explain xkcd - User contributions [en]

3024: METAR

2024-12-13T22:33:50Z

Patallurgist: /* Explanation */ KNYC is legit

{{comic
| number = 3024
| date = December 13, 2024
| title = METAR
| image = metar_2x.png
| imagesize = 640x360px
| noexpand = true
| titletext = In the aviation world, they don't use AM/PM times. Instead, all times are assumed to be AM unless they're labeled NOTAM.
}}

==Explanation==
{{incomplete|Created by an A380 - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In aviation, the {{w|METAR}} (Meteorological Aerodrome Report) is used to give pilots a brief overview of the current meteorological conditions at the airport.
The METAR follows a specific structure and makes heavy usage of abbreviations, which makes it hard to read for anyone not familiar with it.
The comic makes fun of that by assuming meaning of the words based on what non-aviation people might think the different elements of the METAR report may represent.
The METAR in the comic is fairly alarming, describing gale-force winds, a possible tornado, freezing volcanic ash (in New York), lightning, and impossibly high atmospheric pressure.

{| class="wikitable"
|-
! Code !! Real Meaning !! According to the comic
|-
| METAR
| Type: Meteorological Aerodrome Report
| The comic assumes that this is just a spelling error and it should be "meter"
|-
| KNYC
| Station ID: 4 character identifier; for an airport, this would be the ICAO code. In this instance the identifier represents the automated weather station at Belvedere Castle in Central Park, NYC. Airport, weather, and radio station call signs share a common heritage.
| "Station ID", which is actually correct.
|-
| 251600Z
| Time of observation: 25th day of the month at 4 PM UTC. Z is not part of the time, but simply shorthand for GMT or "Zulu" time.
| Misreading the "Z" as a 2, resulting in a nonsensical time. Hours greater than 24 are sometimes used to indicate a time after midnight, e.g., in Japan 17~25h means from 5 P.M. to 1 A.M. the following day. A normal METAR does not use more than 24 hours, instead incrementing the day, so 25 hours further adds to the nonsensical nature of the interpretation.
|-
| 18035G45KT
| Wind direction and speed: Wind direction: 180° (directly from the south, degrees based on 0°=magnetic north), speed: 35 knots, gusts: 45 knots
| Instead of interpreting the first 5 digits as direction and speed, it is assumed that it is one big number and the G45 stands for the time span in which this was observed with "G" standing for "good". 18,035 knots is an unrealistically high wind speed, faster than orbital velocity; the {{w|jet stream}} typically contains the highest winds on Earth, and may reach about 250 knots.
|-
| 6SM
| In weather reports related to aviation, "6SM" stands for 6 statute miles, meaning that objects can be seen clearly up to 6 miles away.<ref>https://weather.cod.edu/notes/metar.html#:~:text=6SM%2DVisibility,SM)%20up%20to%2010%20SM.</ref> This indicates clear enough weather to fly without instruments; the value has a max range of 10SM.
| The comic interprets "6SM" to humorously mean a "Size '''6 Sm'''all".
|-
| VCFCFZVA
| In the vicinity (VC): funnel cloud (FC) and freezing (FZ) volcanic ash (VA).
| A riff on the repeated letters which give off the impression the string is constructed by typing randomly on the keyboard. All the letters are near each other at the lower left of the keyboard (S, D, and X are somehow avoided).
|-
| +BLUP
| Heavy (+) blowing (BL) unknown precipitation (UP)
| Riffing on the fact that it looks like an onomatopoetic word
|-
| NOSIG
| No significant change is expected to the reported conditions within the next 2 hours
| The comic assumes that the transmitter of the METAR report wants the receivers to know that they do not have a significant other, which the comic finds sad. The observer could be trying to abuse the METAR report as a dating platform.
|-
| LTG OHD
| Lightning overhead
| OHD is interpreted as "overheard" instead of "overhead", indicating that they did not observe it themselves and instead just overheard people talking about it.
|-
| A3808
| Altimeter setting: (calculated) air pressure at {{w|Mean_sea_level|mean sea level}} at the airport is 38.08 <ref>The value of 38.08 inHg is extremely high. The standard atmospheric pressure used in aviation is 29.92 inHg, the highest recorded barometric pressure was 32.00 inHg. Given that the weather station is automated, this value cannot be explained by a typo by the METAR sender.</ref> {{w|Inch_of_mercury|inches of mercury (inHG)}} ("A" for inHG, used primarily in USA, Canada and Japan, "Q" would indicate a value in hPa). This is used to adjust the altimeter in the aircraft to the local air pressure, instead of using the standard setting used in higher air spaces.
| The comic says that the observer saw an {{w|Airbus_A380|Airbus A380-800}}. Note: The {{w|List_of_ICAO_aircraft_type_designators|ICAO aircraft type code}} for the Airbus A380-800 is A388 and not A3808.
|-
| RMK
| Beginning of the section with remarks
| Remarkable. Might be a comment about the A380.
|-
| AO2
| The weather station is automated (A) and has a precipitation discriminator (O2)
| Reference to the {{w|fan fiction|fanfic}} site [https://archiveofourown.org/ Archive of Our Own], often abbreviated as AO3
|-
| SLP130=
| {{w|Sea_level_pressure|Sea-level pressure}} is 1013.0 hPa (approx. 29.91 inHg). The equal sign signifies the end of the METAR.
| "SLP" interpreted as abbreviation for sleepy, the numbers as a time, and the = sign as "around" (maybe confused with ≈)
|-
| NOTAM (title text)
| Not part of a METAR report, but instead another aviation abbreviation. It stands for {{w|NOTAM|Notice to Air Missions}} (previously Notice to Airmen).
| Parsed as "not A.M.", indicating that a given time is to be interpreted as P.M. While AM and PM are indeed not used in aviation, as the comic says, they use a 24-hour clock system, not an "A.M.-by-default" 12-hour clock system.
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

