May 21, 1996 Frequently Asked Questions About METAR and TAF

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by	The Editors of AVweb

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

A1. METAR is the international standard code format for hourly surface weather observations which is analogous to the SA coding currently used in the US. The acronym roughly translates from French as Aviation Routine Weather Report. SPECI is merely the code name given to METAR formatted products which are issued on a special non-routine basis as dictated by changing meteorological conditions. The SPECI acronym roughly translates as Aviation Selected Special Weather Report.

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

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

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

A3. The Federal Aviation Administration, which determines aviation requirements in the United States, has determined that the domestic transition to the METAR/TAF code is vital to the standardization of these reports worldwide. The National Weather Service is complying with this requirement.

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

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

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

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 been filed by the U.S. For example, winds will continue to be reported in knots (as opposed to meters per second), ceilings and runway visual range will continue to be reported in feet (as opposed to meters), visibility will continue to be reported in statute miles (as opposed to meters), and altimeter settings will continue to be reported in inches of mercury (as opposed to hectopascals). The only element that will be converted to metric units is the temperature/dewpoint field which will be reported in whole degrees Celsius.

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

A6. In order to accommodate the need for greater temperature resolution by a wide variety of users, the hourly temperature/dewpoint will be in tenths of degrees Celsius in the additive data remarks section of the METAR report in the US in order to allow for a better conversion between Celsius and Fahrenheit.

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

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

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

Here are some sample Celsius temperatures and their Fahrenheit equivalents to help 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 in for all of its meteorological products?

A8. No. All other products that are issued by the NWS will continue to be in the units (including temperature in Fahrenheit) that everyone is used to.

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

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

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

A10. No. The U.S. standard for METAR was developed in a cooperative effort between the NWS , FAA, and domestic and international aviation industry and organizations. As in any standard developed by a multi-agency group, compromise is essential. Some of the coding groups (e.g., GR for hail or FU for smoke) are based on French words, but many English abbreviations have been adopted. For example, the international abbreviations for Fog and Rain are FG and RA respectively. Essentially, the better aspects of the international and North American codes were merged.

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

A11. The current SA observation code has been in place for over 30 years, 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 not feasible. Despite the advances in today's technology, the communication circuits used 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 conversion to a plain language format for thousands of domestic and international observations that are generated each hour of the day is impractical and would easily overwhelm our meteorological communication circuits. However, having now standardized 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 that continue?

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

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

A13. Yes. The upcoming domestic conversion to METAR is really phase 2 of a two-phased project. Phase 1 was completed in July 1993 when the US began converting SA formatted products to METAR for international dissemination. In addition the NWS has issued both terminal forecast (FT) and TAF formatted forecasts for 90 of the larger international airports in the US. There are over 500 additional airports where terminal forecasts are currently produced in only the FT format.

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

A14. On January 1, 1996, the NWS converted to the new international METAR format for international dissemination and to the new international TAF format at 90 locations. On February 1, 1996, TAF formatted forecasts issued for an additional 12 airport locations were instituted. The current plan is to completely convert to the new METAR/TAF code formats for domestic dissemination beginning at 0800 hours UTC on July 1, 1996. At that time, SAs and FTs will be replaced with METARs and TAFs and FTs will be discontinued.

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

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

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

A16. Yes. However the assistance for non-NWS observers such as Supplementary Aviation Weather Reporting Station (SAWRS) operators will be limited to providing training materials and proficiency exams. The NWS will not provide the actual hands-on training for non-NWS observers.

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

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

While the NWS neither endorses any private company nor any commercially available products, there are some commercially available METAR/TAF training and education products on the market that you may wish to consider. For example, the King Schools in San Diego, CA are now developing a METAR/TAF training video that should be available commercially sometime this Spring. In addition, Jeppesen Sanderson, Inc. in Englewood, CO has a chapter on the METAR/TAF code in its Private Pilot Manual, and also has plans to produce a videotape 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 listings of other such commercially available METAR/TAF training products.

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

A18. No. However the implementation date has slipped one month while the time was changed in the interest of air safety. This change in date and time was necessitated by delays in software development and testing that resulted from the government furloughs and shutdowns this past December and January. The time of 0800 hours UTC was chosen as the most optimal time from a safety standpoint. This is a time (0400 hours local daylight time on the East Coast and 0100 hours LDT on the West Coast) of low air traffic volume.

Again, the new METAR/TAF implementation date and time is July 1, 1996, at 0800 hours UTC.