Cold Front

Operations Duty Managers

• The term on its own does not impact operational decisions. The weather associated with a cold front is the consideration, including possible wind shifts that may impact active runway orientation.
• For Situational Awareness- how well defined is the front, how good is the upper-level support, and how quickly is it moving? For thunderstorms in particular - how well is CoSPA performing and when it will impact bedposts/airports? Is there any convective activity ahead of the cold front?
• A close watch will be kept on the front’s position and any initialization of convective activity, including satellite and radar imagery, along with upstream obs.
• Winter cold front focus is mainly on potential snow accumulation and forecast winds both ahead and behind of the frontal passage, as both have the potential to impact operations.

This term is not detailed enough to spark any planning, it would spark a request for detailed event predictions with specifics, it lets us know weather is coming but we need far more specifics before any planning can begin.

ATC (Major and Regional Towers)

Thunderstorms along cold fronts are fun to watch from the control tower.

• We are watching for lightning strikes on radar and advising pilots accordingly.
• Sudden wind shifts may also impact our operation, but usually by the time we’re in those situations, the storms are close and the flying is minimal.
• Some considerations for IFR departures are also given: i.e. deviations from departure routes (SIDs) for weather.
• Variable strong winds can lead to playing runway roulette (Multiple runway changes) in a very short period of time.
• Red Alerts: all ground crews must take cover. Therefore, aircraft can not be marshalled to gates. Aircraft can not push back from gate. Red Alerts cause gridlocks on the maneuvering area and apron which can lead to ground stops.

Cold fronts share the same seasonal variation as warm fronts, but the effects are more intense due to the greater threat of convective cloud and associated severe weather, particularly in summer, as well as the much higher speed of advance of a cold front. Specialists at sites that have weather observation responsibilities must be on the lookout during a Cold Frontal passage during the shoulder seasons to ensure that wet/damp conditions aren’t becoming ice/frost conditions. This not only effects aircraft but also requires notification of airport maintenance crews to begin mitigation operations.

FIC

When presenting information in a Weather Briefing, Synoptic Features such as a Cold Front are referred to initially to explain the strategic view of weather effects. Once the Briefing moves into detail around Departure Point, Enroute Track and Destination Weather at ETA, a Specialist will touch on actual and forecast local conditions, using the Synoptic feature to explain the source of these anticipated conditions. This will influence the Pilot’s choices in whether or not they go, what route and altitude they will take enroute, how much fuel they will need to perform the flight safely – this alone might cancel the flight, if the prevailing wind aloft is unfavorable, as the required fuel burn may exceed the amount of gas the airplane can carry.

The type of Synoptic feature informs the general conditions, subject to seasonal and diurnal effects, that can be expected. This is where the Flight Service Specialist working in a FIC really earns their pay, using their knowledge of meteorology in conjunction with their expertise in the unique factors contained in their FIC’s Area of Responsibility. Due to the dynamic nature of the aviation environment, no two briefings will be exactly the same.

AAS

Advisory specialists will monitor the approach of a cold front by watching for the Convective builds that often lead an advancing Cold Front, in concert with watching the weather radar and maintaining a weather watch on sites upstream. Specialists might also check the GFAs and contact the FIC for more information if required. Frontal passage is accompanied by a wind shift towards the north/northwest and a trend to becoming more gusty, as well as a rapid decrease in temperature and a rise in pressure.

Cold fronts can yield conditions that increase the risk of wind shear and changing wind directions. Thunderstorms associated with cold fronts yield their own increased workload and are covered under that terminology.

The possibility of missed approaches is greatly increased, thus increasing the total traffic load and its complexity.

Runway changes are usually quite short but are some of the highest-workload situations terminal controllers can have.

• The main thing is timing, when the cold front passes the winds will often completely swing around, requiring a runway change.
• If we're unlucky, this will happen during an arrival or departure rush. In that case, controllers must time themselves with the tower, to figure out who the last arrival is and who the last departure is.
• Controllers try to time this the best they can, because if the last arrival has landed and there are still 2-3-4 departures, the next arrivals (who would be going for the opposite runway) will have to hold for a while, which increases the workload a lot. On the other hand, if the last departure has gone out and we still have several arrivals, the next departures will have to hold short of the runway for a long time while the last arrivals land. Getting this timing right helps to reduce delays for everyone.

• When severe weather occurs, usually thunderstorms, aircraft destined for regional airports often proceed to alternate destinations.
• It is important for ATC to inform the pilots (generally smaller aircraft less well suited to fly close to build-ups) of the whereabouts of the severe weather so they can make an informed decision on how to proceed. This is even more important with well-defined cold fronts.
• ATC will also likely be holding aircraft in the enroute in the event of a runway change at peak traffic times as coordination is required between the tower and terminal to sequence and time arrivals and departures properly.
• When cold fronts are projected to pass through a region, planning is very important.
• More airspace sectors may need to be opened and controllers tend to apply vertical altitude protection between aircraft more frequently and must provide pilots with as much information about the location of the severe weather so it can be avoided. Often, aircraft will only see and avoid weather or fronts that are directly in front of them, so a controller can inform the pilot of the best course of action to avoid weather along their route.

