Met Systems Revision Flashcards
How many air masses affect the UK and what are they?
6
Tropical maritime
Tropical Continental
Polar Maritime
Polar Continental
Arctic Maritime
Returning Polar Maritime
What weather would be expected at the coast/expose areas with a Tropical Maritime airmass affecting the UK?
Temp - Near sea temp Humidity - Very moist Stability - Stable Weather - Low cloud, drizzle, fog Visibility - Often poor with coastal fog
What weather would be expected in sheltered areas/inland with a Tropical Maritime airmass affecting the UK?
Temp - Warm Humidity - Moist Stability - Stable aloft Weather - Broken cloud, dry Visibility - Moderate
What weather would be expected in the Summer with a Tropical Continental airmass affecting the UK?
Temp - Very warm or hot
Humidity - Relatively dry
Stability - Stable, becoming unstable with time
Weather - Nil, possibly thundery showers in time
Visibility - Moderate or poor
What weather would be expected in the Winter with a Tropical Continental airmass affecting the UK?
Temp - Average Humidity - Rather moist Stability - Stable Weather - Usually cloudy Visibility - Moderate or poor
What weather would be expected in the Summer with a Polar Continental (long sea track) airmass affecting the UK?
Temp - Cool windward coasts, warm inland
Humidity - Moist near windward coasts, dry inland
Stability - Stable
Weather - Low cloud, drizzle, mist near coasts. Nil inland.
Visibility - Poor near coasts. Moderate or good inland.
What weather would be expected in the Summer with a Polar Continental (short sea track) airmass affecting the UK?
Temp - Warm Humidity - Dry Stability - Stable Weather - Dry Visibility - Moderate or good
What weather would be expected in the Winter with a Polar Continental (short sea track) airmass affecting the UK?
Temp - Cold Humidity - Moist in lower layers Stability - Stable Weather - Very dry Visibility - Moderate or poor
What weather would be expected in the Winter with a Polar Continental (long sea track) airmass affecting the UK?
Temp - Very cold Humidity - Very dry Stability - Unstable Weather - Rain or snow showers Visibility - Moderate or poor
What weather would be expected in the Winter with a Arctic Maritime airmass affecting the UK?
Temp - Cold (colder than Polar maritime)
Humidity - Moist (not as moist as polar maritime)
Stability - Unstable
Weather - Heavy showers, sometimes with snow, hail and thunder. Mainly in Northern Scotland and exposed coastal areas.
Visibility - Very good, poor in showers
What weather would be expected in the Summer with a Arctic Maritime airmass affecting the UK?
Temp - Cool Humidity - Fairly moist Stability - Unstable Weather - Heavy showers or thunderstorms Visibility - Very good, poor in showers
What weather would be expected in the Summer with a Polar Maritime airmass affecting the UK?
Temp - Cool Humidity - Moist Stability - Unstable Weather - Scattered showers Visibility - Good, poor in showers
What weather would be expected in the Winter with a Polar Maritime airmass affecting the UK?
Temp - Rather cold Humidity - Moist Stability - Unstable Weather - Heavy showers, sometimes with hail and thunder. Mainly in exposed western and hilly areas. Visibility - Good, poor in showers
What weather would be expected in the UK with a Returning Polar Maritime airmass?
Temp - Cool (warmer than Polar maritime)
Humidity - Moist (moister than Polar maritime)
Stability - Stable at low levels, unstable aloft
Weather - Variable cloud, possibly showers
Visibility - Variable
What weather is associated with a depression (low pressure)?
.
What weather is associated with an anticyclone (high pressure)?
.
What weather is associated with a Thermal Low?
.
What weather is associated with a Polar Low?
.
What weather is associated with an Orographic Low (lee)?
.
What weather is associated with a Trough?
.
What weather is associated with a Ridge?
.
What weather is associated with a Col?
.
What are the 4 types of fog?
Radiation fog
Advection fog
Hill fog
Arctic sea smoke
If visibility is less than 1000m, and RH > 95%, it is said to be…?
Fog
If visibility is more than 1000m, and RH > 95%, it is said to be…?
Mist
If visibility is less than 1000m, and RH < 95%, it is said to be…?
Haze
What causes advection fog to form + disperse?
Warm air moving over a cold surface.
Disperses due to:
Change in air mass
Winds increase
Temp of the surface rises above the dew point
Explain arctic sea smoke.
See manual NOW!
What conditions are required for a thunderstorm?
Unstable layer extending to high altitudes
High moisture content
Trigger action (EXCEPT TURBULENCE)
What can bring/cause the weather conditions for a thunderstorm?
Thermal lows
Troughs
Active cold fronts
Occlusions
What are the stages of a thunderstorm?
Building
Mature (anvil forms)
Dissipating
What are the 4 types of thunderstorm?
