Professional Pilot, September 2016

between cells a developing cell that has no precipitation and therefore no radar echoes could be building right above or adjacent to the approach path and an airplane may fly into its grip just as the cell matures and drops a massive downburst Because MCS will normally support many convective cells in close proximity flying near beneath or into a cell is a distinct possibility That chance is greatly increased if the aircraft doesnt have onboard radar Even when radar is available attenuation algorithms have their limitations and a severe cell may be masked or underreported when a closer rain shaft is in the way Fortunately meteorologists are able to forecast for MCS with a fair degree of accuracy a few hours ahead The forecasts should provide you with adequate guidance for steering around an MCS or changing your flight times to avoid one intersecting your flightpath However if you have not heeded the advice of the weather briefers forecasts airmets and convective sigmets that will undoubtedly have been issued ahead of time and you do find youve penetrated an MCS you will need to extricate yourself from the situation With a solitary thunderstorm the most commonly advocated guidance by the FAA AC 00 24c and most aviation experts is to maintain positive control of your aircraft and 48 PROFESSIONAL PILOT September 2016 continue to fly a direct path through the storm with only minor course corrections to avoid the heaviest echoes ahead The reason for not turning 180 degrees is that even with radar you do not know what has evolved behind you in the minute it takes to make that turn and dipping a banked wing into a turbulent eddy or strong downdraft can more easily knock the aircraft out of control than if it were flying straight and level Guidance for passing through an MCS is similar but here you are dealing with the possibility of exiting 1 storm only to enter another In a squall line situation turning around is not a good idea because it is quite likely that there will be active cells on either side of the storm youve penetrated At 250 kts a standard rate turn will cover 3 miles more than enough distance to pop you into an adjacent cell The situation may be a little different with an MCC If you have penetrated an MCC and have a pretty good idea of where you are in relation to the overall system continuing straight and level flight may take you through hundreds of miles of storm activity while a 180 degree turn near the MCCs edge will bring you back into clear air Radar no go Under no circumstances should a pilot attempt to use radar information airborne or ground based to pick a flightpath through an MCS MCS are systems in which individual cells can develop at any location and at any time can become severe and may move in directions contrary to the overall movement of the system Ground based radar updates can be 5 or more minutes old an eternity in thunderstorm development and airborne radars can only look ahead and may misidentify cells that are shadowed by others It can become very easy to find yourself surrounded and cut off by cells that have developed or moved unexpectedly over the previous few minutes of flight The same advice goes for flying under or over an MCS Beneath an MCS turbulence downbursts and extreme rain shafts can materialize without warning in almost any location Overflying an MCS can be less dangerous but should only be attempted if you can exceed the highest forecast cloud tops by several thousand feet Strong to extreme turbulence and even hail is quite common in the clear air above an MCS And if you are flying below the potential level of the cumulonimbus tops you can quickly find yourself surrounded by towering cells and no way through ATC especially through Flight Watch or approach control will have access to near real time weather radar and can provide some guidance if requested though such a service should not be expected nor is it even available in many parts of the world A thorough briefing ahead of your flight including weather maps showing fronts radar maps and satellite images that show any MCS cloud patterns should be obtained and heeded In areas where convection is active pireps will help controllers update their information and advice for other aircraft and can help to keep all flights safely away from an MCS Karsten Shein is a climatologist with NOAA in Asheville NC He formerly served as an assistant professor at Shippensburg University Shein holds a commercial license with instrument rating Squall line over Florida as photographed by Space Shuttle astronauts in April 1984 Associated with a cold front the moving air mass displaced warm and humid maritime air to create a very sharp line of nearly continuous convective cells with 55000 ft tops that pummeled the region with hail flash flooding and tornadoes Aircraft would have little choice but to land or deviate hundreds of miles around this mesoscale convective system Image courtesy NASA