DISCUSSION: On any typical day at airports spread around the world, there are dozens of situations wherein aircraft encounter a common wind issue which is most commonly referred to as a crosswind. A crosswind is best defined as a stronger wind which happens to cross the shorter axis of a given airport runway. When this happens to a large enough extent (i.e., with a sufficiently strong wind speed), this often leads to increasingly more hazardous conditions for private and/or commercial aircraft which are looking to either takeoff from or land at a given airport. This is due to the fact that when there is a sufficiently strong crosswind, this can severely affect an aircraft's ability to maintain consistent, stable flight.
This happens as a result of the fact that an aircraft relies on a stable and consistent flow of air both under and over the length of each of the aircraft's wings. When there is a crosswind, this temporarily changes the orientation of the flow of the surrounding air stream which should theoretically run from the front of the aircraft to the back so as to maintain lift. However, when an aircraft encounters a crosswind during takeoff and/or landing, the crosswind compromises the ability for the aircraft to maintain stable flight due to the wind direction changing from the left or right as opposed to coming from front to back. Thus, when this occurs in close proximity to the ground during takeoff and/or landing (i.e., when the plane has a critical need for stable flight due to its need to pick-up sufficient speed for a stable, level ascension from the ground or a safe, balanced landing on the ground), it can make things incredibly dangerous for the pilots, crew, and passengers.
The biggest problem of all is that crosswinds can be incredibly hard to anticipate as a pilot since they often occur without any warning at all. The only real situations where crosswinds can be somewhat anticipated is when there is a strong to severe thunderstorm approaching an airport since then airport and/or airline meteorologists can better predict how wind flow regimes may change both near and within the confines of an airport so as to better protect the aircraft assets which are relying on an accurate short-term forecast during a given thunderstorm event. Attached above is a compilation video courtesy of the Travel TV YouTube account which captures a number of different aircraft experiencing crosswind incidents of different magnitudes.
To learn more about other aviation meteorology stories and topics from around the world, be sure to click here!
© 2018 Meteorologist Jordan Rabinowitz
Image taken from the evening of Thursday, May 18, 2017, where 45 tornadoes broke out across Colorado, Texas, Oklahoma, Kansas, Arkansas, and Missouri.
Have you ever wondered what happens when a flight delay occurs due to weather besides the frustration and confusion? Weather is the largest cause of delays for aircraft, affecting mostly airport arrivals and surprisingly worse for summer storms than winter ones. Unlike winter storms which move slowly and can be forecasted days in advance, summertime thunderstorms can develop quickly over large parts of the country and may follow a less predictable path. Some of these cells may stretch up to 60,000 feet (most commercial aircraft fly around 39,000 feet or lower). This may cause planes to detour as much as 20 or 100 miles around a line of thunderstorms, rather than flying into the tops of thunderstorms. In any case, rain or snow may slicken the runway.
The FAA (Federal Aviation Administration) has a flow control program that prevents an overflow of aircraft taking off for a destination and rerouting traffic around weather. Ground stops are in place for aircraft that have not left the airport and will not be cleared for takeoff until weather conditions improve, reducing the number of flights arriving at the impacted area. Inbound planes that can’t land due to a storm affecting the airport will be asked to slow down or go into a holding pattern and often circle the airport until the storm clears. If the thunderstorms persist, the holding aircraft will have to eventually divert to other airports, wait out the bad weather, refuel, and depart later on to the original destination.
If you are traveling when storms are expected, consider the possibility of delays and plan accordingly. Book flights as early in the day as possible- the afternoon and evenings will have the most potential for thunderstorms during the summer months. The next time your flight gets delayed due to severe weather, think about all the science and coordination that goes into all of it.
To learn more about severe storms and their impacts on aviation, please click here!
© 2018 Meteorologist Sharon Sullivan
Respecting the Convective Threats to Aviation from Severe Thunderstorms (credit: Capital Weather Gang)
DISCUSSION: There is no debate whatsoever that weather and aviation do not ever mix well under any circumstances. Having said that, is important to acknowledge the fact that the aviation industry often tries to challenge the natural threats provided by severe weather (i.e., namely those threats which are generated by deep convective storms). Often times, this leads to tremendous safety and protocol issues across the mediation industry by way of commercial and/or private aircraft trying to race through developing and or request severe storms close to if not at their peak intensity. When aircraft of any size try to do this, there are quite often dangerous if not disastrous results due to aircraft encountering threats created by strong winds (i.e., often realized in the form of strong downdrafts which can affect an aircraft’s ability to maintain level flight), cloud to ground lightning, and/or large damaging hail.