Single Cell
Multicell
Multicell - Squall Line
Supercell
What are the 3 groups of supercell?
Rear Flank (or Low precipitation (LP))
Classic (CL)
Front flank (or High precipitation (HP))
What hazards are associated with thunderstorms?
W - Weather (heavy precipitation) H - Hail I - Icing S - Squall Line T - Turbulence (Rapid pressure changes, Downbursts, Strong winds) L - Lightning E - Electricity (static)
What are some indicators of thunderstorms?
Cloud Precipitation - Rain, hail or snow Radar image Radio crackle Lightning Static electricity St Elmo's Fire Visible discharge of static electricity Weak luminous corona discharges from sharp metallic points on the aircraft
What does METAR stand for?
Meteorological Terminal Aviation Routine Weather Report
When is a METAR issued?
Every 30 mins at 10 mins TO the hour and 20 mins PAST the hour
When are special METARS issued?
When there are significant changes to the current weather
By what speed must gusts exceed the MEAN WIND SPEED in order to be reported?
10kts
What does 0000 vis and 9999 vis mean?
0000 = Less than 50m 9999 = 10km or greater
NOTE - If a second vis is reported following the first, it is the minimum visibility and the direction will be given, e.g. 6000 3000SE
What do the following mean on a METAR: FG PL RA SH SQ TS GR/GS RASN NSW DZ RADZ
FG = Fog PL = Ice pellets RA = Rain SH = Showers SQ = Squalls TS = Thunderstorms GR/GS = Hail RASN = Sleet NSW = No Significant Weather DZ = Drizzle RADZ = Light rain and drizzle
What does the modifiers +, - or no modifier mean?
+ = Severe
No modifier = Moderate
- = Light
E.g. +SHRA = Heavy rain showers
What do FEW, SCT, BKN, OVC, NSC, ///V and SKC mean?
FEW = 1-2 oktas SCT = 3-4 oktas BKN = 5-7 oktas OVC = 8 oktas NSC = No Significant cloud ///V = Sky obscured SKC = Skies clear
What two types of cloud are specifically reported in a METAR?
TCU
CB
What does RE mean in a METAR?
Recent
E.g. RETS = Recent thunderstorms
What does TREND, TEMPO, BECMG and NOSIG mean?
TREND = Indicates significant changes in the weather in the two hours after the observation is made
TEMPO = Temporary changes in one or more elements of the forecast during the stated time period
BECMG = Indicates a gradual change in one or more elements of the forecast during the time period shown
NOSIG = No significant changes are forecast!!!
What are the requirements for colour state GREEN?
Base of lowest cloud layer of 3/8 oktas min (SCT) = 700ft AGL
Surface visibility = 3.7km (2nm)
What is a TAF?
Terminal Aerodrome Forecast
How often are TAFs issued?
Every 3 hours for military airfields and some civil airfields
Most civil airfields are every 6 hours
Valid for stated period
What 3 cells are present on Earth?
Polar Cell (60-90 degrees latitude)
Ferrel Cell (30-60 degrees latitude)
Hadley Cell (0-30 degrees latitude)
What are the directions of the trade winds in the North and South hemisphere?
N = North Easterly
S = South easterly
What are the idealised major pressure systems?
Polar High (high pressure at each pole)
Subpolar low (occurs where the Polar and Ferrel cell meet)
Subtropical High (occurs where the Hadley and Ferrel cells meet)
Equatorial trough (aka ITCZ, between the Hadley cells)
What are the 6 climates?
Polar Temperate Mediterranean Arid/Desert Tropical
Mountainous (occurs where the lad rises above permanent snowline.
What is the zone of confluence between trade winds of the northern and southern hemispheres called + where and when does it move?
Inter-Tropical Convergence Zone (ICTZ)
Moves North in Northern summer
Moves South in Southern summer
Appears as bands of clouds, usually thunderstorms, near the equator.
What is required for hurricane/tropical storm formation?
Source of warm, moist air from the tropics where sea surface temps > 26 degrees
Converging winds forcing the air to rise
Winds which do not vary greatly with height - low wind shear
Sufficient distance from the equator for the Coriolis force to provide sufficient spin/twist
What can we use to classify wind speeds?
Beaufort wind scale
Name 3 types of wind.
Land breeze (night - offshore)
Sea breeze (day - onshore)
Thermal wind (two layers of equal pressure but differing temperature meet. Wind direction is horizontal along the isotherms of mean temperature)
How do standing waves (mountain waves) develop?
Airstream fluctuations behind hills/mountains
Creates strong vertical currents, continuing for miles
Require:
Wind blowing +/- 30 degrees to perpendicular to the ridge
15-30kts + wind speed at the crest
Layer of stability above the mountain, with an unstable layer below
How can we ID mountain/standing waves?
Rotor clouds behind the peak
Lenticular clouds above and down wind of peak
Rotor turbulence
