Mobile Menu - Fr Mobile Search

Microburst

L
Weather Terminology Search
Alphabetical Search 

Legend

Legend

METAR Code

N/A

Weather Symbol

HAZARDS

With the strong winds they produce, microbursts can produce a lot of damage over a relatively small area and in a short amount of time. Microbursts can produce wind damage comparable to that of a tornado, which is why they can also be rated on the EF-Scale. As they are capable of producing winds in excess of 160km/h, they are capable of uprooting trees, damaging infrastructure that is not well secured, and could even flip over smaller aircrafts.

The sudden change in wind speed and direction that a microburst produces is particularly hazardous, as it can cause sudden, severe turbulence.

Associated terms coming soon:

Low-pressure system and mesoscale are terms associated with microbursts that will be coming soon to the Aviation Meteorology Reference.

About

Definition

A microburst is a localized, powerful column of sinking air (downdraft/downburst) within a thunderstorm that is usually less than or equal to 4 km in diameter, which lasts for less than 5 minutes. With wind speeds that can exceed 160km/h, microbursts can cause extensive damage at the surface and pose a serious hazard to structures and aircraft.

Associated Terms

3

Microburst

Visualization

Image 1 of 3

Dissipation

Microbursts dissipate quickly, as the powerful downburst of cool air acts against thunderstorm development, since the spreading cold air at the surface can enter into the updraft region. However, microbursts outflow winds can act as a trigger for new thunderstorms that can develop new microbursts, since this cold outflow can collide with warm air near the system and force it aloft.

Duration

By definition, microbursts are a very short-term event. While conditions building to these intense events can last for several hours, the microburst itself typically lasts less than 5 minutes.

In general, microbursts are more common in regions with a high frequency of thunderstorms, such as the Prairies and the eastern provinces and during the summer months when thunderstorm occurrence is most frequent. However, they can occur in any region where thunderstorms develop.

Microbursts can be difficult to forecast with much lead-time. As microbursts are associated with thunderstorms, this means that an accurate forecast for thunderstorm development is essential for the forecaster to determine whether these thunderstorms could produce microbursts. Thunderstorm forecast areas are typically refined 6-12 hours before thunderstorm development and are continuously updated as necessary.

An analysis of environmental profiles including the amount of moisture available to generate precipitation, mid-level winds and the presence of a dry layer in the mid-levels is key in determining whether a microburst could develop once thunderstorms have formed. Unfortunately, real atmospheric sounding data describing all of these features are only available at fixed times and locations, which do not always line up with thunderstorm development, so forecasters must rely on other data sources and model guidance to help their analyses.

There are many challenges in pinpointing exactly where a thunderstorm will develop within the forecasted area, thus forecasting an exact location for the development of a microburst particularly challenging, especially due to their inherently small nature.

Once thunderstorms have developed, forecasters typically use RADAR signatures to determine whether a microburst is occurring and can estimate the wind speed of the microburst.

GFAs do not specifically mention microbursts. Instead, their risk is captured within the thunderstorm (TSRA) and squall (SQ) group as their occurrence is directly tied to severe thunderstorm formation. Watches and warnings are issued by the Meteorological Service of Canada (MSC) when conditions exist and/or microbursts have been observed.

Similar to GFAs, TAFs do not specifically mention microbursts. The possibility of microburst development is included in the TSRA and SQ group with severity indicated by light (-), moderate (no prefix), or heavy (+) symbols. Watches and warnings for severe thunderstorms, including the possibility of microbursts, will be issued by the MSC when conditions supporting their development exist and/or microbursts are occurring. MSC also briefs commercial dispatchers and air traffic flow managers (NTMU, ACC Operations Duty Managers, etc.) on demand with respect to the risks associated with potential microbursts to help support critical decision-making and safe air traffic services delivery. This critical information is also passed along to pilots in preflight weather briefings from FIC specialists, and while in-flight whenever possible.

Image 1 of 3

SIGMETs are not issued specifically for microbursts but will be issued for thunderstorms when criteria for transmission are reached or exceeded. It is important to note, however, that microbursts can occur within single storms that may or may not be within a SIGMET. As such, proper weather briefings and closely monitoring both forecast and actual conditions along with issued watches and warnings are imperative for this critically significant phenomenon.

MAIN CONCERNS

Microbursts have led to deadly aviation disasters and pose a severe threat to aircraft. Windshear, loss/gain of speed, loss of control of the aircraft are all risks, and all in close proximity to the ground with little room available for recovery. 

Service Providers

YVR

    • It tends not to be something that directly affects running of the airport, but we would want to be aware of and how it is affecting flight operations such as missed approaches, departure delays or business impacts due this weather phenomenon. 
    • Are aircraft able to continue to safely arrive and depart and what impacts is it having on ATC?

      GTAA

        • Normally we would send out an advisory to the airport community if there is a forecast for high winds (30kt gusts or more) so they can ensure any loose equipment on the ramp are secured; this is often the case when thunderstorms are forecast for the area. Since forecasting microbursts is not done formally, if it does occur, it would be more of a reactive response than being proactive. The usual weather-related delays can be expected, such as airborne holds and arrival TMIs, especially if they are associated with thunderstorms.
        • Although not normally applicable to the airport from a planning/forecasting perspective, if microbursts occur in-flight, they could cause aircraft damage or personal injuries to passengers or crew and the airport authority would put emergency response plans into place for the arrival, if the flight does not divert elsewhere.

