IFR Ground School - Lesson 1

we are very pleased to have with us today Natasha Steinbach all the way from San Diego California she'll be teaching lesson number one weather concepts now Natasha is not only a pilot she's a meteorologist she's the weather anchor for Channel 8 k FM B TV a CBS affiliate in San Diego she's earned her BA and telecommunications from the University of Pepperdine or Pepperdine University and she's a member of the American Meteorological Society now besides her strong interest in meteorology Natasha is a big fan and has been involved in aviation her entire life her father of course Bengt Steinbach a longtime commercial pilot and her uncle Roger Staubach owner of Steinbach Communications has been teaching aspiring student pilots for more than 30 years again welcome Natasha we appreciate you being here listen San Diego it's got to be a fun city a great place to fly it is a fun city but yeah a great place for VFR pilots but you know sometimes we get that marine layer so it's really important to have that instrument rating outstanding now you've got a long list of things in Lesson number one what's you going to cover yeah sure enough Matt well basically I'm really excited about presenting the weather lessons in this ground school course and this lesson we'll talk about what influences weather what causes it how it behaves and how it affects you as a pilot it's important for you to recognize signs of weather changes cloud formations and conditions favorable to aircraft icing once you've learned the basic weather principles you'll learn how to avoid the Troublesome weather for safe and smooth flying in this lesson weather fundamentals we'll talk about what influences weather what causes it how it behaves and how it affects you as a pilot now it's important for you to recognize signs of weather changes cloud formations and conditions favorable to aircraft icing once you've learned the basic weather principles you'll learn how to avoid the Troublesome weather spots for safe and smooth flying now throughout this weather course for aviators we'll cover these topics what is weather circulation and wind temperature and moisture atmospheric stability clouds air masses front thunderstorms turbulence airframe icing and the jet stream okay for a first topic what is weather let's join Natasha in the classroom hi I'm Natasha Steinbach your instructor for this lesson covering weather fundamentals because weather is one of the most important factors in flight safety this lesson covers a great deal more detail than what you need to know to pass the FAA instrument knowledge test will cover enough detail for you to decide with confidence whether to operate VFR IFR or make the go no-go decision with that in mind let's begin weather is the state of the atmosphere at any given time day or night and you know whether it's a complex subject the atmosphere is constantly in motion as it tries to reach a point in equilibrium weather influences our daily lives and routines and has a profound effect on all our aviation activities let's talk a moment about the role weather plays in our aviation activities and how it affects our personal minimums the FAA uses the acronym paved to help pilots develop a personal minimums guide pave stands for pilot aircraft environment and external pressures so when considering the minimums to evaluate a pilot's readiness to operate SP IC consider physical condition competency and training next consider the aircraft is it air worthy properly equipped and suitable for the intended mission will it safely handle forecast weather with adequate performance margins when evaluating the environment to consider all relevant weather conditions is the weather forecast improving or deteriorating what about daylight and/or night operations what are the probabilities of icing turbulence strong winds and low visibility finally consider any external pressures affecting do you need to arrive at a certain time is time available to alter your flight should you encounter weather or aircraft problems are there personal or professional pressures affecting your performance and judgement careful considerations of these pave factors will ensure a safe and enjoyable flight okay let's get into the details of weather fundamentals with us in the studio today is Dave Celeste ski for the lesson on weather Dave welcome thanks much Matt background on Dave if you've ever taken an AAS a virtual test prep ground school course you'll be familiar with Dave's charm and expertise now he has a degree in communications and broadcast meteorology from Mississippi State Dave also brings a unique perspective to the table not only is he an accomplished pilot commercial pilot by the way you're the extensive owner operator experienced in the real world of aviation it's also a very seasoned pun intended meteorologist same old AC affiliate in Portland Oregon there's been a weather anchor there for News Channel 8 for more than 21 years bringing Oregonians the weather forecast they either expect rain most of the time or really appreciate warm and sunny days well be that as it may while the rest of the country believes it always rains in Oregon real Oregonians know that the Pacific Northwest weather is actually quite unpredictable true and is challenging for both meteorologists and pilots alike Dave loves aviation and how the weather impacts each flight and it will come out in his answers to our questions Dave again welcome thanks Matt well Dave is weather really affected by geographical location yes and you can look at what's going on across the country here in the Pacific Northwest we have what is the biggest weather making machine in the planet and that's the Pacific Ocean steering moisture into the northwest we also have a couple of mountain ranges the Coast Range in the Cascades and that helps determine what kind of precipitation with a liquid or frozen we're going to be looking at here in the Northwest in the Midwest you get east of the Rockies you have what's called a continental airmass it's dry very warm and in a matter of hours can become very humid and kick off these big 50 60,000 foot high thunderstorms that were also familiar with it curr in the summer and early fall months in the Midwest and then on the East Coast they are under the influence of the Atlantic Ocean and also the Canadian Maritime Provinces and that presents a whole different set of problems and issues for pilots on the East Coast we'll begin with the atmosphere surprisingly oxygen is not the single biggest component of the atmosphere in fact nitrogen makes up about 78% of the atmosphere followed by oxygen at 21% and then other gases like helium and argon at about 1% of the atmosphere a cubic foot of the atmosphere contains anywhere from 0 to about 4 percent water vapor you'll hear mention of the standard atmosphere throughout your aviation weather studies continual fluctuations of temperature and pressure in our atmosphere create problems for engineers and meteorologists who require a fixed standard of reference the atmosphere fluctuates continuously as it tries to reach equilibrium in pressure temperature and humidity the standard atmosphere is an average condition of all these fluctuations it is the standard for calibrating the pressure altimeter and developing aircraft performance data here's a handy weather fact the standard sea-level pressure is 29.92 inches of mercury or about 1,013 millibars the standard sea level temperature is 59 degrees Fahrenheit or 15 degrees Celsius the standard rate of change and pressure is about one inch of mercury per 1000 foot gain in altitude in the troposphere pressure decreases as you increase in altitude or simply stated the further you go up the more the barometer drops to calculate is a use the average lapse rate of two degrees celsius per thousand feet meteorologists look at the atmosphere like you would a layer cake there are several different layers to the atmosphere from the bottom up the atmosphere consists of the troposphere and the stratosphere the mesosphere and the very top layer is the thermosphere virtually all aviation weather takes place in the bottom two