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Question 156-1 : An aircraft over western europe is crossing a jet stream 2500 ft below its core at right angles. while crossing, the outside temperature is increasing. the prevailing wind is ? [ Learning aircraft ]
From the right.
.if the outside temperature is increasing while crossing below its core, it's because you are flying from cold sector to warm sector..the wind comes from your right because if you stand with your back to the wind in northern hemisphere, low pressure and low temperature are on your left.
Question 156-2 : What is the main cause for the formation of a polar front jet stream ?
The north south horizontal temperature gradient at the polar front.
.fundamental to the formation of the polar front jet stream is the physical property that warm air is less dense than cold air when both are at the same pressure. the polar front represents the boundary between higher latitude cold air and lower latitude warm air. this temperature contrast extends from earth's surface up to the polar front jet stream altitude...air pressure is determined by the weight of overlying air. in the vicinity of the polar front, air pressure drops more rapidly with an increase in altitude in the more dense cold air than in the less dense warm air...the effect of temperature on air density results in air pressure at any given altitude being higher on the warm equatorward side of the polar front than on the cold poleward side. when cold and warm air reside side by side, the higher the altitude the greater the pressure difference is between the cold and warm air at the same altitude..across the polar front, at upper levels including the jet stream altitude , horizontal pressure differences cause air to flow from the warm air side of the front towards the cold air side of the front..once air is in motion, it is deflected by earth's rotation coriolis effect. upper level air flowing poleward from higher pressure towards lower pressure is deflected to the right in the northern hemisphere or to the left in the southern hemisphere. the result is a jet stream flowing generally towards the east, parallel to, and above the polar front.
Question 156-3 : Which jet stream is connected with a surface front system ?
The polar front jet stream.
.the polar front is the boundary between polar air and tropical air. 595.you can see that the polar front jet stream is connected with the polar front. for the other jetstreams there is no front for information easterly jet stream is the equatorial jetstream.
Question 156-4 : At approximately what flight level is the subtropical jet stream found ?
Fl 400.
.jet streams vary in height from 20000 ft to 40000 ft, and can reach speeds of more than 240 kt.. 595.the subtropical jet stream is located around 30°n..the subtropical jet stream can be found at fl400 40000 ft...arctic jet stream = 20000 ft..polar front jet stream = 30000 ft..subtropical jet stream = 40000 ft.
Question 156-5 : Flight zurich to rome, etd 1600 utc, eta 1800 utc. at what flight level would you first expect to encounter clear air turbulence on the climb out from zurich. 273 ?
Fl 220.
. 522.cat area n°2 shows moderate cat between fl220 and fl400.
Question 156-6 : At what flight level is the jet stream core that is situated over northern scandinavia . 274 ?
Fl 280.
. 525.the jet stream flight level is indicated below his position. maximum jet stream wind speed is 135 kt.
Question 156-7 : Select from the map the wind for the route zurich london at fl 280. 277 ?
220/60.
. 527.225°/95 kt.220°/55 kt.210°/40 kt.255°/35 kt..average wind is 227°/56 kt...in northern hemisphere, wind turns clockwise with height, and speed increases. it means that normally, at fl280 chart is for fl300 we should expect a wind of 220°/50 kt...anyway, answer 220/60 remains the only valid answer.
Question 156-8 : What name is given to the jet stream lying over north africa b . 280 ?
Sub tropical jet stream.
.the subtropical jet stream is located around 30°n/s.. 590
Question 156-9 : What wind is forecast at fl 390 over paris . 281 ?
210°/40 kt.
. 528.the wind is blowing with a south south west component west of paris, and speed is reducing from 45 kt to 30 kt close to luxembourg..'210°/40 kt' is the correct answer.
Question 156-10 : What is the direction and maximum speed of the jet stream affecting the route between munich and london . 285 ?
220° / 120 kt.
. 529
Question 156-11 : Flight from bordeaux to amsterdam, eta 2100 utc. at eta amsterdam what surface wind is forecast.taf eham 281500z 281601 14010kt 6000 ra sct025 becmg 1618 12015g25kt sct008 bkn013 tempo 1823 3000 ra bkn005 ovc010 becmg 2301 25020kt 8000 nsw bkn020 = ?
120° / 15 kt gusts 25 kt.
