Fzfg Aviation

[Finnis Springer]

Freezingdrizzle relies on moist stratus clouds with weak updrafts to release small droplets as they become too heavy. Unlike freezing rain, freezing drizzle starts as SLD (supercooled large droplets) that coalesce and grow to a size large enough to fall from the clouds as drizzle.

According to the FAA, freezing rain is created when snow falls through a warm layer, then through a sub-zero layer of air - also known as a temperature inversion. These drops fall through the freezing layer so quickly that they don't have time to completely freeze before they get to the ground.

Supercooling is a state where a liquid is below freezing but isn't a solid (in this case, ice), meaning that as the droplets fall through the atmosphere they can't crystalize. But when supercooled droplets impact a surface of your aircraft, they stick and freeze.

Large drops, like you'd expect with freezing rain, can form a heavy glaze on your airframe (clear ice) that can be difficult to remove, especially if ice forms aft of de-icing equipment. Clear ice can also be hard to see because of its smooth, transparent appearance.

Inadvertent icing encounters with freezing rain can be deadly, the NTSB is still investigating a recent Cessna 210 crash in Lubbock, Texas where freezing rain is suspected to be a significant contributing factor.

On January 19th, 2023, northeast upslope winds kept a shallow moisture plume aloft in the Denver area. Paired with the cold surface temperatures, freezing drizzle coated almost everything on the ground. Later in the day as the moist layer of air got thicker, ice crystals began forming aloft. Those ice crystals served as a condensation nuclei, and the freezing drizzle started sticking to the ice crystals aloft. As soon as that happened, the freezing drizzle was replaced by light snow.

The process to create freezing fog is essentially the same as freezing drizzle. What's the difference? Once the visibility drops below 1/2 mile, METARs report freezing fog (FZFG) instead of freezing drizzle (FZDZ).

Just like radiation fog, freezing fog forms on clear, calm nights. Subzero temperatures supercool water droplets in the air. But without any cloud condensation nuclei to adhere to, these super-small droplets freeze to whatever they come into contact with. In most cases trees, the ground, roads, and your aircraft. Everything becomes covered in a glass-like glaze.

Nicolas is a flight instructor from Southern California. He is currently studying aviation at Purdue University. He's worked on projects surrounding aviation safety and marketing. You can reach him at nic...@boldmethod.com.

METAR is a format for reporting weather information. A METAR weather report is predominantly used by aircraft pilots, and by meteorologists, who use aggregated METAR information to assist in weather forecasting. Today, according to the advancement of technology in civil aviation, the METAR is sent as IWXXM model.[1]

Raw METAR is the most common format in the world for the transmission of observational weather data.[citation needed] It is highly standardized through the International Civil Aviation Organization (ICAO), which allows it to be understood throughout most of the world.

In its publication the Aeronautical Information Manual, the United States Federal Aviation Administration (FAA) describes the report as aviation routine weather report,[2] while the international authority for the code form, the World Meteorological Organization (WMO), describes it as the aerodrome routine meteorological report. The National Oceanic and Atmospheric Administration (part of the United States Department of Commerce) and the United Kingdom's Met Office both employ the definition used by the FAA. METAR is also known as Meteorological Terminal Aviation Routine Weather Report[3] or Meteorological Aerodrome Report.[4]

METARs typically come from airports or permanent weather observation stations. Reports are generated once an hour or half-hour at most stations, but if conditions change significantly at a staffed location, a report known as a special (SPECI) may be issued. Some stations make regular reports more frequently, such as Pierce County Airport (ICAO code: KPLU) which issues reports three times per hour. Some METARs are encoded by automated airport weather stations located at airports, military bases, and other sites. Some locations still use augmented observations, which are recorded by digital sensors, encoded via software, and then reviewed by certified weather observers or forecasters prior to being transmitted. Observations may also be taken by trained observers or forecasters who manually observe and encode their observations prior to transmission.[citation needed]

The METAR format was introduced internationally on 1 January 1968, and has been modified a number of times since. North American countries continued to use a Surface Aviation Observation (SAO) for current weather conditions until 1 June 1996, when this report was replaced with an approved variant of the METAR agreed upon in a 1989 Geneva agreement. The WMO's publication No. 782 "Aerodrome Reports and Forecasts" contains the base METAR code as adopted by the WMO member countries.[5]

A typical METAR contains data for the temperature, dew point, wind direction and speed, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as a pilot report or PIREP, colour states and runway visual range (RVR).