Therefore, it definitely goes without saying that when private and/or commercial aircraft attempt to across peak intensity or developing convection, this can lead to major safety issues for both crew and passengers alike. In the case of a recent American Airlines departing from San Antonio, Texas and bound for Phoenix, Arizona, disaster struck when the plane attempted to steer around the periphery of a cluster of deep convective storms which were blossoming and bubbling up at the time of the plane’s approach. Hence, as the American Airlines flight made its approach through the storms, the flight ran into a part of the convective storm cluster which was intensifying more rapidly and allowed for robust hail development which greatly affected the duration of this flight. As a result of this aircraft’s encounter with the hail-producing thunderstorm, there was a forced diverted landing over in El Paso, Texas. Thus, it was a very dangerous (and arguably poor decision) to attempt to fly through this particular bout of severe weather in consideration of the inherent hail threat which increased during the evolution of this particular storm cluster.
In consideration of this severe weather event, it is important to recognize that severe thunderstorms can form in an exceptionally short period of time and can have a profound impact on the aviation industry as a whole. Hence, when there is severe weather threatening, it is imperative for private and/or commercial aircraft to avoid deep convective storms at all times to remain in a safe flying environment. Above all else, it can be optimal to choose times and regions to fly through which typically do not experience major climatological severe weather impacts from deep convective storms during a given part of the year.
To learn more about other aviation weather stories and/or topics from around the world, be sure to click here!
© 2018 Meteorologist Jordan Rabinowitz
For anyone who has traveled commercially, turbulence is a word that describes the “feeling” of being tossed or shaken around while on an airplane. Many different aspects in the weather world can influence turbulence outside of the obvious thunderstorm type impacts. The two most important terms in the turbulence equation for the generation of turbulence are wind shear and buoyancy (a broad example of buoyancy impacts is above), which are in some way related to all the processes/features that will be discussed below.
This article will focus primarily on low level or boundary layer turbulence. Any sort of frontal feature, whether a cold front, warm front, dry line, etc, tends to generate turbulence via the wind shear present across these boundaries. In addition to the wind shear, buoyancy creating thermals within the boundary layer may be rather robust, depending on which side of the front the aircraft is situated. Across these fronts turbulence may be rather robust and a danger for any aircraft flying, ascending, or descending within the boundary layer.
Sea breezes and land breezes are another boundary similar to an outflow boundary, and to a lesser extent a cold front, that can cause turbulence. The change in wind generates horizontal wind shear and depending on the thermodynamics present during this situation, buoyancy becomes important producing rising thermals and hence, turbulent conditions. Above is an example of a sea breeze on radar in Maryland taken during the evening of May 24th (credit to radarscope).
Mountain waves are another source of turbulence. In the lee of a mountain, with the right conditions such as winds perpendicular to the mountain with air rising over the mountain encountering an inversion will create these oscillatory waves with embedded turbulent circulations known as rotor clouds. These mountain waves are often very turbulent and a hazard for aircraft. Similarly, down sloping wind storms originating from this air rising over the mountain can be very dangerous to aircraft. These conditions can produce winds upwards of 50+ knots in the lee of the mountain (Boulder, CO is famous for their down sloping wind storms). This can create some of the worst turbulence for aircraft. Above is a diagram of mountain waves. *
Being that turbulence is a wind phenomenon, most of the time it is not visible. However, turbulence can physically be represented if there is enough moisture present. The turbulence manifests itself as beautiful wave breaking Kelvin-Helmholtz clouds. An example of such is shown above, credit to Brooks Martner, (the physical manifestation of the wind shear is quite evident as the upper levels of the cloud are moving faster than the lower levels, hence causing “breaking waves”).
Next time you look up in the sky and see resemblances of breaking wave type structures, not only will you have a visually pleasing sight, you will know the environment is becoming increasingly turbulent!
*There is a lot more that goes into mountain waves and down sloping windstorms. Be on the lookout and stay tuned to GWCC for Part 2 and one of my next pieces for an in depth look at down sloping wind storms.
To learn more about aviation meteorology click here!
©2018 Meteorologist Joe DeLizio
Augmented Reality Solving Aviation Meteorology Learning (Credit: Western Michigan University, Microsoft)
DISCUSSION: Augmented Reality, according to Google is “a technology that superimposes a computer-generated image on a user’s view of the real world, thus providing a composite view.” With the creation of Microsoft’s HoloLens professors are now able to provide additional avenues for aviation training, that Western Michigan University (WMU) has been the first known university to test within their College of Aviation.
According to Microsoft the HoloLens,” enables you to interact with content and information in the most natural ways possible.” The HoloLens can be used to provide higher level understanding of advanced aircraft systems. Associate Professor of Aviation at WMU Lori Brown was able to marry aviation training and augmented reality to provide a unique teaching experiencing which can allow students to investigate jet engines, interact with cockpits and train in real-world scenarios such as flight simulation.
