Finger Lakes Paragliding
3336 County Road 40
Bloomfield, NY 14469
Weather to fly or fly another day?
Paragliding is a sport that is very dependant on the weather as flying is only possible in
certain conditions. A good flyable day is one where there is light wind and no rain.
Clouds (except Cb) are not a problem; a dull overcast day with light winds can often be
better than one in blazing sunshine.
Before launching into a flight always check the weather forecast. A pilots understanding
of the weather is vital for the safety of a flight. A pilot must know how to interpret
pressure charts, dew points, and others. Take time to read and study. The weather can
be your greatest ally in paragliding but if you are too stubborn to understand the
principles behind it, the weather can be your greatest enemy. Never neglect the power
of nature for it is a force no pilot can defeat.
Knowledge of the weather helps a pilot make sound judgements about flying conditions.
For ridge soaring in a dynamic lift condition, a pilot must know the wind direction and
speed at launch. For thermal flying, as well as flying XC, a pilot should be familiar with
the wind direction and usual launch speeds, the winds aloft, and the atmospheric
instability and height of the cloud base. And in all situations a pilot should know if there
are any wind shear layers, predicted storms, and how the weather conditions will
proceed throughout the day.
If the wind varies by more than 6 mph in less than 3 seconds, you will encounter
turbulent air. Don't launch!
This is the first in a series of columns that will review step by step concepts concerning
weather and flying pointers. Practice the weather concepts daily, even when you aren't
going flying. Begin to identify the trends that make for the best flying, thermal conditions
or exhaust heat sessions. Give your chums a call who flew on days you couldn't and
see how close you can get to predicting the conditions. Be thoughtful about going to
new areas and how powerful some atmospheric influences may be in contrast to your
home sites. There are some sites that become unruly by 10 am in June yet others that
can be flown all day.
There are a couple of clues in the macro view of the atmosphere that can help you
visualize approaching weather as much as 3 days in advance. Planning ahead for the
possibility of flying can sure make the "home" scene and relationship with the "boss"
much easier. You may rather be at home getting through a list of "honey-do's" instead of
driving for 4 hours without any flying.
Through the Internet, television weather reports, and the National Weather Service you
can find Jet Stream maps for as much as 5 days away. For example, you can select
www.weatherchannel.com go to maps and find the Jet Stream forecast for the next 5
days. In general, it seems accurate for only 2 to 3 days out. If the Jet Stream is moving
into your area, within 100 miles, there's a pretty good chance that flying will be switchy
(changing direction dramatically within seconds), demanding (gust differentials beyond
the optimal) or impossible (just too darn strong). Although the Jet Stream is many
thousands of feet over the ground it draws cold fronts, which can then drop the pressure
and lower upper level temperatures thus reducing stability. The Jet Stream can have an
influence on surface winds as strong upper level winds can mix to the ground once the
inversion has melted. You may notice on some days influenced by the Jet Stream that
surface weather conditions can change within a few minutes. You may also notice fast
accumulating cirrus cloud cover with 2nd and 3rd layers of clouds appearing very fast,
indicating degenerating stability. Keep in mind that flying sites at sea level, or near sea
level, will be influenced less than high mountain sites. If you are going to fly in
questionable conditions make sure your glider is user friendly as well as the site - avoid
high performing gliders and sites in rough terrain. Keep an eye on the cloud
development and landing field winds - land before conditions can make your touchdown
Macro Weather - Lows and Highs" and "Isobars
Approaching "lows" and "highs" have powerful effects on the stability of the atmosphere
and the wind intensity and direction. Be watchful of your barometer, information sources
and the sky for evidence of a low. The low is basically a "puddle" of cool air descending
from the poles into a warmer area which is the "high". Weather maps indicate low
pressure zones very clearly with an arced line with dangling triangles. The fine gray
lines surrounding the "lows" and "highs" (isobars) indicate how steeply the pressure is
dropping. Tightly spaced isobars, let's say every 100 miles, generally indicate a high
probability of regional wind flow. So, a weather map showing the jet stream over your
area, a "low" and tightly spaced isobars isn't promising. Study the weather maps for a
couple of days and you'll quickly notice how systems generally move and be able to
anticipate the flying conditions.
