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Revision > flight : A wind of 20 knots corresponds to an approximate speed of ?

Question 130-1 : 10 m/s 50 km/h 40 m/s 10 km/h

.1 kt equal around 0 5 m/s exemple 230 10 m/s.10 m/s.

After a sunny day followed by a long clear night you take off from an airfield ?

Question 130-2 : A sudden strong increase in wind speed and strong veering of the wind a short time after take off large but gradual increase in wind speed and large but gradual veering of the wind up to a height of 5000 ft little increase in wind speed and little veering of the wind up to an height of 5000 ft a squally wind up to great heights

.the long clear night will lead to surface temperature inversion radiation inversion between surface up to 500 ft the strong wind above this layer has a different direction since it is not affected by surface friction the inversion acts like a boundary between the two layers .you will have a sudden change in wind speed and direction exemple 234 a sudden strong increase in wind speed and strong veering of the wind a short time after take-off.a sudden strong increase in wind speed and strong veering of the wind a short time after take-off.

At about what geographical latitude as average is assumed for the zone of ?

Question 130-3 : 50°n 10°n 30°n 80°n

. 596.westerlies average latitude is 50°n and 50°s for south hemisphere exemple 238 50°n.50°n.

At which time if any are polar front jet streams over the south pacific usually ?

Question 130-4 : July january there is no annual variation october

.strongest polar front jet streams are in the winter and in south pacific southern hemisphere winter is in july

During periods of undisturbed radiation weather overland the ?

Question 130-5 : Surface wind speed tends to be highest during the mid afternoon surface wind speed tends to be highest at night angle between isobars and surface wind direction tends to be greatest in the mid afternoon wind tends to back from early morning until early afternoon

.with undistubed radiation weather the ground will get extremely hot reaching a maximum at about 1400 local time the heating will increase turbulence and that will 'pull' more freestream flow down into the boundary layer thus increasing the surface wind .less surface friction at night means none of the freestream gets 'pulled' down so you will have slower speed at night exemple 246 surface wind speed tends to be highest during the mid afternoon.surface wind speed tends to be highest during the mid afternoon.

From summer to winter the polar front jet stream over the north atlantic moves ?

Question 130-6 : Towards the south and the speed increases towards the north and the speed increases towards the south and the speed decreases towards the north and the speed decreases

exemple 250 towards the south and the speed increases.towards the south and the speed increases.

In relation to the polar front jet stream the greatest rate of wind shear is ?

Question 130-7 : Close to the core on the polar side well below the core on the tropical side of the core 5000 ft or more above the core

.the greatest rate of wind shear is most likely to occur close to the core on the polar side it is in the warm tropical air but on the cold air side of the core exemple 254 close to the core on the polar side.close to the core on the polar side.

In summer in the northern hemisphere the maximum wind speeds associated with ?

Question 130-8 : Below the tropopause at about 200 hpa above the tropopause at about 100 hpa below the tropopause at about 300 hpa above the tropopause at about 250 hpa

.the polar front sub tropical and equatorial jet streams are all just below the tropopause the sub tropical jetstream is at about fl390 in summer 200 hpa the highest wind speed is in the core exemple 258 below the tropopause at about 200 hpa.below the tropopause at about 200 hpa.

Isotachs are lines joining equal ?

Question 130-9 : Wind speeds sea level pressures horizontal wind speed gradients wind speed lapse rates

exemple 262 wind speeds.wind speeds.

Maximum wind speeds associated with subtropical jet streams are usually located ?

Question 130-10 : Tropical air below the tropopause tropical air above the tropopause polar air above the tropopause polar air below the tropopause

.the subtropical jet stream is located around 30°n/s . 590.jet streams vary in height from 20000 ft close to the poles to 40000 ft at 30°n/s and can reach speeds of more than 240 kt . 534.it is in the warm tropical air below the tropopause that the maximum wind speeds can be recorded exemple 266 tropical air below the tropopause.tropical air below the tropopause.

Sea breezes are most likely to occur when ?

Question 130-11 : Slack pressure gradient and clear skies result in relatively high land temperatures a strong pressure gradient relatively high sea temperatures and overcast conditions persist a strong pressure gradient relatively high sea temperatures and clear skies at night exist a slack pressure gradient relatively high sea temperatures and overcast conditions persist

.sea breeze circulations most often occur on warm sunny days during the spring and summer when the temperature of the land is normally higher than the temperature of the water . 601.slack pressure gradient means that we are in an area with light or no wind due to the difference of pressure gradient between an anticyclone or a low exemple 270 slack pressure gradient and clear skies result in relatively high land temperatures.slack pressure gradient and clear skies result in relatively high land temperatures.

The length width and depth of a typical mid latitude jet stream are respectively ?

