Meteorology

Question 1

What is this synoptic chart symbol?

Answer 1

A Cold Front - distinguishable either in blue in colour or its triangular symbols

Question 2

What is this synoptic chart symbol?

Answer 2

A Warm Front - distinguishable either in red in colour or its semi-circular symbols

Question 3

What is this synoptic chart symbol?

Answer 3

An Occluded Front - distinguishable either in purple in colour or its symbols containing both triangles and semi circles

Question 4

What is this synoptic chart symbol?

Answer 4

A Stationary Front - distinguishable either in red & blue in colour or its symbols pointing in different directions

Question 5

What is this synoptic chart symbol?

Answer 5

A Front at Height (above ground level) - different to a ground level front due to the symbols NOT being shaded in

Question 6

What is this synoptic chart symbol?

Answer 6

A Dying Front (in this case, Dying Cold Front) - distinguishable from the crosses within the front line

Question 7

What is this synoptic chart symbol?

Answer 7

A Developing Front (in this case, Developing Warm Front) - distinguishable from the dots within the front line

Question 8

What is this synoptic chart symbol?

Answer 8

A Trough Line - an isolated low pressure where the air is particularly unstable. This trough line is a non frontal squall

Question 9

Describe the weather you would experience when APPROACHING a WARM FRONT…
(clouds, precipitation, visibility, pressure, temperature)

Answer 9

Clouds = high to low stratus form (Cirrus, Cirrostratus, Altostratus, Nimbostratus)
Precipitation = light in Altostratus, increasing to moderate / heavy in Nimbostratus
Visibility = reduces
Pressure = reduces
Temperature = slow increase

Question 10

Describe the weather you would experience when AT the WARM SECTOR…
(clouds, precipitation, visibility, pressure, temperature)

Answer 10

Clouds = low cloud remains
Precipitation = decreases to drizzle, fog may form if sea surface temp is high compared to dew point closer to point of occlusion
Visibility = moderatre or poor
Pressure = steady
Temperature = sharp increase

Question 11

Describe the weather you would experience when APPROACHING a COLD FRONT…
(clouds, precipitation, visibility, pressure, temperature)

Answer 11

Clouds = high cumulus form (Cumulonimbus)
Precipitation = starts again
Visibility = steady
Pressure = falls
Temperature = steady

Question 12

Describe the weather you would experience when AT the COLD FRONT…
(clouds, precipitation, visibility, pressure, temperature)

Answer 12

Clouds = high cumulus form (Cumulonimbus)
Precipitation = moderate or heavy short burst
Visibility = sharp increase once past precipitation
Pressure = sharp rise
Temperature = sharp decrease

Question 13

Describe Buy Ballot’s Law…

Answer 13

Buys Ballot’s Law simplifies the matter as follows: face the wind; the centre of low pressure
will be from 90° to 135° on your right hand in the N hemisphere and on your left hand in the S hemisphere.

Question 14

Name some sources of weather information?

Answer 14

• UK Met Office Weather Service
• Shipping Forecast
• Publications (ALRS)
• NAVTEX, SafetyNet, Radio
• Ship’s Met Observations Transmissions
• Met Instruments on board

Question 15

What type of weather charts are available to the Mariner?

Answer 15

1. Admiralty Ocean Routeing Chart (air, sea, dew point temps, % fog & low vis, pressure)
2. Synoptic Chart (pressure, fronts, isobars, troughs)

Question 16

How are frontal systems formed?

Answer 16

2 air masses of different characteristics (warm & cold) meet & interact but don’t mix. The line of boundary of these air masses are known as fronts

Question 17

What is a depression?

Answer 17

Cold air from high latitude meet warm air from tropical areas. Once converge, warm air is forced over the cold air mass. The warm air cools, forming clouds and precipitation, creating a frontal depression

Question 18

What is Geostrophic Wind?

Answer 18

A hypothetical wind in the free atmosphere which would flow parallel to straight equidistant isobars if they were stationary

Question 19

How to predict fog?

Answer 19

1. Take temps on Marine Screen (dry & wet bulbs)
2. With the dry bulb & depression of bulbs (difference between dry & wet), go to the dew point tables (in NP 100)
3. Find the dew point in the table at the time of obs
4. Plot the dew point compared to the sea temp - continue to take obs, when dew point & sea temp meet, that’s the time at which fog can occur

Question 20

Describe Dew Point…

Answer 20

The point / temperature in which an air parcel is saturated and reaches 100% relative humidity. If this air parcels cools, it will start to condensate

Question 21

Describe Adiabatic Cooling…

Answer 21

Parcel of air rises, atmospheric pressure drops and air expands. This expansion causes the air to lose energy in heat form and thus cools as it rises

Question 22

Describe Adiabatic Heating…

Answer 22

Parcel of air falls, atmospheric pressure increases and air compresses. This compression causes the air to gain energy in heat form and thus heats as it sinks

Question 23

Describe Coriolis Force…

Answer 23

The deflection of a path of an object (this case air), on a rotating surface. Northern Hemisphere, deflected to the right, Southern Hemisphere, deflected to the left

Question 24

Requirements for TRS to form?

Answer 24

1. At least +/- 5° N/S of Equator
2. Pre - Existing disturbance/spin
3. Low vertical wind sheer
4. Warm sea surface temperature (>26.5°C)
5. High atmospheric humidity

Question 25

What is Advection Fog?

Answer 25

Relatively warm air passing over a cold sea surface causing the air to cool and the moisture condense.

Occurs in shallower water with a greater temperature variance compared to deep water.

Question 26

What is Radiation Fog?

Answer 26

A cooling land mass causes a rested air to cool below dew point and moisture condences. The fog created will flow out to sea up to 10NM.

Question 27

What is Sea Smoke?

Answer 27

A dry and cold air passing over a relatively warmer sea causing the moisture above sea to condense.

Requires a continuous flow of cold air so remains in stronger winds.