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Aviation Weather Dynamically Speaking

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Presentation on theme: "Aviation Weather Dynamically Speaking"— Presentation transcript:

1 Aviation Weather Dynamically Speaking
+Materials: Beachball Globe, Cloud Charts +Collect Previous HW + Came from Gleim and Kershner +It’s a very dynamic environment +Meteorology 101 +Course Philosophy – Concepts, not minutia +“Weather Kills” – p 18 & 20 of Nall Report Written for the Notre Dame Pilot Initiative By the Pilots of the University of Notre Dame “Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

2 Dedication John H. Fischer, Cadet Captain, CAP Grandmother
Prisoners of War / Missing In Action

3 Quote Just remember, if you crash because of weather, your funeral will be held on a sunny day. –Layton A. Bennett Weather kills pilots, a lot of them. These 75 minutes will be some of the most important of the course.

4 Roadmap Atmosphere & Global Circulation Weather & Climate
Clouds & Stability Weather Forecasting

5 Lesson Plan Will learn Will be able to recite
Atmosphere & Global Circulation Weather & Climate Clouds & Stability Weather Forecasting Will be able to recite Air Mass Types Lapse Rates Stages of Thunderstorm Development Types of Fog & Clouds Will be able to distinguish Pictures of different cloud types

6 The Atmosphere & Global Circulation
“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

7 Atmospheric Composition
Earth's atmosphere has a unique composition of gases when compared to that of the other planets in the solar system.

8 At greater altitudes, the same volume of air contains fewer molecules of the gases that make it up. This means that the density of air decreases with increasing altitude.

9 At 7 miles, or FL350, the air is only ¼ dense of what it was
At 7 miles, or FL350, the air is only ¼ dense of what it was. Hence, increased operating efficiency, less weather, and pressurization The earth's atmosphere thins rapidly with increasing altitude and is much closer to the earth than most people realize.

10 Thermal Model of the Atmosphere
Show how it curves Linear to the tropopause about 2 degrees C per 1000 feet remains at –60 until outside the Ozone layer For next slide What makes the atmosphere change? What is the cause? Wind caused by uneven heating

11 Sunlight Angle On a global, yearly basis, the equatorial region of the earth receives more direct incoming solar radiation than the higher latitudes. As a result, average temperatures are higher in the equatorial region and decrease with latitude toward both poles. This sets the stage for worldwide patterns of prevailing winds, high and low areas of atmospheric pressure, and climatic patterns. When you think of atmospheric changes, think heat. Uneven heating creates wind and pressure areas. Use Globe to show angle of sunlight

12 Global Wind Patterns Hot air rises over the equator due to the fact that it is less dense. This is called the intertropical convergence zone This rising air cools as it rises resulting in precipitation in the region of the ITCZ. The air then travels north and south at high altitude. Use globe to describe in 3-d what is happening Air Goes North and south to fill vacuum created by air filling in for rising air

13 Global Circulation With Globe, Coriolis
Seasons – Have kid stand on table as sun Chris Columbus - trades With Fan, demonstrate orthographic lifting Coriolis with Globe

14 Global Wind Patterns Hot air rises over the equator due to the fact that it is less dense. The cooled air descends to reach the surface at about 24 ON and 24 OS of the equator. This forms a high pressure area The great deserts of the world are located in this high pressure area Sahara, Saudi Arabia, Hawaii, Mexico Go back to previous slide to show the effect.

15 Coriolis Effect Demonstrate throwing a ball off of a merry go around.

16 An object in motion in the northern hemisphere appears to turn to the right.
An object in motion in the southern hemisphere appears to turn to the left.

17 Global Circ Pix Explain Westerlies Part of the generalized global circulation pattern of the earth's atmosphere. The scale of upward movement of air above the intertropical convergence zone is exaggerated for clarity. The troposphere over the equator is thicker than elsewhere, reaching a height of about 12 mi.

18 Air sinks over a high-pressure center that moves away from the center on the surface, veering to the right in the Northern Hemisphere to create a clockwise circulation pattern. Air moves toward a low-pressure center on the surface, rising over the center. As air moves toward the low-pressure center on the surface, it veers to the left in the Northern Hemisphere to create a counterclockwise circulation pattern. Pressure Areas End Atmosphere & Circulation Section

19 Weather and Climate “Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

20 Definition Consider pix from ND Weather is a description of the changeable aspects of the atmosphere, the temperature, rainfall, pressure, and so forth, at a particular time. These changes usually affect your daily life one way or another, but some of them seem more inconvenient than others.

21 Flying into Elkhart, Rwy 35
Notice the blade twist

22 Air Masses Polar air mass Tropical Air Mass Continental Air Mass
An air mass that moves from a cold region Tropical Air Mass An air mass that moves from a warm region Continental Air Mass Moves in from a land mass Maritime Air Mass Moves in from over an ocean How have we defined these air masses then?

