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 METAR/TAF information 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 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 did issue both terminal forecast (FT) and TAF formatted forecasts
for 102 of the larger international airports in the US.
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 NWS completely converted
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 were replaced with METARs
and TAFs, and SAs and FTs were 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.
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