If a "low" is approaching over night or early in the morning, you may notice earlier
thermal activity. This is because the decreasing pressure and lower upper atmosphere
temperatures allows thermals to release easier, particularly with direct sunlight. In the
scenario of a "low" approaching late in the day, where you've had heating throughout
the day, you may notice a thickening cirrus layer of clouds and that your barometer is on
the decline. With this late day "low" you may notice more demanding and erratic
thermals and strong windy conditions on the ground. The arrival of midday to late
afternoon "low" can be of concern to pilots in some areas of the country because
conditions can become very intense. In general, the approach of a low will bring winds
from the Southwest.
Pilots looking for soft and easy conditions will find some "lows" where the flying is just
fine. When a "low" is slow moving, without compressed isobars, there may not be much
regional wind flow. If there isn't much solar heating of the ground the air may be very
pleasant, but be aware that even a few minutes of sunlight can start the thermals
releasing. Be cautious with a "low" that a storm cell can develop and may create strong
lift, sink or gust fronts. A thick mid level (stratus) layer of clouds may keep down the
solar heating, but it can hide a towering cu nim (cumulous nimbus - raincloud).
As the "high" builds you may notice winds on the surface, and at altitude, more from the
Northeast. The jet stream will most likely be far away, to the North is best, and the
isobars will spread apart to over 300 miles between each gray line on the weather map.
With the increase in pressure and warming of the upper atmosphere you should notice
thermals taking much longer to develop and with ever increasing pressure tighter and
more sharply edged thermals once they do release. Many pilots fly during "high"
pressure systems as the conditions tend to be more predictable. You'll find anabatic
flow up East facing slopes in the mornings that can be very user friendly, to a point. Be
aware that thermals are ever building and that a heated area (puddle) reaching just the
right temperature will suddenly release its power. If you choose to fly as trigger
temperature is reached you may need refined glider management skills in pitch and roll
control, and be aware that landing zone conditions can be very unpredictable as
thermals lift off and change the localized wind flow directions. Keep in mind that
thermals will develop and release earlier in the morning in the Summer than in the
Winter as a result of more or less sun exposure.
Winds Aloft - localized upper level atmosphere information
Be sure and study the actual soundings of the upper atmosphere prior to flying each
day. These soundings are taken by the National Weather Service at 5pm and 5am
throughout the U.S.. This information can be found through a number of websites as
well as through a phone call to Flight Service (1-800-WX-BRIEF). Select the "Soaring
Forecast" and choose the "complete report" for your area through 18,000 feet msl. You
will see a few tables and a graph. Take a look at the wind direction and strength.
Direction is given in compass headings (i.e. 0 or 360 degrees is North, 180 degrees is
South). The wind strength is given in knots, a knot is 15% stronger than m.p.h.. Your
analysis is to determine if it is blowing too hard to fly at your local launch or if it might
start blowing too hard at some point during the day. Air can layer itself horizontally
throughout the atmosphere due to temperature, and thus be blowing at different
intensities and directions at different altitudes. It's possible for there to be a "river" of air
just a few 100 feet overhead or below your launch area that's blowing the opposite
direction and more than you like.
On clear nights cool air can "puddle" up on the ground for 100's or 1000's of feet in
depth. This is called an inversion. As you ascend from the ground through the lower
atmosphere you will often find that the air actually gets warmer. This puddle of cool air
is sitting underneath slightly warmer air and it's very possible that an uninformed pilot
may not know that the winds above this layer are actually very strong. Different
temperature layers of air don't mix - similar to oil and water. As the sun warms the
ground the ground warms the air and the puddle of cool air warms up and mixes with
the upper level "river" of air and within seconds you can find yourself in strong wind.