Cold fronts can come into play when we are planning SWAP routes. Often those fronts can have turbulence or convective clouds associated with them. It’s good to know the altitude to which those clouds will reach when planning on how busy we can be.

• The higher the convective clouds get, the more likely planes will need to deviate, and deviations increase the complexity and our workload quite a bit.
• Turbulence also has a strong impact on our workload. Either planes will question a lot on how the turbulence is and/or will ask altitude changes to avoid the turbulence as much as possible.

Generally knowing what fronts are present and their rate of speed allows a pilot to have the macro view while the TAF (micro view) is the way it is.

• A cold front will have the greatest impact on the operations during the summer season, when it is associated with lines of thunderstorms.
• In winter, snow squalls from open water are the biggest challenge with winter cold fronts combined with gusty winds and slippery runways where a quick change (flash freeze) on the runway occurs.
• Similar planning and concepts will apply to flight planning at regional airports.
• The only advantage over hubs is that holding and delays will be less at regional airports.
• A cold front will have the greatest impact on the operations during the summer season, when it will be associated with lines of thunderstorms.
• During pre-flight, pilots look at TAFs, radar, and SIGMETs (if any). Those are our indicators of a cold front, and we will be interested to know if it will trigger a line of thunderstorms, covered under that term.

Enroute

• Cold fronts can have associated weather that is impactful en-route.
• A cold front is high on the list of likely places to get a rough ride. Being aware of the location will allow you to plan for (manage) the cabin so the flight attendants can get their service done and then get everything stowed if required due to the slope of the cold front – or delay the service after departure if the front is close to the beginning of the flight.
• Thunderstorms - At lower altitudes, our main source of information will become our aircraft’s radar, as we try to navigate in the terminal area in between thunderstorms. We will get the latest METAR from the digital ATIS.
• Wind shear - If there is wind shear or a preceding aircraft executes a go-around, that’s the type of information that will be passed on by ATC, either tower or arrival. This is critical information in its relevance to our decision making.

High-level

• A pilot’s main sources of information enroute will be on our aircraft’s radar, our eyes and what see in front of us (if the weather is not embedded), METAR, TAF, and ground radar imagery thru the onboard Wifi. The aircraft’s radar has the priority during the decision making. It’s a good depiction of the current weather 150nm ahead of us, with some limitations that we are trained on.
• For weather deviation enroute, pilots need to assess which direction will be suitable for weather deviation. If either left or right looks good on the aircraft’s radar, we might supplement our decision making with the ground radar imagery.
• It is part of our dispatcher’s flight watch responsibilities to look after the weather enroute, at destination and at our alternate. Most of the time, pilots will get an ACARS message from our dispatcher regarding a new valid SIGMET on our route of flight.
• Throughout the flight, pilots will keep an eye on the line passage at destination and at the designated alternate. Using similar principles to those during flight planning, we will re-evaluate our initial plan to assess if it’s still a suitable course of action. Radar imagery is a great source of information to assess the line passage as the TAF can often be too broad.
• As an example, a TEMPO lasting several hours will not precisely indicate the time passage of the front. SIGMET is a good source of information for us as well. The forecaster can communicate useful information retrieved from all their available tools they have (sct/bkn/solid, tops, hail, motion, tendency). With the motion, pilots can calculate where the SIGMET zone will be and give us an idea of the passage time of the front.
• Turbulence can be encountered in an upper level cold front. Being aware of the location will allow you to plan for (manage) the cabin so the flight attendants can get their service done and then get everything stowed if required due to the slope of the cold front – or delay the service after departure if the front is close to the beginning of the flight.

Hearing the term cold front will set off a few alarm bells.

• The major factor affecting General Aviation (GA) pilots is the chance or presence of thunderstorms and other convective activity. This is often hard to predict and therefore harder to measure in its impact on operations. Its greatest impact is in the summer seasons when these conditions are often forecasted.
• Typically, VFR GA pilots will look at a forecast and try to determine whether the convective activity associated with the cold front is creating a large disturbance or if it is more localized.
• This is where detailed flight planning, including getting weather briefings provided by FIC specialists, becomes critical. Each of the following points can be discussed in depth with specialists. A large disturbance can be more easily tracked and therefore flight planning can occur around it, based on the location, speed, and direction. The more challenging forecast to work with is when a cold front is bringing isolated or scattered conditions, regardless of the severity. Here it can be hard to decide whether or not to depart because the conditions allow for the weather to change rapidly, thereby making it feel unpredictable.
• When electing to fly through or in the vicinity of a cold front, the severity must be established.
• Certain precautions will be taken in flight to reduce the likelihood of turbulence (changes in route or altitude).
• The pilot will need to plan for contingencies with the potentially changing weather and make plans for diversions to alternate airports if this becomes necessary.
• Frontal weather activity is a major concern for us VFR pilots. If we are going somewhere for the day, we want to make sure we get out before the weather prevents us from going. We can’t go around thunderstorms, so we have to go away from them. The speed/timing of the front matters a great deal. We want to have time to fly the mission and be home safely before the front hits.
• Most VFR GA pilots don’t fly above 10k feet ASL and thus don’t often consider the effects of upper level cold fronts. While we do recognize that the weather aloft will have an impact on the weather below, these concepts are poorly understood and therefore usually not considered by us.