Section 6. Weather Information
2-6-1. FAMILIARIZATION
Become familiar with pertinent weather
information when coming on duty, and stay aware of current weather information
needed to perform ATC duties.
2-6-2. HAZARDOUS INFLIGHT WEATHER ADVISORY
SERVICE (HIWAS)
Controllers must advise pilots of
hazardous weather that may impact operations within 150 NM of their sector or
area of jurisdiction. Hazardous weather information contained in HIWAS
broadcasts includes Airmen's Meteorological Information (AIRMET), Significant
Meteorological Information (SIGMET), Convective SIGMET (WST), Urgent Pilot
Weather Reports (UUA), and Center Weather Advisories (CWA). Facilities must
review alert messages to determine the geographical area and operational impact
for hazardous weather information broadcasts. The broadcast is not required if
aircraft on your frequency(s) will not be affected.
a. Controllers within commissioned
HIWAS areas must broadcast a HIWAS alert on all frequencies, except emergency
frequency, upon receipt of hazardous weather information. Controllers are
required to disseminate data based on the operational impact on the sector or
area of control jurisdiction.
NOTE-
The inclusion of the type and number of weather advisory responsible for the
HIWAS advisory is optional.
PHRASEOLOGY-
ATTENTION ALL AIRCRAFT. HAZARDOUS WEATHER INFORMATION (SIGMET, Convective
SIGMET, AIRMET, Urgent Pilot Weather Report (UUA), or Center Weather Advisory
(CWA), Number or Numbers) FOR (geographical area) AVAILABLE ON HIWAS, FLIGHT
WATCH, OR FLIGHT SERVICE FREQUENCIES.
b. Controllers outside of
commissioned HIWAS areas must:
1. Advise pilots of the
availability of hazardous weather advisories. Pilots requesting additional
information should be directed to contact the nearest Flight Watch or Flight
Service.
2. Apply the same procedure when
HIWAS outlets, or outlets with radio coverage extending into your sector or
airspace under your jurisdiction, are out of service.
PHRASEOLOGY-
ATTENTION ALL AIRCRAFT. HAZARDOUS WEATHER INFORMATION FOR (geographical area)
AVAILABLE FROM FLIGHT WATCH OR FLIGHT SERVICE.
c. Terminal facilities have the
option to limit hazardous weather information broadcasts as follows: Tower cab
and approach control facilities may opt to broadcast hazardous weather
information alerts only when any part of the area described is within 50 NM of
the airspace under their jurisdiction.
REFERENCE-
AIM, Chapter 7, Section 1, Meteorology, Para 7-1-5 through Para 7-1-9.
2-6-3.
PIREP INFORMATION
Significant
PIREP information includes reports of strong frontal activity, squall lines,
thunderstorms, light to severe icing, wind shear and turbulence (including clear
air turbulence) of moderate or greater intensity, volcanic eruptions and
volcanic ash clouds, detection of sulfur gases (SO2 or H2S)
in the cabin, and other conditions pertinent to flight safety.
REFERENCE-
FAAO JO 7110.65, Para
3-1-8, Low Level Wind Shear/Microburst
Advisories.
FAAO JO 7210.3, Para 6-3-1, Handling of SIGMETs, CWAs, and PIREPs.
AIM, Para 7-5-9, Flight Operations in Volcanic Ash.
FAAO JO 7210.3, Para 10-3-1, SIGMET and PIREP Handling.
a. Solicit PIREPs when requested or
when one of the following conditions exists or is forecast for your area of
jurisdiction:
1. Ceilings at or below 5,000 feet.
These PIREPs must include cloud base/top reports when feasible.
TERMINAL. Ensure that at least one
descent/climb-out PIREP, including cloud base/s, top/s, and other related
phenomena, is obtained each hour.
EN ROUTE. When providing approach
control services, the requirements stated in TERMINAL above apply.
2. Visibility (surface or aloft) at
or less than 5 miles.
3. Thunderstorms and related
phenomena.
4. Turbulence of moderate degree or
greater.
5. Icing of
light degree or greater.
6. Wind shear.
7. Volcanic ash clouds.
NOTE-
Pilots may forward PIREPs regarding volcanic activity using the format described
in the Volcanic Activity Reporting Form (VAR) as depicted in the AIM,
Appendix 2.
8. Detection of sulfur gases (SO2 or H2S),
associated with volcanic activity, in the cabin.
NOTE-
The smell of sulfur gases in the cockpit may indicate
volcanic activity that has not yet been detected or reported
and/or possible entry into an ashbearing cloud. SO2 is
identifiable as the sharp, acrid odor of a freshly struck
match. H2S has the odor of rotten eggs.
9. TERMINAL. Braking
Action Advisories are in effect.
