Contents:
National Weather Service; …Item
on Weather; …Getting the Weather; …Becoming
Weather Wise; Static Electricity: ...Making
Weather; ...Weather Stability; ...Mesoscale
Weather; ...California
Weather; ...Air Mass Weather; ...Fronts;
…Warm Front; …Cold
Front; …Occluded Front; …Stationary
Front; ...Weather Demonstration; ...Inversions;
...Pressure; ...Moisture and
Weather; Wind Indicators; ...Natural
Wind Indicators; …Wind Shear; ...LLWAS;
...Mountain waves; ...Jet Stream;
...California Surface Winds; ...Headwinds;
…Relative Wind; …The
Weather She is A'changing; …Weather Advice;
…Opinion; …Weather
Aloft; …Weather Notes; ...Reading
Weather Winds; …Whether to Fly in the Weather;
…The Smog Layer; ...PIREP
Wind; ...Deteriorating Weather
Lesson; ...Weather Web Sites; ...
National Weather Service
1. Convective Outlooks (AC) Use connect-the-dots method to define
area.
2. Severe Weather Outlook Charts (graphic of AC) also called Convective Outlook
charts use slgt, mdt, high to describe area weather. The charts connect the
dots.
3. Radar Summary charts (snapshots of past weather and rain clouds can extend
much farther.)
4. SIGMETs (WS) Severe turbulence, icing, wind shear when first detected and
then 55 minutes after every hour. Uses connect-the-dots method to define area.
5. Convective SIGMETs (WSTs) Significant meteorological information of severe,
embedded, and lines or 40% coverage of Level 4
6. Center Weather Advisories (CWAs) ATC frequency will give advance warning of
severe weather.
7. Radar Reports (Rareps)locates weather by direction and distance 060/075; NC
=no change; MT=maximum tops; +/+= strong storms increasing intensity; LN=line;
A=area; C=cell;
8. Terminal Aerodrome Forecasts (TAFs) Airport forecasts every 8-hours mention
adverse weather and thunderstorms
9. Area forecasts (FAs)
10. Hourly Surface Observations (METARs) from airports with weather observers
who mention storm activity.
11. Thunderstorm Forecasts
12. Lifted Index is measure of temperature at altitude; K index is measure of
moisture and saturation. As a fraction the lower the fraction the greater
likelihood of severe weather.
13. Composite Moisture and Stability Chart
14. Severe Weather Watch Bulletins (WWs)
15. PIREPs
Item on Weather
New weather site identifier codes are now in effect. Many remain the same.
Checking the AWC Web site now counts as a legal weather briefing according
to FAA
39 U.S. Towers are are getting what it takes to predict local weather
Getting the Weather
As a pilot you want first of all to get an overview of the big picture.
Begin with the upper-air forecast charts such as the 500-millibar chart, which
is about halfway up the inch-square air column or 18,000 feet. This chart
shows the various pressure centers, troughs, ridges and winds. By becoming
familiar with these charts and the accompanying weather the pilot can begin to
anticipate and interpret weather.
Once you see the relationship of the 500-millibar chart and surface weather
you are better able to understand and orient yourself to weather hazards.
Additional information comes available through the infrared and water vapor.
These visual images show the details of visible weather systems. Infrared
works at night as well as day. Interpretation requires practice. Only by
knowing where a storm is expected to go can you even make preliminary flight
plans. Doppler systems (Nextrad) is giving us a forward step in this weather
process.
Becoming Weather Wise
For a beginning a pilot should make a practice of watching the evening TV
weather and the early morning weather channel. Next, by using DUAT or calling
a Flight Service Station (FSS) available nation wide at 1-800-WX-BRIEF you can
obtain a briefing. These can help you meet the FAR 91.l03 preflight
requirement of having all available information as part of the preflight. When
below freezing level temperatures are encountered an important part of the
preflight is to assure that the oil breather tube is not ice-clogged.
Additionally, when cold weather arrives, the grease in the throttle wire cable
can become so congealed that movement is restricted. Do not takeoff in an
aircraft where throttle movement is restricted in this manner. Climbing into
still colder weather may prevent any movement.
As a minimum a pilot needs to know, for local flights, airport conditions, fog
prediction, freezing level, turbulence, local notams, and winds at 3000.
Weather briefings are rapidly becoming less available except through
computerized access by the pilot.
Radar returns are based only on water. Wet is not always convective. Water is
not a thunderstorm until it includes vertical development and Vertically
developed clouds can contain severe turbulence and icing. Low clouds with flat
tops usually do not have turbulence or icing. Virga is indicative of
evaporation cooling of the air, which accelerates downward as microbursts.
Virga is most dangerous when surface temperature is warm, winds are light, and
dew point spread exceeds 35 degrees.
Static Electricity
Static electricity is a common phenomenon. It is not dangerous unless it
builds enough to produce a spark. It is invisible and silent medium that
causes many aircraft fires. Susceptibility to static electricity exists when
fuel is being
poured between plane and any ungrounded to plane fueling source. Plastic fuel
cans and plastic funnels are the most common sources. Even carrying plastic
fuel cans in plastic truck beds is a potential five hazard. Do not drain fuel
into plastic buckets.
Making Weather
Atmosphere has three levels. Troposphere extends from sea level up to
35,000 feet around the poles and to 65,000 feet at the equator. The standard
temperature lapse rate of the troposphere is 2-degrees C per 1000 feet of
altitude. On top of the troposphere is a thin layer called the tropopause,
which acts as a moisture barrier. The top of the troposphere is the bottom of
the atmosphere. The 850-millibar air pressure level will be lower in true
altitude than warmer air. All air pressure is the measure of the weight of air
above. The stratosphere is next extending to 22 miles high and because of the
tropopause barrier has no moisture and a constant temperature of -55-degrees
C.
50% of the world's atmospheric weight is below 18,000 feet.
Consider a rotating spherical envelope. A mixture of gases-occasionally murky
and always somewhat viscous. Place it around an astronomical object nearly
8000 miles in diameter. Tilt the whole system back and forth with respect to
its source of heat and light. Freeze it at the poles of its axis of rotation
and intensely heat it in the middle. Cover most of the surface of the sphere
with a liquid that continually feeds moisture into the atmosphere. Subject the
whole to tidal forces induced by the sun and a captive satellite. Then try to
predict the conditions of one small portion of that atmosphere for a period of
one to several days in advance.
A pilot must learn to be skeptical about what the weather is for now, what it
is forecast to be, and what he hopes it to become. The entire process is so
capricious that even in 1997 the gigabite computers can't keep up.
All of the factors in the foregoing paragraph are factors in making weather
but only three main factors, heat, water, and wind are of major importance.
There are three kinds of heat transfer in the atmosphere:
--Convection is that which causes thunderstorms.