layers the troposphere ranges anywhere from the Earth's surface to 20,000 feet near the North and South Poles whereas at the equator it ranges from the surface to 65,000 feet the tropopause separates the troposphere from the stratosphere the stratosphere is typify by relatively small changes in temperature with height except for some warming right near the very top in addition to wind this unequal heating also causes variation in pressure and altimeter settings between weather reporting points so let's talk about what causes weather well the major source of all weather is the Sun all weather is caused by a change in temperature the earth is constantly being warmed and cooled at an uneven rate the earth is heated by the Sun which is about 93 million miles away again that heating is not being done at an even rate near the poles you have a greater surface area that's being heated so it's not going to heat as rapidly as the smaller surface area near the equator but at the equator all this energy from the Sun is concentrated on a lower surface area on the planet thus heating the equatorial regions more than the higher and lower latitudes the seasons also greatly affect the planets heating and cooling balance the earth is tilted about 23 degrees on its axis in the summer the northern hemisphere receives most of the heat energy but as the Earth orbits the Sun the southern hemisphere warms up during the Northern Hemisphere winter because the northern hemisphere presents a greater surface area for heating so it's not being heated up as much as at the equator where it's getting more direct energy from the Sun this cycle repeats each year while the earth orbit is not perfectly circular the cooling and heating is not influenced much by the slight fluctuation of the distance between the Sun and the earth here is a close-up of the summer in the Northern Hemisphere and again of the winter in the northern hemisphere this unequal heating of the Earth's atmosphere is what creates wind the warmer low-pressure air has a tendency to rise and the colder high-pressure air has a tendency to settle or descend there are a number of factors that affect how an area heats up the angle of the sun's rays has the greatest effect on temperature types of cloud cover low stratified clouds influence heating more than high cirrus clouds do land changes heating characteristics more than water deserts and barren areas change temperature much more rapidly than say a forest or a farmer's field and we already discussed the effect of the seasons summer produces greater temperature variation than winter does welcome back to the studio now after each topic you'll be given some review questions and an opportunity to answer them I'll provide you with the correct answer if you need additional time before I give you the answer go ahead and pause the lesson all right here's your first question the primary cause of all changes in the Earth's weather is which of these three a B or C your answer is a every physical process of weather is accompanied by or is the result of a heat exchange differences in solar energy create temperature variations these temperature variations create forces that drive the atmosphere in its endless motion okay simple enough all right let's move along another topic circulation and wind back to your classroom and your instructor next up is circulation and wind global circulation is what's needed to make the weather go around check this out hot air rises but it's a little more complicated than just that hot air rising is referred to as convection in a simplified model if the earth didn't rotate convection would cause cold air at the poles to descend down towards the equator then rise by convection and cool and descend toward the poles well the earth as we all know does rotate on its axis and that sets up what is called a 3-cell circulation pattern the three cells are the polar the Farrell and the Hadley cell you have colder air that moves down from the poles toward warmer regions Rises or convex through the polar the Farrell and the Hadley cell this causes a change in pressure and also creates winds in the atmosphere to measure these pressure changes we use a pressure pattern map these lines are called isobars they show constant lines of pressure in the atmosphere think of these isobars as stairs moving up or down in the atmosphere to get down we follow a trough line down towards the atmosphere to our lowest point same thing holds true for higher pressure or staircase is shown by this ridge line going up to reach our highest point in the atmosphere the closer the isobars are together the stronger the wind speeds because the earth rotates this large simple air cell circulation pattern is great distorted by a phenomenon known as the Coriolis force this effect on air circulation is caused by the Earth's rotation imagine the rotation of a disc I want to draw a line straight out right here but suppose I suddenly stopped the CD instead of going straight out the line actually curves down towards the right here let's check it out one more time the Coriolis effect is most noticeable near the poles and least noticeable near the equator and here is another illustration of the Coriolis force note the flight path of the three airplanes there is a difference difference in curvature between destination a destination B and destination C now here's how it affects the general circulation of the atmosphere that Coriolis force turns the air currents to the right this is the low level circulation pattern note the polar easterlies the prevailing westerlies and trade winds here are the general global winds note the polar bear'll and Hadley circulation also note the semi-permanent high and low-pressure areas as well as the prevailing winds shown here now here is a typical summertime weather map high pressure on the East Coast higher pressure on the west coast from about thirty to sixty degrees north latitude so on a typical winter pressure pattern map you'll notice that colder air pushes this ridge of high pressure down a little bit towards the south but they're still there 365 days a year seven days a week now let's talk about how this global circulation pattern results in winds and local breezes we'll talk first about wind in the upper atmosphere now check the winds aloft depiction we talked about high pressure and low pressure here on an ISO bars which show steps to and from low and high pressure at least isobars can also be thought of as pressure gradient force pressure gradient force acts to move air parcels from high pressure to low pressure the pressure gradient force acts as right angles to the isobars isobars that are close together indicate a strong pressure gradient in the upper atmosphere pressure gradient force and the Coriolis effect are equal which means wind direction does not flow from high to low but rather along or parallel to the isobars now at the surface it's a little different story we have a new force called friction no friction results as winds flow near the surface of the atmosphere over mountains and through valleys this changes the speed and wind direction and also changes the strength of the Coriolis force right here and that allows a more direct path of our wind or resulting wind to go from high to low at about a 45 degree angle along those isobars now notice on this map how the wind from the high pressure to the low pressure does not flow directly into that low rather takes a different route counterclockwise moving into the center of low-pressure air flows counterclockwise around low-pressure areas and clockwise around high pressure areas now in the upper atmosphere the wind does not flow directly into the area of low pressure Coriolis and pressure gradient force caused the wind to move along the isobars and take a path along this direction parallel to those isobars at the surface the flow of air between high and low pressure in combination with the Coriolis effect pressure gradient force and friction of the earth creates a flow pattern like the one you see here now prevailing winds can be described this way winds move from high to low pressure modified by Coriolis effect and terrain