A wind of 20 knots corresponds to an approximate speed of ?
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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 ?
At about what geographical latitude as average is assumed for the zone of prevailing westerlies ?
At which time if any are polar front jet streams over south pacific usually strongest A sudden strong increase in wind speed strong veering of wind a short time after take off. strongest polar front jet streams are in winter in south pacific (southern hemisphere) winter in july. 
During periods of undisturbed radiation weather overland Surface wind speed tends to be highest during mid afternoon. with undistubed radiation weather ground will get extremely hot (reaching a maximum at about 1400 local time) the heating will increase turbulence that will 'pul more freestream flow down into boundary layer thus increasing surface wind less surface friction at night means none of freestream gets 'pulle down so you will have slower speed at night. 
From summer to winter polar front jet stream over north atlantic moves Towards south the speed increases. with undistubed radiation weather ground will get extremely hot (reaching a maximum at about 1400 local time) the heating will increase turbulence that will 'pul more freestream flow down into boundary layer thus increasing surface wind less surface friction at night means none of freestream gets 'pulle down so you will have slower speed at night. 
In relation to polar front jet stream greatest rate of wind shear most likely to occur Close to core on polar side. the greatest rate of wind shear most likely to occur close to core on polar side it in warm (tropical) air but on cold air side of core. Question 130-8
In summer in northern hemisphere maximum wind speeds associated with sub tropical jet streams are usually located Below tropopause at about 2 hpa. the polar front sub tropical equatorial jet streams are all just below tropopause the sub tropical jetstream at about fl390 in summer (200 hpa) the highest wind speed in core. Question 130-9
Isotachs are lines joining equal Below tropopause at about 2 hpa. the polar front sub tropical equatorial jet streams are all just below tropopause the sub tropical jetstream at about fl390 in summer (200 hpa) the highest wind speed in core. Question 130-10
Maximum wind speeds associated with subtropical jet streams are usually located in Tropical air below tropopause. the subtropical jet stream located around 30°n/s jet streams vary in height from 20000 ft (close to poles) to 40000 ft (at 30°n/s) can reach speeds of more than 240 kt it in warm tropical air below tropopause that maximum wind speeds can be recorded. Question 130-11
Sea breezes are most likely to occur when Slack pressure gradient clear skies result in relatively high land temperatures. sea breeze circulations most often occur on warm sunny days during spring summer when temperature of land normally higher than temperature of water slack pressure gradient means that we are in an area with light or no wind (due to difference of pressure gradient between an anticyclone or a low). Question 130-12
The length width and depth of a typical mid latitude jet stream are respectively mn 5 mn ft. sea breeze circulations most often occur on warm sunny days during spring summer when temperature of land normally higher than temperature of water slack pressure gradient means that we are in an area with light or no wind (due to difference of pressure gradient between an anticyclone or a low). Question 130-13
The most likely place to encounter clear air turbulence associated with a jet stream Close to core on side facing polar air. the strongest cat in warm tropical air but on cold polar air side of core. Question 130-14
What surface wind forecast 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 Close to core on side facing polar air. eddf 272200z forecast prepared on twenty seventh day of 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 change expected the gradual change will occur at an unspecified time within this time period the wind will change remain unchanged until end of taf (cavok does not change wind) bkn030 becmg 2122 cavok. Question 130-15
What surface wind forecast 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= 4 ° / 2 kt gusts 34 kt. becmg (becoming) indicates a change to forecast conditions expected to occur slowly within period designated in time group immediately following heading the duration of this change normally about 2 hours the elements included in becmg line will supercede some of previous taf groups but it possible all groups may change any group omitted in becmg line will be same during becmg period as indicated in main taf line in this question wind becoming 140°/20 kt gusts 34 kt (14020g34kt) between 13h 15h it will remain unchanged until 23h then wind becoming 340°/10kt between 23h 01h. Question 130-16