.becmg becoming indicates a change to forecast conditions is expected to occur slowly within the period designated in the time group immediately following the heading..the duration of this change is normally about 2 hours. the elements included in the becmg line will supercede some of the previous taf groups, but it is possible all the groups may change..any group omitted in the becmg line will be the same during the becmg period as indicated in the main taf line...in this question, the wind becoming 120°/15 kt gusts 25 kt 12015g25kt between 16h and 18h. it will remain unchanged until 23h..then, the wind becoming 250°/20kt between 23h and 01h.
Question 156-12 : The equatorial easterly jet is a jet stream that occurs ?
Only in the summer of the northern hemisphere at approximately 45 000 ft.
.this jet occurs in the northern summer between 10°n and 20°n, chiefly over or just to the south of high land masses such as in asia and africa. its occurrence is due to a temperature gradient with colder air to the south which produces sufficient temperature differential above 45000 ft, to give wind speeds of over 100 kt..because colder temperatures at height are to the south, it is an easterly jet. this jet is now more usually known as the tropical easterly jet... perhaps more correctly as it lies some distance from the equator.. 533
Question 156-13 : In which zone of a polar front jet stream is the strongest cat to be expected ?
On the polar air side of the core.
.the strongest cat is in the warm tropical air, but on the cold polar air side of the core.
Question 156-14 : What is the minimum speed for a wind to be classified as a jet stream ?
60 kt.
.the heavyline line delineating the jet axis begins/ends at the points where a wind speed of 30 m/s 60 kt is forecast.
Question 156-15 : A wind sounding in the region of a polar front jet stream gives the following windprofile northern hemisphere..900hpa 220/20kt.800hpa 220/25kt.700hpa 230/35kt.500hpa 260/60kt.400hpa 280/85kt.300hpa 300/100kt.250hpa 310/120kt.200hpa 310/80kt.which system is the jet stream associated with ?
With a warm front.
.the highest wind speed is in the core of the polar front jet stream, at 250 hpa, approximately fl340. in the northern hemisphere, the cold front jet is from the sw and the warm front jet is from the nw..at fl340, the jet direction is 310°, it is a north west direction.
Question 156-16 : What is the most significant difference between an equatorial jet stream and all the other jet streams ?
Wind direction.
.its wind direction is from east to west...this jet occurs in the northern summer between 10°n and 20°n, chiefly over or just to the south of high land masses such as in asia and africa..because colder temperatures at height are to the south, it is an easterly jet. this jet is now more usually known as the tropical easterly jet... perhaps more correctly as it lies some distance from the equator.. 533
Question 156-17 : You cross a jet stream in horizontal flight at approximately right angles. while crossing, in spite of a strong wind of 120 kt, you notice the temperature barely changes. which of the following statements is correct ?
This phenomenon is absolutely normal as you are crossing the jet core.
Question 156-18 : What jet streams are likely to be crossed during a flight from stockholm to rio de janeiro 23°s at fl 350 in july ?
A polar front jet stream followed by one or two subtropical jet streams.
. 2535
Question 156-19 : While crossing a jet stream at right angles in western europe 3000 ft below its core and oat is decreasing, what would be the prevailing wind ?
Crosswind from the left.
.if you are moving to an area of decreasing temperature, then you must be moving from an area of warm air to cold, and in the northern hemisphere the frontal jetstream, which is just underneath the warm sector tropopause in the warm sector, close to the front, blows with the cold sector to its left. therefore if you are crossing to the cold sector the jet is blowing from the left.. 595
Question 156-20 : During the winter months in mid latitudes in the northern hemisphere, the polar front jet stream moves toward the ?
South and speed increases.
.in winter, the polar front moves south. 585.during summer, it moves north. 598.winter speed 130 to 150 kt..summer speed 60 to 100 kt.
Question 156-21 : What causes surface winds to flow across the isobars at an angle rather than parallel to the isobars ?
Surface friction.
.friction is a force. it is a force that slows motion and dampens energy...in meteorology friction is important because it causes the wind speeds at the surface to be less and more turbulent than they otherwise would be. rough terrain is more effective in decreasing the wind speed than a water surface. friction processes can help promote surface convergence and uplift...resistance to movement of air flowing along the surface of the earth induces the wind to flow across the isobars at an angle.
Question 156-22 : What prevents air from flowing directly from high pressure areas to low pressure areas ?
Coriolis force.
.pressure gradient tries to move air from high pressure to low pressure but coriolis force deflects it to the right in the northern hemisphere and to the left in the southern hemisphere.
Question 156-23 : What is the approximate speed of a 25 knot wind, expressed in kilometres per hour ?
45 km/h.