--Radiation is that which causes ground fog
--Conduction is that which causes you to drop a nail held by the fingers when
you are heating the other end.
Weather Stability:
The presence of moisture in the air is the determining factor as to
whether a given body of air will become stable or unstable. Colder air is
heavier than warm air. Cold air will not rise unless it is surrounded by even
colder air. It is the relative temperatures of neighboring air bodies that
determine whether air will rise or fall.
When the air contains water it is conditionally unstable and will remain in an
unsaturated state until it reaches near the dew point. At or near the dew
point it will become visible moisture (cloud). Any uplifting of this
conditionally unstable air will eventually cause it to condense, become
saturated (visible) and unstable. Any lifting of unstable air will cause an
acceleration of the lifting action.
The moist air does not cool as much as dry air. This means that any uplifting
is more likely to increase the temperature difference between the warmer moist
air and the surrounding air. The rising acceleration of a moist air column
increases as the temperature difference increases. This increasing
acceleration is a characteristic of unstable air.
A dry air column cools at a standard environmental rate of 5.5 degrees
Fahrenheit for every thousand feet rise in elevation. Without moisture it will
cool and tend to descend or level off at the same level as the surrounding
air. Stability or instability of any air column is determined by its relative
temperature lapse rate to that of its surrounding air.
Atmosphere can be either stable or unstable. Any uplift of stable air will
result in its return to its original level. Any uplift of unstable (warmer)
air will cause it to expand and cool but at a lower rate than the surrounding
air. This air mass will continue and accelerate if the air is either
relatively warm, moist or both. The earth's surface and its immediate air are
heated unevenly. Turbulence is caused when warmer air moves up through cooler
air.
The standard environmental lapse rate of 3.5 F or 2 C per 1000 feet is not
realistic. We can determine approximate lapse rates by taking thermometer
reading every thousand feet. The likelihood of any flight having this standard
is slim. We can determine the approximate freezing level above a known
elevation by deducting 2-degrees Celsius from the initial Celsius
altitude/temperature for every thousand feet, until reaching zero.
Mesoscale Weather
Small area weather conditions. These are the weather that occurs in the
valleys around the bay area. Each small area will have weather distinct from
its neighbors. This is very typical of California coastal regions
California Weather
Ocean water temperatures determine the weather world wide but most
dramatically in California. Warm water in the Gulf Stream (El Nino) causes
precipitation; cold water in the stream causes stratus and fog. California fog
requires cold water and warmer air. This creates an inversion where the colder
air is below the warmer. The temperature increases (instead of usual decrease)
with altitude.
The cold Alaska Current follows the western coast of North America and
increases the moisture content of the air in the Pacific High while decreasing
its temperature. FOG. This California fog would stay along the coast were it
not for the warm interior valleys and desert of California. The heat from the
deserts causes low pressures from rising air, which is very attractive to the
air in the Pacific High. The result is a strong surface pressure gradient
creating winds that carry the fog ashore.
Bay area fog, were it not for occasional fronts, follows a four day cycle of
the fog coming on shore, into the bay, into the east bay and into the Central
Valley. Mesoscale weather will exist in the various areas both during the
four-day fog arrival and during the four-day retreat back to sea.
An air mass extends for over 1,000 miles. The air mass acquires its
properties from the surface below. North America has three air mass areas,
Arctic, Polar and Tropic. Thus air mass types are polar and tropical with
sub-classes of maritime or continental. The formation of air masses is
seasonal. Air masses change as they move. Where two air masses meet we have a
frontal zone where the colder mass moves below the warmer. The air mass may be
far ahead or far behind the surface front. Worst weather is when fronts move
fastest.
Cold fronts are usually in the winter and the passage is shown by clearing,
wind shifts, a rise in pressure and colder temperature. The extent of clouds
depends on the stability of the air.
Fronts:
Warm Front
A warm air mass shows several days ahead of the front with a slow progression
(less than 20-kph) of very high clouds as it overrides relatively cooler air
below. First comes cirrus, lowering to cirrostratus, becoming still lower
altostratus which changes to alto cumulus. Finally comes nimbo stratus with
continuous light rain or snow. Imbedded thunderstorms. Visibility goes below
minimums. Freezing rain occurs in winter. Frontal passage gives good flying
for a few days. Warm and stationary worst weather.
There is a variety of warm and cold fronts. The main difference being
stability. Stable air masses can have weather dependent on the moisture
available. Stable warm air masses can have clouds to 25,000' with icing.
Cold Front:
A cold air mass appears quickly at over 20-kph. Any cirrus becomes altostratus
and altocumulus changing quickly into stratocumulus. When the front hits
strong gusty shifting winds accompanied by nimbostratus or cumulus. Produces
summer thunderstorms and squall lines in front. Heavy bursts of localized rain
can cause flooding. Passes quickly and leaves two days of cumulus clouds for
bumpy flying below. Cold fronts change when they cross mountain ranges.
Pacific cold fronts are moist before the Sierras, dry afterwards. Across the
Rockies it picks up moisture from the Gulf and will intensify. Dry cold fronts
will be bumpy but VFR.
Cold fronts are areas of lowest pressure and strongest winds. Wind coming over
water carries moisture. Wind direction and velocity can vary dew point spread.
If you stand with your back to wind point to the area of low pressure. This
tells you where the fronts are located. Winds over water or blowing up slope
are likely to worsen weather conditions. When forecast winds are in error then
the entire weather forecast is in error. Westerly winds bring better weather.
Southerly winds bring worse weather. Surface winds 100 miles to the west are
likely to arrive at your location in two hours. The pilot who makes note of
frequent changes in altimeter settings is in an area of strong winds.
The cold air of the world descends to the surface near the poles. Moving
southward it deflects to the right. This polar front and its associated low,
the Aleutian low cause much of the U. S. weather. The Aleutian Current is a
north to south cold current that causes the weather along the Pacific coast.
Three elements mix to form thunderstorms, excess moisture, a lifting force,
and unstable air. Thunderstorms are forecast in the area forecast (FA) and
terminal forecasts (TAFs). Any time the lifting index has a negative number
you can expect thunderstorms. Any thunderstorms upwind of your flight with the
three elements present indicates a no-fly zone. Fly to the bright spot and
blue. What your eye sees is just as valid as radar.
Thunderstorms are either air mass which are isolated and easy to avoid or
severe. Severe thunderstorms have hail, 50-knot winds with possible tornadoes.
Avoid flying on the upwind side and the north side of storm lines if given a
choice.
Turbulence beyond the pilot's and aircraft's capability is to be expected in
or near a thunderstorm. PIREPs are a pilot's best friend in turbulence since
it is real time information. Avoid any reported moderate or higher level of
turbulence. Proper interpretation of PIREPS, those real time and position
reports by flying people, is critical to safe weather flying.