One of the innovative ways Brown uses the HoloLens is to provide training using a flight simulator for the Canadair Regional Jet 200 (CRJ-200), a smaller regional aircraft typically transporting 50 passengers. By using the HoloLens, Brown and her team have creatively studied ways to provide weather-training in the flight simulation for the Federal Aviation Administration (FAA). Often those using simulators rely on printed meteorological information, which can prove to become obsolete quickly, as the field of meteorology has only made significant progress beginning in the 18th century, moving to the 21st century where current remote sensing systems, and increased computing power have made effective advancements.
In addition to the developments Brown has created with her team, the future holds promise for a design of a virtual airport. This virtual airport could prove to be crucial during flight simulation for meteorological conditions especially on the CRJ-200, where ceiling, visibility and temperature all play vital roles in the aircraft’s top performance during arrival and departure.
For more information on new and innovative technologies breaching the meteorological world visit the Global Weather and Climate Center!
© 2018 Meteorologist Jessica Olsen
DISCUSSION: As many frequent flyers, atmospheric scientists, pilots, and air-traffic controllers know, atmospheric turbulence is a major hazard across the global aviation community. Whether it is impacting a given aircraft during take-off, at cruising altitude, during descent, or even final approach and landing, there is no debate that atmospheric turbulence remains to be a major threat to the safety of passengers and flight crews around the world every day. Attached above are two stories (the upper-most one being a new story with a piece courtesy of Dr. Paul Williams from the University of Reading and the lower story being narrated by Meteorologist Jordan Rabinowitz of the Global Weather and Climate Center.). These two respective narratives give neat insights into the causes as well as the unique hazards which are directly tied to atmospheric turbulence. Feel free to watch both of them, for a complete perspective on this very complicated and interesting ongoing aviation topic.
To learn more about other global aviation topics, be sure to click here!
© 2018 Meteorologist Jordan Rabinowitz
Winter Weather Cripples Southern Airports, Deicing Operations Begin (Credit: Meteorologist Jessica Olsen)
Amid heavy winter weather experienced in parts of the country as we wrap up 2017, many are still taking this opportunity to conduct last minute travel for the New Year. Despite an extremely cold start to 2018, locations in the middle of the CONUS are experiencing subzero wind chills with temperatures in most locations from the Gulf to the Carolinas below the freezing level.
Heavy delays and cancellations are being seen in Dallas-Fort Worth Airport (DFW) as they contend with ice and temperatures upwards of 30 degrees below normal. Winter weather advisories are issues for western and central Texas while eastern Texas, Louisiana, Mississippi and Alabama are seeing a hard freeze warning all impacting travel this weekend into the start of the work week.
It’s no surprise that DFW is seeing delays however remaining away from cancellations due to the process of deicing. Delays are expected due to deicing, however freezing conditions at the airport play a critical role in how aircraft performance is seen in the skies. Passengers often ask why deicing is necessary, and the process ensures that buildup of snow and ice will not be present on the aircrafts’ control surfaces (ailerons, elevator, stabilizer, flaps, slats, rudder). Deicing fluid is a mixture of glycol and water. This fluid is then heated and sprayed on the control surfaces and fuselage if necessary to prevent buildup. Optimal aircraft performance is achieved when there is little to no accumulation on its surfaces. Note, when aircraft are inflight the subzero temperatures at higher altitudes present difficulties and decrease engine performance, which is why it is critical for any initial accumulation to be removed on the ground.
Airlines are indicating to verify flight statuses before arrival, in addition to possible delays due to the deicing process.
For more information on winter weather and aviation visit the Global Weather and Climate Center!
© Meteorologist Jessica Olsen
This is called a METAR, or Meteorological Aviation Report. They’re generated by weather stations at airports! It’s a shorter way to describe the weather for aviation purposes.
The METAR consists of two parts, the body and the remarks. We’ll talk about the body first.
METAR: There can be two reports, either the standard METAR or a significant weather event, which in that case will begin with SPECI.
KBNA: This is the station name. The first letter will either be a K or a C. U.S. stations start with a K and Canadian stations start with a C. The next 3 letters are the station name. This METAR came from Nashville International Airport in Tennessee.
272153Z: This is the date and time of the report. The first two numbers (27) are the day of the month. In this case, this report came on the 27th. The next 4 numbers (2153) are the time. This was reported at 21:53 Z, which is 4:53 PM CDT.
02005KT: This tells you the wind information. The first 3 numbers (020) tell you the direction of the wind, given in degrees. In this one, the wind is coming from the north east. The next two numbers (05) tell you the wind speed. In this report, the speed is 5 knots.
10SM: This is the visibility. Here, the visibility is 10 statute miles.
BKN070: This is the cloud coverage. The first 3 letters (BKN) show how much of the sky is covered. In this case, BKN means Broken where 51-87% of the sky is cloudy. The next three numbers (070) are the height of the cloud base in hundreds of feet. Here, we have broken clouds at 7000 feet.
