MET Orals Flashcards
Equipment for measuring weather
Aneroid barometer
Barometer
Hygrometer
Barograph
Anemometer
Purpose of Hygrometer
To predict onset of fog through calculation of dew point and relative humidity
How to use a precision aneroid barometer
More precise version of an aneroid barometer
Must be placed in an area lest likely to be effected by movement of the vessel
Push down the button on front
Look through viewing glass and turn the wheel on the outside slowly
When we reach a break in the image in the viewing glass, this is the pressure at the time, read off the dial
This must be calibrated for the height of the bridge via the calibration card
What is a weather routeing chart
Provides the mariner with general weather patterns for each month of the year around the world
What is found on a weather routeing chart
Dew point
Sea surface temp
Average air temp
Average dew point temp
Surface pressure
Atmospheric pressure
Areas of vis less than 5 miles
Wind roses
Ice limits
Load line limits
Ocean currents
Where to obtain weather forecast during passage
RT weather reporting
NAVTEX
Inmarsat C Safety Net
Iridium Safety cast
Internet forecast
Weather routing service
Call coast station via channels found in Vol 1 ALRS
Weather fax system (shipping forecast)
Where to obtain Weather information (publications)
Sailing directions
Weather routeing charts
Ocean passages for the world
Tide tables
Tidal atlases
Mariners handbook
What weather information is found in the Mariners handbook
TRS information
Cloud formation
Ice formation
Different types of ice/cloud
How weather systems develop
Weather associated with the passage of frontal systems
Localised weather (katabatic winds etc)
4 stages of the passage of a low
Stationary front (2 air masses meet)
Developing front (Coriolis effect takes hold)
Mature front (fully developed)
Occluded front
Weather at an occluded front
Lots of rain,
Warmer temperature
Lower pressure
Unstable air and winds
Clouds similar to unstable air pocket, cumulonimbus etc
Poor visibility
SIMILAR to a trough
What is a TRS and how do they develop
Tropical Revolving Storm
Start as a non-frontal low pressure system
Only occur at certain times and places
Need the ITCZ to be in place relative to the area, which draws up/down the equatorial low
Water temp will get to more than 25
Need the Coriolis effect
Develops, feeds off warmer ocean
Pressure gets lower and lower, therefore winds increase
Generally speaking move away from the equator, in a Westerly direction
Signs and symptoms of a TRS
Potentially arising with drop in Mb of 3, accounting for diurnal variation
Definite approach if a drop of 5Mb
Winds increasing to force 6 and up
Buys ballots law relative to the Hemipshere
Low, lazy swell
Significant change in expected wind direction and strength
Heavy rain
Extremely low atmospheric pressure and dark
Large clouds
Lack of wildlife
Weather warnings
Navigating safely away from a TRS
Move towards the equator
Depending on where the wind is relating to you, you will keep the wind on your Port bow or stern, in the SH
Stbd bow or stern, NH