friction cold air is replacing warm air in circulation patterns global wind patterns cause the Earth's overall weather but localized wind patterns are much more important to pilots local weather patterns are caused by the very same forces that cause global wind patterns now sea breeze circulation is a good example of how this works our classic closed cell circulation pattern causes sea breeze and wind breeze circulation pattern typically in late morning and afternoon hours higher pressure develops offshore and lower pressure on Shore this is because the ocean does not heat or cool as rapidly as the landmass does as a result you'll get cooler air denser air creating a higher pressure over the ocean since the landmass heats up more rapidly than the ocean it contains less dense air and lower pressure on shore this causes this classic circulation pattern of high-pressure flow into lower pressure resulting in warm rising circulation this is the closed circulation cell pattern now the land breeze at night has just the opposite effect since the landmass cools much more rapidly than the ocean denser cooler high-pressure air develops over the landmass this air flows offshore over the ocean where it's warm rises and returns again it's the closed cell circulation pattern and in some cases winds from land breezes and sea breezes can reach speeds of about 10 to 25 miles per hour their effects may be felt as high as 2,000 feet over the surface now here's what's known as a valley breeze air currents are moving uphill typically in the afternoon it's warmer air up here because it's less vegetated and the air is a little less dense as you gain altitude denser air down here in the more forested area worms rapidly you have this denser air up here flowing to less dense air up on the mountain slope creating this upslope wind effect here wind speeds may reach about 20 to 25 miles per hour in the mid to late afternoon now mountain breeze at night is just the opposite the higher elevations cool more rapidly then in the valley floor as a result downslope winds or mountain breezes develop cold downslope winds are also known as katabatic winds higher pressure over mountains or glaciers have denser much colder air this air flows off the glaciers off these icy snow fields and down into the valley floor notice they heat up a little note the temperature is zero in the valley and near the summit it's 25 degrees below zero now warm downslope winds are a potentially dangerous situation for pilots typically very strong winds are flowing over mountain peaks they can be denoted by standing lenticular or lens type clouds as these very strong winds roll over the mountain peaks they drop down on the backside of the mountains as that colder air which is much denser up here begins to drop down it actually compresses as it moves down into the atmosphere it heats up because the air is compressed as it drops down to the valley floor some of these wind speeds can reach upwards of 100 miles an hour on the backside of a mountain range and are potentially very dangerous winds in which to fly okay well how do winds what role do winds play and I have our operations simply gonna have to know what kind of course correction you're gonna have as you're flying along also fuel consumption more of a head when you're gonna have the longer it's gonna take you to get from point A to point B which means you can be burning more fuel so we'll have enough fuel to get to your original destination and if you can't because you have low IFR conditions do you have enough fuel to get to your alternate here's a nugget of weather wisdom a land breeze circulation flows out to the sea and occurs at night valley breezes occurred during the day and in the mountains and our upslope wins a katabatic wind is any descending wind caused by inclines or mountains these winds consist of either cold or warm air and in some cases they can reach speeds in excess of 100 knots a sea breeze circulation is an onshore flow and occurs mainly during the day back in the studio again for another FAA test question what relationship exists between the winds at 2,000 feet above the surface and the surface winds a B or C your answer in this case is be close to the earth wind direction is modified by the contours over which it passes and when speed is reduced by friction with the surface also the winds at the surface are at an angle across the isobars due to the stronger pressure gradient at levels 2,000 feet above the surface the speed is greater and the direction is usually parallel to the isobars okay very good moving on to another topic this time temperature and moisture back into the classroom for that topic next up we'll cover temperature and moisture first we'll study humidity and dew points and why these are important to pilots water evaporates into the air water vapor is in most cases invisible like oxygen and other gases that make up our atmosphere the amount of water vapor in the air is expressed as relative humidity and as the dew point well relative humidity relates to the actual water vapor that is or could be present in the atmosphere now here is a weather fact relative humidity by definition is relative relative humidity relates to the actual water vapor to that which could be present this graphic shows how relative humidity works here we have three containers each filled with air at a lower temperature you can only pack in so much water or water vapor in this case shown by the blue specks as the temperature increases you can see the container same size we can pack in a little bit more water vapor and as the temperature becomes very warm we can substantially increase the amount of water vapor that can fit into a parcel of air another weather fact the dew point is that temperature to which air has to be cooled to become saturated by water vapor already present in the air now check this out here are three examples with the dew point at 37 degrees Fahrenheit with the temperature of 55 degrees Fahrenheit and a dewpoint of 37 degrees you can see a nice wide dewpoint spread with a relative humidity of about 50% now for this parcel of air we can still pack in some more water vapor at this temperature this is actual water vapor present this is how much more we can hold we can still pack in another 50% of water vapor at this temperature now as we cool our air parcel down to 44 degrees Fahrenheit same sized container but now we're at 75 percent relative humidity now as we cool that airmass even more we take the air mass down to the dew point temperature they're both 37 degrees it's saturated some type of cloud precipitation or condensation is going to occur our parcel of atmosphere is saturated with water vapor the conclusion is that warm air has the capacity to hold more water vapor than cooler air now here's a little weather wisdom the temperature and dew point spread is very important in anticipating fog as the temperature and dew point spread decreases or comes closer together that relative humidity is going to increase at 100% and fog will form now pilots should be aware when the dew point temperature spread is less than 5 degrees anticipate such an event as fog here are more weather facts water vapor is always present in the atmosphere and can be found in one of three states it can be a gas a liquid or a solid at 100 percent humidity fog will form as water changes from one state to another an exchange of heat or energy occurs energy is contained in latent heat a change of state is the process of latent heat exchange a change of state by vaporization condensation sublimation melting and freezing is called a change to the process of latent heat exchange as water changes from one state to another an exchange of heat occurs and energy is gained and released now here are the states of water here is water in a gaseous form it's in a cloud through condensation energy can be released to make a change by going from a gas into a liquid still releasing more energy through freezing it becomes a solid like a snowflake or it can sublimate directly releasing energy to change into a snowflake here is the reverse effect it can also gain energy through latent