Lesson 4: Avoiding Enroute Thunderstorms
|Welcome to lesson four of our
six part course on "Thunderstorms and Flying." In this lesson
we will learn about and review some of the tips and techniques to get weather
information about what lies ahead on your route of flight.
This week's guest "speaker" is Mr. Randy Baker, a meteorologist with the world's largest parcel delivery service. He is a member of the National Weather Association's Aviation Weather Committee. Keeping airplanes out of harms way of thunderstorms, especially in night flying is an ever-present challenge, especially when the aircraft cover the world.
As a meteorologist at a major cargo airline, my knowledge of thunderstorm activity is vital to the daily planning and operation of Flight Operations. Thunderstorms at an airport can totally disrupt loading and unloading of aircraft, fueling operations, maintenance activities, as well as delay arrival and departure operations. A lightning strike can injure workers and shut down computers, even put an aircraft out of service.
Enroute thunderstorms, particularly organized convection, can be even more disruptive. A large squall line can totally shut down traffic through an ARTCC for several hours, causing massive rerouting and weather delays. When located in the Northeast, massive ATC delays and ground stops are common, which will significantly impact our ability to meet our service commitments.
When I look at thunderstorm potential, I need to know not just the likelihood of convection, but also the mode. Will it just be isolated single cells, or will it be more organized, such as Supercells, Multicell Clusters, Multicell Line, or even the Mesoscale Convective Complex? Once I know the level of organization and the potential hazards, I can brief dispatchers, pilots, and operations management as to the potential impact on our operations. It is critical to our success as a delivery service that they all know where the thunderstorms are located in our route structure at all times.
What we need to know to run a successful world-wide business is just what you need to know to conduct safe flights in the United States and around the world. Please learn from this lesson all you can to keep away from the dangers and disruptions of the thunderstorm hazard.
|And now on to our lecture on
ways to avoid thunderstorms enroute to your destination. Because thunderstorms
are such a dynamic force and a moving target, it is important to keep up
with their locations along your route of flight once you know that they
may play a role in your day of aviating. How can you do that? There are
many ways. The first ways begin during the flight planning process...
Radar plays an important role in thunderstorm detection and avoidance. There are ground based radars at detect where thunderstorms are located. Products that display that information are disseminated to you from a variety of distributors. Let's learn more about these radar systems and the products you use.
Radar theory is not easy. The University of Wisconsin at Madison has an internet course on aviation weather with background material on radars and how they work. Please review that basic material now. The Air Force Flight Standards Agency has more advanced material to help you understand the most advanced weather radar system in the world, the next-generation radar, or NEXRAD, composed of the network of WSR-88D Doppler weather radars.
Before lesson one, we asked you to find a vendor of these products on the internet. See where the WSR-88D radars say thunderstorms are a problem right now. If you don't have the link handy you can always see the radar product at the National Weather Service's website. The product you are looking at is called the Radar Composite based on the input from every WSR-88D in the United States. These products are updated every 15 minutes which is two complete scans of the atmosphere for this kind of radar.
Radar Summary Charts is another way to view where thunderstorms are along your route of flight. This is an hourly product. Review AC-0045 Chapter 7 on Radar Summary Charts now .
Another good way to see the locations of thunderstorms while planning your route is to look at satellite images. One of the top meteorologists in the business, Mr. Gary Ellrod from the National Weather Service (and a Councilor of the National Weather Association) has a special "minicourse" on reading the hazards from satellite imagery.
Now is a good time to review AC-0045, Chapter 3 on radar reports and satellite images using the Resource Menu.
The FAA and the National Weather Service's Aviation Weather Center are working on a new satellite imaging technique that overlays satellite-sensed lightning strikes onto images over the Atlantic and Pacific Oceans. This will make thunderstorm identification easier while "over the water." This program was developed by Dr. Alan Nierow, an NWA member, and Mr. Fred Moser. You can see examples of these products at this link.
Lightning data is another source of real-time information on where thunderstorms are located. It collects and distributes cloud-to-ground strike information collected from sensors all over the United States and displays the strike location within a few seconds. This is the most up-to-date information on thunderstorms while you are on the ground. Many airline dispatch offices use this display because of quickness of this information source. View the National Lightning Map at The Weather Channel's website.
Once you are airborne, there are other ways to keep you informed about thunderstorms. If you know that they will impact your flight, you must keep up with their intensity, direction of movement, heights, and other information that will ALWAYS give you options to avoid this hazardous weather condition. Let's look at some of the ways you can keep up with thunderstorms during flight.
From the June 1998 issue of Flying Safety Magazine comes this portion of the article we first read in lesson one. The article shows different radar signatures that point to significant and severe weather.
Let's hear from someone who does flying around severe weather for a living. I'll bet he has an interesting story to tell about radar usage.
