CHAPTER 14 ARCTIC WEATHER

NORTH TO ALASKA Lies North of the arctic circle 66.5º

Latitude Not very many roads, aviation is the

back bone of transportation between communities.

Suns rays strike at shallow angles in both summer and winter

North pole has 6 months of sun and 6 months of darkness

Taking off at -45 Talus Dome Antarctica -30 F or colder, ice

fog often forms instantaneously in the exhaust gases of cars and aircraft. It lasts from as little as a few minutes to days.

Sunrise at Rothera Antarctica

LONG DAYS AND NIGHTS A profound seasonal change in length

of day and night occurs in the Arctic because of the Earth’s tilt and its revolution around the sun.

Arctic circle has autumn and winter days when the sun stays all day below the horizon

Days in Spring and summer with 24 hours of sunshine

SKY COVER

Cloudiest in summer more moisture less clouds in winter because its dryer

WIND Strong winds occur more often along the coasts

than else where. Greater frequency in the fall and winter. Wind speeds are generally light in the

continental interior. Blowing snow (dry snow) winds in excess of 8

knots may raise the snow several feet off the surface. Can go to 0 visibility. Stronger winds sometimes lift blowing snow to heights above 1000 feet and produce drifts over 30 feet deep.

VISUAL ILLUSIONS Temp inversion Looming illusion, object

appears to be above the horizon/sound travels long distances.

Light - reflection is greater due to the light snow covered surface. Can easily blot out shadows with the reflection of the sun from the snow. Large areas with lack of contrast (no shadows to give depth)– night time lighting from moon and stars

more intense in arctic

Northern lights - like a neon sign, particles illuminate rarified gases along the magnetic lines of flux. Or Aurora Borealis.

HAZARDS Fog most prevalent wx problem for pilots ice fog steam fog advection fog, blowing

snow, icing, frost, white out conditions White out - layer of cloudiness of uniform

thickness overlies a snow or ice-covered surface breaks up and diffuses sunlight. Parallel rays then reflect back and forth several times eliminating all contrast and shadows (the horizon disappears).

SUMMARY Interior areas generally have good

weather. Coastal areas and Arctic slopes often are

plagued by low ceiling, poor visibility and icing.

Whiteout - can cause disorientation no horizon.

Mountain pass weather generally worse If lost fly down water ways. Most airports

are located near water.

CHAPTER 15 TROPICAL WEATHER

LOCATION

latitude of 23.5º N to 23.5º S Intertropical convergence zone - where

the northeast and southeast trades converge (near the equator) fig 137-139 pg. 160

lots of moisture to great heights as a result severe thunderstorms are

possible if air is unstable

SUBTROPICAL HIGH PRESSURE BELTS

Occur over the water generally good weather Lows form over the land because of temp. differential land is

generally warmer inversion is set up under the subtropical high strongest when the east side of the high is over the west edge

of a continent dry weather - California weakest and highest when the west side of the high is over the

east edge of the continent wet and thunderstormy in Florida

TRADE WIND BELTS northeasterly in the Northern hemisphere southeasterly in the Southern hemisphere flying wx is generally good over the ocean

(uniform temp) where they blow from land to sea generally

dry terrain where they blow from sea to land generally

wet terrain

MONSOON

India gets average of 400 inches of rain a year from monsoons

June to October is the monsoon season in summer, wind blows inland (wet air) in winter, wind blows seaward (dry air)

MONSOON, THE MOTHER OF ALL SEA BREEZES

SHEAR LINE

This happens when the air mass has been modified to conditions similar to the present mass it replaces

All that is left is a front line or difference in wind direction. The temp and moisture are virtually the same on both sides of the front.

TROUGH ALOFT

Spreads extensive clouds to the east of the trough line

lots of rain 460” of rain on Mt Waialeale Hawaii

TROPICAL WAVE

Forms on the southeast side of the subtropical high

travel from east to west preceded by good wx followed by cloudiness in a North South

line

TROPICAL CYCLONE

any low that is born in the tropics 1. Tropical depression 34 kts 2. Tropical storm 35 - 64 kts 3. Hurricane or Typhoon above 65 kts

HURRICANE

Low level convergence, high level divergence

sets up a chimney effect large quantities of water release lots of

latent hear furthering the updrafts rise in temp. lowers surface pressure

which increases the low level convergence

CHAPTER 16 SOARING WEATHER

GLIDER TERMINOLOGY

lift = rate of climb sink = rate of descent zero sink = rate is 0 Thermal Soaring occurs during daylight

hours, lots of sun

Several sources

Thermals Frontal Sea Breeze Ridge or Hill Mountain Wave

LOCATING THERMALS Types of Terrain

– Sandy, rocky, plowed fields, cities, factories Sun angles

– eastern slopes morning, southern midday, and western afternoon

Dust and Smoke– rising columns

Dust devils– high turbulence but also may have high amounts of lift

LOCATING THERMALS Birds

– Hawks know where the thermals are Cumulus clouds

– convex shape shows dying thermal– concave shape shows active thermal– sharp outline growing

