Dgca question bank for pilots

the mass of air descending from the cloud is significant enough, a phenomenon known as a microburst

Tropical Continental

Source: N Africa, SE Europe and the Balkans. Mainly summer, warm, dry, stable.

As over the North Atlantic, icing occurs widely and through great depth in Frontal Cloud and is frequently moderate to severe. Freezing Rain (Rain Ice) can cause severe clear ice in cold air under a warm front or warm occlusion. A rare occurrence in UK, it is more common over Central Europe where the ground is generally much colder, indeed the freezing level may frequently be on the surface especially in the East.

Looking at the above plan view you can see a typical polar front depression on the polar front. Notice the intrusion of the tropical maritime air creating the characteristic wedge shape which we call the warm sector. To the right of the warm sector, you can see the warm front. This part of the polar front is marked with red semicircles to signify that warm air is overriding and replacing cold air. To the left of the warm sector you can see the cold front. This part of the polar front is marked with blue triangles to signify that cold air is undercutting and replacing warm.

These depressions are called the Polar Front Depressions or Warm Sector Depressions and they move west to east along the polar front with the general westerly upper winds, reaching NW Europe from the Atlantic Ocean

Icelandic low, large persistent atmospheric low-pressure centre that forms between Iceland-and southern Greenland. It often causes strong winter winds over the North Atlantic Ocean. In winter the ocean is considerably warmer than the continents, and this difference is responsible for the location of the Icelandic low, which dominates the wind circulation over the North Atlantic

The Intertropical Convergence Zone is the broad zone of separation between the air masses either side of the heat equator. The air is conveyed by the Trade Winds north east and south east. Subject to large seasonal movement overland, but much less over the sea. Sometimes known as the Thermal Equator or Equatorial Trough.

the air behind the cold front is colder than the air ahead of the warm front, then a cold type occlusion will be formed. This type of occlusion is more common in summer.

Glaze ice or clear ice is formed when LARGE supercooled drops spread over wings

rime ice is formed WHEN SMALL supercooled drops spread over wings

both happen under 0° Celsius flying through clouds

large supercool water sustain only between 0 to -20 degree

owest forecast QNH  provided by the Met. Office, is used to ensure safe terrain clearance. It is the value below which QNH is forecast not to fall in a given period and area.

The value should be lower than the actual QNH anywhere in the area, and if set on the sub-scale, regional QNH will cause the altimeter to under-read

(the altimeter showing aircraft to be lower than it actually is).

TRS are given different names in different parts of the world. Either side of North America these storms are called Hurricanes. In the Indian Ocean and around Australia they are called Cyclones and around the far east, they called Typhoons. Typhoons are the most violent and have the longest season of any TRS.

Indian Ocean touches Somalia

Nimbostratus is a dense, dark-grey, rain-bearing, stratiform cloud, producing extensive and long-lasting continuous precipitation. Usually the cloud base is between the surface and 10,000ft above ground level.

Since temperature decreases with height it goes to follow that the temperature at the tropopause is controlled by its height. The higher it is, the colder the temperature at the tropopause. The lower it is, the warmer the temperature at the tropopause. The temperature at the tropopause can be as high as -40°C over the poles and as low as -80°C over the equator. However, on average the tropopause is at about 11 km where its temperature is -56.5°C.

Freezing rain occurs when the layer of freezing air is so thin that the raindrops do not have enough time to freeze before reaching the ground. Instead, the water freezes on contact with the surface, creating a coating of ice on whatever the raindrops contact.

Polar front depressions are found along the polar front which lies principally in the higher latitudes at about 40º to 60°, North and South, depending upon the season. You can see these two bands of low pressure in near the top and bottom of the globe. The depressions typically move from West to East across the Earth’s surface, and the process of their formation is complex.

in the diagram above low pressure in Mediterranean gives bora winds in Central Europe
Bora wind are part valley and part katabatic. It blows down the north Adriatic with high pressure over Central Europe and the Balkans and a low over the Adriatic. The wind speed is around 70 kts with great gusts exceeding 100 kts in places. The Bora is strongest and most frequent in winter.

examples of warm Katabatic winds are the Föhn, Chinook, Bergwind and Diablo.

If the RH is less than 100% then the air is considered to be dry

The dew point or dewpoint of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for the water vapour component to condense into water.

A high relative humidity indicates that the dew point is closer to the current air temperature. If the relative humidity is 100%, the dew point will be equal to the current temperature. The dew point can never be more than the ambient temperature.