heat exchange by changing from a solid to a liquid by melting and then from a liquid through evaporation into a gas or it can directly sublimate back to a gas he is always gained or lost through a change of state now here's another important bit of weather wisdom liquid water droplets often persist and exist at temperatures much colder than zero degrees Celsius they're super cool and when they impact an object that impact induces freezing freezing rain can result and that can cause extreme aircraft icing supercooled water drops are often abundant in cumulus clouds ranging between zero and negative 15 degrees Celsius remember frost forms and much the same way as Dew the difference here is the dew point of the surrounding air and that is colder than freezing water vapor then sublimates or changes state directly as ice crystals or Frost rather than condensing as Dew let's review clouds and visible moisture our parcels of air which have reached 100% humidity they are saturated cooling a parcel of air increases its relative humidity a parcel of air has to be cooled to his dew point to become a cloud time once again for another test question this one what is meant by the term dew point again you have three choices and your answer is C dew point is the temperature to which air must be cooled to be saturated very good all right let's move along to another topic now this time out atmospheric stability join your instructor in the classroom for that topic ever wonder how clouds form a parcel of air has to be cooled and reach its saturation point and then clouds will form and how does that coulis and occur there are basically only three ways this happens lifting action causes air to cool if this air mass were lifted by terrain for example clouds would form if warm air is moved over a cooler surface like this clouds can form notice these clouds have nice flat bases stratus clouds clouds will also form due to radiation cooling which is the ground cooling at night this will often produce very flat low clouds typically Stratus or in a lot of cases fog you can estimate Heights of clouds knowing the dew point and temperature for a given location the dry adiabatic lapse rate is five point four degrees Fahrenheit per thousand feet the dew point lapse rate is one degree Fahrenheit per thousand feet the temperature and the dew point converge at about four point four degrees per thousand feet use this formula subtract the dew point from the temperature both in Fahrenheit and divide that by four point four times one thousand here's an example in this case the temperature is 76 degrees the dew point is 40 degrees 76 minus 40 equals 36 divide this by four point four and that equals eight point two multiply this by 1000 and you get roughly 8200 feet so the cloud base is about 8200 feet what makes an air stable or unstable and how does that affect your flying well check out this balloon now all you have to do is think of this balloon as simply an enclosed parcel of air as this balloon or parcel of air rises up in the atmosphere it's going to expand because there's less pressure or force being put on that balloon at higher altitudes due to decreased pressure anytime air rises it's going to expand and cool it's a simple principle of physics the average lapse rate the air parcel is going to cool is about two degrees Celsius for a thousand foot gain in altitude look at this example as air expands and rises it's going to cool and as air descends in the atmosphere it's going to warm up now these changes are adiabatic meaning no heat is removed or added from that parcel of air the adiabatic rate of change of temperature is virtually fixed an unsaturated or a dry air parcel here are more weather facts as air expands and rises it cools as air descends it compresses and warms these changes are adiabatic so that means no heat is removed or added the adiabatic rate of change of temperature is virtually fixed and unsaturated or a dry air parcel the adiabatic rate of change of temperature varies in saturated air latent heat is released through condensation which offsets the expansion cooling process the saturated adiabatic rate of cooling is lower than the dry adiabatic rate air full of water vapour is going to cool at a slower rate than a dry parcel of air will the adiabatic rate of change of temperature varies in saturated or wet air because latent heat is released through condensation which then partially offsets the expansion cooling process the saturated adiabatic rate of cooling is lower than the dry adiabatic rate in other words air full of water vapor is going to cool at a lower or slower rate than dry parcel of air will let's talk about adiabatic lapse rates here we have three balloons all at the bottom of the atmosphere three enclosed parcels of air now if we take a look at this first parcel of air instantaneously fly it all the way up to five thousand feet and you'll notice the temperature inside our parcel of air is 16 degrees Celsius but outside is 13 degrees it's warmer than the outside air it's an unstable or rapidly rising parcel of air now in this example we have a stable lapse rate we take our balloon from the surface up to 5000 feet just like that and notice our parcel of air is at 16 degrees Celsius but the outside air is warmer it's 18 degrees Celsius this is cooler and it's denser it's going to descend it's a stable laughs rate neutral stability looks like this we take our balloon from the surface up to 5000 feet in a matter of a couple seconds and we have the same temperature right here 16 and 16 is a neutrally buoyant parcel of air here are more weather wisdoms an air mass temperature which decreases rapidly with altitude favors instability an air mass temperature which changes little with altitude tends to be stable this saturated adiabatic rate of cooling is lower than the dry adiabatic rate an air mass temperature which increases an altitude tends to be very stable here are more weather facts the lapse rate is the rate of change in the temperature with a change in altitude lapse rate varies from dry air of about 3 degrees Celsius per thousand feet to moist adiabatic lapse rates of about one and a half degrees celsius per thousand feet this standard lapse rate is 2 degrees Celsius with a thousand-foot altitude gain an unstable air is an air mass that cools more rapidly than 2 degrees Celsius for each 1000 foot altitude game this graphic depicts the lapse rates this is a standard laughs rate and as you can see temperature cools with height great visibility and a few Fairweather cumulus clouds out there but you know although could be a far flying just the opposite is true when you have a temperature inversion a temperature inversion occurs when air temperature does not cool with height rather the atmosphere warms up with altitude at the top of the inversion it begins to cool this inversion layer greatly reduces visibility maybe because of some fog low-lying clouds or Stratus or even pollutants it's a great ride you just can't see where you're going now here's another example of stability in the early morning hours the air is typically very stable temperatures are cool at the surface and also aloft by midday as the atmosphere begins to heat up that warm air rises it creates an unstable condition and you get a bumpy ride now just the opposite occurs in the evening hours as you can see temperatures cool aloft and at the surface it's a nice smooth ride again welcome back time once again for another review question this time what feature is associated with a temperature inversion what feature a B or C your answer is a a temperature inversion occurs when the temperature increases with altitude a stable layer of air is characterized by warmer air lying above colder air with an inversion the layer is stable and convection is suppressed alright let's move right along to another topic and for you this time in the classroom clouds back to Natasha let's look up and talk about clouds clouds are divided into four families according to their height range there are low clouds middle clouds high clouds and clouds with vertical development check this out take a look at these clouds we have low