Towering Cu can be violent due to strong vertical shear

Wet ground very little thermal activity

TYPES OF THERMALS

Chimney thermal - continuous from the ground upward– it can lean with the wind fig. 147-150

Bubble thermal - when heating is slow or intermittent a bubble may pinch off

5-10 knots favors more organized thermals Thermal streets - Parallel to the wind fig 159 distance between the streets is 2 to 3 times the depth

of the layer or the height of the clouds

TYPES OF THERMALS

downdrafts can be strong between the streets

form behind cold fronts in the cold air of polar outbreaks

can fly in a straight line without having to circle

THERMALS

Thermals need calmer winds Wind shear can disorganize the thermal The more instability, the greater the

thermal The best thermals can be found after

cold front has passed cold air over warm ground = thermals

SEA BREEZE SOARING

Breeze blowing inland forces warm inland air upwards

reaches max during afternoon can reach 50 to 75 miles inland in flat tropical areas 150 miles is

possible LA - intense thermal activity

RIDGE OR HILL SOARING

Wing has to be within 30 to 40º of the ridge line

15 kts or more upslope lift winds being pushed up

orographically

MOUNTAIN WAVE SOARING

soaring to 35,000 feet possible convection tends to break down the wave need at least 15 to 25 kts of wind wind should be within 30º of the mountain

line wave length directly proportional to wind

speed and inversely proportional to stability

MOUNTAIN WAVE SOARING

the greater the wave amplitude the more lift

usually 150 to 300 miles long downdrafts and dangerous turbulence is

found below the crest and on the leeward side

REVIEW FOR TEST #2

In the winter when can you expect the highest rate of icing accumulation?– Thick stratified clouds producing

continuous precipitation– Near the top of stratified clouds– Between +2 and -20 C

Test #2 review

If you encounter ice pellets during flight this would be evidence of what?– A warm front is probably in your area– FZRA and severe icing is probable– Warm air exists above

Test #2 review

Which cloud family is least likely to give icing?

Which cloud family is more likely to give icing?

Which condition is most favorable to the formation of carb icing?– Temps between 32F and 80 F with high humidity– Read Jeppesen 2-20– Can get carb ice at temps as high as 38C

Test #2 Review

Frost is hazardous to flight why?– Early airflow seperation/loss of lift– One study showed that 0.1 inch of evenly

distributed frost on the aircrafts wings will increase the stall speed by 35%. This roughly doubles the required takeoff run. Dole 169

Test #2 Review

List some visual cues that a thunderstorm is well organized?– Well defined edges– Sharp contrasts of white, grey and black– Cap clouds– Roll clouds/shelf clouds– Frequent lightning– Anvil– Tornados/hail/green or blue shapes on base– Wx alert on weather radar– …

Test #2 Review

What are the three stages of a TS? What signals the start of the 2nd stage? What is normally associated with the 1st

stage? What normally happens in the 3rd

stage? What kind of thunderstorm frequently

has destructive winds and tornados?

Test #2 Review

Which weather phenomenon is always associated with a TS?– Strong turbulence (lots of shear)– Lightining

Test #2 Review

What does embedded TS mean to you? Which stage is a TS at its greatest

intensity? Where can wind shear exist?

– Near fronts– Obstructions– Anywhere (can form both vertically and

horizontally

Test #2 Review

Radiation fog normally forms when? Where does radiation fog form? Why can warm frontal systems produce fog? What can lift advection fog into a low stratus

cloud? What does advection mean to you? Which types of fog require wind to exist?

Test #2 Review

What are the ingredients to make a cloud?– CCN – Temp drop– Moisture

Test #2 Review

The jet stream in the mid-latitudes during the winter does what?

When can you expect a lot of turbulence associated with a jet stream?

With a jet core where can you expect the most turbulence?

Thermals can be identified visually how?

Test #2 Review

CAT is more common at which times during the year?

Where do you normally find jet streams?

How many knots does the wind need to be, to be considered a jet stream?

Test #2 review

What is the most important thing you learned about icing?

In order to get ice on your aircraft you need to be flying through what?

Is it easy to fly through a squall line? Which kind of TS are easy to navigate

around?

Test #2 review

Which kind of TS often lasts for several hours?

Why do monsoons happen?