If the RH is less than 100% then the air is considered to be dry hence dry air will have the greatest difference

Cumulonimbus clouds are clouds that the aviator should avoid. Cumulonimbus clouds consist of vigorous convective cloud cells of great vertical extent. In the later stages of their development, cumulonimbus clouds display a characteristic anvil top, as the upper part of the cloud hits the Tropopause. The upper parts of a cumulonimbus cloud often consist of super-cooled water droplets and ice crystals. The base of cumulonimbus clouds is often very dark, with ragged cloud appearing beneath the main cloud cell. Usually the cloud base is between 2,000 ft and 5,000 ft.

A= closely packed iso bars indicate low pressure

B= Widely spaced isobars indicate high pressure

flying from low to high pressure true altitude will increase

EMBD for close cb

ISOL for isolated cb

the air behind the cold front is colder than the air ahead of the warm front, then a cold type occlusion will be formed. This type of occlusion is more common in summer.

TS – means thunderstorm

W – means coming from west

Athenia- (it means meant for athens)

MOV E- means moving east

depression means low pressure system like cyclone or thunderstorm

relates to high wind, rain, snow

This amount of space in the air that can hold water changes depending on the temperature and pressure.

The maximum amount of water vapour that can be in the air depends on the air temperature

If the sky at an aerodrome is obscured for reasons other than cloud cover, and cloud coverage cannot easily be determined, the code VV is used in place of the cloud information. VV is followed by the vertical visibility in hundreds of feet

The height above aerodrome level of the lowest layer of cloud of more than 4 oktas”

upper level divergence means lower level convergence , hence low pressure system

Air is stable whenever the ELR is less than 0.6°C/100m.

In inversion ELR is less than 0.6°C/100m.as temp increases with height

Air is stable whenever the ELR is less than 0.6°C/100m.

In isotherm lapse rate is 0 as temp remains same

When temperature and dew point are same saturation occurs and fog formation takes place

subsidence occurs in high pressure

1. Inversion is also called negative lapse rate

Where the temperature increases with an increase in height, then we have what is called an inversion. We have already seen that at night we can expect an inversion above the surface, but this can occur in many different ways.

Vertical windshear is change in  horizontal wind velocity with height. It is typically measured in knots per 100ft.

Horizontal windshear is change in wind velocity with horizontal distance and is common with the passage of fronts

The pampero is a burst of cold polar air from the west, southwest, or south on the pampas in the south of Brazil, Argentina, Uruguay, Paraguay and Bolivia

in winters aircraft flying to the west from bombay will experience western disturbance , headwind

in summer you will experience tropical easterly jet stream

celandic low, large persistent atmospheric low-pressure centre that forms between Iceland-and southern Greenland. It often causes strong winter winds over the North Atlantic Ocean. In winter the ocean is considerably warmer than the continents, and this difference is responsible for the location of the Icelandic low, which dominates the wind circulation over the North Atlantic

o know the temperature of the air you need to know two things, the indicated altitude on QNH and the true altitude. You know this because if it’s warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED.

In the question then, whilst you have the true altitude they have not given you the indicated on QNH. They have given you a flight level which you can use to work out the indicated on QNH. So, get off the flight level 1013 and onto 1003.

You now see that the INDICATED on QNH is 9730 FT. Notice that this is less than the TRUE altitude of 10,000ft. Therefore the TRUE altitude is more than the INDICATED altitude.

Looking back to the second paragraph this can only happen if the air is warmer!

level at which temperature is zero is called freezing level

freezing rain occurs when falls from an inverion layer into an area below 0 deg celsius

rain in the warm air falls from above 10000 feet as 10000 feet is freezing level

12000 feet can be considered inversion as it is warmer being in the warmer sector

Refer the chart

500 hpa is 18000 pressure altitude

ignificant Weather (SIGWX) charts provide invaluable meteorological information to  aircraft operators and flight crew. Particularly for longer flights, or when weather issues may be a factor, SIGWX charts can be a vital flight planning tool.

the only cloud shown in waf sigwx chart is CB  moderate and severe icing is associated to a cb

They are concentrated in a burst which is up to 3nm (5km) in horizontal length and have a lifetime of about 5 minutes. (A Macroburst is a similar event but over a bigger area.)

Cumulonimbus clouds are clouds that the aviator should avoid. Cumulonimbus clouds consist of vigorous convective cloud cells of great vertical extent. In the later stages of their development, cumulonimbus clouds display a characteristic anvil top, as the upper part of the cloud hits the Tropopause. The upper parts of a cumulonimbus cloud often consist of super-cooled water droplets and ice crystals.