Decoding a METAR Report:

[A METAR report is shown with annotations. The report is:]

<code>
METAR KNYC 251600Z 18035G45KT 6SM VCFCFZVA +BLUP NOSIG LTG OHD A3808 RMK A02 SPL130=
</code>

[The annotations are:]

* <code>METAR</code> "METER" (Usually misspelled)
* <code>KNYC</code> Station ID
* <code>251600Z</code> Time (25:16:002)
* <code>18035G45KT</code> Wind speed has been 18,035 knots for a good 45 minutes now
* <code>6SM</code> Observer is a size 6 small
* <code>VCFCFZVA</code> Sorry, the station cat walked on the keyboard
* <code>+BLUP</code> Weird noise the sky made earlier
* <code>NOSIG</code> Observer has no significant other :(
* <code>LTG OHD</code> We overheard someone saying there was lightning
* <code>A3808</code> Hey look, an Airbus A380-800!
* <code>RMK</code> Remarkable!
* <code>A02</code> Fanfic Archive equipped with a precipitation sensor
* <code>SPL130=</code> Observer got sleepy around 1:30

==References==
{{reflist}}
[https://e6bx.com/metar-decoder/ Metar Decoder]
{{comic discussion}}

3024: METAR

2024-12-13T22:21:49Z

Patallurgist: /* Explanation */

{{comic
| number = 3024
| date = December 13, 2024
| title = METAR
| image = metar_2x.png
| imagesize = 640x360px
| noexpand = true
| titletext = In the aviation world, they don't use AM/PM times. Instead, all times are assumed to be AM unless they're labeled NOTAM.
}}

==Explanation==
{{incomplete|Created by an A380 - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In aviation, the {{w|METAR}} (Meteorological Aerodrome Report) is used to give pilots a brief overview of the current meteorological conditions at the airport.
The METAR follows a specific structure and makes heavy usage of abbreviations, which makes it hard to read for anyone not familiar with it.
The comic makes fun of that by assuming meaning of the words based on what non-aviation people might think the different elements of the METAR report may represent.
The METAR in the comic is fairly alarming, describing gale-force winds, a possible tornado, freezing volcanic ash (in New York), lightning, and impossibly high atmospheric pressure.