          Operations Duty Managers

          There are no microburst-specific tools or technology available to diagnose potential occurrences at the airport. Impacts and planning here are the same as for thunderstorms.

          • Being warned of possible microburst activity by forecasters allows us to communicate these risks to customers and relevant ATC units.
          • This phenomenon occurs quite often in Calgary and can lead to missed approaches. Overall this remains a tactical approach specific to when thunderstorms are impacting the operation.
          • We end up holding when this happens and we tend to try to wait and hold aircraft rather than switch configurations as it tends to be a short lived event.
            • When occurring at an airport are extremely dangerous. Impossible to plan for in traffic management but in severe cases would mostly likely result in approaches being cancelled until it was safe to resume.
            • The NTMU relies on forecasters to advise of microburst risk to operations.

            ATC (Major and Regional Towers)

            • ATC will anticipate the possibility of microbursts with thunderstorms. Specific aircraft types (ex: A220) can warn us of microbursts with their onboard weather radar.
            • Canadian airports are not equipped with microburst detection technology present at select American airports, and therefore rely heavily on forecast products, observations, forecaster input, and communications between ATC and pilots. This is where forecaster input becomes critical and allows for everyone to be aware of the possibility of microbursts. Multiple anemometers can help detect microburst. CYUL, for example, only has one.

            FIC

            Microburst potential is greatest when there are thunderstorms with high bases, usually 6000ft AGL or higher, but these dangerous downdrafts can be formed by smaller Cumuliform clouds, too. When conditions exist that could allow microbursts to form, it is prudent for the Weather Observer to advise local ATC to be on the lookout for these anywhere around the airfield, with solicitation for PIREPS. Microbursts are particularly dangerous for Aircraft in critical phases of flight, such as during takeoff or landing. Enroute FISE positions can also assist pilots in maintaining situational awareness by requesting PIREPS on any Microburst observed inflight by VFR aircraft. 

            AAS

            Advisory Specialists keep a keen eye out for signs of microburst activity when there is a risk they may be occurring. Be it watching the grass, trees, and windsocks for divergent wind directions, birds having difficulty staying aloft, dust clouds kicked up, etc. That said it is often very difficult to detect a microburst from visual sightings only. Aircraft will always be warned about the potential for Microbursts, and targeted PIREPs will be solicited.

            • Wind shear is often associated with thunderstorm cells in close proximity to the airport and may necessitate go-arounds on short final due to unsuitable landing conditions. We have no way to predict this so we rely on PIREPS to warn us and others of these conditions.
            • See thunderstorm term for additional ATC impacts. 
            • Microbursts occur with very little notice and will often force aircraft to overshoot their approach. They may also force a runway change as the winds shift. When a microburst arrives at an airport, the instinct of a controller is to prepare for the thunderstorm that will follow it and be ready for a possible ground stop.
            • Enroute controllers watch for the arrival of thunderstorms and do not try to predict a microburst. When a microburst hits a hub, the terminal controller deals with missed approaches and coordinates with the enroute controller to hold or provide delay vectors to aircraft.
            • A controller will prepare for delays when they begin to receive PIREPs.

            Users

            • Microbursts are a significant threat to aviation operations as aircraft will be a low altitude in a potentially low energy state.
            • There are few products specifically designed to forecast microbursts as it is but one of the hazards associated with the thunderstorms. When a thunderstorm is forecast, wind shear is generally expected as a potential hazard.
            • As such, it is a tactical situation that must be managed by flight crew.
            • PIREPS are the primary means of anticipating a microburst.
            • Some airports (in the USA) have microburst/wind shear detection equipment that can warn flight crew as to the potential presence of a microburst.
            • All the mitigations planned for thunderstorms hold true for a potential microburst situation (increased fuel carriage, alternate safe airport).
            • Microbursts are to be avoided at all costs. Significant damage can also be incurred on the ground to aircraft parked outside. This can lead to a total loss of aircraft. Aircraft owners can add extra tie-downs to aircraft but unless they own a hangar, the plane is often at risk for damage.
            • Microbursts can be hard to predict; however if one is predicted, light General Aviation (GA) aircraft should not be flying in proximity.
            • Most light GA pilots don’t have good tools to identify the risk of a microburst, but they are aware of the possibility existing if a thunderstorm is present.
            • Typically, a good pilot will not be flying in close proximity to a thunderstorm, however sometimes it can be hard to tell the severity of a storm and predict the likelihood of a microburst; therefore, extra caution must always be taken around thunderstorms.
            • If a microburst occurs while already in flight, the risks to light GA aircraft are significant. If occurring in the downdraft part of the microburst, a light aircraft will almost certainly not be able to achieve a rate of climb high enough to climb out of it, resulting in impact with the ground. If occurring in the updraft or increased performance portion of the microburst (farther from the storm cell) the light aircraft will have similar but more exaggerated effects to flying in the updraft related to a less severe storm. These include the risks of entering a nosedive or excessive speed condition, climbing and entering cloud, general loss of control or aerodynamic/wing stall.