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Justins OOW/Masters flash cards > Meterology > Flashcards

Meterology Flashcards

1
Q

Veering wind changes n which direction

A

Clockwise

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2
Q

Backing wind changes in which direction

A

Anti clockwise

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3
Q

Buys ballots law

A

Back to the wind inn the northern hemisphere low on the left

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4
Q

What is anabatic wind?

A

Wind traveling up a valley during the day

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5
Q

The three cells

A

Hadley Ferrel Polar

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6
Q

What is katabatic wind

A

Strong wind traveling down a valley. On a clear night Wind subsides down a valley but the surrounding cold landmass cools the air faster than the a adiabatic lapse rate and sinks very quickly.

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7
Q

What and how does advection fog form

A

Advection fog is formed when warm air moves over cold sea. It may persist in wind. Also know as sea fog

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8
Q

What is sea smoke

A

Type of fog that forms when cold air moves over warmer sea. Will disappear in wind and sun.

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9
Q

What is frontal fog

A

Air masses involved in a frontal system are forced to mix.

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10
Q

Radiation fog

A

On calm cloudless nights Land looses heat and cools down. The cold land now cools the air and fog is formed. Does not occur at sea but may be blown on to the sea surface by land breeze.

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11
Q

What is a lapse rate

A

The lapse rate is the rate at which air cools while it rises. 1*c per 100m

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12
Q

What is a aneroid barameter

A

Measures atmospheric pressure. Partially exhausted/vacuumed compressible box which is connected to a spring. Air pressure distorts the box and and moves a needle which is preset. No correction at sea level

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13
Q

What is a Barograph

A

A barograph is a barometer which is connected to a recording device. It makes tracking changes in barometric pressure easier

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14
Q

What is a wet and dry bulb hygrometer and how does it work

A

It is used to measure realtime humidity. Two Mercury filled thermometers. One has muslin cloth wrapped around the bulb and is dampened by water, the other is exposed. Evaporation causes the wet bulb to be cooler than the exposed bulb. The depression between the two and the air temp compared in psychometric tables. The hygrometer is usually housed in a Stevenson screen.

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15
Q

Where can you get met information while under way/on passage?

A

MSI (navtex, Inmarsat)

Own ship oservations

VHF, MF, HF radio listing to coast stations for weather broadcasts. ALRS vol 3 (To obtain weather report broadcast times from coast stations)

Weather routing services

Weather fax

Internet - Government Met offices (NOAA, UK MET Office)

Local radio

Harbour master

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16
Q

What is a whirling phsycrometer

A

Spinning wet and dry bulb hygrometer.

17
Q

Requirements for a TRS to form

A

Warm Air Mass, Warm air contains more moisture, Warm air rises cools condenses and sinks creating vertical circulation.

Low upper atmospheric winds, If high upper atmospheric winds exist they will essentially decapitate the top section of the vertical circulation required for TRS formation.

Warm seas, Ocean temp above 27 Celsius through at least 50m water coloumn. Warm seas increases water vapour absorption encourage vertical circulation.

Strong Coriolis effect. Sufficient coriolis effect only exitsts from more than 5-10 Degrees North or south of the equator. (5 and 25 degrees northern hemisphere 10 and 20 degrees Southern Hemisphere).

18
Q

Avoiding a TRS

A

If wind veers (northern hemisphere) them in dangerous semi circle. Proceed with wind on starboard bow as close as is safe. If wind back. (Northern hemisphere) then in navigable semi circle. Proceed with wind on starboard quarter Opposite for Southern Hemisphere. Wind on port how or port quarter

19
Q

Precursors condition of TRS

A
  • Long large swell from direction of Centre of low..
  • When between 500 and 100 miles extensive cirrus cloud followed by altostratus, nimbostratus and strato cumulos
  • Atm pressure change of 3mb below average for time of year. When corrected (height of eye and diurnal variation(sailing directions))drop is more than 5 mb then it must be assumed that storm exists.
  • Appreciable change in wind direction
  • Radar may show the leading edge, but by this time the weather would already be severe.
20
Q

How to report TRS or any unpredicted severe weather.