Occluded Front:
Occurs when faster cold front catches and winds around a warm front. Worst of
both systems. Stratocumulus and cumulonimbus clouds lower slowly but clear
quickly. If a low-pressure area is gaining strength rapidly, it will slow
down. The fronts will rotate around the low. The cold front will overtake the
warm front and result in an occlusion.
Stationary Fronts:
Sometimes spring fronts blend together without any clearing and bring days or
a week of weather having nothing but low levels of fog, haze and smog.
Following cold fronts are needed to clear out stationary fronts.
In the winter where cold air is under the warm layer and the temperature
difference is over 10 C, forecasts of improving weather are inaccurate. The
conditions are too stable to make a change likely.
Weather Demonstration
Place pencil horizontally between praying hands out in front of you. Left
hand is northern cold air and the right is southern warm air. The low exists
between your hands. Move left palm down to roll the pencil. The pencil rolls
cyclonically to the left.
The cyclone draws warm air down from the south and sends it above the sinking
cold air. The cold front moves to the southwest and a warm front forms east.
The bigger the cyclone low the stronger the weather.
Inversions:
Any time the air temperature is warmer above than the air below is called
an inversion. An inversion may be surface based or an inversion aloft.
Inversions can be the cause of poor visibility and turbulence. Inversions are
most common in late spring and early fall.
Surface inversions begin at sunset when the earth's surface temperature cools
rapidly on a cloudless clear night. This allows the air close to the surface
to cool while the air only a few feet higher remains warm. This condition can
last till mid-morning. The condition is most likely to exist when winds are
very light and unable to cause a mixing of the air layers. The heat from a
rising sun will increase the mixing of the layers and eliminate the
inversions. In regions like Alaska such inversions can be dangerous to
aircraft due to frost forming on the aircraft.
The inversion aloft is caused when air masses flow in such a way as to cause
the warm air to pass over the cold air. If the upper layer of air is also
descending its increased pressure will cause further warming. This is a common
summer condition on the west coast of the U. S. This is also called a
subsidence inversion. This condition causes the stratus (layered) clouds of
avection fog, smog layers, and reduced visibility.
Inversions exist by providing warmer air aloft than exists in air at lower
altitudes. The temperature lapse rate is upside down. An inversion prevents
vertical air motion. Large, slow-moving high-pressure systems are a common
source of inversions. The top of an inversion layer is flat.
There are four pilot clues to the existence of an inversion:
1. Cloud formations can occur with as much as a 6 degree dew point spread.
2. An illusion in inversion visibility conditions makes things seem further
away.
3. There is an increased possibility of low level wind shear.
4. The air will be very stable and give smooth flight above the inversion of
either type.
Pressure
High pressure has a clockwise down spiraling cold air mass giving good
flying weather. This is generally true about highs moving in from the Pacific
Ocean but not true if they come down from Canada. Where it comes from is
important. The Bermuda High brings days of poor visibility to the Eastern U.
S.
Low-pressure areas are counterclockwise upward spiraling systems that bring
bad weather. The Low draws in moist air and forms spiraling cloud formations
of low cumulo or stratocumulus rain clouds. The cold front formed by a Low is
{,} comma shaped.
Flying from warm air into cold air is effectively flying from high to low
pressure. The effect in a standard lapse rate is 35' for every degree Celsius.
Every three degrees colder with a constant altimeter setting and altitude
effectively puts you 100 feet lower.
As altitude increases above sea level the pressure of the air decreases at a
rate of two pounds per square inch for every 2000' below 18,000'. This
pressure altitude in used to determine oxygen requirements for humans. When
the temperature change (lapse rate) is greater than standard the density
altitude will be higher than the pressure altitude. This affects aircraft
operation by decreasing power, lift, and thrust.
The barometer is a lineal scale used for weighing the air on a square inch of
the earth surface. The aneroid barometer uses a closed bellows and a circular
scale to do the same thing. The barometer that uses the weight of air to
measure altitude above the earth is called an altimeter. The standard setter
for all forms of barometers is the mercury barometer, which reads in Hg on a
scale in which one inch of mercury movement in a tube is equivalent weight of
one thousand feet of air if in the same tube. This change is weight is known
as the lapse rate.
At sea level the weight of the air column is 14.7 pounds per square inch or
the air pressure required to raise the mercury column to 29.92 inches or
1013.2 millibars. For aeronautical purposes measures are varied through the
use of a kollsman window which computes weight from mean sea level (msl)
without regard to terrain. As daily air pressures vary the altimeter is re-set
to read changes due to the adjusted lapse rate.
By FAR you must have your altimeter set from a figure given within 100 n.m. in
a worse case situation. Fact is, settings should be obtained from the closest
source available. All radar facilities are required to give this setting at
least once during any continuous contact with an aircraft. This setting can be
confirmed + 300 feet just be having the pilot read back his altitude.
From a weather viewpoint changes in air pressure are always significant. The
pressure trend that is to lower pressure means that air is being drawn in
along with moisture that at will at some point condense into visible moisture.
Rising air pressure reverses this process. These pressure changes in the U.S.
mean that the rise and fall will cause fronts to move across the country. On
average, one front crosses a given point once a week in summer and two or
three such passages in the winter. Warm or cold in the passage of the fronts
is always relative to the front preceding. Cold fronts move faster than warm
fronts and tend to wrap-up on them when they touch. The wrapped area is known
as an occluded front, which usually has the worst aspects of both the warm and
cold fronts. It would not be nature's way to have the best qualities survive
as offspring.
Moisture and Weather
The movement of moisture is reminiscent of a multiple juggling act where
the three forms of ice take turns going through six different stages of
transformation. Vapor can condense into liquid and sublimate into ice while
liquid can evaporate back into vapor and the ice can sublimate into vapor. The
ice that sublimated from vapor can melt into liquid and be created by freezing
liquid. This entire process can be diagramed as the three forms in a line with
a large circle connecting vapor and ice on the outside while liquid in the
center is connected by two smaller circles one to vapor and the other to ice.
The required words along the arcs of the circles are only sublimation twice
hot and cold from vapor to ice and ice to vapor. Liquid and vapor are
connected by the hot condensation arc and the cold evaporation arc. Liquid and
ice are connected by the hot freezing and the cold melting. With a little
effort the diagram can be made.
In the diagram we have the three phases of moisture gas, liquid and solid. All
are forms of water. The forms are determined by the speeds at which the
molecules move. The molecular speeds are determined by temperatures. Air is
saturated when for every molecule evaporated another is condenses. The
relative humidity is 100%. When dew point rises above 60 degrees we have a
condition of high humidity. The dewpoint is the temperature where dew forms.
When the air temperature and dew point are close together contaminants in the
air facilitate the formation of liquid molecules which form visual
obscuration.
The form changes of water while being caused by temperature changes, in turn
cause temperature changes.