Question 130-12 : 1000 mn 150 mn 10000 ft 1000 mn 150 mn 30000 ft 1000 mn 5000 to 8000 ft 30000ft 200 mn 5 mn 10000 ft

exemple 274 1000 mn, 150 mn, 10000 ft.1000 mn, 150 mn, 10000 ft.

The most likely place to encounter clear air turbulence associated with a jet ?

Question 130-13 : Close to the core on the side facing the polar air well below the core on the tropical side of the core 5000 feet or more above the core

. 534.the strongest cat is in the warm tropical air but on the cold polar air side of the core exemple 278 close to the core on the side facing the polar air.close to the core on the side facing the polar air.

What surface wind is forecast for 2200 utc .eddf 272200z 280624 vrb05kt 4000 br ?

Question 130-14 : 260°/10 kt variable/05 kt variable/15 to 25 kt calm

.eddf 272200z forecast prepared on the twenty seventh day of the month at 22h00 utc 280624 vrb05kt 4000 br sct005 ovc013 becmg 1314 9000 shra ovc015 prob40 tempo 1416 vrb15g25kt 1600 tsra ovc010cb becmg 1618 26010kt the time period when the change is expected.the gradual change will occur at an unspecified time within this time period the wind will change and remain unchanged until the end of the taf cavok does not change the wind bkn030 becmg 2122 cavok exemple 282 260°/10 kt.260°/10 kt.

What surface wind is forecast for eta 1700 utc at kingston .mkjp 160430z 160606 ?

Question 130-15 : 140° / 20 kt gusts 34 kt 360° / 10 kt 340° / 10 kt 140° / 27 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 140°/20 kt gusts 34 kt 14020g34kt between 13h and 15h it will remain unchanged until 23h .then the wind becoming 340°/10kt between 23h and 01h exemple 286 140° / 20 kt gusts 34 kt.140° / 20 kt gusts 34 kt.

When and where is an easterly jet stream likely to be encountered ?

Question 130-16 : In summer from south east asia extending over southern india to central africa in winter along the russian coast facing the arctic ocean in summer from the middle east extending over the southern part of the mediterranean to southern spain throughout the year to the south of the azorian high

.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 exemple 290 in summer from south-east asia extending over southern india to central africa.in summer from south-east asia extending over southern india to central africa.

When compared to the geostrophic wind in the northern hemisphere surface ?

Question 130-17 : Back and decrease back and increase veer and decrease veer and increase

.at low elevations friction will slow the air and hence the coriolis force will be less effective in its deflection of the wind . 561.as the elevation decreases the direction backs changes direction in an counter clockwise motion in northern hemisphere .at mid latitude over land wind speed in friction layer decrease by 50% angle between wind direction and isobars changes by 30° value to be used in examinations exemple 294 back and decrease.back and decrease.

Which area of a polar front jet stream in the northern hemisphere has the ?

Question 130-18 : Looking downstream the area to the left of the core looking downstream the area to the right of the core in the core of the jet stream above the core in the boundary between warm and cold air

. 534.the jet is always below the tropopause and the strongest turbulence is in the warm tropical air but on the cold polar air side of the core looking downstream the area to the left of the core exemple 298 looking downstream, the area to the left of the core.looking downstream, the area to the left of the core.

Which of the following statements concerning the variation in wind speed ?

Question 130-19 : Is greater in the winter remains the same all along the year almost about zero in winter is greater in the summer

.the polar front jet on the north atlantic moves south and increases speed in the winter then moves north and decreases speed in the summer exemple 302 is greater in the winter.is greater in the winter.

Which of the following types of jet streams can be observed all year round ?

Question 130-20 : Subtropical jet stream and polar front jet stream equatorial jet stream and polar front jet stream arctic jet stream and subtropical jet stream equatorial jet stream and arctic jet stream

. 590.polar front jet stream and subtropical jet stream can be observed all along the year exemple 306 subtropical jet stream and polar front jet stream.subtropical jet stream and polar front jet stream.

Where as a general rule is the core of the polar front jet stream to be found ?

Question 130-21 : In the tropical air mass in the polar air mass just above the warm air tropopause just below the cold air tropopause

. 595. 534.the polar jet stream is always below the tropopause and in the warm tropical air mass exemple 310 in the tropical air mass.in the tropical air mass.

Where is the projection of the polar front jet stream on the surface most ?

Question 130-22 : 50 to 200 nm behind the cold front and 300 to 450 nm ahead of the warm front up to 100 nm either side of the cold front and up to 200 nm either side of the warm front up to 200 nm either side of the cold front and up to 200 nm either side of the warm front 300 to 450 nm behind the cold front and 50 to 200 nm ahead of the warm front

.a cold front has an inclined plane of 1/50 and a warm front an inclined plane of 1/150 the projection of the polar front jet stream on the surface which is most likely to be found in relation to the cold and warm fronts of a depression will be located closer behind the cold front and far behind the warm front exemple 314 50 to 200 nm behind the cold front and 300 to 450 nm ahead of the warm front.50 to 200 nm behind the cold front and 300 to 450 nm ahead of the warm front.