Within cumulonimbus, very strong upcurrents and downdraughts are continually at play, producing severe precipitation in the form of heavy showers of rain and hail.

1 metre above msl pressure reduces by 8 hpa

200 metre above msl pressure increases by 25 hpa

Current pressure 1000 plus 25 gives qnh

as in the table pressure falls

hence qfe and qnh will fall

temperture remains the same With the approach of a cold front as the leading air mass is warm

QFF is The value of pressure reduced to MSL in accordance with isothermal conditions.

Isobars are line joining places of the same atmospheric pressure (usually MSL pressure QFF).

Vertical windshear is change in wind velocity with height. It is typically measured in knots per 100ft. This type of windshear is very common during an inversion, therefore expect them at night and in well developed high pressure systems such as those found under the sub tropical high pressure belt. As an aeroplane fly’s through an inversion, not only will the change of temperature cause the engine performance to change, but the abrupt change in wind speed and direction may significantly alter the flight path.

These are outbreaks of cold air from near the poles. These outbreaks are usually characterized by a cold front at their leading edge.

Although surface temperature anomalies such as cold pools are not evident on surface pressure charts, they can be found most notably by looking at pressure charts in the middle to upper atmosphere. You may remember that cold air causes pressure to fall more rapidly with height, reducing the pressure in the upper atmosphere. Therefore by analyzing a pressure chart in the middle to upper atmosphere you can identify cold air pools by the low pressure they create,

Low pressure is accompanied by showers and thunderst

• Temperature inversion, also called thermal inversion, a reversal of the normal behaviour of temperature in the troposphere (the region of the atmosphere nearest Earth’s surface), in which a layer of cool air at the surface is overlain by a layer of warmer air. (Under normal conditions air temperature usually decreases with height.)
• Inversions play an important role in determining cloud forms, precipitation, and visibility.
• An inversion acts as a cap on the upward movement of air from the layers below.
• As a result, convection produced by the heating of air from below is limited to levels below the inversion.
• Diffusion of dust, smoke, and other air pollutants is likewise limited.

Wind speed is usually given in knots, but some countries give the speed in metres per second and the Met.

Wind direction is always given as the direction from which the wind is blowing. It is normally given in degrees true, but wind direction given to a pilot by ATC or in an ATIS will be given in degrees magnetic

metar is issued every 30 minutes almost everywhere in the world

Wind speed – coded as two or three digits (08) immediately follows the wind direction. Wind speed is determined by averaging the speed over a 10-minute period and is coded in whole knots (kts).

Terminal Aerodrome Forecasts (TAFs) are forecasts of meteorological conditions at an aerodrome, as opposed to the report of actual, present conditions as given in a METAR.

TAFs usually cover a period of between 9 and 24 hours.

9-hour TAFs are issued every 3 hours, and 12 to 24-hour TAFS every 6 hours.

Freezing rain is the most dangerous form of icing and it occurs in rain which becomes supercooled by falling through an inversion into air below 0°C. The supercooled water droplets are now rain sized. The rain does not freeze in the air but once it impacts the aerofoil it freezes to form clear ice with significant flowback.

Freezing rainbuilds up very quickly and a pilot’s action should be to turn onto a reciprocal heading immediately. If the pilot perceives the rain ice very late, then the course of action would be to climb into the warmers layers above. Turning at a late stage into the icing conditions will increase the stall speed and the return journey back out of the rain ice zone will double the ice on the aircraft from when the pilot first elected to turn around.

THE CONSTITUENTS OF THE ATMOSPHERE

Nitrogen 78 % Argon 0.95% Oxygen 21 % Carbon Dioxide 0.05%

Plus traces of:

Neon Nitrous Oxide Helium Nitrogen Dioxide Krypton Carbon Monoxide Xenon Sulphur Dioxide Hydrogen Ammonia Methane Iodine and Ozone Water Vapour

Of all the trace gases, water vapour is by the far the most significant. Without it there would be no weather.