In addition, a short period forecast called a TREND may be added at the end of the METAR covering likely changes in weather conditions in the two hours following the observation. These are in the same format as a Terminal Aerodrome Forecast (TAF).

METAR code is regulated by the World Meteorological Organization in consort with the International Civil Aviation Organization. In the United States, the code is given authority (with some U.S. national differences from the WMO/ICAO model) under the Federal Meteorological Handbook No. 1 (FMH-1), which paved the way for the U.S. Air Force Manual 15-111[6] on Surface Weather Observations, being the authoritative document for the U.S. Armed Forces. A very similar code form to the METAR is the SPECI. Both codes are defined at the technical regulation level in WMO Technical Regulation No. 49, Vol II, which is copied over to the WMO Manual No. 306 and to ICAO Annex III.

Although the general format of METARs is a global standard, the specific fields used within that format vary somewhat between general international usage and usage within North America. Note that there may be minor differences between countries using the international codes as there are between those using the North American conventions. The two examples which follow illustrate the primary differences between the two METAR variations.[7][8]

North American METARs deviate from the WMO (who write the code on behalf of ICAO) FM 15-XII code. Details are listed in the FAA's Aeronautical Information Manual (AIM), but the non-compliant elements are mostly based on the use of non-standard units of measurement. This METAR example is from Trenton-Mercer Airport near Trenton, New Jersey, and was taken on 5 December 2003 at 18:53 UTC.

METARs can be expressed concisely using so-called aviation flight categories, which indicates what classes of flight can operate at each airport by referring to the visibility and ceiling in each METAR. Four categories are used in the U.S.:[16]

METAR abbreviations used in the weather and events section. Remarks section will also include began and end times of the weather events.[17] Codes before remarks will be listed as "-RA" for "light rain". Codes listed after remarks may be listed as "RAB15E25" for "Rain began at 15 minutes after the top of the last hour and ended at 25 minutes after the top of the last hour."

Meteorological service for international aviation is provided by meteorological authorities designated by States.

The actual weather observations at aerodromes and offshore structures are made by aeronautical meteorological stations. The specific types of observations and related reports are disseminated either locally, or to other aerodromes.

Observations of meteorological conditions are made by means of instruments and visual estimation and are used for landing and take-off, en-route navigation and flight performance, and as a basis for forecasting.

High-quality and timely meteorological observations and reports for international air navigation are the foundation upon which an effective aeronautical meteorological service is based and of direct consequence to aviation safety.

OPMET information includes aerodrome reports, landing forecasts, aerodrome forecasts, special aircraft observations, SIGMET and AIRMET information, tropical cyclone and volcanic ash advisories and WAFS forecasts.

When required as a result of specified operationally significant changes in the meteorological conditions, special observations and reports are made whenever such changes occur between routine observations.

Depending on their use, the reports are presented in two forms:

ㅤ- Aerodrome routine meteorological report named METAR is local routine and special reports in abbreviated plain language intended for dissemination and use at the aerodrome of origin

ㅤ- Aerodrome special meteorological report named SPECI is intended for dissemination and use beyond the aerodrome of origin.

A SPECI is identical to a METAR with the difference that it is not created regularly but from time to time. It is a special observation message showing a punctual meteorological event that occurred since the last METAR or SPECI published. The issuance of a SPECI is not necessary if METAR are issued at half-hour intervals.

The METAR and SPECI code forms were developed by the World Meteorological Organization on the basis of aeronautical requirements established by ICAO. These codes and local reports use the approved ICAO abbreviations contained in the Procedures for Air Navigation Services.

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