Flashcards in Weather Deck (82):
What is the difference between handling air carriers and GA aircraft in
Air carriers can generally handle encounters with adverse
weather much better than GA, air carriers are expected to
handle a certain amount of in-flight weather phenomena where
as GA are expected to avoid hazardous weather and exit the
What advantages do air carrier pilots and aircraft have over GA?
• 2 pilots, more experience in bad weather
• Must meet their equipage and engineering standards, airborne
weather radar (is not as good as ground radar), de-icing and
Provide additional services to the extent possible contingent only
• Higher priority duties, limitations to radar, volume of traffic,
frequency congestion, controller workload
• Additional services include weather dissemination
What are ATC responsibilities in regards to weather?
Be familiar with weather conditions when coming on duty and
stay aware while on duty, advise pilot of hazardous weather that
may impact operations within 150 NM of their sector, solicit
PIREPS, relay PIREPS in a timely manner, relay all operationally
significant PIREPS to the facility weather coordinator
When must you solicit PIREPS?
• When requested or weather is or is forecast to be:
• Ceilings at or below 5000 ft (include base and top)
• Visibility at or less than 5 miles (surface and aloft)
• Thunderstorms and related phenomena
• Turbulence (moderate or greater)
• Icing (light or greater)
• Wind shear
• Volcanic ash clouds
What would be considered an URGENT PIREP?
• Tornados, funnel clouds, waterspouts
• Severe or extreme turbulence (including CAT)
• Severe icing
• Low level wind shear (within 2,000 ft of surface)
• Volcanic eruptions and volcanic ash clouds
• Any other weather phenomena reported which are considered
by you to be hazardous or potentially hazardous to flight
What must the controller do when a PIREP is received?
Record, classify and disseminate when any of the above
conditions are reported
What should be recorded with a PIREP?
Time, aircraft position, aircraft type, altitude, icing type/intensity
and air temp in which icing is occuring
Who should you relay PIREPs to in a timely manner?
All concerned aircraft and weather coordinator
What is done with urgent PIREPs?
• Immediately broadcasted over the frequency and distributed via
local and national directives
• As a radar associate you are responsible to immediately ensure
that urgent PIREPS are forwarded to facility weather coordinator
by passing the information to your supervisor and then verbally
coordinating with other sectors/facilities that may be affected by
the hazardous weather
Define Urgent PIREP.
Weather phenomenon reported by a pilot which represents a
hazard or a potential hazard to flight operations
What should be issued when giving weather information?
• Pertinent information observed/reported weather or chaff areas
• Echo intensity when available- moderate heavy extreme
• Radar navigational guidance and or approve deviations around
weather or chaff areas when requested
• Weather and chaff information by defining the areas of coverage
in terms of azimuth and distance from aircraft
What should you do when a deviation cannot be approved as
• If situation permits suggest an alternate course of action
Who should receive PIREPs?
All affected pilots, controllers, and facilities
What actions are required by the controller?
• Advise pilots of hazardous weather that may impact operations
within 150 NM of their sector or area of jurisdiction
• Become familiar with and stay aware of current weather
conditions in your sector and surrounding sectors when coming
on duty and throughout your shift
• Issue pertinent weather information including echo intensity
when that information is available to the pilot on observed/
reported weather or chaff areas
How are forecasts of aviation weather differentiated?
By the target audience
• A concise description of the occurrence or expected occurrence
of specified en route weather phenomena which may affect the
safety of aircraft operations, but at intensities lower than those
which require the issuance of a SIGMET
• Intended for the dissemination to all pilots in flight to enhance
safety and are particular concern to operators and pilots of
aircraft sensitive to phenomena described and to pilots without
• A concise description of the occurrence or expected occurrence
of specified en route weather phenomena which may affect
safety of aircraft operations
• Provides aircraft operators and crews notice of potentially
hazardous en route phenomena such as thunder storms and
hail, turbulence, icing, sand and dust storms, tropical cyclones,
and volcanic ash
• Intended for all pilots
What are convective SIGMETs issued for?
• Thunderstorms in the lower 48 states (other states regular
• Center weather advisory is an aviation weather warning for
conditions meeting or approaching national in flight advisory
(AIRMET SIGMET Convective SIGMET) criteria.
• An unscheduled in flight, flow control, air traffic, and crew
advisory. By nature of its short lead time the CWA is not a flight
planning product. It is generally a short term forecast for
conditions beginning within the next 2 hours
• Issued by national weather service at center weather service
What is a CWSU?
