Conditional Messages

A static message in Airport Conditions or NOTAMs can be included in the ATIS only while certain things are true, instead of being switched on and off by hand. There are two kinds of condition, and a message can use both:

• Controllers online: include the message only while specific VATSIM controllers are online, or only while they are offline.
• Weather: include the message only when the METAR meets a condition you write, such as ceiling < 200ft.

Typical uses are a frequency NOTAM that depends on whether Delivery is staffed, and a Low Visibility Procedures in operation airport condition that follows the weather.

Conditions are set in the message editor, which opens when you add a message with New or change one with Edit in the Airport Conditions or NOTAMs dialog. A message with no conditions is always included. A message whose checkbox is not selected is never included, whatever its conditions say.

When both kinds of condition are set, both must be met for the message to be included.

The Airport Conditions and NOTAMs lists show each message’s conditions under its text, in smaller italic type, so you can see which messages are conditional without opening them. Messages without a condition show only their text.

A checked message that has a condition is included in the ATIS only while its condition is met, so a checked row in the list does not always mean the message is being broadcast.

Controllers Online

In the Include row, choose when the message applies:

• Always: The message has no controller condition.
• When online: The message is included while at least one of the listed callsigns is online.
• When offline: The message is included while none of the listed callsigns is online.

When you choose When online or When offline, enter one or more callsigns, separated by commas or spaces. Callsigns are not case-sensitive, and the whole callsign must match. Use * as a wildcard for any run of characters:

Entry	Matches
EPWA_DEL	Only EPWA_DEL
EPWA_APP, EPWA_F_APP	Either callsign
EPWW_*_CTR	EPWW_W_CTR, EPWW_E_CTR, … (but not EPWW_CTR, which has only one underscore)
EPWW_*CTR	EPWW_CTR, EPWW_W_CTR, EPWW_E_CTR, …
EPWA_*	Any EPWA_ position, including Tower and Ground

Observers and ATIS connections are not counted as controllers.

Example: Frequencies that depend on who is staffed

Some airports give different instructions depending on which positions are staffed. These NOTAMs are set on the same station, and in each pair only one is included at a time. The wording is only an example:

NOTAM	Include	Callsigns
REPORT READY FOR START UP ON DELIVERY 121 DECIMAL 605	When online	EPWA_DEL
REPORT READY FOR START UP ON TOWER 119 DECIMAL 980	When offline	EPWA_DEL
AFTER DEPARTURE CONTACT APPROACH 121 DECIMAL 075	When online	EPWA_APP
AFTER DEPARTURE CONTACT TOWER 119 DECIMAL 980	When offline	EPWA_APP

Where the online list comes from

vATIS reads the list of online controllers from the VATSIM data feed.

• The feed is refreshed every 30 seconds, so a controller logging on or off can take up to 30 seconds to show up.
• If the feed cannot be reached, vATIS keeps the last list it received. Until it has received one, nobody is considered online: When offline messages are included and When online messages are not.

Weather

Type a condition in the Weather box. The message is included while the METAR meets the condition. A message with an empty Weather box is not affected by the weather.

A condition is made of comparisons, such as ceiling < 200ft, joined with AND and OR, negated with NOT, and grouped with parentheses:

ceiling < 200ft AND (rvr < 550m OR visibility < 100m)

Field names, units and keywords are not case-sensitive, and conditions can be spread over several lines. If the condition is not valid, vATIS shows what is wrong and where, and will not save the message until it is fixed.

Suggestions

vATIS suggests what can come next as you type: field names, comparisons, units and weather codes. The list appears as you type a word, after a space and after an opening parenthesis, and you can open it at any time with Ctrl+Space. Choose a suggestion with the arrow keys and press Enter or Tab, or double-click it. Typing anything else just closes the list, so your own text is never replaced.

Comparisons with numbers

Write a field, a comparison, and a number with an optional unit. Without a unit, the first one listed for the field is used.

Field	Also written	Compares	Units
ceiling		Height of the ceiling: the lowest cloud layer of the types set as ceiling in the Clouds format (broken and overcast by default)	ft, m
cloudbase		Height of the lowest cloud layer of any coverage	ft, m
rvr		The lowest runway visual range reported	m, km, ft
visibility	vis	Prevailing visibility. CAVOK counts as 9999 m	m, km, ft
windspeed	wind	Mean wind speed	kt, kmh, mps
gust	windgust	Gust speed	kt, kmh, mps
winddir	winddirection	Mean wind direction. Variable winds (VRB) never match	deg
temperature	temp	Air temperature	c, f
dewpoint	dew	Dewpoint	c, f
qnh	pressure, altimeter	The pressure setting, converted if the METAR uses the other unit	hpa, inhg
depth	runwaydepth	The deepest deposit in the METAR’s runway condition groups	mm

The comparisons are < (below), <= (at or below), > (above), >= (at or above) and = (equals). The number is converted from the unit you write, so ceiling < 200ft works whether the METAR reports the ceiling in feet or in meters. Units can follow the number directly or after a space: 200ft and 200 ft are the same.