REFERENCE-
FAAO JO 7110.65, Para
3-3-5, Braking Action Advisories.
P/CG Term- Braking Action Advisories.
b. Record with the PIREPs:
1. Time.
2. Aircraft position.
3. Type aircraft.
4. Altitude.
5. When the PIREP involves icing
include:
(a) Icing type and intensity.
(b) Air temperature in which icing
is occurring.
c. Obtain PIREPs directly from the
pilot, or if the PIREP has been requested by another facility, you may instruct
the pilot to deliver it directly to that facility.
PHRASEOLOGY-
REQUEST/SAY FLIGHT CONDITIONS.
Or if appropriate,
REQUEST/SAY (specific conditions; i.e., ride, cloud, visibility, etc.)
CONDITIONS.
If necessary,
OVER (fix),
or
ALONG PRESENT ROUTE,
or
BETWEEN (fix) AND (fix).
d. Handle PIREPs as follows:
1. Relay pertinent PIREP
information to concerned aircraft in a timely manner.
2. EN ROUTE. Relay all
operationally significant PIREPs to the facility weather coordinator.
3. TERMINAL. Relay all
operationally significant PIREPs to:
(a) The appropriate intrafacility
positions.
(b) The FSS serving the area in
which the report was obtained.
NOTE-
The FSS is responsible for long line dissemination.
(c) Other concerned terminal or en
route ATC facilities, including non-FAA facilities.
(d) Use the word gain and/or
loss when describing to pilots the effects of wind shear on airspeed.
EXAMPLE-
“Delta Seven Twenty-one, a Boeing Seven Twenty-seven, previously reported wind
shear, loss of Two Five knots at Four Hundred feet.”
“U.S. Air Seventy-six, a D-C Niner, previously reported wind shear, gain of
Twenty-Five knots between Niner Hundred and Six Hundred feet, followed by a loss
of Five Zero knots between Five Hundred feet and the surface.”
REFERENCE-
AIM, Para 7-1-24, Wind Shear PIREPs.
2-6-4. WEATHER AND CHAFF SERVICES
a. Issue pertinent information on observed/reported weather and chaff areas by defining the area of
coverage in terms of azimuth (by referring to the
12hour clock) and distance from the aircraft or by
indicating the general width of the area and the area
of coverage in terms of fixes or distance and direction
from fixes.
NOTE-
Weather significant to the safety of aircraft includes such
conditions as funnel cloud activity, lines of thunderstorms,
embedded thunderstorms, large hail, wind shear,
microbursts, moderate to extreme turbulence (including
CAT), and light to severe icing.
REFERENCE-
AIM, Paragraph 7114, ATC Inflight Weather Avoidance Assistance.
PHRASEOLOGY-
WEATHER/CHAFF AREA BETWEEN
(number)O'CLOCK AND (number) O'CLOCK
(number) MILES,
or
(number) MILE BAND OF WEATHER/CHAFF FROM
(fix or number of miles and direction from fix) TO (fix or
number of miles and direction from fix).
b. Inform any tower for which you provide
approach control services of observed precipitation
on radar which is likely to affect their operations.
c. Use the term “precipitation” when describing
radar-derived weather. Issue the precipitation
intensity from the lowest descriptor (LIGHT) to the
highest descriptor (EXTREME) when that information is available. Do not use the word “turbulence” in
describing radar-derived weather.
1. LIGHT.
2. MODERATE.
3. HEAVY.
4. EXTREME.
NOTE-
Weather and Radar Processor (WARP) does not display
light intensity.
PHRASEOLOGY-
AREA OF (Intensity) PRECIPITATION BETWEEN
(number) O'CLOCK AND (number) O'CLOCK, (number)
MILES, MOVING (direction) AT (number) KNOTS, TOPS
(altitude). AREA IS (number) MILES IN DIAMETER.
EXAMPLE-
1. “Area of extreme precipitation between eleven o'clock
and one o'clock, one zero miles moving east at two zero
knots, tops flight level three niner zero.”
2. “Area of heavy precipitation between ten o'clock and
two o'clock, one five miles. Area is two five miles in
diameter.”
3. “Area of heavy to extreme precipitation between ten
o'clock and two o'clock, one five miles. Area is two five
miles in diameter.”
REFERENCE-
P/CG Term- Precipitation Radar Weather Descriptions.
d. When precipitation intensity information is not
available.
PHRASEOLOGY-
AREA OF PRECIPITATION BETWEEN (number)
O'CLOCK AND (number) O'CLOCK, (number) MILES. MOVING (direction) AT (number) KNOTS, TOPS (altitude). AREA IS (number) MILES IN DIAMETER, INTENSITY UNKNOWN.