A joint FAA/NWS weather support team located in all en route
centers. The team consists of NWS meteorologists and FAA
traffic management personnel
When do you not have to broadcast to pilots of hazardous weather
within 150 NM?
When the aircraft on your frequency will not be affected
What should be done upon receipt of hazardous flight information
within commissioned HIWAS areas?
Broadcast a HIWAS alert on all frequencies except emergency
What should be done upon receipt of hazardous flight information
NOT within commissioned HIWAS areas?
Advise pilots of the availability of hazardous weather advisories
with instructions to request further information from flight watch
or flight service
A continuous recorded hazardous in flight weather forecast
broadcasted to airborne pilots over selected VOR outlets defined
as HIWAS broadcast areas
As a radar associate what is your responsibility in regards to receiving
SIGMETS, AIRMETS, CWAsetc?
• Must ensure the radar controller is made aware of them in a
• Controllers must electronically acknowledge hazardous weather
information messages which may be received via the SIGMET or
GI views after appropriate action has been taken
What are the most hazardous icing conditions?
Encounters with freezing rain FZRA and freezing drizzle FZDZ
(no aircraft is evaluated for these conditions)
Can ground based weather radar and airborne weather radar systems
provide precise real time information on areas of ice?
Icing forecasts are heavily dependent upon what?
What is structural icing? When does it form? And what are the 2
conditions necessary for it to form?
• Ice that forms on the surface
• +2 and -20 degrees c
• Visible moisture and temperature at which the moisture hits the
aircraft must be 0 degrees c or colder
When does icing occur?
365 days a year
How does structural icing affect an aircraft?
Reduces aircraft efficiency by either slowing the aircraft down or
forcing it downward
What happens if an aircraft is in icing conditions for too long?
It may not be capable of climbing to exit the icing conditions
Half an inch of ice and reduce lift by how much?
What are the three types of ice? Define each.
• Clear Iceo
o Translucent or clear and generally smooth
o Temp- 0 to -10
o Can accumulate very rapidly and is difficult to remove
• Rime Iceo
Appears rough and milky
o Temp- -15 to -20 degrees C
o Formed by the instantaneous freezing of super-cooled
droplets as they strike the aircraft
• Mixed Iceo
Mixture of both clear and rime
o Temp- -10 to -15 degrees C
o Appears as layers of relatively clear and opaque ice
o Occurs when drops very in size
o Similar to clear ice in that it can spread over more of the
airframes surface and therefore more difficult to remove
What are the four intensities of structural icing?
Trace, light, moderate, severe
What icing intensity is potentially hazardous with short encounters
and use of anti-ice/de-ice equipment is necessary?
Structural icing affects aircraft by _____weight and _____thrust.
Increasing weight and decreasing thrust
When VFR conditions are present, where can a VFR flight encounter
In freezing rain and freezing drizzle
What is the most important source of information for icing?
Why is icing intensity subjective?
• Icing conditions are extremely variable in space and time and
depend on the ice type and ice protection of the reporting aircraft
• A few hundred feet or a few minutes can make a huge difference
• Type aircraft makes a huge difference
When soliciting/receiving icing OIREPS it is essential to collect what
Time, aircraft position, Aircraft type, altitudes icing was
encountered, temperature, and type and intensity (good
technique to ask if FZRA or FZDZ are present (it is also helpful
to record if the aircraft was in a climb or descent since more
surfaces are subject to accretion
Severe icing is considered what type of PIREP and what needs to be
Urgent PIREP and needs to be delivered to the CWC
immediately and broadcasted over the frequency
Is it important to know when aircraft are not receiving icing?
Yes it can be equally important for both controllers and pilots.
Can also be used to improve icing forecasts
PIREPs are always given in___, since altitudes are reported by pilot’s
As a radar associate what you your responsibility for PIREPs?
Accurately writing down the information and giving it to the
Supervisor for forwarding to CWC
Why are top reports important?
Indicate how quickly a storm is building…height indicates
Why do controllers have a good idea of where icing exists?
• Because our display shows precipitation (visible moisture)
• Does not show light precipitation nor does it display FZRA or
What are good controller practices?
• Keep pilots out of icing all together
• Be familiar with the weather
• Know your bases and tops
• Be aware of freezing levels
• Maintain the SIA with updates
What are controller requirements when there are known icing
• Solicit a PIREP
• Include icing conditions in position relief briefing
• Always keep aircraft advised of known icing conditions
When must a controller solicit PIREPs in regards to icing?
