BASICS FOR AIR TRAFFIC CONTROL – FORECASTS AND ADVISORIES

A TAF is a concise statement of the expected meteorological conditions significant to aviation for a specified time period within _ of an airport that is used to anticipate weather changes that will affect aircraft operations at specified terminals.

5 NM

TAFs issued by the National Weather Service (NWS) provide a forecast of the following meteorological elements:

Wind

Visibility

Significant weather

Cloud and vertical obscuration

Non-convective low-level wind shear (LLWS)

_, _, and _ are not included in the forecast.

Temperature/dew point

altimeter

remarks

The three types of reports:

Routine forecast - TAF

Amended forecast - TAF AMD

Corrected forecast - TAF COR

Routine TAFs are issued _ times per day:

4 times per day; 0000, 0600, 1200, 1800Z

TAFs are amended whenever they become, in the forecaster's judgment,

unrepresentative of existing or expected conditions

The valid period is the time period during which the TAF is valid. Routine TAFs are valid for

either 24- or 30- hour time periods.

In the U.S., _-hour TAFs are only issued for airports with significant international traffic

30

The non-convective LLWS group is included whenever LLWS is expected within _ feet of the surface

2,000 ft

LLWS can severely impact airplanes, especially within 2,000 feet AGL, because of

limited vertical airspace for recovery

LLWS is always assumed with _ activity. The group is omitted if LLWS is not expected to occur.

convective

The FM (“from”) change indicator group is used to indicate

a significant and rapid change to a new set of prevailing conditions.

All elements of the TAF are included in each _ group regardless of whether they are forecast to change or not.

FM

All forecast conditions listed before an FM group are

superseded by those within the FM group at the indicated time

The TEMPO change indicator group is used to indicate

temporary fluctuations to forecast meteorological conditions.

Only those weather elements forecast to _ are required to be included in the TEMPO group

temporarily change

The PROB30 group is used to forecast a _ of a thunderstorm or precipitation event and its associated weather elements (wind, visibility and/or sky condition).

low probability (30 percent chance)

The PROB30 group is located within the same line as the

prevailing condition (i.e., FM) group

A _ is a weather advisory concerning weather significant to the safety of all aircraft

SIGMET

A SIGMET may be issued when specified conditions are affecting or in the judgment of the forecaster, are expected to affect an area of at least _ square miles or an area judged to have a significant impact on the safety of aircraft operations.

3,000

Within the contiguous U.S. (CONUS), SIGMETs are issued for the following weather phenomena:

Severe or greater turbulence

Severe icing

Widespread duststorms

Widespread sandstorms

Volcanic ash

Outside of the CONUS (OCONUS), SIGMETs are also issued for the following weather phenomena:

Thunderstorm of the following types: obscured, embedded, widespread, squall line, and isolated severe

Tropical cyclone

Radioactive cloud

A SIGMET is an _ weather report issued any time conditions reaching SIGMET criteria are occurring or expected to occur within a _

unscheduled, 4-hour period

A SIGMET can have a maximum valid period of _ hours, except for _ SIGMETs outside the contiguous U.S., which can be valid up to _ hours.

4, volcanic ash (VA) and/or tropical cyclone (TC), 6

If conditions are expected to persist after the SIGMET's valid period,

a statement to that effect is included in the last line of the text.

SIGMETs for continuing phenomena will be reissued at least every _ hours as long as SIGMET conditions are expected to continue.

4

A Convective SIGMET is a weather advisory concerning

convective weather significant to the safety of all aircraft.

Convective SIGMETs are ONLY issued for

the contiguous U.S. instead of SIGMETs for thunderstorms.