Each form change there is an exchange of heat. Every storm is a heat engine
during which the change in water form either releases or collects heat.
Wind Indicators
Wind often is very stressful to the pilot. Takeoffs and landing techniques
require greater skill under the influence of wind. Even the light and variable
wind adds complexities that are difficult to plan for. Having specific wind
information can either add to or subtract from a pilot's stress.
Runway selection is primarily based on wind direction except where noise
abatement rules prevail. With experience a pilot learns to read winds from
water, dust, DME, GPS, the windsock and weather forecasts. Regarding the
latter, one thing you can be certain of is that the winds will NOT be as
forecast. It is not a good idea to read the wind from a tetrahedron. Most
tetrahedrons have locks that allow them to be positioned for the preferred
runway without regard to wind direction. The windsock is the best wind
indicator at an airport and should be noted on downwind and especially on
final. What you see on downwind will enable you to make a wind adjusted
pattern. A disproportionate number of landing accidents are caused by a
pilot's failure to adjust the pattern for wind direction and velocity.
The FAA wind cone (sock) can be of several colors but usually orange and
either 8 or 12 feet long. Windsocks are fully extended in 15-knot winds. I
make a practice of having student's practice reading windsocks by comparing
ATIS or tower wind directions and velocities with their guesses from the
windsock. At one time Concord, CA had five windsocks. It was not unusual to
have them all showing different direction and velocity.
A weather related accident is most likely to be blamed on the wind. Wind does
have a lot to do with your flying. The unequal heating of this planet's mixed
surfaces of land and water causes wind. The time of the year and the weather
is related to wind direction and velocity. The world is not heated evenly as
it moves around the sun, changes distance, leans, and turns. The uneven
heating causes the movement of air masses seeking equilibrium. This uneven
heating also causes pressure differences and pressure gradient forces. This
causes wind. The greater the pressure differences in you altimeter setting the
stronger will be the winds. The warmth of the earth causes vertical movement
of air.
Local small-scale winds are caused by the flow of air to replace the air that
is rising. Water instead of absorbing heat reflects most of it. Land absorbs
instead of reflecting. The hotter land causes rising air thermals. When the
sun goes down the land gives back to the atmosphere much of the heat acquired
during the day. Land makes this change at five times the efficiency of water.
At night the water is warmer than the land and the flow of the wind reverses.
Where the pressure isobars bend the effect of centrifugal force is greatest.
This is the force the wind has upon itself due to differing pressure
gradients. The rotation of the earth also creates a force against the air
surrounding the earth. This coriollis effect causes the winds in our hemisphere
to be deflected right. This coriollis effect deflects anything projected into
space. The winds of the southern hemisphere are deflected left. This effect is
weakest at the equator, which explains the absence of extreme highs and lows
there.
Gustave Coriollis mathematically described the effect of the earth's rotation
on moving objects in the atmosphere. The effect begins at the equator a zero
and increases toward the poles. The effect also increases as the wind speed
increases.
Winds should flow parallel to isobars but frictional force affects the flow of
air below a couple thousand feet. Wind strength increases above this level.
This frictional force makes the wind turn across the isobars into the low at a
30-degree angle. It is only above the frictional layer that the winds parallel
the isobars.
When conditions indicate strong wind conditions take an early look at the Va
for your aircraft and its present weight. The higher winds are the slower you
should go. This is usually done beginning with the Va for gross weight and
find the percentage you are under that weight. Easy to do on the E6B or on
paper by making the following equation.. (One way to do it.) Make a fraction
with your 'actual weight as the numerator over the gross weight as the
denominator equals N over 100. Multiply the diagonal numbers actual weight by
100 and divide by gross weight. This is the percentage of actual weight to the
100% of gross weight. Subtract the two percentages to find the difference.
Divide this difference by three and using the answer as knots use it as the
amount to reduce your Va speed. Example: If you find that you are 10% below
gross then you would lower your Va at gross speed by three knots. Not at
complicated as it seems once you do it several times.
A mountain wave can be dry and cloudless with as much turbulence as if a
visible cloud exists. Winds of 25-knots perpendicular to mountain ridges with
increasing velocity at higher altitudes will contain such waves. Wide areas of
weather instability are the best souses of mountain waves. The same wave
system can last for a couple of days. Waves can occur over low hills if the
winds are strong enough.
A Foehn wind (Chinook) are warm dry winds descending off mountains that can
melt two feet of snow in a day. They are as dangerous as mountain waves. Any
encounter with a downdraft demands that the pilot be prepared to do a 180 or
have sufficient excess altitude to allow him to 'dive out' of the situation.
This can be considered mountain drainage winds, which have thunderstorm like
gust fronts.
These winds can be microscale weather involving less than one hour and a very
few miles. Pilots flying in such conditions need to know the warning signs of
markedly different barometric readings of neighboring mountain airports. Rotor
clouds and unsteady lenticulars in a line serve as a warning of such
conditions. Virga usually indicates extreme turbulence. These conditions may
be of very short duration about mid-morning. The cloud type tells the kind of
turbulence to expect.
Flying in turbulence is best done with a very light yoke and lots of rudder.
Bring up a dropped wing with rudder not yoke. Rudder use otherwise must be
coordinated and in choppy conditions do a rudder dance. If turbulence causes
pitching of the nose, make major correction with power changes. I have found
it better to put in the initial power change I feel necessary and then take
half of the change off immediately the correction begins to occur. Use
elevator to adjust for altitude excursions. When the aircraft acts like a
bronco or a canoe counter primarily with rudder input and gentle yoke
pressures.
NTSB reports that up to 40% of all weather related light aircraft accidents
occur where the pilot cannot cope with the winds near the surface. The best
way of avoiding adverse winds is just to stay on the ground. If airborne,
barring engine failure, landings are optional. If the winds contribute to a
bad approach make the easy choice of throwing in your hand and going around. A
given airplane accident is the final result of decisions made by pilots. When
an accident occurs that can be attributed to poor decision-making it is
difficult to find why an otherwise cautious and competent pilot would do such
a thing.
Natural Wind Indicators
Calm 1 mph vertical smoke, water like mirror
Light air 1-3 drifting smoke, ripples
Light breeze 4-7 wind felt, leaves rustle, vane moves wavelets, crests do not
break
Gentle breeze 8-12 leaves always move, light flags extend large wavelets,
crests break, foam,
scattered caps
Moderate breeze 13-18 branches move, dust and paper raised, small longer
waves, frequent caps
Fresh breeze 19-24 trees sway, crested wavelets on lakes, moderate waves,
whitecaps, spray
Strong breeze 25-31 large branches move, wires whistle, large waves, spray
white foam crests
Moderate gale 32-38 whole trees move, heaping waves seas, white waves breaks
in windblown streaks
Wind Shear
Low level wind shear alert system (LLWAS) is a predictive system when wind
changes of 20 knots are measured. Will give a 90-second warning of a
microburst ahead. By carrying extra speed into such conditions you can trade
speed for altitude. Do not bank and do not change configuration
Invisible atmospheric phenomenon can be present on all sides of the
thunderstorm, in the downdraft under the cell, and in a gust front which can
precede a thunderstorm by 15 miles or more. Wind shear is a local variation,
at a given time, of wind velocity with distance. It is measured by dividing
two-velocity variation by the distance between them. A wind speed difference
of 50 knots over one mile would be a shear of 50 knots per mile. Wind shear is
caused by thermal eddies near the ground or by strong winds crossing rough
terrain.