Which statement is correct for the southern hemisphere ?

Question 130-23 : In the friction layer the wind backs with increasing height the jet streams are easterly the wind veers at the passage of a cold front if the wind veers with increasing height then warm air is advected

exemple 318 in the friction layer the wind backs with increasing height.in the friction layer the wind backs with increasing height.

What is the best approximation for the wind speed at flight level 250 ?

Question 130-24 : By interpolation of the wind information available from the 500 and 300 hpa charts while also considering the maximum wind information found on the significant weather chart by simple interpolation of wind information available from the 500 and 300 hpa charts by reading wind direction and speed from the 300 hpa chart by reading wind direction and speed from the 500 hpa chart

exemple 322 by interpolation of the wind information available from the 500 and 300 hpa charts, while also considering the maximum wind information found on the significant weather chart.by interpolation of the wind information available from the 500 and 300 hpa charts, while also considering the maximum wind information found on the significant weather chart.

What is the average wind forecast for fl 300 between edinburgh and madrid . 340 ?

Question 130-25 : 280°/30kt 300°/45kt 240°/25kt 180°/20kt

.from edinburgh to madrid .above england almost no wind .over the manche wind from 280° for 30 kt .above atlantique wind from 280° for 45 to 50 kt .above spain wind from 280° for 35 kt.average forecast wind 280°/30kt exemple 326 280°/30kt.280°/30kt.

At 40°n 20°w the forecast wind at fl 390 is . 345 ?

Question 130-26 : 090°/45 kt 060°/45 kt 070°/30 kt 270°/45 kt

. 617.pennants correspond to 50 kt .feathers correspond to 10 kt .half feathers correspond to 5 kt.4 feathers + 1 half feather = 45 kt exemple 330 090°/45 kt.090°/45 kt.

What characteristics will the surface winds have in an area where the isobars ?

Question 130-27 : Strong and flowing somewhat across the isobars very weak but gusty and flowing somewhat across the isobars strong and flowing parallel to the isobars moderate and flowing parallel to the isobars

.when the isobars are close together the pressure gradient force is greater and wind velocities are stronger .the wind will be parallel to the isobars but surface friction will make the wind direction change to flow at an angle to the isobars exemple 334 strong and flowing somewhat across the isobars.strong and flowing somewhat across the isobars.

What is necessary for the development of a polar front jet stream ?

Question 130-28 : Strong horizontal temperature gradients strong vertical temperature gradients a uniform pressure pattern an unstable atmosphere up to great heights

.the horizontal temperature gradient is essential for the formation of the thermal wind exemple 338 strong horizontal temperature gradients.strong horizontal temperature gradients.

The average forecast wind for the leg from madrid to dhahran at fl 390 is . 361 ?

Question 130-29 : 270/50 270/30 320/70 310/50

. 625. 45 + 40 + 30 + 45 + 40 + 45 + 50 + 50 + 50 + 65 + 65 + 45 / 12 = 47 5 kt exemple 342 270/50.270/50.

In the mid latitudes of the northern hemisphere the wind blows ?

Question 130-30 : Clockwise around anticyclones and anti clockwise around cyclones clockwise around anticyclones and cyclones clockwise around cyclones and anti clockwise around anticyclones direct from high to low pressure areas

exemple 346 clockwise around anticyclones and anti-clockwise around cyclones.clockwise around anticyclones and anti-clockwise around cyclones.

In the northern hemisphere with an anticyclonic pressure system the geostrophic ?

Question 130-31 : 050°/10 kt 060°/10 kt 060°/20 kt 070°/20 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°.the wind blows parallel to the isobars and in the northern hemisphere the surface wind will back and slowdown compared to it exemple 350 050°/10 kt.050°/10 kt.

At which height and at what time of the year can an aircraft be affected by the ?

Question 130-32 : Fl 500 from june to august fl 500 from november to february fl 400 during the winter in the northern hemisphere fl 400 during the winter in the southern hemisphere

.the equatorial jet is located between 5° and 15°n it is a seasonal zonal wind.it is generated by the high thermal gradients and barometrics between equator and asia and by the latent heat released above the indian sub continent humid monsoon begins in june.it is located around an axis tibet senegal in summer.the tropopause is lower and warmer above the poles and higher and colder at the equator equatorial tropopause is around 14 to 16 km in summer .the equatorial jet is located just below the equatorial tropopause exemple 354 fl 500 from june to august.fl 500 from june to august.

According to the extract of the surface isobar map the surface wind direction ?