By the way, he will use the term LEWP. This means Line Echo Wave Pattern and is a squall line that has developed into a wave-like pattern due to acceleration at one end of the line and deceleration along the portion immediately adjacent. A Line Echo Wave Pattern (LEWP) indicates possible tornadoes, large hail and high winds
|It is now my privilege to introduce Mr. Jack Parrish, a meteorologist with the NOAA Aviation Operations Center (AOC). It is his responsibility to guide research aircraft around and through thunderstorms and hurricanes, all in the name of science. He has some interesting stories about flying, especially where you don't want to be. Please listen for the lessons from his experiences.|
NOAA Aircraft Operations Center (AOC) flies two types of aircraft, the
WP-3D Orions and the Gulfstream G-IV SP, into severe weather. Our remaining
fleet of light aircraft, including a Cessna Citation II, several DeHavilland
DHC-6 Twin Otters, the AC690A Turbo Commander, several Lake Seawolves,
and Bell 212 and Hughes 500D helicopters, fly NOAA missions as well, but
encounter severe weather only when necessary, and make all attempts to
avoid it. Due to their respective designs, cruise altitudes and true air
speeds, we naturally are much more willing to take the P-3s into more
potentially severe conditions than the G-IV. Most of this description
will fall back on P-3 experiences, with high-altitude insights from the
G-IV thrown in when it further clarifies the picture.
The last section stressed experiences
with the stormy tropical environment, generally found between 30? north
and south of the equator, especially in that hemisphere’s summer.
Much of the hurricane conventional wisdom holds true for Florida summer
thunderstorms and sea breeze squall lines as well. That is not to say
that there aren’t occasions of very large hailstones, tornadoes,
and aircraft killing shears in tropical summer thunderstorms. But by and
large, thunderstorms that paint vividly in the tropics contain flight
hazards of a lesser degree than similar appearing storms in the mid-latitudes.
Why? For numerous reasons dynamic and thermodynamic, some well described
in earlier lessons, they simply do not foster the meteorological organization
of the granddaddy of all thunderstorms, the supercell.
Use of Radar in Hurricanes
From this point, figuring that
we are getting a clear picture of the storm’s reflectivity (and
sometimes turbulence spectra, although it thresholds low for our purposes),
basic knowledge and experience play into our decisions. For hurricane
rainbands, and most tropical thunderstorms, we are aware that the embedded
updrafts are not strong enough to maintain large hailstones or produce
extreme shears. Reflectivities approaching 60dBz are occasionally flown
through, although values in the high 40s and low 50s are more the norm.
Very sharp reflectivity gradients on the inside edge of well-organized
eyewalls are inevitable and unavoidable; quite often, other than a sharp
updraft inward from the gradient, these areas are simply the edge of very
heavy rainfall. On the other hand, highly-reflective cells in outer rain
bands well away from the high wind hurricane core often possess very disruptive
shears, small hail and rotating mesocyclones that occasionally produce
small tornadoes (no tornado/waterspout should ever be considered ‘small’
to an aviator). The good news about flying into the hurricane’s
eye is that, most often, once inside the ring of greatest weather hazards,
there is ample time to maneuver in much calmer conditions while hunting
the exact wind center at flight level. Because of this fact, we usually
fly attitude and airspeed through the eyewall, regardless of wind shifts
while in heavy precipitation, and then make course adjustments once we’re
in the clear. During the actual eyewall penetration, close scrutiny is
maintained on the upcoming gradients and signs of small-scale rotation
(hooks, protuberances, small-scale asymmetries), but the flight crews
rarely need to turn away from features on the flight path.
|Thank you, Mr. Parrish. And
now back to our lesson...
Having your own sensing system on your aircraft is a very good way to avoid thunderstorms while flying. It is NOT the course's intention to ever endorse any product. However I must let you see the state of radar technology. With that in mind, we will explore the current state of radar and lightning displays for aircraft. Some systems have even evolved to show wind shear locations. The next step for radar, will be to display turbulence locations. That's coming very soon.
Radar displays on the Flight deck
If you are interested, Honeywell describes its commercial aircraft doppler radar in this pdf file
American Airlines' Flight Operations Safety Department published this article on using the newest radar systems. Its called "Weather Radar 101."
By the way, Mr. Tom Horne, Editor-at-Large for AOPA Pilot Magazine and a member of the NWA Aviation Weather Committee, published this article on the "Realities of Radar." You might find it interesting.
Lightning displays on the Flight deck
So what is a lightning display for the flight deck? BF Goodrich, the manufacturer has the following website with a brochure on the product.
For those interested, here is an article from Flying Magazine on Stormscope tips.
The second lightning display is the StrikeFinder manufactured by Insight. Check this website for information on the display.
Some pilots may want to know which is better, radar or lightning displays? I have never flown with a lightning display so it wouldn't be fair for me to say. But I do want you to know some recent findings from science about lightning...
1. Lightning strikes get very numerous during the development stage of thunderstorms with rapid movements of air and water upward. However, as soon as the storm is about to dispense its worst weather hazards like downdrafts, macrobursts, microbursts, and tornadoes, there is a dramatic decrease in the number of lightning strikes. If you see a storm suddenly stop its lightning strikes still don't go there.