clouds milk clouds high clouds and clouds with vertical development now here's a depiction of the various cloud types we have here cumulonimbus Cirrus altostratus stratocumulus zero cumulus altocumulus and stratus clouds I started out in aviation so I've always been looking at the clouds as a pilot and later as a meteorologist what I've determined and it's fairly easy to tell if you look at the vertical development of clouds how high that cloud is going up in the atmosphere if it has big vertical development it obviously means that you have a very unstable atmosphere which means you're gonna have a fairly rough ride and could be some thunderstorm issues if those clouds are obviously laying down flat or stratus clouds that we call them typically means you'll have a smooth ride but could have poor visibility the high clouds here cirrostratus clouds Stratus they're flat serious because they're very high up in the atmosphere typically they're made up of supercooled water droplets that are now ice their way up in the sky about 20,000 feet nice blue sky but you begin to see these wispy horse tail shaped clouds they're very thin and they tell you that you're looking at a weather change about 36 to 48 hours from your present time now here are cirrocumulus clouds a little bit of heaping going on out there a little thicker cloud pattern there's still high clouds with bases right about 20,000 feet now here are middle to high clouds altostratus clouds 6,500 to 20,000 feet above the ground nice flat based clouds they are stratus clouds but they're also middle clouds we move into middle clouds or the altocumulus between about 6,500 to about 20,000 feet for the bases and you can notice right here they're also known as fair weather cues nice day out there with the little bit of vertical development might be a little bumpy below this cloud but very smooth above it now here are interesting middle to high clouds these are Alto cumulus lenticular x' standing lenticular clouds or lens shaped clouds very well defined you see them over mountain peaks and they're also telling you one more thing they range from 6500 to 20,000 feet it's very windy at this level in the atmosphere it's going to be a very bumpy ride and if you're on the leeward side of a mountain range and you're seeing an altocumulus standing lenticular cloud watch out now into the lower clouds these are the stratus clouds and these are cumulus so a little bit of definition to them but about 6500 feet four straight out cues here are more low clouds this is just a plain old Stratus base right here about 6500 feet but look at this virtually no definition to cloud basis at all nice flat Stratus cloud these are vertical development clouds here are cumulus or the beginning of our heap clouds they range from 6,500 to 20,000 feet notice it kind of looks like mashed potatoes all kind of heaped up in a bowl flat basis now here our cumulonimbus very flat down here at the base giving you an awful lot of vertical development up to 45,000 feet they indicate a very unstable atmosphere an awful lot of moisture in here up and down movement and a very rough ride towering cumulus look at this 45,000 feet in height for their tops and in some cases much higher than this even airliners avoid this stuff a huge amount of water vapor going up and down condensing and freezing and becoming liquid again thunderstorms are in here ice hail all kinds of problems avoid these give them a very wide berth and even more of a wide berth when you get towering cumulonimbus towering cumulonimbus is the Greek water God these are chuck full of water and they're going to be thunder storm makers and can potentially become tornado makers as well 45,000 feet tops a lot of water in them very rough ride steer clear of these clouds will cover fog next fog forms much the same as clouds when cloud bases are less than 50 feet AGL they are officially fog fog that is less than 20 feet thick is called ground fog fog is a surface based cloud restricting visibility and composed of either water droplets or ice crystals as we talked about earlier fog may form by cooling the air to its dew point or by adding moisture to the air near the ground a small temperature dew point spread is the essential for the formation of fog fog is classified by the way it forms there is advection fog radiation fog upslope fog precipitation or drizzle induced fog and steam fog advection fog warm air moves over a cooler surface it requires a sea breeze it's common along the coastline where a warmer air mass coming perhaps off of a warm body of water moves over cooler land and the fog forms classic Pacific Coast or Atlantic coast fog conditions even in the Gulf Coast as well radiation fog this is found in most low-lying areas during calm clear cool nights often in river valleys where the air is cool its moist it's very abundant and you get this radiation fog forming it dissipates once the Sun pops up and things begin to warm up slope fog requires very moist stable air mass it's forced uphill up that landmass it can form in moderate and strong winds and often under cloudy skies as well precipitation or drizzle induce fog is most commonly associated with frontal activity and is formed by relatively warm drizzle or rain falling through cooler air this fog is especially critical because it occurs in the proximity of precipitation and other possible hazards such as icing turbulence and thunderstorms steam fog cold air over warmer water it rises upward and almost resembles smoke coming off the water alright this time we have a couple of reef you questions for you the first standing lenticular clouds in mountainous areas indicate which of these three your answer C standing lenticular altocumulus clouds are formed on the crests of waves created by barriers to the wind flow the clouds show little movement hence the name standing however wind can be quite strong blowing through such clouds the presence of these clouds is a good indication of very strong turbulence and should be avoided okay let's take the next question here what types of fog depend upon wind in order to exist your answer here C advection fog forms when moist air moves over clout rather colder ground or water upslope fog forms as a result of moist stable air being cooled adiabatically as it moves up sloping terrain okay very good let's tackle another topic air masses join Natasha in the classroom so far we've talked about fog clouds their types and characteristics stable and unstable air we'll talk about how this all fits into the big picture of airmass whether an air mass is quite simply a big uniform massive atmosphere that takes on the characteristics of its source region in this case its source region is up over Canada and the northern part of the US there are various types of source regions for various types of air masses let's go over a few of them which are characteristic of North America first there is the Marine polar or cool air mass that influences much of the weather here in the Pacific Northwest the maritime or marine polar air mass influences most of the eastern seaboard all the way from Maine down as far as portions of Pennsylvania even at times in sections of Kentucky and Tennessee there is a cold continental polar airmass here it's a drier airmass polar meaning cool next is the marine tropical airmass it's warm and moist the marine tropical or warm moist air influences much of California and portions of Southern Nevada a marine tropical airmass or a warm moist airmass influences all of Florida much of Georgia the Gulf Coast and Baja Mexico finally there is the continental dry tropical or a very warm air mass this is typical to Arizona New Mexico and portions of Texas air masses can be modified temperature and moisture can be added or removed from an air mass they can be sped up or slowed down an air mass can be warmed or cooled from below and water vapor can be added or removed from an air mass here's an example of modifying an air mass we'll start out with a nice dry stable cool continental or CP air mass it comes in and out of Canada this air mass rolls across the Great Lakes it's a large body of water and water tends to