Forecasts ElementDefines a collection of weather forecasts. The collection is made of TAF elements.
As National Weather Service Operations Manual [WSOM D-31] states,
Aviation terminal forecasts -- which may be referred to as terminal or aerodrome forecasts -- serve the pre-flight and in-flight meteorological service requirements of aviation operations by providing a forecast of weather conditions at an airport. It is the policy of the United States that, to the extent practicable, terminal forecasts shall be prepared, issued, and distributed on a timely basis to meet requirements of the United States Aviation Authority, the Federal Aviation Administration (FAA), and the International Civil Aviation Organization (ICAO) in a code format designed by the World Meteorological Organization (WMO) for both domestic and international use.Terminal forecasts are scheduled to be issued every six hours and are valid for a 24-hour period. Amendments are issued as needed. These forecasts are used by a wide variety of aviation customers, including domestic and international commercial airlines, general aviation, civilian, and military customers.
The OMF markup described in this document only annotates the raw text of a forecast, without altering it or omitting a single letter. Thus it is possible to recover the original text of the forecast from the marked-up version.
| XML DTD | |
|---|---|
<!ELEMENT Forecasts ( TAF )* > |
TStamp |
||
|---|---|---|
| Time Stamp of the moment this group of forecasts was created. Normally it is the time the corresponding TAF request was fulfilled by a Metcast server and is being transmitted. | ||
<!ATTLIST Forecasts %TStamp;> |
TAF Forecast
This element defines one particular TAF forecast. This element contains (in its children elements) the raw text of a forecast, a sequence of words as they appear in a TAF bulletin. Groups of related words are annotated to tell their type and to communicate their meaning in a more uniform and machine-friendly way: For example, time stamps are always presented in EPOCH seconds, airport references are annotated with the airport's full name and location, forecasts change periods are clearly separated and timestamped.
| XML DTD | |
|---|---|
<!ELEMENT TAF ( VALID, PERIOD+ ) > |
TStamp |
||
|---|---|---|
| Time Stamp of forecast origin, a time moment when the forecast was completed and was about to be reported | ||
LatLon |
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| Terminal's geographical location | ||
BId |
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| Station identifier | ||
SName |
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| Terminal's location identifier (ICAO id) and the full name, if any | ||
LimitTo, LimitRecd |
||
| Access Restrictions | ||
<!ATTLIST TAF %TStamp; %LatLon; %BId; %SName; %AccessLimit; > |
VALID ElementThe VALID element specifies a forecast valid period. This markup annotates the corresponding words of a forecast header.
It is a basic minor VALID element described in the introduction.
PERIOD ElementThis element specifies the complete set of prevailing weather condition elements that are forecast for a specified period. The set includes surface wind, visibility, significant weather, clouds and obscurations, and, when expected, non-convective low-level wind shear.
A TAF element contains at least one PERIOD element for the initial period of the forecast. If prevailing conditions are expected to change significantly, additional PERIOD elements may follow.
| XML DTD | |
|---|---|
<!ELEMENT PERIOD ( PREVAILING, VAR* )> |
TRange |
||
|---|---|---|
| Time range, the beginning and the end points of the forecast period | ||
Title |
||
| A forecast change indicator that introduces the present forecast period | "FMhhmm" or omitted
| |
A FROM group of the TAF report that begins a new subdivision of the forecast, when a significant change in the weather is expected. [Section 7.2.9 of the WSOM D-31 document].
The Title attribute is omitted for the initial forecast period.
| ||
<!ATTLIST PERIOD %TRange; Title NMTOKEN #IMPLIED > |
PREVAILING ElementThe complete set of prevailing weather condition elements, as it appears in the text of a forecast
| XML DTD | |
|---|---|
<!ELEMENT PREVAILING (#PCDATA)> |
VAR Element
The VAR elements describes variations or fluctuations in forecast meteorological conditions that are expected to occur or develop within a forecast period. This forecast period is specified by the parent (containing) PERIOD element. The content of the VAR element is weather conditions groups (tokens) as they appear in the raw forecast text. This set of weather condition elements is not complete: only the weather element tokens that are expected to change or fluctuate are specified.