23 Air Mass Types Temperature/Moisture Hot Cold Wet Tropical Maritime
Polar Maritime Dry Tropical Continental Polar Continental Coldest temperatures = polar continental Most Humid days = tropical maritime

24 Current Weather Notice Hurricane & how it got pushed out of the way
What goes here? Get Current Chart at

25 Clouds and Stability “Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

26 Types of Clouds Cumulus (heaped) Stratus (layered) Cirrus (curled)
Nimbus (rain) What’s outside today? Yesterday? Tomorrow? Owl

27 How a Cloud Forms Temperature and Dewpoint Converge
Water Condenses on Particles (Dirt, Dust, Smoke) Fog is a cloud very near to the surface Guess Bridge? Owl

28 Precipitation Precipitation is water in the liquid or solid form that returns to the surface of the earth. The precipitation you see here is liquid, and each raindrop is made from billions of the tiny droplets that make up the clouds. The tiny droplets of clouds become precipitation by merging to form larger droplets or by the growth of ice crystals that melt while falling. Note Verga – precipitation that does not hit the ground New Mexico Desert – Why is verga so common there?

29 Condensation Nucleus (0.2 microns)
Average Cloud Droplet (20 microns) Large Cloud Droplet (100 microns) Drizzle Droplet (300 microns) Average Rain Drop (2000 microns) Flying through a cloud is like flying through air, same consistency Close the Vents when you fly through a cloud This figure compares the size of the condensation nuclei to the size of typical condensation droplets. Note that 1 micron is 1/1,000 mm.

30 Stability Air may be: Unstable (vertically) Cumulus clouds
Stratus clouds

31 Cumulus Fair weather Fair weather

32 Lapse Rate Avg Lapse Rate = 2 deg C (3.5 deg F) / 1K !!! (Environment) In Thermal, it is 3 deg C (4.4 deg F) / 1K B/C of heat & expansion Who knows what 15 C = ? F (59 F) Got that math, now we start hauling through 60 pictures The average lapse rate (rate of cooling) is 2° C per 1,000 feet or 3.5° F per 1,000 feet In order to calculate the base of thermal driven cumulus clouds, divide the temperature / dewpoint spread by the lapse rate (4.4 ° F per 1,000 feet )

33 Altocumulus Mackerel sky

34 Altocumulus at Sunrise
We’ll see later that this means bad weather tomorrow Altocumulus at Sunrise

35 Temperature Inversion
Refer to previous slide on stability

36 Note inversion and fog found below 100 feet

37 Fog is a cloud very near to the surface

38 Types of Fog Radiation (ground) fog Advection fog
Requires wind Warm air over cold land or water Upslope (orographic) fog Steam fog Lake or ocean source of water Cold air over warm water Precipitation fog (rain fog) Show slides of different types of Fog

39 Radiation Fog From the Air Radiation found on calm nights,
often under an inversion, Farmer’s Field – Driving on a clear road w/fog on sides

40 Advection Fog Three times now we’ve seen this picture. Isn’t it beautiful? Not if you’re going into SFO! Warm air over cold land or water

41 Upslope Fog Orographic Fog = Why mountains are often in clouds, air gets squeezed and moisture condenses Which way is wind blowing?

42 Upslope Fog

43 Steam Fog That’s a lake in the background
Most types of fog form in stable atmospheric conditions. The exception is steam fog, shown in this picture of Maligne Lake, Alberta, Canada, just after sunrise in late summer. The land cools off overnight while the water retains heat from the summer. As the cooled air slips over the lake, heat and moisture are added from below, resulting in a fog that twists and writhes-- hence the term "steam fog".

44 Orchard Orchards try to eliminate the inversion Anyone from FL? Fans like this one are used to mix the warmer, upper layers of air with the cooling air in the orchard on nights when frost is likely to form.

45 Ice possible in the tops
Stratocumulus Ice possible in the tops

46 Stratocumulus from above

47 Stratocumulus Red sky in the morning, sailors take warning
Red sky at night, sailors’ delight—only applies in the tropics

48 Types of Clouds Cumulus (piled up) Stratus (layered) Cirrus (curled)
Nimbus (rain) Review cumulus and stratus

49 Cirrus Overrunning moisture

50 Cirrostratus Moisture increasing

51 Cirrostratus Hazy circle round the moon
Means that rain is coming soon!

52 Cirrostratus Condensation Trails (Contrails)

53 Cirrocumulus Warm front is getting closer

54 Thunderstorms Thunderstorms require T-storms always have lightning
Unstable air Moisture Lifting mechanism T-storms always have lightning Thunder is the sound of lightning T-storms are reported when thunder is heard Only true for manned observation posts Automatic Reporting (AWOS) detects lightning discharge Note reporting criteria OWL Lightning is not that dangerous to an airplane, turbulence is No such thing as heat lightning Proper way to avoid getting struck by lightning = arms to knees Boy Scout Tip of the Day

55 Updrafts from thermals
Three stages in the life of a thunderstorm cell. (A) The cumulus stage begins as warm, moist air is lifted in an unstable atmosphere. All the air movement is upward in this stage.

