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Question 144-1 : Above and below a low level inversion the wind is likely to ? [ Certification weather ]

Change significantly in speed and direction

Admin .a low level inversion means that a temperature inversion forms near the surface the airstream flowing over ground or water produces a turbulent layer the friction layer up to 500 feet deep in light winds or 3000 feet plus in strong winds .the wind above the inversion often increases because it is insulated from the frictional influence of the surface . 574.above and below a low level inversion the wind is likely to change significantly in speed and direction exemple 244 Change significantly in speed and direction.

Question 144-2 : Which of the following statements concerning the core of a polar front jet stream is correct ?

It lies at a height where there is no horizontal temperature gradient the slope of the pressure surfaces at the height of the core is at its maximum

. 637.the polar front jet core is in the warm air but above the cold air tropopause at a point where the temperature in the warm air troposphere is the same as the cold air stratosphere if the cold tropopause is 40°c then above that point in the cold sector the temperature is constant in the warm air at the same level as the cold tropopause the temperature will be warmer say 34°c but will decrease with altitude .at the point where the temperature in the warm air is the same as the 40°c in the cold air stratosphere you will find the strongest wind speed exemple 248 It lies at a height where there is no horizontal temperature gradient, the slope of the pressure surfaces at the height of the core is at its maximum.

Question 144-3 : On a particular day part of a polar front jet stream runs from north to south in the northern hemisphere this means that ?

The polar air is below and to the east of the core of the jet

Admin .normaly the polar front jet stream runs from west to east and it will be found in the warm air of the ferrel cell sub tropical air mass . 575.now let's assume the direction is north to south polar front jet remains in warm air above the cold air .the polar air remains below and to the east of the core of the jet exemple 252 The polar air is below and to the east of the core of the jet.

Question 144-4 : For a similar pressure gradient the geostrophic wind speed will be ?

Greater at 30°n than at 60°n

Admin .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 .we can deduce that for a similar pressure gradient the geostrophic wind speed will be greater at 30°n than at 60°n exemple 256 Greater at 30°n than at 60°n.

Question 144-5 : For the same pressure gradient at 60°n 50°n and 40°n the speed of the geostrophic wind will be ?

Greatest at 40°n

Admin .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 .we can deduce that for a similar pressure gradient the geostrophic wind speed will be greater at 40°n than at 50°n or 60°n exemple 260 Greatest at 40°n.

Question 144-6 : Under anticyclone conditions in the northern hemisphere with curved isobars the speed of the gradient wind is ?

Greater than the geostrophic wind

Admin .we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels .if the isobars are curved an additional force centrifugal force is introduced and always tries to throw the parcel of air outwards from the centre of its rotation and the resulting movement of air is called the gradient wind . 583.with an area of high pressure anticyclone the centrifugal force is acting in the same direction as pgf effectively increasing it coriolis balances the total force pgf + centrifugal force and the gradient wind is 'high round a high' i e for a given gap between the isobars the gradient wind is stronger than the geostrophic wind .with an area of low pressure cyclonic system the centrifugal force is opposing the pgf effectively decreasing it coriolis balances the total force pgf centrifugal force and the gradient wind is 'low round a low' i e for a given gap between the isobars the gradient wind is weaker than the geostrophic wind exemple 264 Greater than the geostrophic wind.

Question 144-7 : Considering that portion of the route indicated from 30°e to 50°e the upper winds in january above fl 300 are most likely to be . 321 ?

A subtropical westerly jet stream maximum speed exceeding 90 kt

Admin . 589.the subtropical jet stream is located around 30°n jet streams vary in height of 20000 ft to 40000 ft and can reach speeds of more than 240 kt . 590 exemple 268 A subtropical westerly jet stream, maximum speed exceeding 90 kt.

Question 144-8 : The core of the polar front jet stream is usually located in the ?

Tropical air below the tropopause

Admin . 595 exemple 272 Tropical air below the tropopause.

Question 144-9 : A wind of 20 knots corresponds to an approximate speed of ?

10 m/s

Admin .1 kt equal around 0 5 m/s exemple 276 10 m/s.

Question 144-10 : After a sunny day followed by a long clear night you take off from an airfield at mid latitudes an hour before sunrise the field is not situated close to the coast .though the pressure gradient is rather large the easterly surface wind is weak and makes ?

A sudden strong increase in wind speed and strong veering of the wind a short time after take off

Admin .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 280 A sudden strong increase in wind speed and strong veering of the wind a short time after take-off.

Question 144-11 : At about what geographical latitude as average is assumed for the zone of prevailing westerlies ?

50°n

Admin . 596.westerlies average latitude is 50°n and 50°s for south hemisphere exemple 284 50°n.

Question 144-12 : At which time if any are polar front jet streams over the south pacific usually strongest ?

July

.strongest polar front jet streams are in the winter and in south pacific southern hemisphere winter is in july exemple 288 July.

Question 144-13 : During periods of undisturbed radiation weather overland the ?

Surface wind speed tends to be highest during the mid afternoon

Admin .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 292 Surface wind speed tends to be highest during the mid afternoon.

Question 144-14 : From summer to winter the polar front jet stream over the north atlantic moves ?

Towards the south and the speed increases

exemple 296 Towards the south and the speed increases.

Question 144-15 : In relation to the polar front jet stream the greatest rate of wind shear is most likely to occur ?

Close to the core on the polar side

Admin .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 300 Close to the core on the polar side.