| XML DTD | |
|---|---|
<!ELEMENT VAR (#PCDATA)> |
TRange |
||
|---|---|---|
| Time window within which the variation or fluctuation in weather conditions is expected to take place | ||
Title |
||
| A forecast change indicator that introduces the present variation in the TAF report | "BECMG bbee" or "TEMPO bbee" or "PROBnn bbee"
| |
<!ATTLIST VAR %TRange; Title CDATA #REQUIRED > |
KLYH 300116Z 300124 00000KT 5SM BR BKN250
BECMG 0507 2SM BR
FM0900 00000KT 1SM BR SCT005
TEMPO 0912 3/4SM BR BKN005
FM1400 VRB03KT 4SM HZ SCT025
FM1700 22007KT P6SM SCT050=
KPKB 300128Z 300124 03006G12KT P6SM BKN250^M^M
BECMG 0304 VRB03KT 3SM BR BKN250^M^M
TEMPO 0812 1SM BR SCT001^M^M
FM1400 VRB03KT 5SM HZ BKN250^M^M
TEMPO 1416 3SM HZ^M^M
FM1800 21006KT P6SM SCT040=^M^M
|
would be represented as
<!DOCTYPE Forecasts SYSTEM "OMF.dtd"> <Forecasts TStamp="901767600"> <TAF TStamp="901761360" LatLon="37.333, -79.200" BId="724100" SName="KLYH, LYNCHBURG/P. GLENN"> <VALID TRange="901760400, 901843200">300116Z 300124</VALID> <PERIOD TRange="901760400, 901789200"> <PREVAILING>00000KT 5SM BR BKN250</PREVAILING> <VAR Title="BECMG 0507" TRange="901774800, 901782000">2SM BR</VAR> </PERIOD> <PERIOD TRange="901789200, 901807200" Title="FM0900"> <PREVAILING>00000KT 1SM BR SCT005</PREVAILING> <VAR Title="TEMPO 0912" TRange="901789200, 901800000">3/4SM BR BKN005</VAR> </PERIOD> <PERIOD TRange="901807200, 901818000" Title="FM1400"> <PREVAILING>VRB03KT 4SM HZ SCT025</PREVAILING> </PERIOD> <PERIOD TRange="901818000, 901843200" Title="FM1700"> <PREVAILING>22007KT P6SM SCT050</PREVAILING> </PERIOD> </TAF> <TAF TStamp="901762080" LatLon="39.350, -81.433" BId="724273" SName="KPKB, PARKERSBURG/WILSON&"> <VALID TRange="901760400, 901843200">300128Z 300124</VALID> <PERIOD TRange="901760400, 901807200"> <PREVAILING>03006G12KT P6SM BKN250</PREVAILING> <VAR Title="BECMG 0304" TRange="901767600, 901771200">VRB03KT 3SM BR BKN250</VAR> <VAR Title="TEMPO 0812" TRange="901785600, 901800000">1SM BR SCT001</VAR> </PERIOD> <PERIOD TRange="901807200, 901821600" Title="FM1400"> <PREVAILING>VRB03KT 5SM HZ BKN250</PREVAILING> <VAR Title="TEMPO 1416" TRange="901807200, 901814400">3SM HZ</VAR> </PERIOD> <PERIOD TRange="901821600, 901843200" Title="FM1800"> <PREVAILING>21006KT P6SM SCT040</PREVAILING> </PERIOD> </TAF> </Forecasts> |
WSOM D-31 Aviation Terminal Forecasts
http://www.nws.noaa.gov/oso/oso1/oso12/d31/D31links.htm
What is a TAF?
http://www.erh.noaa.gov/bgm/what_is_a_taf.html
National Weather Service Aviation Weather Center
http://aviationweather.gov/
OMF DTD
The OMF Data Definition Document in XML format
Current terminal forecasts from the Metcast database
http://www.metnet.navy.mil/cgi-bin/oleg/get-taf
The TAFs are presented in the OMF format described in this document
Reconstructing TAF WMO messages from an OMF document
A well-commented source code (a Perl script). It parses an OMF XML document containing TAF forecasts and reconstructs WMO messages in the FM 51-X TAF code. This script proves that it is indeed possible to recover the original text of a forecast from a marked-up version.