A rapid agitation and whirl of air which changes or varies wind velocity by 15
knots, or a change of vertical velocity of 500 fpm or a change in direction.
Wind shear includes lateral shear, rotor winds, dust devils, macro bursts and
micro bursts. Vertical velocities of over 4000 fpm and wind speed changes over
90 knots have been recorded. Between 1% and 2% of all thunderstorms create
severe wind shear.
Wind shear can be a problem for all aircraft and becomes a problem for light
aircraft especially when encountered when operating at full power with no
reserve performance available as for climb or takeoff. Unlike jets, the
propeller aircraft gets a rapid response from power applications so where
reserve performance is available the effects of wind shear can be corrected.
You can expect wind velocity to decrease as you get closer to the ground. The
wind direction will shift clockwise at the same time.
Majority of wind shear accidents occur in Colorado and California. A
thunderstorm need not be close by. Even distance storms or virga can cause
potential danger. Moisture is not a necessary factor. The best technique is
avoidance. Be aware that wind shear is likely in the vicinity of virga,
convective activity in formation of thunderstorms and frontal passage. About
ten "wind shear accidents" occur every year with 9 of these light
aircraft. The area of greatest danger for wind sheer is when landing or taking
off.
The winds will vary in both direction and speed with altitude. The landing
pilot must be prepared to have higher velocities and different directions even
from pattern altitude to touchdown. ATIS winds are taken about twelve feet
above the surface by a multi-cup wind turbine called an anemometer. This means
that all winds above and below this height will be of a different velocity and
direction. The closer to the ground the more to the right will be the wind
direction and of less velocity due to earth friction. Thus running out of
rudder authority at 500 feet above the airport means that some of that
authority will be regained at ground level.
With the advent of the Low Level wind shear Alert System (LLWAS) and Terminal
Doppler Weather Radar (TDWR) you can expect at larger busy airports to receive
wind shear alert notices on the ATIS. Along with the previous aircraft's PIREP
you have been properly advised.
You know it is there, but not where or how long or strong. Wind shear
conditions involve a low altimeter setting, rain, cool weather, and gusty 20
to 40-knot winds and variable directions. Any pilot would be ready for an
instant abort. Any rapid change in decent, speed is sufficient reason to
initiate the go around. Light aircraft should be in a clean configuration to
begin with and you should not fixate on any single instrument until the VSI
has a clear constant indication of a climb. While in the tailwind wind shear,
power will not increase speed nor stop descent. Should you first experience
the increased performance headwind side of the wind shear be aware that the
tailwind effect is yet to come. Get all the altitude you can because you will
quickly use it up.
Definition
Wind shear is change of wind speed or direction in a short time. When shear
exceeds ability of plane to
accelerate or decelerate its affects performance.
LLWAS
Low level wind shear alert system has some defects.
Inversions can affect the operation of the anemometers.
Radios may be so busy that pilots don't understand warnings
Instruments fail to give warning
Placement of anemometers allow errors to occur
Not enough anemometers on approach corridor
Mountain Waves
To have a mountain wave, you need a mountain obstruction to the airflow of
25 knots or more at an angle within 30 degrees perpendicular to the
obstruction. The wind velocity should increase with height and exist in a
stable air mass. The smooth updraft on the windward side gives severe
turbulence on the lee side. Turbulence can occur below lenticular clouds.
Always cross ridges at 2000' AGL and remember at 10000' you have lost 30% of
your engine power. To get out, terrain permitting turn downwind. In wave
conditions, a mile one way or the other can make a big difference. Actually
there are two different mountain waves, one that is smoothly flowing and
another that is breaking much as would an ocean wave be smooth before
breaking.
Three types of clouds come with the mountain wave which comes with strong
winds over jagged terrain. The basic cause is large differences in ressure in
a stable air mass across a mountain range. The mountains force the air by
orographic lifting to higher altitudes. The stable air will go lower once past
the mountain and may be forced into a series of cycles much like a wave. The
wave can extend for hundreds of miles with the top of each cycle indicated by
a lenticular cloud.
During January and February pay particular attention to weather reports of
rapidly falling pressure, temperature changes across mountains, winds over
thirty knots and strong surface winds. Oddly, a difference of a couple of
miles can make significant difference in the mountain wave effect. The problem
is, which couple of miles.
Strong winds perpendicular to mountain ridges generate altocumulus standing
lenticular clouds (ACSL) which are lens shaped and stationary on the lee side
of the ridge. Below the ridge on the lee side can be rotor clouds but the roll
may or may not be visible. A rotor is capable of crashing an airliner. An
unusual cloud called the Kelvin-Helmholtz can be a part of the mountain wave
sequence.. Kelvin-Helmholtz clouds look like multiple breaking waves. Flight
in the vicinity of Kelvin-Helmholtz clouds will cause multiple excursions in
altitude and airspeed. Advise ATC when this is happening and request a block
altitude that will allow these deviations.
Jetstream
The jet stream is a belt of high altitude winds just at the tropopause
level. The easterly wind speeds increase in winter and shifts from the poles
toward the mid-latitudes. Wind shear and turbulence is common on the northern
side of the stream. The speed is caused by temperature differences. The
presence of a jet stream is best detected by temperature. Wind must be over 50
knots and can be up to 200 knots.
The jet stream was actually discovered and became a factor in flying in WWII.
B-29s on high altitude bombing missions over Japan found that the bombsights
were often unable to cope with both the slow and fast ground speeds being
encountered by bombers flying in the jet stream. The great inaccuracies that
were occurring prompted the low level fire bombing that resulted in the
collapse of Japan.
California Surface Winds
42% of accidents, mostly while landing, are caused by wind factors. Most
non-winter California winds are near calm until the sun factor kicks in about
10 a.m. The winds continue until near sunset as which time as the sun factor
decreases so do the winds. These diurnal (daily) conditions are most constant
in the coastal areas.
California valley winds are like other diurnal winds. They are controlled by
the cycles of heating and cooling via the sun. Winds go up the valley during
heating and down the valley during cooling. Knowing this you can make an early
decision as to probable runways. In most accidents, poor judgment, not strong
winds, seems to be the biggest problem. A majority of wind shear accidents
occur in Colorado and California. Thunder storm need not be close by. Even
distant storms or virga can cause potential danger.
