Frequently Asked Questions About METAR and TAF

AVweb's comprehensive METAR FAQ!


Q1. What is METAR/SPECI and what do the acronyms stand for?

A1. METAR is the international standard code format for hourly surfaceweather observations which is analogous to the SA coding currently used in theUS. The acronym roughly translates from French as Aviation Routine WeatherReport. SPECI is merely the code name given to METAR formatted productswhich are issued on a special non-routine basis as dictated by changingmeteorological conditions. The SPECI acronym roughly translates as AviationSelected Special Weather Report.

Q2. What is TAF and what does the acronym stand for?

A2. TAF is the international standard code format for terminalforecasts issued for airports. The acronym translates to Terminal AerodromeForecast , and is analogous to the terminal forecast (FT) coding formatcurrently used in the US.

Q3. Why is the National Weather Service changing these aviationweather formats?

A3. The Federal Aviation Administration, which determines aviationrequirements in the United States, has determined that the domestic transitionto the METAR/TAF code is vital to the standardization of these reportsworldwide. The National Weather Service is complying with thisrequirement.

Q4. What are some of the benefits of having the US standardize tothese new code formats?

A4. Hourly and special observations are used both as stand alone datafor the sites and as inputs to global weather models for both analysis andforecasting. It is this global use of each small bit of information which drivesthe need for standardization. Additionally, the increase in internationalflights between the U.S. and other nations from more U.S. locations than everbefore (there are 3 flights per week alone between Memphis and Beijing) lendsitself to developing a more "seamless" international standard foraviation. Moreover, standardization becomes vital for the general aviationcommunity for flights to Canada, the Caribbean Area, and Mexico from the U.S.

Q5. Will the METAR and TAF information be presented in metricmeasurements?

A5. For the most part, no. In order to lessen the burden on the U.S.aviation community, a number of exceptions in metric reporting units have beenfiled by the U.S. For example, winds will continue to be reported in knots (asopposed to meters per second), ceilings and runway visual range will continue tobe reported in feet (as opposed to meters), visibility will continue to bereported in statute miles (as opposed to meters), and altimeter settings willcontinue to be reported in inches of mercury (as opposed to hectopascals). Theonly element that will be converted to metric units is the temperature/dewpointfield which will be reported in whole degrees Celsius.

Q6. The Celsius temperature scale does not have the same resolution asthe Fahrenheit scale. What will happen if I need the better resolution providedby Fahrenheit?

A6. In order to accommodate the need for greater temperatureresolution by a wide variety of users, the hourly temperature/dewpoint will bein tenths of degrees Celsius in the additive data remarks section of the METARreport in the US in order to allow for a better conversion between Celsius andFahrenheit.

Q7. What do I need to do to convert degrees Celsius to degreesFahrenheit?

A7. The home page has two conversion tables for your use in this.However, for those who like formulas, the simple conversion formulas fromCelsius (C) to Fahrenheit (F), and for the conversion of F back to C are asfollows:

   F = 1.8xC + 32   C = (F - 32)/1.8

Here are some sample Celsius temperatures and their Fahrenheit equivalents tohelp you give a better feel for the Celsius scale:

   Celsius     Fahrenheit    -50.0      -58.0    -40.0      -40.0 (Our favorite anomaly)    -30.0      -22.0    -25.0      -13.0    -20.0      - 4.0    -15.0       5.0    -10.0       14.0    - 5.0       23.0     0.0       32.0 (Freezing Point of Water)     5.0       41.0    10.0       50.0    15.0       59.0    20.0       68.0    25.0       77.0    30.0       86.0    37.0       98.6 (Normal body temperature)    40.0      104.0    45.0      113.0     50.0      122.0    55.0      131.0    100.0      212.0 (Boiling Point of Water)

Q8. Is this an attempt by the NWS to convert to metric units infor all of its meteorological products?

A8. No. All other products that are issued by the NWS willcontinue to be in the units (including temperature in Fahrenheit) that everyoneis used to.

Q9. What other changes can I expect and will I continue to get thesame data elements that I get today?

A9. The biggest change in converting to METAR is the change in theorder of how elements are reported, for example the winds field (a moreimportant aviation feature) will be reported first rather than in the middle ofthe observation. However, remarks and additive data will continue to be includedand reported much as they are today. The sea-level pressure that you were usedto seeing in the body of the observation will now be reported in the remarkssection. Please see the technical aids later in the home page for more specificformatting information.

Q10. I heard that the METAR code uses a lot of non-English words, willI have to learn a new language to use the METAR code?