You will also find temperatures aloft information on the internet or through a call to Flight
Service and this information helps us predict stability. We will discuss the thermal and
lifted indexes in the next article.
The "lifted index" is the "thermal index" at the 18,000 ft msl level, which is generally
higher than the realm we fly within - so we'll simply look at the thermal index, which is
the surface puddles of heat compared to any level above the ground. When you gather
temperatures at different AGL's you can chart how strong the thermals may develop. Air
basically cools at 5.5f/1000ft. i.e. if it's 100f at sea level you'd expect air at 10,000ft
above sea level to be 45f. If the "sounding" (see previous articles) shows that the air at
10,000ft was 35f then you have a -10 thermal index. The stronger the negative number,
the stronger the thermals, usually.
Different ground surfaces heat differently - a golf course is pretty "cool" compared to an
exposed dirt field. Take a thermometer and place it on different surfaces to get an idea
of how much heat can develop on the ground - you'll be shocked. You'll find
temperatures of 130f within 10 minutes midday on some "hot" surfaces. We take the
forecasted high for the day and the temps we get from actually measuring the surface
heat and split the difference to derive a "puddle" temperature basis, i.e. forecasted high
for Denver is 85f and the dirt slope below Lookout Launch showed 115f after 10
minutes, so the puddle temperature would be around 100f. We'll use 6,000ft as our
ground level and compare this 100f to a reported 32f at 12,000msl. This gives us a
thermal index to 12,000msl of -35 (VERY STRONG!!). You will also want to note the
barometric pressure level and keep some notes as to how the flying went for you, or
your buddies. Didn't like the air because it was too bumpy? Learn to anticipate it by
knowing the models of thermal index, pressure, and the other factors we discussed in
previous articles. We'll talk about the "K" index later in this article.
The "K" index makes an attempt to "rate" the possibility of thunderstorms. An index of
15 is low and 40 is high. We want to avoid flying in conditions where thunderstorms are
likely. If you note that cumulous clouds are starting to billow taller than they are wide
you may expect strong areas of lift and sink that may exceed your abilities to manage
turbulence. Growing cumulous can create such strong lift that you may become trapped
in the cloud, which is illegal, cold, disorienting and can lead to hypoxia. Some cumulous
clouds can be 10's of thousands of feet in height. Even if rain or virga is miles away it
can create sudden gust fronts (called "out-flow boundaries" by the NWS). Virga, which
is rain that doesn't fall all the way to the ground because of evaporation, can create
strong gust fronts because the chilled air falls to the ground and flows outwardly. Keep
in mind that a cloud dropping virga or rain as much as 10 miles away from your flying
site can cause high winds. Virga looks like a veil or can appear wispy.
When studying the underside of cumulous clouds or a layer of clouds, "stratus", look for
lumpiness, called "mammatus", in addition to virga. These can indicate the possibility of
impending rain. To fly uneventfully shouldn't mean you survived a potentially dangerous
situation, it means you've learned to anticipate what may happen and then either
choose not to fly or to land to avoid flying under duress. You wouldn't knowingly walk
across a thin layer of ice, don't fly in conditions that are clearly dangerous. Your
accident could shut down a flying site..
Flying Site Weather
If you want to become more successful in your ability to fly with confidence and
competence it's not only important to develop your weather model for the day and your
glider management skills, it's important to start noticing what the air is doing on launch,
then within the mass of air you're currently flying and then at your targeted landing area.