EXAMPLE-
“Area of precipitation between one o'clock and three
o'clock, three five miles moving south at one five knots, tops
flight level three three zero. Area is three zero miles in
diameter, intensity unknown.”
NOTE-
Phraseology using precipitation intensity descriptions is
only applicable when the radar precipitation intensity
information is determined by NWS radar equipment or
NAS ground based digitized radar equipment with weather
capabilities. This precipitation may not reach the surface.
e. EN ROUTE. When issuing Air Route Surveillance Radar (ARSR) precipitation intensity use the
following:
1. Describe the lowest displayable precipitation
intensity as MODERATE.
2. Describe the highest displayable
precipitation intensity as HEAVY to EXTREME.
PHRASEOLOGY-
AREA OF (Intensity) PRECIPITATION BETWEEN
(number) O'CLOCK and (number) O'CLOCK, (number)
MILES, MOVING (direction) AT (number) KNOTS, TOPS
(altitude). AREA IS (number) MILES IN DIAMETER.
EXAMPLE-
1. “Area of moderate precipitation between ten o'clock
and one o'clock, three zero miles moving east at two zero
knots, tops flight level three seven zero.
2. “Area of moderate precipitation between ten o'clock
and three o'clock, two zero miles. Area is two five miles in
diameter.”
f. When operational/equipment limitations exist,
controllers must ensure that the highest available
level of precipitation intensity within their area of
jurisdiction is displayed.
g. When requested by the pilot, provide radar
navigational guidance and/or approve deviations
around weather or chaff areas. In areas of significant
weather, plan ahead and be prepared to suggest, upon
pilot request, the use of alternative routes/altitudes.
1. An approval for lateral deviation authorizes
the pilot to maneuver left or right within the limits of
the lateral deviation area.
REFERENCE-
AIM, Paragraph 7114b, 1. (a) ATC Inflight Weather Avoidance
Assistance
2. If a pilot enters your area of jurisdiction
already deviating for weather, advise the pilot of any
additional pertinent weather which may affect his
route.
3. If traffic and airspace (i.e., special use
airspace boundaries, LOA constraints) permit,
combine the approval for weather deviation with a
clearance on course.
PHRASEOLOGY-
DEVIATION (restrictions if necessary) APPROVED,
WHEN ABLE, PROCEED DIRECT (name of
NAVAID/WAYPOINT/FIX)
or
DEVIATION (restrictions if necessary) APPROVED,
WHEN ABLE, FLY HEADING (degrees), VECTOR TO
JOIN (airway) AND ADVISE.
EXAMPLE-
1. “Deviation twenty degrees right approved, when able
proceed direct O'Neill VORTAC and advise.”
En Route: The corresponding fourth line entry is
“D20R/ONL” or “D20R/F.”
2. “Deviation 30 degrees left approved, when able fly
heading zero niner zero, vector join J324 and advise.”
En Route: In this case the free text character limitation
prevents use of fourth line coordination and verbal
coordination is required.
4. If traffic or airspace prevent you from
clearing the aircraft on course at the time of the
approval for a weather deviation, instruct the pilot to
advise when clear of weather.
PHRASEOLOGY-
DEVIATION (restrictions if necessary) APPROVED,
ADVISE CLEAR OF WEATHER.
EXAMPLE-
“Deviation North of course approved, advise clear of
weather.”
En Route: In this case the corresponding fourth line entry
is “DN,” and the receiving controller must provide a
clearance to rejoin the route in accordance with paragraph
2115 c.
h. When a deviation cannot be approved as
requested because of traffic, take an alternate course
of action that provides positive control for traffic
resolution and satisfies the pilot's need to avoid
weather.
PHRASEOLOGY-
UNABLE DEVIATION, FLY HEADING (heading),
ADVISE CLEAR OF WEATHER
or
UNABLE DEVIATION, TURN (number of degrees)
DEGREES (left or right)FOR TRAFFIC, ADVISE CLEAR
OF WEATHER,
EXAMPLE-
“Unable deviation, turn thirty degrees right vector for
traffic, advise clear of weather.”
i. When forwarding weather deviation
information, the transferring controller must clearly
coordinate the nature of the route guidance service
being provided. This coordination should include,
but is not limited to: assigned headings, suggested
headings, pilotinitiated deviations. Coordination can
be accomplished by: verbal, automated, or
prearranged procedures. Emphasis should be made
between: controller assigned headings, suggested
headings, or pilot initiated deviations.