A10. No. The U.S. standard for METAR was developed in a cooperativeeffort between the NWS , FAA, and domestic and international aviationindustry and organizations. As in any standard developed by a multi-agencygroup, compromise is essential. Some of the coding groups (e.g., GR for hail orFU for smoke) are based on French words, but many English abbreviations havebeen adopted. For example, the international abbreviations for Fog and Rain areFG and RA respectively. Essentially, the better aspects of the international andNorth American codes were merged.

Q11. Why are you converting to a code when all I want is my weatherdata in plain language format? Isn’t this possible with all the high speedcomputers and communications that we have today?

A11. The current SA observation code has been in place for over 30years, and the conversion to METAR is a follow-on which is not very different.As for having these products reported in a plain language format, this is notfeasible. Despite the advances in today’s technology, the communication circuitsused for transmitting the large and diverse suite of meteorological products(radar, upper air, climatological data, forecasts, watches, warnings, outlooks,etc.) have a finite capacity and are overloaded as it is today. The conversionto a plain language format for thousands of domestic and internationalobservations that are generated each hour of the day is impractical and wouldeasily overwhelm our meteorological communication circuits. However, having nowstandardized to a considerable extent does allow computer programs to expand the"code" into plain language.

Q12. If I am getting plain language observations today, will thatcontinue?

A12. If you are getting plain language reports, it is because theservice you subscribe to (DUATS, WSI, Pan Am data, etc.) is providing that foryou. They are aware of the transition to METAR and should continue providing thesame service that they do today. You should check with your weather provider andask what their plans are for METAR.

Q13. Has the US ever dealt with METAR and TAF codes prior to thistime?

A13. Yes. The upcoming domestic conversion to METAR is really phase 2of a two-phased project. Phase 1 was completed in July 1993 when the US beganconverting SA formatted products to METAR for international dissemination. Inaddition the NWS has issued both terminal forecast (FT) and TAF formattedforecasts for 90 of the larger international airports in the US. There are over500 additional airports where terminal forecasts are currently produced in onlythe FT format.

Q14. What are some of the significant dates in the changeover from SAto METAR, and from FT to TAF?

A14. On January 1, 1996, the NWS converted to the newinternational METAR format for international dissemination and to the newinternational TAF format at 90 locations. On February 1, 1996, TAF formattedforecasts issued for an additional 12 airport locations were instituted. Thecurrent plan is to completely convert to the new METAR/TAF code formats fordomestic dissemination beginning at 0800 hours UTC on July 1, 1996. At thattime, SAs and FTs will be replaced with METARs and TAFs and FTs will bediscontinued.

Q15. Will people who are certified observers have to be tested andcertified on the new METAR format?

A15. Currently certified aviation weather observers will not have tobe re-certified. Instead they will have to demonstrate proficiency with the newMETAR code. After July 1, 1996, new observers will have to be certified in theMETAR code.

Q16. Will local National Weather Service offices offer trainingassistance for current and new observers?

A16. Yes. However the assistance for non-NWS observers such asSupplementary Aviation Weather Reporting Station (SAWRS) operators will belimited to providing training materials and proficiency exams. The NWS willnot provide the actual hands-on training for non-NWS observers.

Q17. What materials will the NWS or other organizations haveready to help people learn the new METAR and TAF codes?

A17. There are a series of technical aids that are posted on this homepage. In addition, review questions and coding exercises with answers will beprovided to help currently certified NWS observers. A similar document isalso being prepared and will be provided to SAWRS observers. This home page alsoprovides access to the FAA Academy’s METAR/TAF Home Page where some additionaltraining documents are located.

While the NWS neither endorses any private company nor anycommercially available products, there are some commercially available METAR/TAFtraining and education products on the market that you may wish to consider. Forexample, the King Schools in San Diego, CA are now developing a METAR/TAFtraining video that should be available commercially sometime this Spring. Inaddition, Jeppesen Sanderson, Inc. in Englewood, CO has a chapter on theMETAR/TAF code in its Private Pilot Manual, and also has plans to produce avideotape with METAR/TAF training information.

This is by no means a complete list of such commercially available products.We suggest that you consult aviation publications and associations for listingsof other such commercially available METAR/TAF training products.

Q18. Is it true that the METAR/TAF domestic implementation date hasslipped significantly?

A18. No. However the implementation date has slipped one month whilethe time was changed in the interest of air safety. This change in date and timewas necessitated by delays in software development and testing that resultedfrom the government furloughs and shutdowns this past December and January. Thetime of 0800 hours UTC was chosen as the most optimal time from a safetystandpoint. This is a time (0400 hours local daylight time on the East Coast and0100 hours LDT on the West Coast) of low air traffic volume.

Again, the new METAR/TAF implementation date and time is July 1, 1996, at0800 hours UTC.