Notice and consider whether or not the air is moving because of regional flows,
localized valley/sea breezes, or from the anabatic/thermal flows. You want to make the
best choices of when to launch, where to locate yourself within the air mass and then
make an uneventful landing based upon your skill to make sense of the
micrometeorological airmass. Monitor conditions from the moment you arrive at launch,
note everything while preparing your gear. Note what was occurring on launch before
and after the other pilots take-off and see what they get - if they do well catching the
"right" air, you can use the model of what was occurring on launch. Knowing when to
launch can make a HUGE difference in your success at getting off launch easily and
then finding the air you want. Many newer pilots launch at the end of the cycle and then
wonder why they get non-lifting air. Quite often the best thermal is out in front of launch
which requires launching when conditions are very soft on launch, a good reason to
practice light-wind launch skills. While in the air be sure to continually observe the other
pilots, birds and what you are sensing of the conditions. Take advantage of that
information to help you move to areas of lift. Keep an eye on the landing areas and note
which direction the other pilots face when landing and that they have, in fact, landed into
the wind. If there aren't easily readable wind indicators in the landing area be sure and
observe your ground track as you fly nearer the ground to determine your drift and thus
the wind direction.
Simple air should be easily identifiable as air movement from one source, like flying a
coastal site late in the day. Complex air could include regional air flows compressing
through valleys then merging with anabatic flows with a large thermal within and a
microburst gust front pushing the whole area. If you want ridiculously complex air fly in
rotor on top of everything else, (just kidding). Until you begin to appreciate how different
flow sources work together, purposely stay well within very easy flows, or combinations
An example: Although a sea breeze coastal site seems simple they can develop glider
tossing thermals. Flying a coastal ridge site midday in the Summer can be turbulent, just
like most sites at midday, you must still look at your stability models.
Another example: Many evenings offer heat release conditions that may be smooth and
simple, but if the pressure is dropping and the upper level temperatures drop late in the
day the evening conditions can become very windy and even bumpy. Be very thoughtful
in the evenings, stay out in front so that you aren't blown back if the winds increase.
Another example: Many mornings are very mellow with nice light breezes, but can
become very windy with strong turbulent conditions within a minute or two towards
midday. Be sure and check for an inversion that may mask the strength of upper level
wind flows. As the inversion warms up it can spontaneously mix with the upper level
winds and be more than you bargained for.
Another example: A dark cloud showing virga/rain some miles away may lead to a gust
front. Although you don't feel any wind for the time being, it's very likely you could have
what is technically called an "outflow boundary" (gust front in some books) blow
through. If the cell is 15 miles away and the outflow is 30 miles per hour is will take
about 30 minutes to reach you.
Another example: The pressure is high, the stability index is moderate to high. The
atmosphere seems pretty stable and mellow. At some point midday, between noon and
3pm, the whole area triggers and it becomes very windy with all of the oppressed heat
letting go for extremely strong conditions.
Anabatic flow occurs on a heated slope. Stand on a sunward facing hillside without a
strong countering regional wind or thermal blocking and you'll usually find a steady
upslope flow from heat rising. Thermal blocking can be felt/seen as a wind sock slows
down to a stand still or has a possible "blowing down" type of appearance - the wind
sock is being drafted towards a thermal in front of launch. The huge mass of thermal
lifting in front of launch can actually block air flows and suck air away from a hillside. A
windsock that is whipping around and/or changing intensity may indicate the influence
of regional and or thermal flows affecting the anabatic flow. Valley/sea breezes are from
warm air being replaced by cooler air. Stand on a warm sea cliff and you'll feel a breeze
as warm air rising is fed by the cooler air over the water.
Rotor is found on the backside of an object facing the wind, not a happy place. Rotor
can be found behind hills, trees and buildings. You need to know that you aren't trying to
launch, fly or land in rotor. Your upper level model should help you determine this as
well as your observance of valley flows and gust fronts. You need to make sure the
thermal strength is within your abilities, so do your stability models, look at the pressure
and monitor the gust differentials on launch. You'll notice that large mountain sites can
have booming thermals with light conditions on launch. Small hills may be more
manageable in stronger cycles, but be sure that the gust differentials, how fast the gusts
increase/decrease in a few seconds, aren't beyond your skill. As you spend more time
ground handling in different conditions you'll become more aware of how gusts and top
wind speeds put demands on your skill. In general it's best for recreational pilots to
restrict themselves to winds less than 15mph, but if you're flying in the mountains you
need to restrict yourself to winds less than 8mph, or less. Recreational pilots should
restrict themselves to gust differentials of no more than a 5 mile per hour change in less
than 5 seconds. Take the time to actually monitor these winds with a good wind meter.