56 Updrafts and downdrafts, starts when rain touches the ground
(B) The mature stage begins when precipitation reaches the ground. This stage has updrafts and downdrafts side by side, which create violent turbulence.

57 Only downdrafts “There is no reason to fly through a thunderstorm in peacetime.” –Sign over squadron ops desk at Davis-Monthan AFB, AZ (C) The final stage begins when all the updrafts have been cut off, and only downdrafts exist. This cuts off the supply of moisture, and the rain decreases as the thunderstorm dissipates. The anvil-shaped top is a characteristic sign of this stage.

58 Lightning Develop charge from the friction between rising and falling air currents. Like scuffing across the floor and touching a metal ball Different parts of a thunderstorm cloud develop centers of electric charge. Lightning is a giant electric spark that discharges the accumulated charges.

59 Thunderstorms Types of thunderstorms Air mass Frontal
Upslope (orographic) Air Mass can often be sporadic and sparse but can reach upwards of FL600 Frontal are usually more organized often as squall lines ahead of cold fronts, usually more powerful Upslope often are only a problem on the upwind side while the lee remains in cool dry air (Sierra Nevadas or Cascades)

60 Hail Hail most commonly thrown up to many miles from the anvil head of a t-storm These hailstones fell from a thunderstorm in Iowa, damaging automobiles, structures, and crops.

61 Cumulonimbus Distance to a Storm Thunderstorm Nimbus means rain
5 sec per mile at the speed of sound Thunderstorm

62 Bad Idea Thunderstorm from an MD-80 at 30,000 feet

63 Cumulonimbus From Space

64 Boundaries between air masses = fronts
Types of Fronts Cold Warm Stationary Occluded These are the four types of fronts

65 Weather Fronts Front A boundary between two different air masses
Cold Front When a cold air mass moves into a warmer area, displacing the warm air mass Provides lift to adiabatically cool the warm air, resulting in towering cumulus and thunderclouds. Blue Triangles on Charts Cold Air pushes under Warm Air forcing it upwards Squall lines are areas of thunderstorms about miles ahead of a cold front

66 A cold air mass is similar to a huge, flattened bubble of cold air that moves across the land. The front is the boundary between two air masses, a narrow transition zone of mixing. A front is represented by a line on a weather map, which shows the location of the front at ground level. Cold Front Pix See Kershner Chapter 22 for outstanding cross-sections of fronts Notice how the front aloft is many miles behind where it is on the ground

67 When a warm air mass moves into an area, displacing the cold air mass
Warm Front When a warm air mass moves into an area, displacing the cold air mass A gently sloping front as the Warm air moves over top of the cooler air. Stationary Front When the edge of a front ceases to advance Red Semicircles denote Warm Red and Blue denotes Stationary

68 Warm Front Pix An idealized warm front, showing a warm air mass overriding and pushing cold air in front of it. Notice that the overriding warm air produces a predictable sequence of clouds far in advance of the moving front.

69 Occluded Front One that has been lifted completely off the ground
Has a low pressure center and cyclonic activity Purple Triangles Often caused by a fast moving cold front overrunning a warm front

70 Show how weather develops in next three slides


72 Take a look at these three again.

73 Cyclones L Cyclone A low pressure area with winds moving into the low pressure area and being forced upward. Friction and the Coriolis effect cause the air to move to the right of the direction of movement. Anticyclone A high pressure center Lows are usually in Red, Highs usually in Blue A very small L means a tropical depression. A severe tropical depression is a tropical storm/hurricane marked with a squiggle H

74 Hurricane John This is a satellite photo of hurricane John, showing the eye and counterclockwise motion

75 Storm Tracks Note SE track, trough tracks, and Alberta Clippers Cyclonic storms usually follow principal storm tracks across the continental United States in a generally easterly direction. This makes it possible to predict where the low-pressure storm might move next.

76 Weather Forecasting “Weather forecasts are horoscopes with numbers. “
“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

77 Computer Models Note different models on left side

78 Weather Predictions Weather predictions are based on information about air masses, fronts, and associated pressure systems in an area. This information is used to produce a model of behavior for weather using a computer. Many models are used and then summarized when the different models agree fairly closely to a model of the weather. The closer the forecast is the more accurate it will be. Computes have taken an artform and forced a science upon it. A science that does not fit well I laugh at the 10 day forecasts Why do you think the weather channel has the money barometer (it’s easier to forecast the stock market!) They seem to have trouble predicting the past!

79 Surface Pressure/Precipitation Plot

80 Predicted Notice no storm in OK, weakened storm in Ontario and dissipating cold front on the Atlantic Coast Actual

81 Forecast for today ????????? Add today’s forecast

82 Supercomputers Supercomputers make routine weather forecasts possible by solving mathematical equations that describe changes in a mathematical model of the atmosphere. This "fish-eye" view was necessary to show all of this Cray supercomputer at CERN, the European Center of Particle Physics.

83 Example of Atmospheric Refraction
Home of the Flyin’ Irish! Aviation Weather, last slide Skyspotter HW due on THU (print certificate, or something) Where’s the pot of gold?

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