hold in heat more than land does and as that water evaporates it rises up it makes this air mass moist and unstable so it is a moist unstable air mass and this creates precipitation it causes snow in much of the southeast it gives the nice big Appalachian mountain snow events we have in the winter months here's an example of cooling an air mass from below here is a warm tropical air mass coming up off the Pacific Ocean nice wet air it's warm buoyant air and then it runs across a cooler landmass here in the Sacramento and San Joaquin Valley of California so this air mass is cooled from below and this allows for large areas of low clouds and fog low Stratus type clouds to reach out up and down the entire length of the valley and bring fog into the Bay Area air masses can be stable and unstable with an unstable air mass you can expect cumuliform clouds that was nice puffy heat type clouds like mashed potatoes you'll experience showery precipitation not continuous but showery and a very bumpy ride with good visibility now for a stable air mass it's the opposite you'll see stratiform clouds flat clouds with extensive areas of fog and continuous but not heavy precipitation the air will be smooth providing a nice ride but you're going to pay for it with poor visibility lots of smoke and haze and again the rides great but you can't see a whole lot ok let's take a break once again for a review question a stable air mass is most likely to have which characteristic which of these three your answer you see stable air mass equals smooth air but poor visibility ok let's go back to the classroom and another topic here fronts your instructor please let's talk about weather fronts you hear about these all the time on TV and radio they're classified by types there are cold fronts warm fronts stationary fronts and occluded fronts and you can see the Front's depicted here you have the cold front the warm front stationary front and occluded front now here's a bit of weather wisdom a front is simply a boundary line between two masses of cold air or warm air on each side of this front it's all it is it's a boundary line between two air masses the easiest and most recognized way to look for a frontal band look for a change in temperature and a change in dew point also watch for a change in wind speed and wind direction a front lies in a pressure trough and pressure generally is higher in the cooler air and lower in the warmer air here's a cold front with a boundary line with warmer air ahead of it here's the cold drier air all moving off in this direction here is the typical weather you can expect in a cold you can she see the showery activity along with the thunderstorms and the uprising air now here's what to look for with a cold front passage prior to the passage look for cirrus towering cumulus cumulonimbus clouds and look for some showers visibility will be fair too hazy the winds will be out of the south-southwest the temperature out ahead of this cold front passage will be warm the dew point will be high warmer moist air and the barometer will be falling now during passage of a cold front here's how things change we have towering cumulus clouds and cumulonimbus clouds the precipitation will be heavy shower is resulting in poor visibility and the winds will be variable and gusty because the frontal passage will result in a change in direction the temperature becomes suddenly cooler prior to cold front passage the dew point will drop and the bottom of the barometer will begin to go up after the passage look for cumulus or heaped type clouds precipitation will be light a little bit of a shower activity visibility suddenly improves and the winds have gone from south southwest to Northwest after the passage the temperature is cooler the dew point keeps on dropping and that barometer keeps on rising now here's a warm front note the warm air mass sloping over the cold dry air and overtaking it here is the expected weather you can see snowflakes falling from above you have altostratus and nimbostratus clouds now check out this table prior to a warm front passage look for Cirrus and stratus clouds and some fog so there's some flat cloud decks precipitation moderate rains a possibility drizzle and sleet and some snow prior to passage the visibility will be poor the winds prior to passage out of the south southeast temperatures cold to cool the dew point will begin to rise and the barometer is going to drop now during a passage of a warm front look for stratiform clouds drizzle and maybe nothing as far as precipitation goes visibility little bit better but still on the poor side the winds will be variable the temperature begins to rise now remember we're going through a warm front passage the dew point will hold and the barometer will also begin to hold now after passage of our warm front we're going to look for some stratocumulus clouds right here maybe a few cumulonimbus rain or some showery precipitation and that's just a maybe visibility fair in haze got a warm front passage the winds are now out of the south-southwest the temperature will be warm because we've had a warmer air mass move on through the dew point will rise and then it's going to hold and then the barometer will rise and then begin to fall after that frontal passage an occluded front is simply to frontal systems coming together note how the cold front and warm front are joined now here are the characteristics of a cold front occlusion colder air being denser and heavier is digging under this warmer lighter air and now our air mass is moving up in one direction here so our warm front and cold front are being moved in the same direction but the colder front being denser and heavier travels more rapidly than the latter warm front now here are the cloud decks to look for them both Stratus a rather flat type of cloud and our precipitation is going to be light occasionally on the heavy side now temperature changes we will go from some cool air to some very cold air back in behind of our cold front occlusion now with a warm front occlusion it's a different story in this case we have a cold and warm front note how the cold front is rising above the warm front we get embedded cumulonimbus clouds we get nimbostratus we get altostratus we have warm air that is rising it is buoyant and as that air rises it becomes unstable and you get this type of cloud pattern it's indicative of very bad weather and a bumpy ride temperatures will go from cold air and some fog and Stratus to cooler air back and behind that warm front illusion now check out this table these are some characteristics to go with an occluded front clouds prior to passage Cirrus and stratiform precipitation can be light too heavy depending on whether it's a cold front or a warm front occlusion visibility will be poor the wind will be out of the southeast to south temperature going from cold to cool dew point will hold steady and the barometer prior to passage will be on the following side now during passage our clouds will be nimbostratus towering cumulus and cumulonimbus lots of violent weather lots of precipitation light to heavy visibility still poor the wind variable because we're now going through our frontal passage temperature will go cold and of course with our cold front occlusion it's going to drop with our warm front occlusion that temperature will bring in and warmer air so will tend to rise dew point will drop a little bit and the barometer will begin to stabilize now after passage of our occluded front look for cloud cover to include some nimbostratus I'll get to the right side of the map here for you and of course nimbostratus and perhaps some of the altostratus as well precipitation light to moderate at times a visibility will improve and pass the frontal passage now here's a look at the winds will be out of the West to northwest temperatures with our cold front occlusion we'll be colder and with a warm front occlusion it's going to be a bit milder the dew point will rise then hold steady the pressure down with a cold occlusion will drop with a warm front occlusion it's going to rise with the operating IFR are you still concerned if there's a little