Headwinds
For all the years of my flying my wife has contended that I always fly
into headwinds. Once again a greater wisdom proves her right. A headwind is
determined by the difference between your true airspeed and your ground speed
regardless of direction. The airplane, once airborne, does not 'know' there is
a wind.
There will always be more headwinds than tailwinds because a portion of the
near direct crosswinds will require the aircraft to crab into those winds to
track the desired course. Thus, the fact that there is a crosswind the
reduction in ground speed to obtain the desired course results from a headwind
component. The faster you fly into this crosswind the better but there will
always be that residual headwind component.
Relative wind
---Any wind created by motion will act opposite to the direction of motion.
---The relative wind is not always where the nose points as in slip or
skid
---The stall is caused by angle of attack not lack of relative wind
The Weather She Is A'changing
Weather forecasting is making huge advances and disseminating the
information to pilots is not keeping up. Pilots need to know where the
moisture and instability is. The weathermen locate the moisture and find where
movement toward instability makes weather of interest to pilots. The critical
element is the timing involved.
Weather cannot be forecast in spaces less than fifty miles across and
airplanes take time to cover that distance. Before, during, and after weather
can be quite different while the pilot passes through this much space. The
timing of the forecast and the pilots passage coincide only incidentally.
The best sources of moisture and instability come from the some 700 balloons
that are sent aloft every day from widely scattered places in the U.S. It is
the paucity of soundings that places pilots at risk. The voids can only be
filled by PIREPS, ASOS> AWOS and satellites. Now mathematics and
statistical theory are available to help the weathermen more accurately
predict the meeting times of moisture and instability. This system is called
the Rapid Update Cycle model and allows three-hour updates through the use of
sounding simulations.
The charts and graphs from these simulations will soon become an important
part of a pilots preflight planning. When making a trip you can go to:
http://weathere.admin.niu.edu/cgi-bin/getmodel
use the directions and click on Skew-T diagrams and go to your local or
enroute AWOS or
ASOS sites and get forecast soundings for your time enroute. By comparing the
dewpoint of the clouds, winds and temperatures you can determine their
predictive accuracy with what occurs as you fly.
Weather Advice (Roger
Halstead)
When it comes to inadvertent VFR into VMC Too many pilots think it's pretty
much "If I'm careful it won't happen, no it can't happen to me!"
Unless a pilot makes it a practice to stay on the ground unless it's very
low humidity, calm, and clear there is a very high chance that pilot will some
day have some hair-raising stories to tell.
It happens along the coasts, it happens in the Midwest, it happens in the
great lakes and it happens in the mountains. And there is a *lot* more to
staying out of the clouds than just getting a good briefing and watching the
clouds ahead with the idea that you can always turn around.
I've had weather close in from ahead, from behind, from above, and from below.
The weather can be sneaky, or it can be quicker than any thing most of us
around here fly. There are a number of things to remember about the weather if
you wish to stay out of trouble. The instrument rating is a great place to
start, but it comes with no guarantees and is no substitute for good judgment,
nor is it a cure for bad judgment.
First, remember that the weather is always changing whether for better or
worse is often up for debate.
Second, remember that although the science of weather prediction has come a
long ways, it has a long ways to go.
Third, Remember that the most current conditions come from others flying
around out there too. OH! 3.B: Automated and computerized weather stations
will be quite happy to lie to you.
Fourth, the weather as based on those Pilot Reports (PIREPS) is a whole lot
more accurate than the briefing you may have had an hour or two...or more
back. So it does pay to learn a few things about how the weather behaves where
you are flying.
There are just two kinds of weather patterns. Normal and not normal!
We are just heading into a season where, particularly East of the Mississippi,
a front can move through, stop, back up and take a whack at the stuff still
standing that it missed the first two times through. Nor is this unique to the
country East of the Mississippi. Just because a front moved through an hour or
two ago, does not mean
that it will keep going. Particularly in Spring and again in Fall, but it's
not unheard of for them to put it in reverse most any time of the year. Now,
for those who thing they will always be able to turn around I can site one
specific case.
Fifth: Remember storms can form in place! Sometimes a small place and
sometimes they cover thousands of square miles. A couple of years back, I was
checking the weather on a beautiful clear, warm summer day. Not a cloud in the
sky and nothing on RADAR. It was humid, but there was a wide dewpoint/temperature
spread so I grabbed my DUATS briefing and headed for the car.
I was getting ready to start the car, but something seemed strange. It looked
like close to 30% cloud cover, yet less than 5 minutes prior it was clear. I
decided to go check the RADAR again. There were now clouds over a
wide area and what looked like a tiny thunderstorm clear over by Grand
Rapids...(90 miles SW). I decided to wait for one more update on the RADAR.
Low and behold in less than 2 minutes that storm was over 30 miles across.
five minutes later I was operating a weather net on the local 2-meter repeater
and that storm covered an area about 150 miles SW through NE
and about 60-80 miles from north to south. It then sat there and beat the crap
out of us for a good hour or more with a whole bunch of level 4s and 5s.
Remember that entire line formed in about 5 minutes. That's a long way
to go with a 150, 172, or Cherokee. *Any one* near the center of that line in
a small plane would have been in
deep doggie do as it formed over an area too fast for some one to fly out. To
top it off when they form like that you really don't know if you are flying
out or in.
Sixth: *Always*, and I emphasize that always keep one eye over your shoulder.
Some years back my wife and I headed for home from Zypher Hills Florida. It
was a tad hazy, but the ceiling was over 2000. So we headed north and hit rain
by Dade City. That's a whole ten miles. So it was back the ZH for an hour and
then another try.
This time we headed over toward Tampa Bay Exec. Not too bad. It looked a
little stinky right in the Tampa bay area, but exec which is NE looked pretty
good . So...we started up the coast. After all it was only about 30 miles to
sunshine. Unfortunately we were down to counting gaiters before we made the
sunshine and although I'd been keeping an eye over my shoulder, it was a lot
thicker back there than I'd thought. I headed back for Tampa bay Exec just as
fast as I could go. We got out of there around 1:00 PM the next afternoon.
Seventh: Keep aware of your surroundings If you ever get caught up at twilight
and the temperature/dew point
spread is small you may get to experience one of those adrenaline rushes first
hand. The entire landscape can be hidden in clouds faster than you can say
"Look!". The fog formation can follow the terminator if conditions
are just right. That is as fast as you can point to the eastern horizon and
swing your arm to point at the western Horizon. It's like waving a wand to
watch the fog form. Remember that for fog to form it has to give off some
heat. *Sometimes* that heat is just enough to cause the fog to clear for five
or ten minutes. Just don't bet your life on it.