When icing exists or is forecast to exist at a light degree or
• Any irregular motion of the aircraft in flight, especially when
characterized by a rapid up and down motion, caused by a rapid
variation in wind speed or direction
• Can be caused by convection, wind shear, or obstruction to wind
• Described in terms of intensity and altitude
Define wind shear.
• A change in wind speed or direction within a short distance
(horizontal or vertical)
• Turbulence can occur with wind shear
What causes wind shear?
Jet stream, fronts, temperature inversions and thunder storms
What is significant about LLWS?
• Particularly dangerous form of wind shear and is hazardous to all
• Caused by thunderstorms
• Always present if there is a downburst
• Microburst is the most severe form of a downburst
• Pilots and affect facilities must be advised immediately of LLWS
• Causes dramatic changes in head wind and tail wind during the
most critical phases of flight
What is Clear Air Turbulence?
Often encountered in the vicinity of the jet stream typically where no
clouds are present
Often cause by and found near the jet stream
Most common between 20,000 and 50,000 ft
Sometimes found in mountain range
What are the effects of CAT?
No visible indication
Rely on PIREPs for location
AIRMETs and SIGMETs may also contain information about CAT
What are the turbulence intensities and define them.
o Momentarily causes slight, erratic changes in altitude and
o Similar to light turbulence but of a greater intensity.
Changes in altitude and or attitude occur but the aircraft
remains in positive control at all times
o Variations in airspeed are small, occupants feel strains
against seat belts, unsecured objects dislodged, food
service and walking are difficult
o Causes large, abrupt changes in altitude and or attitude.
Usually causes large variations in IAS. Aircraft may be
momentarily out of control
o Occupants are forced violently against seatbelts, unsecured
objects are tossed about, food service and walking are
o The aircraft is violently tossed and is practically impossible
o Structural damage is possible
What turbulence intensity is described when occupants feel strain
against their seatbelts, there is difficulty walking and loose objects
What form of turbulence can result in large and abrupt altitude
Severe and extreme
What is the only source of real time info on intensity and location of
What must be done when moderate degree or greater turbulence or
Define occasional, intermittent, and continuous.
• Occasional- less then 1/3the time
• Intermittent- 1/3 -2/3 the time
• Continuous- more that 2/3 the time
How does turbulence impact ATC?
Reduces unusable airspace, frequency congestion, capacity to
utilize routine control techniques may be reduced (speed control,
vectoring in trail), increased workload due to re routes
Where do thunderstorms usually occur?
In warm weather in unstable air
What can higher surface temperatures create?
Temperature instability leading to strong convective updrafts and
Can the ATC radar show all of a thunderstorm?
No only precip…thunderstorm is much bigger
What are embedded thunderstorms? And why are they dangerous?
Embedded in clouds, some or haze and are not visible to pilots,
thunderstorms that are closest to an aircraft can mask the
presence of embedded storms further along with some types of
on board radar, difficult to deviate around because the are often
part of a line of thunderstorms
Why are thunderstorms hazardous?
Severe to extreme turbulence, sever icing, nail, lightening,
downbursts, LLWS , tornados, low cieiling and reduced visibility
How far to hazards of a thunderstorm reach?
How many miles should be between storms to fly through?
Where can hail occur?
Top of a thunderstorm all the way to the surface and can be
found several miles away from the cumulonimbus cloud
What are the affect of hail?
Damage windshield, damage aircraft and make it difficult to
control, break nose cone and on board radar, damage and
disrupts the airflow over the airfoils reducing lift
Where does lightening occur?
Within several miles away from the main thunderstorm, can
occur within the anvil or our of the sides of the cumulonimbus,
can extend could to could, cloud to air, or cloud to ground
Why is lightning a hazard to aircraft?
Can damage or disable aircraft by disabling electrical systems,
igniting fuel vapors, temporarily blinding pilots
When do tornados occur?
With supercell thunderstorms and are usually brief lasting only a
few minutes but can last over an hour
What information is available to the controller about the presence of
• METAR reports
• Convective SIGMETS
What type of precipitation does WARP/NEXRAD not show?
How do you issue precipitation information?
“Moderate precipitation between 9 o clock and 2 o clock 3-0
miles. Precipitation area is 4-0 miles in diameter”
What does a convective SIGMET imply?
Severe or greater turbulence, severe icing, and LLWS
• Issued as in unscheduled aviation weather warning for
conditions meeting Convective SIGMET criteria
• May precede or refine a Convective SIGMET
• May also highlight significant thunderstorms not meeting
Convective SIGMET criteria
• Used to alert pilot of existing of anticipated adverse weather
conditions that are expected to occur within 2 hours of the time