moisture in the air just other than ice but well yeah because you're gonna want to know what you have as far as type of precipitation is gonna be rain is it gonna be snow also if you're flying into IFR how long is that flight going to be in actual IFR conditions what kind of clouds are you'll be going into and then on your letdown procedure how low are those clouds going to be and will you be encountering any kind of fog that may require you to have an alternate Airport further away than your original destination a cold front is depicted with these little barbs you can see right here now the way the barbs are pointed indicate which way the front is moving out ahead of a cold front we have warmer air and back in behind we have of course colder air a warm front is depicted by little half circles see them right here but again which way the little half circles are pointed indicates which way the front is moving out ahead of a warm front we have colder air and back in behind it we have warmer air for a front occlusion we have that marriage of a warm front and cold front and here we have our half circle our Barb and then another half circle now out of our frontal occlusion colder air down here cooler air back in behind the front and then also out ahead of our frontal occlusion we have warm air aloft now for the stationary front neither front is making any forward progress so basically what we have are colder air moving in this direction but it's been stopped in its tracks by our warm front right here going in the opposite direction now look for air like this back in behind the front also look for a direction of movements here we have colder air with high pressure turning clockwise behind our stationary front and we have warmer air with lower pressure turning counterclockwise back in behind for tallis is the end of a front here we have a stationary front it's our boundary line between the two air masses colder air and warmer air and as this boundary line begins to weaken these two areas of air pull apart our front becomes a little trough that's indicated right here by this dashed line and then as the two air masses become even weaker you can see nothing exists here at all so there is no trough it becomes too widely separated air masses for front of Genesis or the birth of a front we have our two source regions warmer air colder air that draws closer together so our boundary line is beginning to form right here here is a stationary front the warm air mass the cold air mass both of them relatively equal in strength so no front making any progress on each other frederik Genesis and frontal assist is simply the birth and death of a front in this case it's a stationary front some very good information covered on that topic now another FAA review question which weather phenomenon is always associated with the passage of a frontal system which of these three and your answer here is a wind always changes across a front wind discontinuity may be in direction in speed or in both temperature and humidity also may change okay let's tackle yet another topic here this time out thunderstorms back to your classroom and your instructor okay let's talk about thunderstorms now pilots should avoid thunderstorms by careful pre-flight weather briefings and planning basically just never fly into a thunderstorm here's what to look for the tops of these monsters reach up to 60,000 feet that's twice the height an airliner typically flies there are clouds with extensive vertical development the presence of cumulonimbus Momentis clouds up at the bases indicate the probability of thunderstorm activity try to get out of this as soon as possible now there are three stages to a thunderstorm the cumulus stage the mature stage and the dissipating stage now in this abstract watch for the examples of the three stages and how they typically met fest themselves begin with the cumulus stage then it changes into the mature stage then finally the dissipating stage now the three stages shown here illustrate the vertical air movement there are lots of updrafts going on also the beginning of some heavy precipitation and you'll notice right here Oh boom and they're warming on our cloud indicating which way the upper-level winds are going lightning hail king Kesari of golf balls and that can cause some serious destructive damage to even the largest airplanes but of course the last stage is deine stage of a thunderstorm lots of downdrafts in here few updrafts still going on with this storm we still see a lot of precipitation going on in these systems now a thunderstorm can be very unpredictable and the reason for that is there are very short live storms the birth to death of a thunderstorm maybe only 45 - perhaps 90 minutes and makes them very dangerous very strong storms and also very difficult to predict again here's what to look for in a thunderstorm lots of updraft activity going on with this one here we have our highest anvil-shaped cloud indicating storm movement down here at lower levels is that colder dense air now falling out ahead of it this first Gus cloud as the storm is moving toward you and watch for these little rotors or roll clouds right here they are the start of what can become a tornado now any thoughts on how pilots can judge an appropriate distance from thunderstorm activity especially when they're operating in IMC there's some great things that have come out in the last few years first of all you can always get a hold of ATC air traffic control and they will alert you if there are severe thunderstorms or if there's large thunderstorms in your presence obviously if you're in do IFR you're under positive control other things you can have a lot of airplanes now are having their own onboard radar both either panel melted or a lot of the portable systems now that are available can give you near or real-time radar imagery showing you where thunderstorm activity may be popping up along your flight welcome back to the studio and another FAA review question during the life cycle of a thunderstorm which stage is characterized predominantly by downdrafts which of these a B or C your answer is B dissipating downdrafts characterize the dissipating stage of the thunderstorm cell and the storm dies rapidly hey let's tackle yet another topic coming up turbulence join your instructor in your classroom for that topic it's blue it's sunny the flight is smooth but then all of a sudden you encounter this turbulence and perhaps even some wind shear here's what to look for and how to avoid it now what do you do when you encounter turbulence I usually try not to stay away stay away exactly usually I'm going to be looking at you know before I depart how rough the it might be whether the atmosphere is stable or if I've got some kind of a mountain pass to go through I usually try to stay out of the turbulent weather unless I have to go into it for whatever reason or if I get caught into it usually trying to climb above it or get down below it and look at those winds at various levels in the atmosphere here we are flying along in the upper atmosphere above these nice cumulus clouds almost always smooth but for most of us we fly of course down below and that's going to include some turbulence from time to time and also down below the air current as they move along they take on the characteristics of a landmass in this case your mountains and valleys ridges and peaks and hey look at this here we have our wind lower atmosphere flows up this mountain peak back down the valley on the backside you see right here some rotors or some Eddy circulations developing same thing at even lower levels look at this flying over a valley now in a forested field right here we fly up and fly down the air currents and the backside of that forest once again and a little eddy current we can see that moving right here same thing can happen in a crosswind situation on a landing and takeoff here we have runway two-four and this classic crosswind the wind flows up hits the side of the hanger goes up over the roof then drops back and here again is our eddy current causing turbulence now flying along in the upper atmosphere again pretty smooth