Eighth: Be flexible! Don't be afraid to wait to take off, or to set down and
wait awhile if you are already up there. It's a whole lot cheaper to stay over
night, or have someone come and get you than it is for the insurance company
to take care of the survivors.
Then there is the wind! It shows up when un-forecast and sometimes isn't there
when you expected to get another hundred miles out of that tank of gas.
And...sometimes it's there as a head wind instead, when you really, really did
need that extra hundred miles.
You may find convective activity, or even fog when FSS is still reporting
clear. Particularly in the great plains, or western areas it's a long, long
ways between RADAR and reporting stations. There are many areas (including
valleys out east) where they can not see even as low as 5000 AGL. It usually
does blow in the right direction, sooner-or-later, but just how close to the
forecast time is still a crapshoot. Although....A front only has to move a
tad, north, or south, or it can be early or late and have the wind 180 degrees
to what was expected.
Some times the only way to keep from getting the snot beat out of you and the
passengers is to climb higher, only to find that you've been watching that
same town for the last hour. And....isn't that the second train
you've seen? And then again sometimes you climb higher only to find that today
is the day the jet stream decided to come down and give us mere mortals who
fly airplanes with propellers a look at what see normally rides high above us.
Now, I'll guarantee that none of your passengers will get bored in that case.
Ninth: Always have a way out!
Finally, There is no real secret about staying out of the weather. You can't
with 100% certainty, but you can keep those odds acceptably low.
Get a good briefing, listen for PIREPs, keep looking outside, look over your
shoulder once in a while and talk with FSS. Notice if the weather is getting
better, or worse. Is it better, or worse than forecast? Don't be too proud to
call time and spend a night or two in a four corners truck stop. If things are
going really good, don't forget to pay attention as that is natures way of
lulling you into a false sense of security just before striking.
Above all! If the trip is one of appreciable distance where you are likely to
be put under pressure to end up some where on a schedule...Go commercial, or
take a train.
Yes, I know that is why most say they got the license, but with others along,
you may be the only one having any fun...And you would like to have company
next time? But that's another story.
Opinion
There's so much detailed but vital information to learn about aviation
weather, from whether hail's ahead of the storm or behind it, to why it's to
important to reset the altimeter on a trip, that a beginner concentrating on
the mechanics of clear-air flying can seriously underrate how much data has to
be pasted into the brain. Not just memorized, but made second nature. You
can't put everything on checklists. A lot of it has to be properly filed
in the brain.
StellaStar
Weather Aloft
--Chart temperatures in Celsius and winds with arrows in 5/10knot
increments
--Text figures local with first two digits wind direction with added zero and
two digit wind speed.
--Performance charts use temperature
--Area forecast predicts VFR clouds and weather
--AIRMET Sierra gives IFR conditions and mountain obscuration
--AIRMET Tango gives turbulence
--AIRMET Zulu gives icing conditions
--Constant pressure charts AC00-45E, www.faa.gov/avr/afs/afs400/
--Low pressure areas should be avoided
--Isobars close together indicate strong winds
--Upper winds flow parallel to lines
--A three-digit number by lines indicate meters of altitude by adding a zero
--Station models give data of temperature, dew point, wind, wind speed, meters
of altitude (above) and change
--700 millibar is for about 10,000 feet and 500 millibar for 18,000 feet.
--500 millibar lines east and west portray calm winds
--North/south lines mean winds will mix warm and cold temperatures, expect
storms.
--Forecasting of turbulence is right only half the time.
--A SIGMET requires a forecast of severe turbulence. (rare)
Weather Notes
--When winds aloft are not as forecast, neither will the weather.
--Stronger southerly winds mean worse weather
--The arrival of fog is more accurately forecast than its dissipation.
--Never fly into a known fog situation with the expectation that it will lift.
--The closer you get to bad weather the higher you can expect the cloud tops
to be.
--Airframe icing requires lifting and moisture. New buildups are more likely
to have ice than old clouds.
--Expect severe turbulence where occluded fronts exist.
--Between two areas having separate strong southwesterly winds, expect an
occlusion.
--A closed low aloft makes a complete circle is called a cut-off low are
difficult to forecast. May move west.
--500 millibar is 18,000' and determines significant weather since upper
levels support what happens below.
--When multiple lows exist, one will become dominant.
--A cold front that passes and has behind it northerly winds is slowing and
may stop.
--Stationary fronts breed new fronts.
--The strength of a cold front is directly related to lthe extend of the
temperature drop.
--A narrow frontal zone with heavy rain is bad news.
--Area with widely scattered thunderstorms can be flown through, carefully.
--Area with scattered presents more problems.
--Broken or clusters of thunderstorms are best watched from the ground.
--Severe turbulence should be expected from any thunderstorm
--When it looks bad it probably is bad; the meaner it looks the meaner it is.
--Thunderstorms are weakest in midmorning.
--Lower is better in area of thunderstorms.
-- The visual illusion when flying in precipitation is that you will be higher
than your actual path.
--Mentally fly every day when 'weather' exists to see what you might be doing.
Reading Weather Winds
FEET ICT
3000 9900 - Wind less than 5 knots and variable
4000 2507 - Wind 250 @ 7
6000 2521+11 - Wind 250 @ 21 Temp +11 degrees C
9000 2432+06
12000 2538-01
18000 2465-15
24000 2591-24
30000 750239 - Wind 250 @ 102 knots temp -39 degrees C
34000 750149
39000 760861
On the last three you subtract 50 from the first two digits and put a 1 in
front of the second two digits. Then the last two digits are the temp in
Celsius (below 0). So 750239 gives you:
75 - 50 = 25: 250 degrees
02 plus the one = 102 knots
39 is -39 degrees below zero.
-Richard, PP-ASEL wannabe
Whether to Fly in
Weather
--Preflight sources are your eyes, TV weather, newspapers, FSS weather,
DUATs, internet and PIREPS
--Best webs are www.nws.noaa.gov and wwww.dispatcher.org
--Best VFR charts are significant weather prognostic, constant pressure
analysis and the radar summary
--Best IFR charts are the VFR charts plus icing forecassts and 12-hour low
level significant progs
--Route weather can be obtained by phoning an FSS and using the TIBS
recordings
--Present weather is best from PIREPS through the 122.0 flight Watch frequency
--Local airport weather is becoming more available through AWOS and ASOS with
radio and phones.
--In flight icing is number one cause of inflight G.A weather accidents
--Thunderstorms are the main cause of flight delays
--Weather forecast improvements are on their way.
--Greatest error is not 'if'. It is 'when" the weather will happen that
is now the greatest variable.
