Weather / Meteorology Flashcards
What are ways to get weather forecasts?
Internet Coastguard broadcasts Local radio stations Marina notice boards NAVTEX receiver for passages
In the Northern Hemisphere, which direction do low pressure systems revolve?
Anticlockwise
In the Northern Hemisphere, which direction do high pressure systems revolve?
Clockwise
The deeper and faster moving the depression indicates
The worse the weather is likely to be.
From where do low pressure systems approach the UK?
The Atlantic
The closer isobars are on the chart indicate what about the wind?
The stronger the wind is.
Which angle does the wind blow along the isobars of low pressure system - inward or outward?
Slighting inwards.
Which angle does the wind blow along the isobars of high pressure system - inward or outward?
Slightly outwards
When a low pressure system is moving in, what kind of clouds would you see in the sky up to 12 hours ahead?
High, thin, wispy clouds against a blue sky.
As a low pressure system (depression) approaches, how will clouds appear?
lower, thicker, and darker
What kind of winds are produced by high pressure systems?
Light winds
If average wind speed is expected to be F8 or more, or gusts 43-51 knots
Gale Warning
If average wind is expected to be F6 or F7
Strong Wind Warnings “Yachtsman’s Gale”
Within 6 hours of time of issue of warning
Imminent
Within 6-12 hours of time of issue of warning
Soon
More than 12 hours from time of issue of warning
Later
Good visibility in miles
> 5 miles
Moderate visibility in miles
2 < x < 5 miles
Poor visibility in miles
<2 miles
Wind changing in an anticlockwise direction (e.g., NW to SW)
Backing
Wind changing in a clockwise direction (e.g., NE to SE)
Veering
Term meaning No significant precipitation
Fair
Wave height for a Smooth sea state
0.2-0.5m
Wave height for a Slight sea state
0.5-1.25m
Wave height for a Moderate sea state
1.25-2.5m
Wave height for a Rough sea state
2.5-4.0m
Wave height for a very rough sea state
4.0-6.0m
Wind in knots for Beaufort Scale 1
light airs 1-3 knots
Wind in knots for Beaufort Scale 2
light breeze 4-6 knots
Wind in knots for Beaufort Scale 3
gentle breeze 7-10 knots
Wind in knots for Beaufort Scale 4
moderate breeze 11-16 knots
Wind in knots for Beaufort Scale 5
fresh breeze 17-21 knots
Wind in knots for Beaufort Scale 6
strong breeze 21-27 knots
Wind in knots for Beaufort Scale 7
Near gale 28-33 knots
Wind in knots for Beaufort Scale 8
Gale 34-40 knots
Wind in knots for Beaufort Scale 9
Severe gale 41-47 knots
Wind in knots for Beaufort Scale 10
Storm 48-55 knots
What is a Sea Breeze?
Land warms at a faster rate than the sea, heating the air above it. This rises and is replaced by cooler air from the sea. Warm air moves from land to sea and cooler air from sea back to land. Resulting wind can be up to force 4.
What is a land breeze?
Far weaker than a sea breeze. Warm air from sea rises to moves to land. Cooler air from land moves back to sea. Occurs on clear nights.
What are some physical things you can look at to determine wind speed?
Look for trees and flags tossing about Fast moving clouds Boats further down river heeling over
Besides wind strength, what 4 factors will determine how rough conditions are
- The fetch, or how far the wind has been blowing over the sea. 2. Direction and strength of tidal stream 3. Swell 4. Depth of water
Will sea fog burn off as the sun comes up?
No, it may actually get worse.
What do you call it when wind changes in an anticlockwise direction (e.g., NW to SW)?
Backing
What do you call it when wind changes in an clockwise direction (e.g., NE to SE)?
Veering