Comparisons with codes

weather and cloudtype check for codes in the METAR, using INCLUDES or EXCLUDES:

Field	Also written	Looks for
weather	wx	Present weather codes, e.g. TS, FZRA, +SN, FG
cloudtype		Cloud types CB and TCU

weather INCLUDES TS is met while a thunderstorm is reported. To look for more than one code, separate them with commas, weather INCLUDES TS,FZRA, or put them in quotes, weather INCLUDES "TS FZRA". INCLUDES is met when any of the codes is found, and a code matches inside longer ones: RA matches -RA, +RA and TSRA. EXCLUDES is met when none of them is found.

Conditions without a comparison

windshear is met while wind shear is reported, and cavok while the METAR reports CAVOK. Use NOT for the opposite, e.g. NOT cavok.

Note

A comparison is not met when the METAR does not report the value it needs. With no RVR reported, both rvr < 550m and rvr > 550m are false. Use NOT or EXCLUDES to test for something being absent. Before the first METAR has been received, no weather condition is met.

Combining comparisons

AND is evaluated before OR, as in ordinary logic, so

ceiling < 200ft AND rvr < 550m OR visibility < 100m

means (ceiling below 200 ft and RVR below 550 m) or visibility below 100 m. Use parentheses to change the order:

ceiling < 200ft AND (rvr < 550m OR visibility < 100m)

means the ceiling is below 200 ft, and either the RVR is below 550 m or the visibility is below 100 m. Parentheses can be nested, for example ((A OR B) AND C) OR D. NOT applies to the condition or group that follows it: NOT (windshear OR cloudtype INCLUDES CB).

Examples

Each row shows a different part of the condition language.

Message	Weather condition	Shows
STRONG GUSTY WINDS	gust >= 30kt	A number field with a unit and >=
CALM WIND	windspeed = 0kt	The = comparison
LOW CLOUD IN THE VICINITY	cloudbase < 500ft	The lowest cloud layer of any coverage, unlike ceiling
LOW PRESSURE, CHECK ALTIMETER SETTING	qnh < 1000hpa	A pressure setting and its unit
STRONG WESTERLY WIND	winddir >= 240deg AND winddir <= 300deg AND windspeed >= 20kt	Wind direction, and AND with three comparisons
RWY CONTAMINATED	depth > 3mm	Runway deposit depth in millimeters
ICING POSSIBLE	temperature <= 3c AND dewpoint >= -3c	<=, AND, and a negative number
FOG, EXPECT DELAYS	wx INCLUDES FG AND vis < 800m	The alternative field names wx and vis
THUNDERSTORMS IN THE VICINITY	weather INCLUDES TS OR cloudtype INCLUDES CB	INCLUDES with weather and cloudtype, and OR
DEICING NOT REQUIRED	temperature > 3c AND weather EXCLUDES "FZRA FZDZ"	EXCLUDES with more than one code in quotes
WINDSHEAR REPORTED ON FINAL	windshear	A condition without a comparison
VISUAL APPROACHES AVAILABLE	cavok	cavok, also without a comparison
ILS APPROACHES IN USE	NOT cavok	NOT in front of a condition: the opposite of the row above
NO WINDSHEAR OR CUMULONIMBUS REPORTED	NOT (windshear OR cloudtype INCLUDES CB)	NOT in front of a group in parentheses
LOW VISIBILITY PROCEDURES IN OPERATION	ceiling < 200ft AND (rvr < 550m OR visibility < 100m)	Parentheses to group OR before AND

When Conditions Are Checked

• When a station is connected, the ATIS is rebuilt as soon as a new METAR arrives, or when a controller logging on or off changes which messages apply. vATIS only rebuilds when the set of included messages actually changes.
• The ATIS letter is not advanced by these changes. It advances for a new METAR in the usual way, but a controller logging on or off will update the ATIS text under the same letter.
• The free-form text area in the main window lists the static messages that currently apply, so you can see what will be broadcast.
• The Sandbox evaluates weather conditions against the METAR in its METAR field, and controller conditions against the current list of online controllers.