27/11: This is the temperature and dew point, in Celsius. Here, the temperature is 27°C while the dew point is 11°C. This converts to ~81°F and ~52°F.
A3008: This is the altimeter reading. This gives the pressure in inches of mercury. This would be the pressure if this station were at sea level.
Now we have the Remarks section. This section is only added when appropriate. This will start with RMK.
AO2: This says that there is a precipitation discriminator at this station, and it is an automated station!
SLP180: This is the sea level pressure. SLP stands for sea-level pressure. The three numbers after it (180) give reading in hectopascals. If the number is less than 500, a 10 is put in front. If it’s more than 500, a 9 goes in front. A decimal goes in between the second and third numbers. In this case, the sea level pressure would read as 1018.0 hectopascals.
T02720111: This is the precise temperature and dew point, as before it is given in degrees Celsius. The first four set of digits (0272) is the temperature. The reason for the 0 in front is that it designates the sign. If it’s a 0, it’s positive. If it’s a 1, it’s negative. In this case, the temperature is 27.2°C. Same process for the dew point. In this case, the dew point is 11.1°C.
To learn more about aviation weather, click here!
©2017 Weather Forecaster Jennifer Naillon
Discussion: With 12 active fires as reported by CalFire it is no surprise that residents and travelers in the Southern California region have growing concerns regarding the reach of the current wildfires. Of major concern is the Thomas Fire, having burned 237,500 acres in Santa Barbara and Ventura Counties.
Severe fire weather has continued in the area as crews are fighting to increase containment beyond 25%. Reviewing the synoptic picture, we see that the United States is dominated by several key features which are impacting the continued devastation of this fire and the 11 others in the immediate area. With a large ridge in the West coast and high-pressure system placed seemingly strategically to the north with a strong low in the upper mid-west this allows the feeding of the Santa Ana winds in the Southern California region. These winds couples with warmers than average December temperatures and extremely low-relative humidities are making this a head on fight for fire personnel.
Earlier this month California Governor Jerry Brown declared a state of emergency as these fires threaten Los Angeles, Santa Barbara, San Bernardino and other cities which included threats to the 405 and other freeways that are the backbone of the Southern California commute. Delays were initially issued for buses servicing the Los Angeles (LAX) and Van Nuys General Aviation (VNY) airports, but have been lifted. Additionally, no aircraft delays have been reported in correlation with fires however it is expected that increased traffic throughout the region may pose delays in arrivals to the airport. With regional airports such as San Luis Obispo (SBP), Fresno (FAT), and Monterey Regional (MRY), these will provide the much-needed safety net for any issues that may arise in diversion situations for LAX and VNY.
For more information on local wildfires and aviation concerns visit the Global Weather and Climate Center!
© Meteorologist Jessica Olsen
DISCUSSION: On the evening of Friday, July 7,2017 at approximately 11:15 PM PDT, an Air Canada Airbus A320 operating as Air Canada flight 759 was preparing to land onto Runway 28R at San Francisco International Airport after a nearly five-and-a-half-hour flight from Toronto’s Pearson Airport. However, Flight 759 was instead lined up with taxiway C (Charlie). However, the taxiway had two United Airlines Boeing 787s, a Philippine Air Lines Airbus A340 and a United Boeing 737 on it all lined up for Runway 28R. The Air Canada Airbus A320 nearly missed the four waiting jets by about 60 feet above one of the 787s as it pulled up in time to circle around. This near-miss could have been possibly the worst air disaster in history as the total number of passengers in all the jets would be twice as many as those who died in the Tenerife Accident in 1977. This incident also comes two days after the fourth anniversary of the Asiana Airlines accident in San Francisco, coincidentally on the same runway, Runway 28R.
However, the weather played a role in preventing this near-miss into being a repeat of Tenerife. Prior to the incident, several of the local Bay Area airports were calling clear skies in the hourly METARs. Also, there was a steady west-northwest wind that was roughly 7 knots, according to the KSFO METAR nearest the time of the accident. Normally, during the summer, there would be a layer of stratus coming in about the time of the near-miss. However, this was not the case as there were clear skies due to a very strong ridge and mainly dry conditions aloft. A stratus deck would have increased the likelihood of the crash as it would make it impossible for the pilots on Air Canada to have a visual of the runway lights or the approach lighting. Also, the air traffic controllers would not have been able to see the A320 and its approach. Wind was not an issue as it was oriented with Runway 28R in a way that crosswinds would be minimal which would not affect the direction of the plane.
Therefore, in the end, weather may have been the reason that the worst aviation disaster in the United States and the world was averted. Moreover, the primary catalyst for this incident was quite plausibly due to pilot error as weather conditions was favorable and visibility affected. You can read about more aviation and other applied meteorology topics here.
© 2017 Meteorologist JP Kalb