Question 144-16 : In summer in the northern hemisphere the maximum wind speeds associated with sub tropical jet streams are usually located ?

Below the tropopause at about 200 hpa

Admin .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 304 Below the tropopause at about 200 hpa.

Question 144-17 : Isotachs are lines joining equal ?

Wind speeds

exemple 308 Wind speeds.

Question 144-18 : Maximum wind speeds associated with subtropical jet streams are usually located in the ?

Tropical 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 312 Tropical air below the tropopause.

Question 144-19 : Sea breezes are most likely to occur when ?

Slack pressure gradient and clear skies result in relatively high land temperatures

Admin .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 316 Slack pressure gradient and clear skies result in relatively high land temperatures.

Question 144-20 : The length width and depth of a typical mid latitude jet stream are respectively ?

1000 mn 150 mn 10000 ft

exemple 320 1000 mn, 150 mn, 10000 ft.

Question 144-21 : The most likely place to encounter clear air turbulence associated with a jet stream is ?

Close to the core on the side facing the polar air

. 534.the strongest cat is in the warm tropical air but on the cold polar air side of the core exemple 324 Close to the core on the side facing the polar air.

Question 144-22 : What surface wind is forecast for 2200 utc .eddf 272200z 280624 vrb05kt 4000 br sct005 ovc013 becmg 1314 9000 shra ovc015 prob40 tempo 1416 vrb15g25kt 1600 tsra ovc010cb becmg 1618 26010kt bkn030 becmg 2122 cavok ?

260°/10 kt

Admin .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 328 260°/10 kt.

Question 144-23 : What surface wind is forecast for eta 1700 utc at kingston .mkjp 160430z 160606 36010kt 9999 few025cb becmg1315 14020g34kt few015cb sct025 prob30 tempo 1720 6000 +shra sct010 bkn015cb becmg 2301 34010kt few025= ?

140° / 20 kt gusts 34 kt

Admin .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 332 140° / 20 kt gusts 34 kt.

Question 144-24 : When and where is an easterly jet stream likely to be encountered ?

In summer from south east asia extending over southern india to central africa

.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 336 In summer from south-east asia extending over southern india to central africa.

Question 144-25 : When compared to the geostrophic wind in the northern hemisphere surface friction will cause the surface wind to ?

Back and decrease

Admin .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 340 Back and decrease.

Question 144-26 : Which area of a polar front jet stream in the northern hemisphere has the highest probability of turbulence ?

Looking downstream the area to the left of the core

. 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 344 Looking downstream, the area to the left of the core.

Question 144-27 : Which of the following statements concerning the variation in wind speed between summer and winter on the north atlantic between fl 300 and fl 400 is most correct .the average westerly component ?

Is greater in the winter

Admin .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 348 Is greater in the winter.

Question 144-28 : Which of the following types of jet streams can be observed all year round ?

Subtropical jet stream and polar front jet stream

. 590.polar front jet stream and subtropical jet stream can be observed all along the year exemple 352 Subtropical jet stream and polar front jet stream.

Question 144-29 : Where as a general rule is the core of the polar front jet stream to be found ?

In the tropical air mass

Admin . 595. 534.the polar jet stream is always below the tropopause and in the warm tropical air mass exemple 356 In the tropical air mass.

Question 144-30 : Where is the projection of the polar front jet stream on the surface most likely to be found in relation to the cold and warm fronts of a depression ?

50 to 200 nm behind the cold front and 300 to 450 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 360 50 to 200 nm behind the cold front and 300 to 450 nm ahead of the warm front.

Question 144-31 : Which statement is correct for the southern hemisphere ?

In the friction layer the wind backs with increasing height

exemple 364 In the friction layer the wind backs with increasing height.

Question 144-32 : What is the best approximation for the wind speed at flight level 250 ?

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

exemple 368 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.

Question 144-33 : What is the average wind forecast for fl 300 between edinburgh and madrid . 340 ?

280°/30kt

Admin .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 372 280°/30kt.

Question 144-34 : At 40°n 20°w the forecast wind at fl 390 is . 345 ?

090°/45 kt

Admin . 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 376 090°/45 kt.

Question 144-35 : What characteristics will the surface winds have in an area where the isobars on the weather map are very close together ?

Strong and flowing somewhat across the isobars

Admin .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 380 Strong and flowing somewhat across the isobars.

Question 144-36 : What is necessary for the development of a polar front jet stream ?

Strong horizontal temperature gradients

Admin .the horizontal temperature gradient is essential for the formation of the thermal wind exemple 384 Strong horizontal temperature gradients.

Question 144-37 : The average forecast wind for the leg from madrid to dhahran at fl 390 is . 361 ?

270/50

Admin . 625. 45 + 40 + 30 + 45 + 40 + 45 + 50 + 50 + 50 + 65 + 65 + 45 / 12 = 47 5 kt exemple 388 270/50.

Question 144-38 : In the mid latitudes of the northern hemisphere the wind blows ?

Clockwise around anticyclones and anti clockwise around cyclones

exemple 392 Clockwise around anticyclones and anti-clockwise around cyclones.

Question 144-39 : In the northern hemisphere with an anticyclonic pressure system the geostrophic wind at 2000 ft over the sea is 060°/15kt .at the same position the surface wind is most likely to be ?

050°/10 kt

Admin . 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 396 050°/10 kt.

Question 144-40 : At which height and at what time of the year can an aircraft be affected by the equatorial jet stream ?

Fl 500 from june to august

Admin .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 400 Fl 500 from june to august.


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