When and where 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 northern summer between 10°n 20°n chiefly over or just to south of high land masses such as in asia africa its occurrence due to a temperature gradient with colder air to south which produces sufficient temperature differential above 45000 ft to give wind speeds of over 100 kt because colder temperatures at height are to south it an easterly jet this jet now more usually known as tropical easterly jet perhaps more correctly as it lies some distance from equator . Question 130-17
When compared to geostrophic wind in northern hemisphere surface friction will cause surface wind to In summer from south east asia extending over southern india to central africa. at low elevations friction will slow air hence coriolis force will be less effective in its deflection of wind as elevation decreases direction backs (changes direction in an counter clockwise motion) in northern hemisphere at mid latitude over land wind speed in friction layer decrease 50% angle between wind direction isobars changes 30° (value to be used in examinations). Question 130-18
Which area of a polar front jet stream in northern hemisphere has highest probability of turbulence Looking downstream area to left of core. the jet always below tropopause the strongest turbulence in warm tropical air but on cold polar air side of core (looking downstream area to left of core). Question 130-19
Which of following statements concerning variation in wind speed between summer and winter on north atlantic between fl 300 and fl 400 most correct the average westerly component Is greater in winter. the polar front jet on north atlantic moves south increases speed in winter then moves north decreases speed in summer. Question 130-20
Which of following types of jet streams can be observed all year round Subtropical jet stream polar front jet stream. polar front jet stream subtropical jet stream can be observed all along year. Question 130-21
Where as a general rule the core of polar front jet stream to be found In tropical air mass. the polar jet stream always below tropopause in warm tropical air mass. Question 130-22
Where the projection of polar front jet stream on surface most likely to be found in relation to cold and warm fronts of a depression 5 to 2 nm behind cold front 3 to 45 nm ahead of warm front. a cold front has an inclined plane of 1/50 a warm front an inclined plane of 1/150 the projection of polar front jet stream on surface which most likely to be found in relation to cold warm fronts of a depression will be located closer behind cold front far behind warm front. Question 130-23
Which statement correct the southern hemisphere In friction layer wind backs with increasing height. a cold front has an inclined plane of 1/50 a warm front an inclined plane of 1/150 the projection of polar front jet stream on surface which most likely to be found in relation to cold warm fronts of a depression will be located closer behind cold front far behind warm front. Question 130-24
What the best approximation the wind speed at flight level 250 By interpolation of wind information available from 5 3 hpa charts while also considering maximum wind information found on significant weather chart. a cold front has an inclined plane of 1/50 a warm front an inclined plane of 1/150 the projection of polar front jet stream on surface which most likely to be found in relation to cold warm fronts of a depression will be located closer behind cold front far behind warm front. Question 130-25
What the average wind forecast fl 300 between edinburgh and madrid 340 By interpolation of wind information available from 5 3 hpa charts while also considering maximum wind information found on significant weather chart. from edinburgh to madrid above england almost no wind over manche wind from 280° 30 kt above atlantique wind from 280° 45 to 50 kt above spain wind from 280° 35 kt average forecast wind 280°/30kt. Question 130-26
At 40°n 20°w forecast wind at fl 390 345 By interpolation of wind information available from 5 3 hpa charts while also considering maximum wind information found on significant weather chart. pennants correspond to 50 kt feathers correspond to 10 kt half feathers correspond to 5 kt 4 feathers + 1 half feather = 45 kt. Question 130-27
What characteristics will surface winds have in an area where isobars on weather map are very close together Strong flowing somewhat across isobars. when isobars are close together pressure gradient force greater wind velocities are stronger the wind will be parallel to isobars but surface friction will make wind direction change to flow at an angle to isobars. Question 130-28
What necessary the development of a polar front jet stream Strong horizontal temperature gradients. the horizontal temperature gradient essential the formation of thermal wind. Question 130-29
The average forecast wind the leg from madrid to dhahran at fl 390 361 Strong horizontal temperature gradients. (45 + 40 + 30 + 45 + 40 + 45 + 50 + 50 + 50 + 65 + 65 + 45) / 12 = 47 5 kt. Question 130-30
In mid latitudes of northern hemisphere wind blows Clockwise around anticyclones anti clockwise around cyclones. (45 + 40 + 30 + 45 + 40 + 45 + 50 + 50 + 50 + 65 + 65 + 45) / 12 = 47 5 kt. Question 130-31
