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
DISCUSSION: As is almost always the case when it comes to commercial aviation, nearly all pilots and co-pilots are trained to constantly avoid moving near or through any parts of deep convective storms. The reason for this is chiefly due to the fact that deep convective storms nearly always have strong updrafts and downdrafts. As pilots encounter deep convective storms they are trained to avoid such storms since they have historically had a tendency to compromise the safety of both commercial and private aircraft since they destabilize the ability for aircraft to remain in flight in a stable manner. This a direct result of the fact that flying near and/or directly through convective updrafts can lead to a given aircraft to lose altitude in a violent and rapid manner which can cause an aircraft to lose control temporarily or permanently in some cases. Hence, commercial and private pilots alike are always taught to fly around convective storms such as those captured in the images above which were taken by commercial pilots flying over #Austria before heading on over towards Croatia!
To learn more about other topics in applied meteorology, be sure to click here!
©2017 Meteorologist Jordan Rabinowitz
DISCUSSION: As strong to severe thunderstorms continued to develop during the early to late morning hours on this first Sunday of April 2017, many commercial and private aircraft were already being affected. As if often the case during large-scale severe weather events, both commercial and private aviation interests are typically forced to deviate from scheduled flight paths. Due to the fact that severe thunderstorms often become quite deep in terms of their maximum cloud growth, this creates particularly dangerous situations for pilots who are thinking about or attempting to navigate through or around such thunderstorms. This is due to the fact that as severe thunderstorms move through any region, there are always consequential updrafts and downdrafts which can cause aircraft to loose control of their balanced flight.
Therefore, since the late 1960's there has been a consistent strong initiative towards improving the forecasting of wind shear and turbulence in association with various types of thunderstorms which occur throughout the year. As shown in the two images attached above, you can clearly see how the progression of the strong to severe thunderstorms forced hundreds of flights to divert from their original flight tracks due to the presence of the aforementioned severe thunderstorm outbreak which began to crank into high-gear much earlier today. Although this can create significant delays across many different parts of the aviation industry, "it is always to have a safe arrival than no arrival."
To learn more about other interesting weather- and weather-related stories in applied meteorology, be sure to click here!
©2017 Meteorologist Jordan Rabinowitz
DISCUSSION: As is known across all of commercial and private aviation, one of the most common issues to general aircraft and passenger safety is the presence of turbulence. However, something which many people do not know is that there are several different types of turbulence which are unique unto themselves. This includes varieties such as atmospheric turbulence, wake turbulence, and clear air turbulence (CAT). Having said that, these different types of turbulence are respectfully different and pose different threats at different points of a given flight. Per the article from "Insider," attached below are some more neat insights which were collected from many different pilot-based experiences from around the world as well as long-term data collected and archived within the long-term records of the Federal Aviation Administration.
Atmospheric and wake turbulence are often lumped together, but one is caused by nature and other is driven by mechanics. To explain atmospheric turbulence, many pilots liken the experience to traveling through a river in which air is the water. Like water in a river, air is constantly moving and can be influenced by several things, including obstacles (think mountains), moisture, uneven heating of the earth’s surface, weather, and temperature changes. Flights over mountain ranges, for example, often fall prey to mountain wave turbulence, which feels like a roller coaster speeding down its first big hill. "If you're in a small boat and the water isn't smooth, the faster you go, the rougher the ride will be," says Mike Arman, a flight school instructor and author of books about piloting Cessnas and operating cockpit computers. "Airplanes are exactly the same -- the faster you go, the rougher the ride can get." Commercial jets can go as fast as 600 mph, which can impact the plane’s reaction to the air current changes.
There are also mechanical factors that cause turbulence during takeoff and landing, including the wind streams that are created from a combination of the plane's propulsion and wings. In fact, wake turbulence is one big reason why takeoffs are timed several minutes apart.
On November 12, 2001, American Airlines Flight 587 took off from JFK Airport and crashed moments later into Belle Harbor, Queens. Investigators theorized that the pilot may have taken off 15 seconds too fast and run into wake turbulence from the Japanese Airlines jumbo jet that had left before it. The incident killed 260 people on board and five people on the ground. That being said, such reactions to wake turbulence are rare, particularly because the beginning of flights are so closely monitored by air traffic controllers.
Clear Air Turbulence
While passengers may expect the plane to thump and wriggle while taking off or steadying for a landing, clear air turbulence can be even more disconcerting. Here's how it happens: You’re watching the latest James Bond flick, sipping on a martini, and suddenly it feels like someone hit the ejector seat button, hurtling your stomach into space. Pilots discover clear air turbulence when everyone else does -- about the time the peanuts leap off the tray table. Clear air turbulence (CAT) doesn't show up on a radar -- a ground technology system that's currently being tested is able to listen to the infrasonic sound it emits. "In the next few years, I'd expect this technology to be in use to detect CAT for airline traffic," says Arman.
Hence, there is much we already understand about the impacts of turbulence on commercial aviation, but there is still much we do not understand as well.
To learn more about other neat weather-related topics in applied meteorology, be sure to click here!
©2017 Meteorologist Jordan Rabinowitz