RVR is the maximum distance that a pilot 15 ft above the runway in the touchdown area can see marker boards by day or runway lights by night when looking in the direction of take-off or landing

RVR is reported when normal visibility is 1500 m or less, or when shallow fog is reported or forecast

Nimbostratus is also a medium-level cloud, but it may also extend into both the lower and upper levels of the atmosphere

As the name suggests “CLOUD CIELING” or height

QNH values are given in hectopascals (HPA) rounded down to the nearest lower whole hectopascal

8 parts also called oktas

Qnh is 1013 only under isa conditions

which is hypothetical

The wet season (November – April)
The wet season in Darwin is characterised by high humidity, monsoonal rains and storms. Average temperatures range from 24.7 – 32 °C (76.5 – 89.6°F), and humidity can push past 80 per cent. The average annual rainfall is 1727.3 mm (68 inches) and January is the wettest month. Despite this, January and February is considered by many as the most beautiful time of year in the Top End. Sunny days and afternoon storms refresh the landscape, and animals and plants flourish.

Radiation fog is caused by radiation of the earth’s heat at night, and the subsequent conductive cooling of the air in contact with the ground to below dew point.

If there is a light wind, then fog will form, in calm conditions the result will be the formation of dew. The fog is not usually more than a few hundred feet thick.

If temperature is warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED.

HURRICANE IS THE NAME GIVEN TO TRS IN THE CARIBBEAN /GULF OF MEXICO AREA. FREQUENCY OF HURRICANES IS 3 PER YEAR FROM AUGUST TO OCTOBER

THEY TRAVEL WESTWARDS 10-15 DEG NORTH LAT

THEN THEY CROSS BAY OF MEXICO OR TURN RIGHT ALONG SUB TROPICAL HIGHG TO TRACK

NW,N,NORTH EAST UP THE USA COAST

In a HIGH there is divergence of wind to low pressure region ,there is no vertical movement of air and fog mist or haze stands still hence poor visibility

inversion occurs in high

TRS are given different names in different parts of the world. Either side of North America these storms are called Hurricanes. In the Indian Ocean and around Australia they are called Cyclones and around the far east, they called Typhoons. Typhoons are the most violent and have the longest season of any TRS.

Indian Ocean touches MADAGASCAR

December and January Has high humidity and trade winds hence trs forms during this time

TREND forecast is valid for 2 hours after the time of the observation of the METAR, and constitutes the final section of the METAR. The change in weather conditions indicated by the code, TREND, can be further qualified by the codes, BECMG, meaning becoming, or TEMPO meaning temporarily.

Under normal conditions, pressure varies by 1 hPa per 27 feet.

1038 hPa is (1038-1013.25) = 24.75 hPa higher than standard

24.75 x 27 = 668.25 ft

So FL75 will be at 7500 plus 668.25 = 8168.25 ft msl
So, 8168.25 – 1500 = 6668.25 ft agl, rounded up to 6670 ft agl

VV IS vertical visibility

100 is in feet as the visibility is always in feet not metre

triangles,are the standard symbols denoting a cold front.

semi-circular Are denoting warm front

A col, also called saddle point or neutral point, is in meteorology, the point of intersection of a trough and a ridge in the pressure pattern of a weather map. It takes the form of a saddle where the air pressure is relatively higher than that of the low-pressure regions

Polar front jetstreams form in the polar front region in both hemispheres ,in southern around 50° S and near any front which is separate from the polar front.

The upper winds will blow such that looking downstream the cold air will be to the left hand side in northern hemisphere and to the right hand side in the southern hemisphere.

polar air is cold air hence if pfj travels south polar air will be east

The direction of jet streams is generally westerly, maximum speeds occur near the tropopause, 200 kts have been recorded in Europe/N Atlantic and 300 kts in Asia.

In equatorial regions there are however some easterly jets.

Surface wind is measured by a wind vane which aligns itself with the wind direction, and an anemometer which measures the speed. An anemometer is a set of 3 hemispherical cups which rotate on a shaft with the effect of the wind. The speed of rotation of the shaft is directly proportional to the windspeed. The rotation is used to drive a small generator, the output of which is then displayed on a gauge which is calibrated in knots.

Both vane and anemometer are positioned 33 ft (10 m) AGL and they are located clear of buildings and obstructions which could affect the airflow and hence accuracy. An anemograph records windspeed and sometimes direction.

Forget about the part in which aircraft is at aerodrome with 1023 setting

at pressure altitude

altitude Measured from 1013 (SPS)setting

will be less than altitude measured at 1023 setting

90 km =  48.6 nautical mile

The Intertropical Convergence Zone is the broad zone of separation between the air masses either side of the heat equator. The air is conveyed by the Trade Winds north east and south east. Subject to large seasonal movement overland, but much less over the sea. Sometimes known as the Thermal Equator or Equatorial Trough.