A

SOLAS requires all vessels to report the presence of a TRS. To vessels in the vicinity and to a coats station. Information required: - position course and speed of vessel - position of the storm at UTC and date - current barometric pressure, not corrected for diurnal variation. - The change in barometric pressure form the past 3 hours - true direction and force of wind - Sea state - height of swell and direction Security message must be sent every three hours

21
Q

Where can you find psychometric tables and what are they used for

A

In the Mariners handbook. Used to determine due point

22
Q

How to determine if fog will develop

A

When Air temp approached or matches dew point temp fog will most likely form. Viz is likely to start hazing with in about 2 - 5 degrees difference. To determine, Due point and air temp must be checked every 10minutes and the dew point and air temp plotted against time. average line can be extended and when the two meet fog is likely to develop, there fore it is possible to predict the development of fog by the graphs

23
Q

What is an anamometer

A

Relative wind speed

24
Q

What is the Mean atmospheric pressure at mean sea level?

A

1013 mb

25
Q

What are the expected meteorological conditions as a frontals system passes over, including warm front, warm sector and cold front.

A
26
Q

What are land and sea breezes?

A

Seabreeze - Wind from sea, during day hot land air rise cool air form sea replace

Land breeze - Wind from land, Night air cools over land pushed out over sea.

27
Q

What is Orographic Wind?

A

Air being forced up by a land mass(mountain range) forcing to cool, condense and rain

28
Q

Name 5 ways in which an air parcel can be cooled.

A

Radiation: Water vapour radiates heat and cools the layer with out upward movement.

Thermal Convection: Air is heated by direct contact with earths surface forcing to rise, as it rises it cools. Likely to condense and form Cumulos or Cumulo nimbus clouds

Frontal: Cooler air mass forces a warmer air mass to rise

Orographic: Land mass forces a parcel of air to rise.

Turbulence:Moist air being carried up by turbulence caused by unevenness in earths surface.

29
Q

What is Relative humidity?

A

It is the description of how much water vapour is contained with in an airmass compared to the maximum quantity it can hold at that temperature.

30
Q

Sources of met Info for Passage planning

A

Routing charts

Sailing Directions

Np 100

Ocean Passages of the world

ALRS VOL3 (Weather reporting times and stations)

31
Q

Stages of development of TRS.

A

Tropical Wave

Tropical disturbance

Tropical depression

Tropical storm

Tropical revolving storm.

32
Q

Where to find barometric height of eye and temp correction tables.

A

Nautical almanac.

33
Q

Info found on routing chart

A
  1. Wind roses - wind force and direction percentage for that month, number of observations, days of calms,
  2. Ice limits and iceberg sightings
  3. Ocean current - Direction and consistency
  4. Load line limits
  5. Shipping routes
  6. TSS tracks
  7. Winds force 7 and above.
  8. Atmospheric pressure aver
34
Q

Wet and Dry Bulb Hygrometer and determining dew point

A

Mercury filled thermometer x 2

1 wrapped in muslin cloth and dipped in water

difference in temp due to evaporation of water out of cloth

Input difference into psychometric table to work out due point.

35
Q

Maletmi Wind

A

Strong N

Aegean sea

Summer

Balken High pressure ridge

Anatolian low pressure

36
Q

Mistral Winds

A

Strong NW

France

Winter and early spring

HP over bay of Biscaye

Low pressure in gulf of Genoa

37
Q

Prep for operations in ICE

A

Clothing

Footwear

Sunglasses

Food

Vitamins

Medical supplies

Fuel

Batteries

Antifreezee

Survival kits

38
Q

When reporting Barametric pressure what must be done to it

A

Corrected to mean sea level, using the height of eye correction table.

Justins OOW/Masters flash cards (47 decks)

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