.1 kt = 1.852 km/h..use this formula 25 kt x 2 10% = 45 km/h.
Question 156-24 : What is the approximate speed of a 90 km/h wind, expressed in knots ?
50 kt.
.1 kt = 1.852 km/h..use this formula 90 km/h + 10% /2 = 49.5 kt.
Question 156-25 : What is the approximate speed of a 40 knot wind, expressed in m/sec ?
20 m/sec.
.1 kt equal around 0.5 m/s.
Question 156-26 : Where, in central europe, are the highest wind speeds to be found ?
Just below the tropopause.
.the strongest winds in this area are the polar front jetstreams which are just below the warm air tropopause.
Question 156-27 : If paris reports a wind of 19015kt on the metar, what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?
22030 kt
. values to be used in examinations.over sea, wind speed in friction layer decrease by 30%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 10°..over land, wind speed in friction layer decrease by 50%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 30°.
Question 156-28 : If paris reports a wind of 08010kt on the metar, what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?
11020kt
. values to be used in examinations.over sea, wind speed in friction layer decrease by 30%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 10°..over land, wind speed in friction layer decrease by 50%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 30°.
Question 156-29 : If paris reports a wind of 16020kt on the metar, what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?
19040kt
. values to be used in examinations.over sea, wind speed in friction layer decrease by 30%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 10°..over land, wind speed in friction layer decrease by 50%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 30°.
Question 156-30 : If paris reports a wind of 30012kt on the metar, what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?
33025kt
. values to be used in examinations.over sea, wind speed in friction layer decrease by 30%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 10°..over land, wind speed in friction layer decrease by 50%, the wind in the friction layer blows across the isobars towards the low pressure. angle between wind direction and isobars changes by 30°.
Question 156-31 : Which of the following is true of a land breeze ?
It blows from land to water.
.land breeze during the night land is cold, sea is warm. 600.during the day the situation reverses and the wind will blow from the sea sea breeze. 601
Question 156-32 : An aircraft is approaching under visual flight rules an airfield whose runway is parallel to the coast. when downwind over the sea, the airfield is on the right. what wind effect should be anticipated on final approach and landing during a sunny afternoon ?
Crosswind from the right.
.during a sunny afternoon sea breeze is likely to occur. 601.if the coast and runway are aligned east/west, a right hand circuit would mean runway 27 in use, sea to the north and land to the south..at touch down the northerly sea breeze would be from the right.
Question 156-33 : An aircraft is approaching under visual flight rules an airfield northern hemisphere whose runway is parallel to the coast. when downwind over the sea, the airfield is on the left..what wind effect should be anticipated on final approach and landing during a sunny afternoon ?
Crosswind from the left.
.during a sunny afternoon sea breeze is likely to occur. 601.we should expect a crossing from the left on final approach and landing. 544
Question 156-34 : When will the surface wind in a metar record a gust factor ?
When gusts are at least 10 knots above the mean wind speed.
Question 156-35 : Select from the map the average wind for the route zurich rome at fl110. 303 ?
230/10.
. 548.a feather corresponds to 10 kt..if you look at the wind close to rome, it comes approximately from 235°..average wind is 230°/10 kt.
Question 156-36 : Select from the map the average wind for the route athens geneva at fl 160. 304 ?
240/40.
.on the chart, we find an average wind of 245° ==> 240+235+245+255 /4.this chart is for flight level 180 and they ask the average wind at fl160, thus, the wind will be less than 245° northern hemisphere...we find a wind speed of 46,25 kt, wind force will also be less. only one answer remains correct 240/40.. 484
Question 156-37 : Select from the map the average wind for the route zurich hamburg at fl 240. 305 ?
230/20.
.on the left of zurich, we notice a wind of 200°/20 kt..on the right of zurich, the wind is from 250°/25 kt..the average wind will be 230°/20 kt.
Question 156-38 : Select from the map the average wind for the route shannon lisboa at fl 290. 306 ?
360/80.
. 551.the wind comes clearly from the north, at a speed of. 70 + 90 + 90 + 85 + 80 /5 = 83 kt..the map is for fl300, the speed at fl290 will be slower than 83 kt.
Question 156-39 : When otherwise calm and clear conditions exist a station on the shore of a large body of water will experience wind ?
From the water in daytime and from the land at night.
.land breeze during the night land is cold, sea is warm. 600.during the day the situation reverses and the wind will blow from the sea sea breeze. 601
Question 156-40 : The greater the pressure gradient the ?
Closer the isobars and the stronger the wind.
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