EXAMPLE-
“(call sign) assigned heading 330 for weather
avoidance"
“(call sign) deviating west, pilot requested…"
REFERENCE-
FAA Order JO 7110.65 2114 Coordinate Use Of Airspace
FAA Order JO 7110.65 545 Transferring Controller Handoff
FAA Order JO 7110.65 546 Receiving Controller Handoff
FAA Order JO 7110.65 5410 Prearranged Coordination
FAA Order JO 7110.65 5411 En Route Fourth Line Data Block
Usage
j. En Route Fourth Line Data Transfer
1. The inclusion of a NAVAID, waypoint, or /F
in the fourth line data indicates that the pilot has been
authorized to deviate for weather and must rejoin the
route at the next NAVAID or waypoint in the route of
flight.
REFERENCE-
FAA Order JO 7110.65 5411 En Route Fourth Line Data Block
Usage
EXAMPLE-
“Deviation twenty degrees right approved, when able
proceed direct O'Neill VORTAC and advise.” In this
case, the corresponding fourth line entry is
“D20R/ONL” or “D20R/F.”
2. The absence of a NAVAID, waypoint, or /F in
the fourth line indicates that:
(a) The pilot has been authorized to deviate
for weather only, and the receiving controller must
provide a clearance to rejoin the route in accordance
with paragraph 2115c.
EXAMPLE-
“Deviation twenty degrees right approved, advise
clear of weather.”
(b) The free text character limitation prevents
the use of fourth line coordination. Verbal
coordination is required.
EXAMPLE-
“Deviation 30 degrees left approved, when able fly
heading zero niner zero, vector join J324 and
advise.”
k. The supervisory traffic management
coordinatorincharge/operations
supervisor/controllerincharge shall verify the
digitized radar weather information by the best means
available (e.g., pilot reports, local tower personnel,
etc.) if the weather data displayed by digitized radar
is reported as questionable or erroneous. Errors in
weather radar presentation shall be reported to the
technical operations technician and the air traffic
supervisor shall determine if the digitized radar
derived weather data is to be displayed and a NOTAM
distributed.
NOTE-
Anomalous propagation (AP) is a natural occurrence
affecting radar and does not in itself constitute a weather
circuit failure.
2-6-5.
CALM WIND CONDITIONS
TERMINAL. Describe the wind as calm
when the wind velocity is less than three knots.
REFERENCE-
FAAO JO 7110.65, Para
3-5-3, Tailwind Components.
FAAO JO 7110.65, Para
3-10-4, Intersecting Runway Separation.
2-6-6.
REPORTING WEATHER CONDITIONS
a. When the prevailing visibility
at the usual point of observation, or at the tower level, is less than 4 miles,
tower personnel must take prevailing visibility observations and apply the
observations as follows:
1. Use the lower of the two
observations (tower or surface) for aircraft operations.
2. Forward tower visibility
observations to the weather observer.
3. Notify the weather observer when
the tower observes the prevailing visibility decrease to less than 4 miles or
increase to 4 miles or more.
b. Forward current weather changes
to the appropriate control facility as follows:
1. When the official weather
changes to a condition which is below 1,000-foot ceiling or below the highest
circling minimum, whichever is greater, or less than 3 miles visibility, and
when it improves to a condition which is better than those above.
2. Changes which are classified as
special weather observations during the time that weather conditions are below
1,000-foot ceiling or the highest circling minimum, whichever is greater, or
less than 3 miles visibility.
c. Towers at airports where
military turbo-jet en route descents are routinely conducted must also report
the conditions to the ARTCC even if it is not the controlling facility.
d. If the receiving facility
informs you that weather reports are not required for a specific time period,
discontinue the reports. The time period specified should not exceed the
duration of the receiving controller's tour of duty.
e. EN ROUTE. When you
determine that weather reports for an airport will not be required for a
specific time period, inform the FSS or tower of this determination. The time
period specified should not exceed the duration of receiving controller's tour
of duty.
REFERENCE-
FAAO JO 7110.65, Para
3-10-2, Forwarding Approach Information by
Nonapproach Control Facilities.
2-6-7. DISSEMINATING WEATHER INFORMATION
TERMINAL. Observed elements of
weather information must be disseminated as follows:
a. General weather information,
such as “large breaks in the overcast,” “visibility lowering to the south,” or
similar statements which do not include specific values, and any elements
derived directly from instruments, pilots, or radar may be transmitted to pilots
or other ATC facilities without consulting the weather reporting station.
b. Specific values, such as ceiling
and visibility, may be transmitted if obtained by one of the following means:
1. You are
properly certificated and acting as official weather observer for the elements
being reported.
NOTE-
USAF controllers do not serve as official weather observers.
2. You have obtained the
information from the official observer for the elements being reported.
3. The weather report was composed
or verified by the weather station.
4. The information is obtained from
an official Automated Weather Observation System (AWOS) or an Automated Surface
Observation System (ASOS).
c. Differences between weather
elements observed from the tower and those reported by the weather station must
be reported to the official observer for the element concerned.
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