{| class="wikitable"
|-
! Code !! Real Meaning !! According to the comic
|-
| METAR
| Type: Meteorological Aerodrome Report
| The comic assumes that this is just a spelling error and it should be "meter"
|-
| KNYC
| Station ID: 4 character ICAO airport identifier; in this instance the general area code for New York City (not an actual airport, but a weather station for general observations in the New York area)
| Radio station, likely parodying WNYC radio. US radio stations west of the Mississippi River usually start with K and those east of it usually start with W, though there have been exceptions. For example, KDKA in Pittsburgh was one of the first commercially licensed radio stations. Airport, weather, and radio station call signs share a common heritage.
|-
| 251600Z
| Time of observation: 25th day of the month at 4 PM UTC. Z is not part of the time, but simply shorthand for GMT or "Zulu" time.
| Misreading the "Z" as a 2, resulting in a nonsensical time. Hours greater than 24 are sometimes used to indicate a time after midnight, e.g., in Japan 17~25h means from 5 P.M. to 1 A.M. the following day. A normal METAR does not use more than 24 hours, instead incrementing the day, so 25 hours further adds to the nonsensical nature of the interpretation.
|-
| 18035G45KT
| Wind direction and speed: Wind direction: 180° (directly from the south, degrees based on 0°=magnetic north), speed: 35 knots, gusts: 45 knots
| Instead of interpreting the first 5 digits as direction and speed, it is assumed that it is one big number and the G45 stands for the time span in which this was observed with "G" standing for "good". 18,035 knots is an unrealistically high wind speed, faster than orbital velocity; the {{w|jet stream}} typically contains the highest winds on Earth, and may reach about 250 knots.
|-
| 6SM
| In weather reports related to aviation, "6SM" stands for 6 statute miles, meaning that objects can be seen clearly up to 6 miles away.<ref>https://weather.cod.edu/notes/metar.html#:~:text=6SM%2DVisibility,SM)%20up%20to%2010%20SM.</ref> This indicates clear enough weather to fly without instruments; the value has a max range of 10SM.
| The comic interprets "6SM" to humorously mean a "Size '''6 Sm'''all".
|-
| VCFCFZVA
| In the vicinity (VC): funnel cloud (FC) and freezing (FZ) volcanic ash (VA).
| A riff on the repeated letters which give off the impression the string is constructed by typing randomly on the keyboard. All the letters are near each other at the lower left of the keyboard (S, D, and X are somehow avoided).
|-
| +BLUP
| Heavy (+) blowing (BL) unknown precipitation (UP)
| Riffing on the fact that it looks like an onomatopoetic word
|-
| NOSIG
| No significant change is expected to the reported conditions within the next 2 hours
| The comic assumes that the transmitter of the METAR report wants the receivers to know that they do not have a significant other, which the comic finds sad. The observer could be trying to abuse the METAR report as a dating platform.
|-
| LTG OHD
| Lightning overhead
| OHD is interpreted as "overheard" instead of "overhead", indicating that they did not observe it themselves and instead just overheard people talking about it.
|-
| A3808
| Altimeter setting: (calculated) air pressure at {{w|Mean_sea_level|mean sea level}} at the airport is 38.08 <ref>The value of 38.08 inHg is extremely high. The standard atmospheric pressure used in aviation is 29.92 inHg, the highest recorded barometric pressure was 32.00 inHg. Given that the weather station is automated, this value cannot be explained by a typo by the METAR sender.</ref> {{w|Inch_of_mercury|inches of mercury (inHG)}} ("A" for inHG, used primarily in USA, Canada and Japan, "Q" would indicate a value in hPa). This is used to adjust the altimeter in the aircraft to the local air pressure, instead of using the standard setting used in higher air spaces.
| The comic says that the observer saw an {{w|Airbus_A380|Airbus A380-800}}. Note: The {{w|List_of_ICAO_aircraft_type_designators|ICAO aircraft type code}} for the Airbus A380-800 is A388 and not A3808.
|-
| RMK
| Beginning of the section with remarks
| Remarkable. Might be a comment about the A380.
|-
| AO2
| The weather station is automated (A) and has a precipitation discriminator (O2)
| Reference to the {{w|fan fiction|fanfic}} site [https://archiveofourown.org/ Archive of Our Own], often abbreviated as AO3
|-
| SLP130=
| {{w|Sea_level_pressure|Sea-level pressure}} is 1013.0 hPa (approx. 29.91 inHg). The equal sign signifies the end of the METAR.
| "SLP" interpreted as abbreviation for sleepy, the numbers as a time, and the = sign as "around" (maybe confused with ≈)
|-
| NOTAM (title text)
| Not part of a METAR report, but instead another aviation abbreviation. It stands for {{w|NOTAM|Notice to Air Missions}} (previously Notice to Airmen).
| Parsed as "not A.M.", indicating that a given time is to be interpreted as P.M. While AM and PM are indeed not used in aviation, as the comic says, they use a 24-hour clock system, not an "A.M.-by-default" 12-hour clock system.
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

Decoding a METAR Report:

[A METAR report is shown with annotations. The report is:]

<code>
METAR KNYC 251600Z 18035G45KT 6SM VCFCFZVA +BLUP NOSIG LTG OHD A3808 RMK A02 SPL130=
</code>

[The annotations are:]

* <code>METAR</code> "METER" (Usually misspelled)
* <code>KNYC</code> Station ID
* <code>251600Z</code> Time (25:16:002)
* <code>18035G45KT</code> Wind speed has been 18,035 knots for a good 45 minutes now
* <code>6SM</code> Observer is a size 6 small
* <code>VCFCFZVA</code> Sorry, the station cat walked on the keyboard
* <code>+BLUP</code> Weird noise the sky made earlier
* <code>NOSIG</code> Observer has no significant other :(
* <code>LTG OHD</code> We overheard someone saying there was lightning
* <code>A3808</code> Hey look, an Airbus A380-800!
* <code>RMK</code> Remarkable!
* <code>A02</code> Fanfic Archive equipped with a precipitation sensor
* <code>SPL130=</code> Observer got sleepy around 1:30

==References==
{{reflist}}
[https://e6bx.com/metar-decoder/ Metar Decoder]
{{comic discussion}}