A Convective SIGMET is issued when:

A severe thunderstorm with 50 knot winds or greater, hail ¾ inch or greater in diameter, or tornadoes

A line of thunderstorms at least 60 miles with 40% active

An active area of thunderstorms 3,000 square miles with 40% active

Expected to occur for more than 30 minutes regardless of size

Weather phenomena meeting Convective SIGMET criteria that are NOT within the contiguous U.S. would result

in a SIGMET being issued

Convective SIGMET bulletins for the Eastern (E), Central (C), and Western (W) regions of the contiguous U.S. are issued

hourly at 55 minutes past the hour.

Convective SIGMETs are valid for _ hours or until superseded by the next hourly issuance.

2 (2-6 hours for outlook)

A _-to-_-hour outlook is included at the end of each bulletin.

2, 6

An _ is an in-flight advisory concerning weather phenomena that are of operational interest to all aircraft and potentially hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualifications.

AIRMET

AIRMETs concern weather of _ severity than that covered by SIGMETs or Convective SIGMETs.

less

AIRMET bulletins, each containing all valid AIRMET messages, are issued on a _ basis for each forecast region.

scheduled

AIRMET Sierra designates

for Instrument Flight Rules (IFR) and extensive mountain obscuration

AIRMET Tango designates

for moderate turbulence, sustained surface winds greater than 30 knots, and nonconvective low-level wind shear (LLWS) potential

AIRMET Zulu

for moderate icing and freezing levels

AIRMET messages are valid for no more than _ hours

6

A CWA is an _ weather advisory issued by _ for Air Traffic Control (ATC) use to alert pilots of existing or anticipated adverse weather conditions within the next _ hours

unscheduled, Center Weather Service Unit (CWSU) meteorologists, 2

A CWA is NOT a flight planning product because of its

short lead time and duration.

CWA criteria include:

Thunderstorms

1. Severe (SEV TS)

2. Embedded (EMBD TS)

3. Line (LN TS)

4. Area (AREA TS)

Icing

1. Moderate (MOD ICE)

2. Severe (SEV ICE)

Turbulence

1. Moderate (MOD TURB)

2. Severe (SEV TURB)

CWA criteria also include:

Heavy precipitation (HVY PCPN)

Freezing precipitation (FZ PCPN)

Low Instrument Flight Rules (LOW IFR)

Surface wind greater than or equal to 30 knots (STG SFC WND)

Non-convective low-level wind shear (LLWS) (surface – 2,000 feet AGL)

Duststorm (DS)

Sandstorm (SS)

Volcanic ash (VA)

Low Instrument Flight Rules (IFR) is defined as ceiling less than _ and/or visibility less than _.

500 ft AGL, 1 SM

An MIS is an _ discussion product issued by _ that summarizes anticipated weather conditions with potential impact on air traffic flow control and flight operations in an _’s area of responsibility.

unscheduled, CWSU meteorologists, Air Route Traffic Control Center (ARTCC)

The MIS provides a unique _, non-technical description of weather expected to occur over an extended period ranging from _.

plain language, several hours up to about two (2) days

An MIS is distributed to:

ARTCC personnel, including Traffic Management Unit (TMU) personnel

Other supported centers

An MIS is NOT intended to be used by _.

pilots

An MIS enables ATC personnel to include the impact of specific weather conditions in their _.

flow control decision making

Air traffic weather concerns include but are not limited to:

Thunderstorms

Operationally significant ceilings/visibility

Cloud tops

Wind and temperatures (surface and aloft)

Wind shear

Operationally significant pressure changes

Precipitation

Turbulence

Icing

Duststorm, sandstorm, and volcanic ash

Air traffic weather concerns for thunderstorms include:

Timing

Tops

Movement

Intensity

Character (such as broken lines or large clusters)

An FB is a computer-generated forecast of _, _, and _ at selected _, _, and _.

wind direction, wind speed, temperature

times, altitudes, locations

FBs are used by Air Traffic Control (ATC) to help avoid _.

clear air turbulence

AIRMETS are issued _ times per day

4 and varies

Wind and Temperature Aloft Forecast (FB) are issued at _ and valid for _.

00Z, 06Z, 12Z, 18Z

7, 9, or 12 hours