The Smog Layer
Most of my flying is within 3000' AGL because I like it there. I once flew from California and back from Oshkosh
with an average AGL altitude below 1000'. This means that I had no forecasts
of winds because local climate is dominant. It means that I see plenty of smog
when in densely populated areas. I will be warm in the summer and cold in the
winter and freezing rain most common. I know the cooler it is the more shallow
will be the weather condition. Weather conditions here will be mostly IFR
between the smog and the surface. I will find most of the water, hot winds and
cumulo-granite. Up and downdrafts and whirling winds will be likely. All of
this still unable to be forecast but well publicized as it occurs..
It is here that every flight begins and ceases. Local charts are more
likely to warn me of obstacles and experience has taught me to fly low in the
good times to set my limits when conditions are less than ideal. I know that I
do better flying in my home area by knowing the micro-climate of very valley
and community. Still I will find the unexpected but I will keep always one
last option available.
Doug
PIREP Wind
The Problem
For purposes of filing an in-flight PIREP, how do you calculate or estimate wind velocities and directions you are experiencing? I have been told this is easy if you have a GPS.
Solution #1
1) Start with your indicated airspeed, OAT, and altitude, and compute TAS (most ASI's have an IAS/TAS function built right in). Read your heading off the DG (or compass).
2) Get your GS (ground speed) and track from the GPS.
3) Plug these two vectors into an E6B (whiz wheel or electronic) to compute wind speed and direction.
Roy Smith
Solution #2
A lot of GPS units will calculate it, you have to put in some information, like your heading and your indicated airspeed. Also, if the winds are close to 90 degrees to your direction of travel, you need
VERY accurate heading information.
An easier way, and very accurate, is to turn into the wind until you have your slowest GS. Then take the difference between it and your TAS.
That's your wind.
Doug
Deteriorating Weather Lesson
Bob,
Thanks for the 'star wars' bit. I had a similar experience only today but not
nearly as touching. I am re-treading a pilot 20 years out of the cockpit who
purchase a two year old Grumman AA5-B with all the goodies. However today we
are going flying intentionally head on into a weather front. My pilot friend
learned to fly in Hawaii and is weak in dealing with weather problems.
Before we started I told him we were going to contact FSS and get a route
specific briefing. We were sitting near the hangar door and during the
preflight briefing and weather discussion were able to watch the weather
changes as the front approached some 40-50 miles away.
The weather was making fairly rapid changes in ceiling, wind velocity and
temperature. We departed directly toward the front, knowing that the leading
edge to our left would be hooking around behind us and having the potential to
make our return more difficult. 25-miles out we contacted Center for flight
following. Shortly thereafter Center told us that the weather at our destination
was rapidly deteriorating. and asked of our intentions.
My student gave a sequence of altitude, visibility and general weather condition
reports to Center as we proceeded toward the Front. We had to climb because of
terrain and our visibility soon dropped to less than ten miles with very light
rain. As we approached 4000' the digital temperature gauge dropped over one
degree a minute soon to reach zero Celsius. We put on pitot heat and watched the
rain quickly turn to heavy. We initiated our reversal of flight direction
immediately while reporting the sudden change in conditions. Soon things were
much improved and my student wanted to take another look to the south, as though
we might be able to fly around the front. This direction would soon require a
change in frequency from Center to Norcal. Even though we had previously given
our aircraft information the controller asked again what we were flying. A
Grumman Tiger", said my student adding that his instructor was giving him
an introductory flight into rapidly deteriorating weather conditions.
At once the controller began to initiate casual conversation regarding his Tiger and the places he had taken his Tiger to various aircraft-type gatherings in the past few months. All of which my student had attended. He was very interested and complementary about the purpose of our flight. Granted the weather was such that he was not at all busy but it made the flight all the more enjoyable that my student while under stress from the MVFR weather found a kindred spirit on the other end of the radio.
We only flew an hour but my student came away with much more confidence that he could now study the weather books knowing what was important. He could get a weather briefing and have ready-made questions that need to be asked.
Weather Web Sites
Here are some links to get you started.
http://www.wunderground.com/Aviation/
These websites provide METAR decoding information.
http://homepage.ntlworld.com/booty.weather/metinfo/codes/METAR_decode.htm
http://www.met.tamu.edu/class/METAR/quick-metar.html
This website provides decoding information for the GFA (graphic area
forecast)
http://www.msc-smc.ec.gc.ca/msb/manuals/manair/html/chapter4/chap_4_e.html
This website provides information regarding the FD (winds and temperatures
aloft)
http://www.msc-smc.ec.gc.ca/msb/manuals/manair/html/chap_3_e.html
This website has information on interpreting weather-satellite images
http://funnel.sfsu.edu/satlab/
These websites provide more complete information on aviation weather
observations.
http://www.met.tamu.edu/class/METAR/metar.html#INDEX
http://www.msc-smc.ec.gc.ca/msb/manuals/manair/html/index_e.cfm
Jet stream
http://weatheroffice.ec.gc.ca/jet_stream/index_e.html
http://www.weatherimages.org/data/imag213.html
http://squall.sfsu.edu/gif/jetstream_pac_init_00.gif
Satellite vis+ir
Satellite GEOS west large vis+ir
http://weatheroffice.ec.gc.ca/data/satellite/goes_wcan_vvi_100.jpg
Satellite GEOS west medium animated vis+ir
http://weatheroffice.ec.gc.ca/satellite/index_e.html
NavCan local area aviation weather manuals (these are excellent and while
they provide good general information for everyone they should be required
reading for anyone planning to fly in Canada. The first chapters are
generic and the rest is location specific)
http://www.navcanada.ca/NavCanada.asp?Language=en&Content=ContentDefinitionFiles\Publications\LAK\default.xml
BC local area aviation weather manual (NavCan)
http://www.navcanada.ca/ContentDefinitionFiles/publications/lak/bc/BC31E-V.PDF
Mountain Weather Education (for climbers)
http://pafc.arh.noaa.gov/classroom.php
http://pafc.arh.noaa.gov/classroom_practical_mountain.php
We both are Amatuer Astronomers, and that is actually how
I met him, and
there is this site/tool we use called the "Clear Sky Clock", and even
though
it is done by the Canadian Government, there are Clear Sky Clocks for many
places in the U.S, he has one for the observatory (converted garden shed) in
his back yard :-). So, after looking at the weather forecast and going,
"hmmm...", he was like "Hey... maybe saturday looks ok... Clear
Sky clock
says it will be clear Friday and since these guys don't forecast more than a
few hours out, maybe we will get lucky... :-)"
If you are curious, his Clear Sky Clock is for the "Highlands
Astro-shack"
in Renton, Washington, and you can find all the clear sky clocks at at
http://cleardarksky.com/csk/
He also has a reciever in his basement that can pick up the signals from the
weather satelites as they go over and processes the signals and posts the
pictures on a web page... sometimes they are better than the ones from NOAA,
and sometimes his computer is on the fritz or they are noisy.
Wade Hasbrouck
PP-ASEL
http://spaces.msn.com/wadehas
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