entity. For these approved users, the weather analyses and forecasts produced by their approved EWINS are considered primary weather products as defined in paragraph 2.2.1, Primary Weather Products.
2.3.3 Commercial Weather Information Providers Commercial weather providers are a major source of weather products for the aviation community. In general, they produce proprietary weather products based on NWS products with formatting and layout modifications but no material changes to the weather information itself. This is also referred to as “repackaging.”
Commercial providers may also produce forecasts, analyses, and other proprietary weather products and substantially alter the information contained in NWS-produced products. Hence, operators and pilots contemplating using such services 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 (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. Commercially-available proprietary weather products that substantially alter NWS-produced weather products, or information, may only be approved for use by part 121 or part 135 operators or fractional ownership programs if the commercial provider is EWINS-qualified (see paragraph 2.4.2, above). Government products that are only repackaged and not altered, or products produced by EWINS-approved source, are considered primary weather products as defined in paragraph 2.2.1, Primary Weather Products.
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 3 OBSERVED TEXT PRODUCTS
3.1 Aviation Routine Weather Reports (METAR) and Aviation Selected Special Weather Reports (SPECI) Surface weather observations are fundamental to all meteorological services. Observations are the basic information upon which forecasts and warnings are made in support of a wide range of weather sensitive activities within the public and private sectors, including aviation.
Although the METAR/SPECI code is used worldwide, each country is allowed to make modifications or exceptions to the code for use in their particular country. This section will focus on the U.S. modifications and exceptions. METAR/SPECIs are available online at:
http://adds.aviationweather.gov/metars/
3.1.1 Aviation Routine Weather Report (METAR) Aviation Routine Weather Report (METAR) is the primary observation code used in the U. S. to satisfy World Meteorological Organization (WMO) and International Civil Aviation Organization (ICAO) requirements for reporting surface meteorological data. A METAR report includes the airport identifier, time of observation, wind, visibility, runway visual range, present weather phenomena, sky conditions, temperature, dew point, and altimeter setting. Excluding the airport identifier and the time of observation, this information is collectively referred to as “the body of the report.” As an addition, coded and/or plain language information elaborating on data in “the body of the report” may be appended to the end of the METAR in a section coded as “Remarks.” The contents of the “Remarks” section vary with the type of reporting station. The METAR may be abridged at some designated stations only including a few of the mentioned elements.
3.1.2 Aviation Selected Special Weather Report (SPECI) An Aviation Selected Special Weather Report (SPECI) is an unscheduled report taken when any of the criteria given in Table 3-1 are observed during the interim period between the hourly reports. SPECI contains all data elements found in a METAR plus additional plain language information which elaborates on data in the body of the report. All SPECIs are made as soon as possible after the relevant criteria are observed.
Whenever SPECI criteria are met at the time of the routine METAR, a METAR is issued.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
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 or exceed:
a. 3 miles
b. 2 miles
c. 1 mile
d. The lowest standard instrument approa ch 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 or exceed 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
a. is observed.
b. disappears from sight, or ends.
5 Thunderstorm a. begins (a SPECI is not required to report the beginning of a new thunderstorm if one is currently reported).
b. ends.
6 Precipitation a. hail begins or ends.
b. freezing precipitation begins , ends, or changes intensity.
c. ice pellets begin, end, or change intensity 7 Squalls When they occur 8 Ceiling The ceiling (rounded off to reportable values) forms or dissipates below, decreases to less than, or if below, increases to equal or exceed:
a. 3,000 feet.
b. 1,500 feet
c. 1,000 feet
d. 500 feet
e. The lowest standard instrument approa ch 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 was reported below 1,000 feet in the preceding METAR or SPECI.
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 which, in the opinion of the observer, is critical.
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