BGS - Post Its Flashcards
What is a blocking ainticyclone and where can you find them?
A quasi-stationary warm anticyclone, usually situated 50-70deg N.
What do isobars on a surface pressure chart represent?
Lines of equal QFF.
When and where is the easterly jet encountered?
In NH summer and it extends from SE Asia over southern India to central Africa.
Why is the rate of cooling of saturated air less than that of dry air?
Because heat is released in the condensation process.
What accumilates ice easier/quicker our of high and low performance wings?
high performance wings, due to travelling faster and therefore picking up ice quicker.
What is a GAMET?
An area forcast in abbreviated plain language for low level flights.
What time of year are polar front jet streams strongest?
Winter for both hemispheres
What are westerly waves and what kind of weather is experienced in them?
Polar front depressions.
Very changable weather.
What kind of cloud are TS usually preceded by?
AC castellanus due to very unstable weather.
What is the most significant location for ice to form?
Aft of the de-icing equipment.
What is the wind equation?
V = PGF/2*(pi)*(rho)*w*sin(lat)
What is the weather like on either side of a quasi-stationary front?
Heavy rain on both sides.
What is the average frequency of TRSs around the world?
SCS = approx 16
West of Darwin = approx 6
Everywhere else = approx 9
Where are pressure altitudes?
FLs (1013 set)
What defines a CAVOK situation?
No cloud below MSA and or 5000ft, whichever is higher
no CBs or TCBs
9999 vis.
How often are METARs issued and when are they valid for?
They are issued 1/2 hourly and are valid at the time of issue.
What are TRENDs and how long are they valid for?
A forecast at the end of a METAR and are valid for 2hours.
How frequently are TAFs issued and how long are they valid for?
Issued 3 hourly and are valid as stated in the TAF.
What forces are balanced in a geostrophic wind?
Coriolis force and PGF
What forces are balanced in a gradient wind?
Coriolis force, PGF and centrifugal force.
What is the mean time between polar front waves in western europe.
1 - 2 days
How does RVR usually compare to visibility?
RVR is usually better.
What do the codes for reporting CBs mean?
ISOL - individual
OCNL - well separated
FRQ - little or no spacing
EMBD - embedded in other cloud.
How are gust fronts formed?
From cold air outflow from a TS.
What is the mean temperature in a polar climate?
below +10degC
What kind of precipitation will a cloud containing both ice crystals and water vapour produce?
Snow initially which then melts into large raindrops at the surface.
Where are squall lines most likely to be expected?
In front of a cold front.
What do significant weath charts show?
A weather forecast for the time stated on the chart.
What can satellite images be used for?
Locating fronts in area with few observation stations.
What is the mean height of the tropical 0degC isotherm?
approx 16000ft.
What characteristic weather is required for air masses to form?
High pressure and stable.
Where is the RVR value shown in a METAR measured from?
The touch down point.
Where do snow grains come from?
Frozen drizzle (stratus)
When is tornado season?
Late spring, early summer.
When do you consider a BECMG to have taken place?
For an improving situation, at the end of the stated time.
For a deteriorating situation, immediately.
How is prevailing visibility worked out?
It is the greatest visibility reached by at least half the horizon circle.
What is the visibility like in a cirrus cloud?
More than 1000m
Where is the CAT in relation to a jet stream?
Within 6000ft of a jet stream core.
How long can the conditions stated in a TEMPO last in any one instance and all together in the stated time?
No longer than an hour, and the total time spent in the conditions will be less than half the time stated.
In the mid latitudes, what is the season variation of the tropopause height?
Approx 10000ft, FL250 - FL350
What kind of precipitation reflects enough energy to be seen by a weather radar?
Hail and large rain drops.
What is the life span of a tornado?
Up to 30mins
What wind flows into the adriatic?
The Bora.
What words are used to decribe:
Towing cumulus; capillatus; Fractus; Humulis?
Resembles cauliflower; ‘hairy’ top; broken into pieces; small vertical extent.
What is fair weather Cu often an indication of?
Turbulence at and below the cloud level.
What kind of precipitation does the coalescence process produce in the mid-latitudes?
Drizzle or light rain.
What is the Mediteranean climate like?
Hot dry summers; warm wet winters; less than 700mm rainfall annually.
Do polar and thermal lows occur over land or sea?
Polar lows only occur over the sea
Thermal lows can occur over either land or sea.
What does the vertical extent of the friction layer depend on?
Stability, wind speed and roughness of surface.
Where do the greatest number of TRSs occur globally?
NW Pacific affecting Japan, Taiwan, Korea and the Chinese coastline.
Which way do rotors rotate in the mountain waves and TS gust fronts?
In mountain waves - clockwise
In TS gust fronts - anti-clockwise
By how much should TSs be avoided by in low and high levels?
Low level - 10nm
High level - 20nm
What is the difference between an AIRMET and a GAMET?
A GAMET is a low level area forecast whereas an AIRMET is more of a warning of weather that has not been forecast in the last GAMET.
What type of stratus cloud can extend into multiple layers?
NS
What is the variable location of the ITCZ around West Africa?
5deg - 20degN
What kind of air mass is produced at the polar ice cap?
Arctic.
Where are SNOWTAMs foudn and what do they look like?
In a METAR and are of the format:
RR T E DD BB
RR - runway
T - type of deposit
E - extend of runway coverage
DD - depth of deposot
BB - braking conditions
How does saturation mixing ratio vary with temperature?
it increases exponentially.
When metiorological phenomena should be included in PIREPs (special air reports)?
Mod/Sev Turb
Mod/Sev icing
Sev MW
OBSC/EMBD TS
Heavy dust/snowstorms
Volcanic ash cloud
(pre)eruption activity.