2. Lightning displays must assume an average lightning strike to determine distance. Like all things in nature, there is not a standard value to lightning but only a bell-curve distribution of values. Like all things in aviation, please leave yourself room to maneuver away from and around storms. Don't get too close.
FLIGHT INFORMATION SERVICES
There are also ways to get information about thunderstorms from your radio and NAVAIDS. These methods give you the bigger picture and help you see BEYOND your sensors and eyes.
Terry Lankford, a retired FSS specialist, author, and co-chair of the NWA Aviation Weather Committee, is a good source of information on the roles of the Flight Service Stations and how they can assist you in getting the 'big picture.'
Flight Service Stations (FSS)
are FAA air traffic facilities that provide preflight and inflight weather
briefings, along with flight planning and other services. Selected facilities
provide Enroute Flight Advisory Service—radio call "Flight
Watch" and Hazardous Inflight Weather Advisory Service "HIWAS"
broadcasts. (HIWAS is a continuous broadcast of weather advisories and
urgent pilot weather reports (PIREPs) over selected navigational aids.)
You can take a tour of the ABQ Flight Service Station if you want.
Let's now explore the local FSS that you deal with. Go to the FAA's FSS links page and find out which FSS serves your area. .
(The link provided in the original program is no longer active. Since the FAA frequently changes its web site, the best bet is simply to go to www.faa.gov, and search from there for the particular information you need. Be patient -- it can be a difficult process.)
Hazardous Inflight Weather Advisory Service
HIWAS is a significant way to find out about the big weather picture. Recorded by FSS, they are broadcast on the frequencies of selected NAVAIDS. The station and frequencies are usually on the enroute charts you fly with or check the FSS websites in the previous paragraph of this course.
Center Weather Service Unit (CWSU) at ATC facilities and thunderstorms
|The following lesson on the
role of the meteorologist at the CWSU's came from Mr. S. Douglas Boyette
who is a former dispatcher who has worked with the National Weather Service
since 1986. He now serves as an Aviation Forecaster at the CWSU in Memphis,
Role of the ARTCC Meteorologist Pertaining to Thunderstorms
The FAA presently maintains
Center Weather Service Units (CWSUs) within each of their 21 Air Route
Traffic Control Centers across the lower 48 states and Alaska. Each of
these CWSUs are staffed by National Weather Service meteorologists, generally
operating during the peak traffic hours between 5:30 am and 10:00 pm seven
days a week. The CWSUs came into being in 1980 due to a recommendation
by the NTSB.
Want to interact with ATC? See where there are real-time CWAs happening now.
View the CCFP for today.
|NWA Aviation Weather Committee
member Steve Walden sent in this briefing showing just what
an ATC enroute controller sees with the current and with the new radar
screens. This program is called the WARP.
Pilot to Metro (USAF)
For members of the United States military, there is usually a weatherman only a radio call away while airborne. Usually, your needs are one of the highest priorities of the base weather stations.
The staff of the Directorate of Weather at Headquarters USAF prepared a lesson on the Pilot-to-Metro Service (PMSV) and the important information available on thunderstorms for this course.
Finally, contact your Dispatcher (if you are flying commercially and have one) for the big picture as time allows.
B efore we end this lesson, we want to make you aware of some research that taking place to help you and those involved with aircraft operations know where thunderstorms are located.
For those of you who fly over the ocean, there is the National Center For Atmospheric Research's Oceanic Convective Nowcasting project.
Well, thank you for joining us again for Lesson 4. We hope you've picked up some pointers on places to get thunderstorm information while you are airborne.
|Your "homework" for the next lesson is to read the Microburst Handbook for Visual Identification.|
1. What is the difference between an older weather radar and the newer doppler radar?
2. What is the name of the new weather radar network now used in the United States?
3. How long does it take a WSR-88D to make one scan of the atmosphere and update a picture?
4. What does the word MESO mean on a Radar Summary Chart?
5. What does the word HAIL mean on a Radar Summary Chart?
6. What is the different types of satellite images?
7. How do you identify thunderstorms on a visible image?
8. How do you identify a thunderstorm on an IR image?
9. How fast does the National Lightning map update?
10. What is an LEWP?
11. What are the hazards that Mr Parrish mentions he has seen in thunderstorms?
12. How does Mr Parrish say NOAA crews avoid the worst weather?
13. What hazards do the NOAA crews avoid?
14. What is the most important lesson the NOAA crews receive about their radar?
15. What is attenuation?
16. What has happened that put NOAA crews in the worst hurricane experiences?
17. What is the newest technology on aircraft radars?
18. What is a lightning display?
19. How can the FSS help you avoid thunderstorms on the ground and in the air?
20. What is a HIWAS? How will it help you?
21. Do PIREPs help others?
22. What is a CWA? Who creates them? What is the CWSU?
23. When is there a meteorologist on staff at an ATC facility? When ISN'T there a meteorologist on staff?
24. What is the CCFP?
25. What is the role of the Central Flow Command Center?