In northern hemisphere with an anticyclonic pressure system geostrophic wind at 2000 ft over sea 060°/15kt at same position surface wind most likely to be Clockwise around anticyclones anti clockwise around cyclones. values to be used in examinations over sea wind speed in friction layer decrease 30% wind in friction layer blows across isobars towards low pressure angle between wind direction isobars changes 10° over land wind speed in friction layer decrease 50% wind in friction layer blows across isobars towards low pressure angle between wind direction isobars changes 30° the wind blows parallel to isobars in northern hemisphere surface wind will back slowdown compared to it. Question 130-32
At which height and at what time of year can an aircraft be affected the equatorial jet stream Fl 5 from june to august. the equatorial jet located between 5° 15°n it a seasonal zonal wind it generated the high thermal gradients barometrics between equator asia by latent heat released above indian sub continent (humid monsoon begins in june) it located around an axis tibet senegal in summer the tropopause lower warmer above poles higher colder at equator equatorial tropopause around 14 to 16 km in summer the equatorial jet located just below equatorial tropopause. Question 130-33
According to extract of surface isobar map surface wind direction over sea approximately 365 Fl 5 from june to august. in northern hemisphere if you stand with your back to wind low pressure on your left (buys ballot's law) we are in southern hemispere situtation reversed if you stand with your back to wind low pressure on your right so wind blows parallel to isobars from 130° over sea wind speed in friction layer decrease 30% wind in friction layer blows across isobars towards low pressure angle between wind direction isobars changes 10° so answer 140°. Question 130-34
In appendix are shown four sections of 700 hpa wind chart the diagram representing most accurately wind direction and speed 366 3 °/3 kt (diagram a). if you stand with your back to wind in northern hemisphere low pressure on your left (buys ballot's law) in southern hemisphere if you stand with your back to wind low pressure on your right as in diagrams a c on upper wind charts 'feather on wind arrows are on low pressure/low isohypse side of arrow which only correctly shown in diagram a. Question 130-35
At fl 300 between geneva and tunis what mean wind would be most likely 367 3 °/3 kt (diagram a). wind direction from (230+240+250+260)/4 = 245° wind speed is (60+35+45+55)/4 = 48 75 kt. Question 130-36
The mean wind that may be expected to affect route segment from coast of se england to geneva at fl 270 367 3 °/3 kt (diagram a). be careful ! we are looking at wind only the part from 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 mean wind at fl270. Question 130-37
Judging the chart what wind speeds can you expect at fl 310 above london 372 3 °/3 kt (diagram a). a jet stream 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. Question 130-38
When in northern hemisphere at same latitude distance between isobars equal then The gradient wind in a low pressure area weaker than in a high pressure area. Pressure gradient the difference in pressure between high low pressure areas wind speed directly proportional to pressure gradient this means strongest winds are in areas where pressure gradient the greatest the stronger pressure gradient (the more tightly packed isobars are) stronger wind speed. Question 130-39
Which of following statements correct concerning geostrophic wind It present at latitudes higher than about 5 degrees north/south. to have a geostrophic wind we need to have a pressure gradient force coriolis force (create earth's rotation depending on geographic latitude) we need to have two differents air mass to have a pressure gradient force (pgf) since earth rotates objects that are above earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion caused the coriolis force in northern hemisphere objects will be deflected to their right while in southern hemisphere objects will be deflected to their left the magnitude of deflection also a function of distance from equator velocity so farther from equator object is greater deflection the faster an object moving greater deflection these 'object can be anything from airplanes to birds to missiles to parcels of air the effect of coriolis force various latitudes we can see that coriolis force maximum at high latitudes minimum at equator thus geostrophic wind present at latitudes higher than about 15° north/south. Question 130-40
What the significance to aviation of breaks or steps in tropopause They indicate position of strong upper winds. The 'break or 'step in tropopause are at polar front at boundary between tropical sub tropical air which where polar front sub tropical jet streams are located this the position of strong upper winds.
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