If you get in the air and don't like the conditions, make sure you know what was going
on and make notes to yourself so you can avoid those conditions in the future.
Obviously make notes about the atmosphere you like as well.
All in all, it's best to fly in pure base wind without heat, or within pure heat without a
If you don't develop your observational skills you're not training an important aspect to
your flying success. REMEMBER, this sport is unlike anything you've ever done before,
you need to learn a whole new set of rules - watch, listen and read.
The low Winter sun angle in our Northern Hemisphere heats less surface area. Behind
every bush, blade of grass, and tree is more shadow throughout more of a shorter day
than during the Summer, so less heat is accumulating. Thermals may still exist even in
the Winter when the pressure is low and the upper atmosphere is cold, so still do your
"thermal index" modeling and don't ever get complacent. Expect the triggering of the
thermals to generally occur later in the day than in the Summer and for a shorter
duration and interval. Very late in the day look for thermals over the forest areas as they
give up their accumulated heat. Just because you're freezing cold doesn't mean there
aren't thermals, heat still wants to rise. Get yourself some long johns, a good windproof
flight suit, a bali clava, and some warm gloves. The thermals generally won't rise very
far and for very long, but it's a hoot to make the most of light conditions. Getting good at
using nominal lifting air may very well become your favorite kind of flying. It's sure fun to
work super light lift as a possible welcome change from the Summer time "events" of
"hanging on" in "nuclear" air. Leave the vario behind and fly by the "seat of your pants".
Keep horizon reference, even while making circles. Try and feel yourself being lifted, the
sink and being pushed sideways through the air. Work on using every bit of buoyancy to
maximize your stay in the air.
Winter flying might also bring your local area widespread regional wind flows that can
be soared for hours with relative ease. Watch for a day when you have a stratus
clouded sky and look at the winds aloft for a model of upper level wind flow that isn't too
strong for your skills and aircraft. Be aware that a cloudy day that breaks into sunshine
may develop thermals very quickly and be sure to account for this potential increase in
your ever updated evaluation of your immediate atmosphere. It can take only a few
minutes of direct heating for the air to get turbulent on an unstable day, even in the
Winter. More advanced pilots that have solid active piloting skills will look for areas of
direct sunshine and boat around those potentially "productive" spots looking for a "lift".
This can be a great time of year for pilots to begin flying unfamiliar sites that have been
unapproachable in the Summer.
Take advantage of the soft Winter conditions to make loads of flights. Sled rides are
great, really! You can often fly all day in the Winter and make many flights and thus
perfect your abilities on many levels. Try bringing up your glider in all sorts of conditions
and make clean and straight launches. Actually make a mark on the ground and try to
make your launch without running to the side. To "loaf" off launch as you stare up at
your glider often causes failed launches. A key to your success is to keep moving with
your eyes on the horizon so your glider has more airspeed and is consequentially more
Get those accurate landings down pat. Keep your eyes on your landing target with your
knees as a reference point. If the target is getting higher on your horizon you'll need to
straighten out your flight path and get a better glide with your hands at "trim". If your
target is getting lower on your horizon, then you better do something to reduce your
glide. Glide reduction to avoid over-flying a target can be accomplished by making "s"
turns while holding about 1/3rd brake. Keep an eye on your target, as well as the traffic,
while making the turns and you'll notice your slope angle changing and you'll be able to
straighten out your path and make your target.
Be safe and have fun!