Question 130-33 : 140° 310° 220° 110°

. 463.in the northern hemisphere if you stand with your back to the wind low pressure is on your left buys ballot's law.we are in southern hemispere situtation is reversed .if you stand with your back to the wind low pressure is on your right so the wind blows parallel to the isobars from 130° .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° so answer is 140° exemple 358 140°.140°.

In appendix are shown four sections of the 700 hpa wind chart the diagram ?

Question 130-34 : 030°/30 kt diagram a 210°/30 kt diagram b 030°/30 kt diagram c 210°/30 kt diagram d

.if you stand with your back to the wind in the northern hemisphere low pressure is on your left buys ballot's law .in the southern hemisphere if you stand with your back to the wind low pressure is on your right as in diagrams a and c.on upper wind charts the 'feathers' on the wind arrows are on the low pressure/low isohypse side of the arrow which is only correctly shown in diagram a exemple 362 030°/30 kt (diagram a).030°/30 kt (diagram a).

At fl 300 between geneva and tunis what mean wind would be most likely . 367 ?

Question 130-35 : 245°/50 kt 225°/25 kt 265°/40 kt 265°/25 kt

. 630.wind direction is from 230+240+250+260 /4 = 245° .wind speed is 60+35+45+55 /4 = 48 75 kt exemple 366 245°/50 kt.245°/50 kt.

The mean wind that may be expected to affect the route segment from the coast ?

Question 130-36 : 220/70kt 245/55kt 240/90kt 270/70kt

.be careful we are looking at the wind only for the part from the coast of se england to geneva not from dublin to tunis.over manche at fl240 wind is 200°/55 kt .before geneva at fl240 wind is 220°/55 kt .over manche at fl300 wind is 230°/80 kt .before geneva at fl300 wind is 240°/80 kt.whitout calculation answer 220/70 seems to be the mean wind at fl270 exemple 370 220/70kt.220/70kt.

Judging by the chart what wind speeds can you expect at fl 310 above london . ?

Question 130-37 : 90 kt 300 kt 140 kt 110 km/h

. 632.a jet stream is passing right above london at fl310.pennants correspond to 50 kt .feathers correspond to 10 kt .half feathers correspond to 5 kt.1 pennant + 4 feathers = 90 kt exemple 374 90 kt.90 kt.

When in the northern hemisphere at the same latitude the distance between ?

Question 130-38 : The gradient wind in a low pressure area is weaker than in a high pressure area the geostrophic wind speed is less than the gradient wind speed in a low pressure area the coriolis force in a high pressure area is smaller than the gradient force in a high pressure area the wind around a low pressure area is stronger than around a high pressure area

Pressure gradient is the difference in pressure between high and low pressure areas wind speed is directly proportional to the pressure gradient this means the strongest winds are in the areas where the pressure gradient is the greatest . the stronger the pressure gradient the more tightly packed the isobars are the stronger the wind speed exemple 378 the gradient wind in a low pressure area is weaker than in a high pressure area.the gradient wind in a low pressure area is weaker than in a high pressure area.

Which of the following statements is correct concerning the geostrophic wind ?

Question 130-39 : It is present at latitudes higher than about 15 degrees north/south it is present in a pressure system consisting of curved and non parallel isobars a horizontal temperature difference of at least 5 degrees celsius per 100 km is required to have geostrophic wind conditions it is only present in the friction layer

.to have a geostrophic wind we need to have a pressure gradient force and coriolis force create by earth's rotation and depending on geographic latitude.we need to have two differents air mass to have a pressure gradient force pgf . 564.since the earth rotates objects that are above the earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion is caused by the coriolis force .in the northern hemisphere objects will be deflected to their right while in the southern hemisphere objects will be deflected to their left .the magnitude of the deflection is also a function of distance from the equator and velocity so the farther from the equator the object is the greater the deflection and the faster an object is moving the greater the deflection .these 'objects' can be anything from airplanes to birds to missiles to parcels of air . 565.the effect of the coriolis force for various latitudes . 566.we can see that coriolis force is maximum at high latitudes and minimum at the equator .thus the geostrophic wind is present at latitudes higher than about 15° north/south exemple 382 it is present at latitudes higher than about 15 degrees north/south.it is present at latitudes higher than about 15 degrees north/south.

What is the significance to aviation of breaks or steps in the tropopause ?

Question 130-40 : They indicate the position of strong upper winds they indicate the position and movement of anticyclones they indicate the position and movement of tropical revolving storms they indicate light winds at the surface the 'horse latitudes'

The 'breaks' or 'steps' in the tropopause are at the polar front and at the boundary between tropical and sub tropical air which is where the polar front and sub tropical jet streams are located . 595.this is the position of strong upper winds exemple 386 they indicate the position of strong upper winds.they indicate the position of strong upper winds.

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