TRS are given different names in different parts of the world. Either side of North America these storms are called Hurricanes. In the Indian Ocean and around Australia they are called Cyclones and around the far east, they called Typhoons. Typhoons are the most violent and have the longest season of any TRS.

Indian Ocean touches MADAGASCAR

november December and January Has high humidity and trade winds hence trs forms during this time

PRESSURE WILL FALL , ALTIMETER INCREASE

PRESSURE WILL RISE , ALTIMETER DECREASE

Radiation fog is caused by radiation of the earth’s heat at night, and the subsequent conductive cooling of the air in contact with the ground to below dew point.

If there is a light wind, then fog will form, in calm conditions the result will be the formation of dew. The fog is not usually more than a few hundred feet thick.

Glaze ice or clear ice is formed when LARGE supercooled drops spread over wings

rime ice is formed WHEN SMALL supercooled drops spread over wings

both happen under 0° Celsius flying through clouds

large supercool water sustain only between 0 to -20 degree

TEMP IS -20 WHICH IS -ISA

AERODROME IS 4000 FT ABOVE MSL

HENCE QFF IS GREATER THEN QNH

IF QFF> QNH

AND QNH IS 1025

QFF WILL HAVE A VALUE 1025 OR ABOVE AND AS PER PRESSURE LEVEL CHART

ALTIMETER WILL READ LESS THAN 0 FEET

Altocumulus castellanus is a “bubbly” form of normal altocumulus. The “towers” that form in altocumulus castellanus are like battlements on castles, hence the name. These clouds are significant because they often herald a change to showery, thundery weather and are a feature of summer weather in temperate latitudes.

Cumulonimbus clouds sometimes develop from altocumulus castellanus, when instability is present at medium levels of the Troposphere.

Radiation fog is caused by radiation of the earth’s heat at night, and the subsequent conductive cooling of the air in contact with the ground to below dew point.

If there is a light wind, then fog will form, in calm conditions the result will be the formation of dew. The fog is not usually more than a few hundred feet thick.

850 hpa is 5000 feet

800 HPA WOULD BE 6000 feet

rime ice is formed WHEN SMALL supercooled drops spread over wings

happen under 0° Celsius flying through clouds

CB EXTENDS FROM LOWEST LEVEL TO FL 450, IN PRESENCE OF CB HAIL CAN BE EXPECTED

The automatic provision of current, routine information to arriving and departing aircraft throughout 24 hrs or a specified portion thereof

Voice-ATIS broadcasts normally contain the following information in the order listed:

• name of aerodrome;
• arrival and/or departure indicator;
• contract type, if communication is via D-ATIS;
• designator;
• time of observation, if appropriate;
• type of approach(es) to be expected;
• the runway(s) in use; status of arresting system constituting a potential hazard, if any;
• significant runway surface conditions and, if appropriate, braking action;
• holding delay, if appropriate;
• transition level, if applicable;
• other essential operational information;
• surface wind direction (in degrees magnetic) and speed, including significant variations and, if surface wind sensors related specifically to the sections of runway(s) in use are available and the information is required by operators, the indication of the runway and the section of the runway to which the information refers;
• visibility and, when applicable, RVR;
• present weather;
• cloud below 1 500 m (5 000 ft) or below the highest minimum sector altitude, whichever is greater; cumulonimbus; if the sky is obscured, vertical visibility when available;
• air temperature;
• dew point temperature;
• altimeter setting(s);
• any available information on significant meteorological phenomena in the approach and climb-out areas including wind shear, and information on recent weather of operational significance;
• trend forecast, when available; and
• specific ATIS instructions.

MEANS HEAVY INTENSITY

– MEANS LIGHT

CB GIVES HEAVY INTENSITY TSRA (THUNDER SHOWER AND RAIN)

With your back to the upper wind, the cold air is to your left in the northern hemisphere and to your right in the southern hemisphere.”

jet streams are mostly from west to east

This secondary may deepen and form the next depression along the PF and equal the size of the primary. At this stage, the depressions tend to rotate around each other cyclonically

True altitude in High pressure or warm atmosphere is always more than cold/low ,

hence qnh more than 1013 and temp more than isa

“watch out below when you are low”

As the cold air advances, it forces the warm air upwards causing the warm air to cool. The water vapour in the warm air mass, consequently, condenses, and clouds are created. The slope of the cold front boundary is steeper than that of the warm front, with a gradient of approximately one in fifty.