until you crumb across a situation like this it's classic in the mountain west of the US the Cascades and the rocky mountain areas this is the mountain wave for the Lee wave pattern it's pretty smooth until you hit the backside of the mountain and the wind direction and and then here you have this wave pattern indicating turbulence well to recognize it look for a lenticular cloud or even further downstream a rotor cloud again indicating intense turbulence and certainly a bumpy ride here we have a strong downdraft or a microburst we're on takeoff flying into this headwind airspeed is on the increase at the center of the Microverse we start to fly into the downdraft as we pass the downdraft we are experiencing a significant tale with as this happens the wind is increasing and the airspeed is decreasing and unless you can power out of this you're going to fly right into the ground welcome back for another brief break and a review question this one where does wind shear occur which of these answers is correct your answer this time is C wind shear may be associated with either a wind shift or a wind speed gradient at any level in the atmosphere all right moving on airframe icing is the topic join your instructor in the classroom for that topic airframe icing is a very serious atmospheric condition it can bring down anything from a simple single-engine airplane to a full-sized passenger jet now let's talk a little about IFR all right what are your primary weather concerns when you plan and execute an IFR flight number one ice if you're flying into actual IFR conditions are you gonna be in company or going into any icing scenarios would that is B clear ice would that ice be rime ice that's my number one issue if I'm going to be flying IFR okay ice can form on any exposed surface during flight with visible moisture at or below zero degrees Celsius icing increases drag increases weights reduce thrust lift and aircraft performance as little as just a half inch of ice can reduce the performance of an airplane by 50% cool water is the most dangerous ice and can build up to 3 inches in just 5 minutes exposure there are three types of airframe icing the first is rime ice this is a little ram shaped ice pattern and you'll notice that it's rather milky color as well this kind of ice typically four in stratiform clouds or flat clouds and sometimes it can be precipitation that's already frozen or near freezing and it strikes the wing of the airplane not a lot of flow here but it builds upwards and can really cause an awful lot of drag and substantial loss of performance on your aircraft's wing next up is clear ice and here we have a case of water droplets or supercooled water droplets forming and cumulus clouds they strike the weak flow back over and keep building up this adds a lot of weight it's a clear color and also adds weight and inhibits wing and aircraft performance finally there's mixed icing which can form in either cumulus or Stratus type clouds and here is that float pattern associated with clear icing and the milky color and the very rough edges associated with a rime ice condition frost is a variation on ice frost is described as ice deposits formed by sublimation on a surface when the temperature of the collecting surface is at or below the dew point or the adjacent air and the dew point is below freezing frost causes early airflow separation on an airfoil resulting in a loss of lift therefore all Frost should be removed from the lifting surfaces of an airplane before flight or it may prevent the airplane from becoming airborne time for another FAA review question this on aircraft icing in which environment is aircraft structural icing most likely to have the highest accumulation rate which environment a B or C the answer in this case is C freezing rain gives you the most likely and the highest accumulation rate of icing all right our final topic in this lesson will be covered by Natasha's jet stream back to the classroom our final area of discussion covers the high altitude weather in the jet stream most general aviation pilots will not fly into the jet stream but the jet even though it's high up in the atmosphere does affect the weather below what are some of the global weather patterns at pilots should be on the alert for the thing I keep my eye on the most is the upper level winds or the jet stream the jet stream is simply the steering currents in the atmosphere and if you look at the jet stream and where that's going it's either gonna be pulling or it's going to be pushing the lower level atmosphere which contains the clouds and the moisture and that's going to be containing your weather so whether the jet stream goes the lower level atmosphere which contains all the moisture the warm air and the cold air and most the cloud cover will be following a few hours behind here's how the jet stream works the jet core is about 40,000 feet up in the atmosphere but the closer you move toward the polar tropopause the lower the jet will occur in the atmosphere consequently the further south you travel towards the warmer air and the tropical tropopause the higher up in the you're going to find the core the Jetstream core width can average anywhere from 100 to 400 miles the core height is typically anywhere from about 3,000 to 7,000 feet in the jet stream itself the actual river in the atmosphere can be anywhere from a few hundred miles long to upwards of 1,000 to 3,000 miles in length there can be one or two jet streams at a time here is a northern branch and a weaker southern branch of the jet stream what weather factors help you decide whether you'll fly through the weather select an altitude above it or make the no-go decision I'm gonna be looking at my in route forecast I'm gonna be looking at a number of things what the weather is gonna be at my destination what the forecast weather is going to be within three or four or five hours of my destination also enroute if I am going to be encountering conditions that I don't like whether its visibility winds or turbulence can i plot my way around that can I go to the north south east or the west around that and also is it just better to maybe sit on the ground and wait things out not above doing that you know maybe eight ten hours or put the entire flight off 24 hours if I have to until weather phenomena moves through the area this is great information especially meteorologist pilot you're getting some good info here one final question we did what kind of weather detention equipment do you use in an IFR mission ify mission I'm going to be using a radar a portable radar set up in the aircraft like a Garmin system onboard the airplane using that I'll also be talking with ATC IR traffic control are they encountering along the line from other pilots giving pilot reports back in inclement weather icing turbulence rain or fog does it change much if you're operating in VFR changes as far as you don't have that positive control that you would have if you are flying IFR as opposed to VFR if you're flying IFR you have positive control with ATC if you're flying VFR you don't have that same outstanding well there you have it terrific information from Dave Celestia guy who should know meteorologist and we highlight your information on weather thanks again for joining today truly a great job natasha appreciate it now I certainly understand better how weather concepts apply to pilots in their pre-flight and in-flight decision-making and certainly it applies to everyday life as well now moving on how do pilots gather this information and how do they use it well there's a process to it we're going to learn how to apply that weather information all in lesson two

Channel: In the Left Seat

Views: 36,518

Rating: 4.9186993 out of 5

Keywords: Flight Training, IFR Ground School, Instrument Rating Ground School, IFR Exam, IFR Rating, Instrument Pilot Written Exam, Instrument Rating Airplane, How to fly IFR, What is IFR, What is an instrument rating, IFR Flying Skills, IFR Refresher, Instrument Pilot Exam, IFR Weather, Weather for Pilots, Pilot Weather, FAA Weather

Id: AccGQG8A2xE

Length: 78min 42sec (4722 seconds)

Published: Mon Jun 29 2020