The unstable air just ahead of the cold front is, forced to rise vigorously. Causing pressure to reduce and altimeter reading increased

Hurricanes.
Hurricane is the name given to Tropical Revolving Storms in the Caribbean/Gulf of Mexico Area. Frequency of developed Hurricanes is average 3 per year. They occur from August to October, tracking westwards across the Atlantic near 10°N-15°N latitude and at 10-15 knots. Internal windspeeds can exceed 100 knots. They then cross the Bay of Mexico or turn right around the sub tropical high to track NW, N, NE up the USA East Coast. They are energised by the latent heat of condensation and are therefore more active over the sea. Each season they are named alphabetically in order of occurrence using alternate male/female first names.

over the poles, the tropopause can be between 8 -10 km and over the equator 16 – 18 km

The lower it is, the warmer the temperature at the tropopause. The temperature at the tropopause can be as high as -40°C over the poles and as low as -80°C over the equator.

CLOSED PACKED ISOBARS MEAN LOW PRESSURE

true altitude and indicated altitude remains same hence no cross wind

AS PER BUY BALLOTS LAW

Radiation fog is caused by radiation of the earth’s heat at night, and the subsequent conductive cooling of the air in contact with the ground to below dew point.

If there is a light wind, then fog will form, in calm conditions the result will be the formation of dew. The fog is not usually more than a few hundred feet thick.

CB EXTENDS FROM LOWEST LEVEL TO FL 450, IN PRESENCE OF CB HAIL CAN BE EXPECTED

THERE IS NO REASON FOR THE READING TO CHANGE IF THERE WAS NO PRESSURE CHANGE

Since both the places have same pressure it is obvious that we are flying to a warmer place

true altitude increases in warmer atmosphere

If temperature is warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED.

If the QNH was 1013mb, you’d be at 13,500 feet when at FL135. if you increased the subscale setting to 1019 the indication would increase, but as per radio altimeter it remains 13500 , this means that air mass was cold as true altitude decreases in cold air

If the airmass is lying over a warm tropical ocean, the airmass is classified as Tropical Maritime (TM).

If the airmass lies over a cold continent in winter, the airmass is classified as Polar Continental (PC).

THERE IS NO REASON FOR THE READING TO CHANGE IF THERE WAS NO PRESSURE CHANGE

Ebbr falls ahead of a warm front

this will be the weather ahead of a warm front

Ahead of a warm front

Surface W/V – Speed increasing, slight backing, usually southerly.
Temperature – Steady low.
Dew Point – Steady low.

Pressure – Steady fall.
Cloud – Increasing to 8/8, base lowering.

Initially cloud changes from Ci to Cs to As, then very close to the front Ns.
Precipitation – Light continuous from As becoming moderate continuous from Ns.

Visibility – Reducing to poor.

As a thumb rule

if it’s warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED.

altimeter shows indicated altitude

hence lower altitude than summit

The area lying between the two fronts is known, since it is covered by tropical air, as the warm sector.

In the warm sector.

Surface W/V – Steady, usually from the SW.

Temperature – Steady.

Dew Point – Steady.

Pressure – Steadily decreasing.

Cloud – Uniform 6/8 to 8/8, some large breaks may occur, base low, St, Sc.

In summer over land – fair weather cumulus

Precipitation – Light rain, drizzle Visibility – Poor.

PFJ ARE LOCATED IN WARM AIR

Altocumulus castellanus is a “bubbly” form of normal altocumulus. The “towers” that form in altocumulus castellanus are like battlements on castles, hence the name. These clouds are significant because they often herald a change to showery, thundery weather and are a feature of summer weather in temperate latitudes.

Cumulonimbus clouds sometimes develop from altocumulus castellanus, when instability is present at medium levels of the Troposphere.

An inversion in the atmosphere is where temperature rises with an increase in height. This produces extreme stability and inhibits the formation of cloud

In a high pressure system, air descends at the centre. As the air descends it will be heated adiabatically  and will be warmer than the air at a lower level adjacent to the surface. This is called a Subsidence Inversion.

Glaze ice or clear ice is formed when LARGE supercooled drops spread over wings

rime ice is formed WHEN SMALL supercooled drops spread over wings

both happen under 0° Celsius flying through clouds

across the jet core, there is very little horizontal temp difference. There is, however, a big horizontal pressure difference.

Heat, or airmass type (more common in summer time).
Also called isolated

are formed by thermal triggering

not by frontal uplift