Local Wind Systems Flashcards
What are the 4 types of winds ( coastal and mountains ) that are diurnal?
Including direction of wind and strenth
Sea Breeze - day time (10 am 3pm ) onshore, 10 - 15 kts
Land Breze - night time - offshore - 3 - 4 kts
Anabatic - day time, mountains - upslope
Katabatic - night time, mountains - downslope
Describe why a sea breeze forms?
Include weather to expect
As the sunrises it heats up the land, creating a thin layer of L ( as the air is rising )
Water heats slower, so the wind goes from sea to land.
Creates circulation, up to 3,000 ft.
Upto 40km inland
Expect fair weather cumulus
Describe why a land breeze forms
Including weather
At night, land cools faster than sea.
Results in high pressure
Wind from land to sea ( light 3 - 4 kts )
How can a seabreeze create fog inland?
Fog formed over the ocean is pushed inland because of the seabreeze.
What happens ( and what weather ) when a seabreeze is coming from both sides of a penisula or land mass?
Creates a convergent zone.
Results in Towering Cumulus and can form storms.
Why would windsocks be opposing
If there is a sea breeze and the prevailing wind is offshore.
Always try to land in the direction which provides headwind over the runway ( as opposed to on final )
With mountains what is a Anabatic wind and why does it form?
Upslope wind.
During daylight
Mountian sides are heated.
Stronger winds if mountain are snowcaped ( larger temp diff and therefore pressure diff ).
What is a katabatic wind ( mountains ) and why does it form?
Nighttime.
Downslope
Valley cools faster, creating a low pressure.
Wind flows downwards.
Snowcapped = stronger winds.
How does wind flow along the coast?
The wind will follow the headlands.
In areas where there are obstacles, the wind will compress and accelerate ( Ventrui effect )
What happens as wind heads towards mountains? ( where will it flow )
It will head toward a pass, if availalbe.
The winds will accelerate through the pass.
Creating updrafts on the windward side and downdrafts on the lee side.
How is wind deflected by mountains?
If the angle > 30 degrees, it will deflect.
If parallel , no affect.
If < 30 degrees generally go over.
Where are some specific places in NZ where wind channelling occurs?
And conditions
Cook Straight
Fovo Straight
Manuwhatu valley
Winds can exceed 60kts with large gusts.
Describe effects of mountain waves.
Include expected clouds and area of affect ( both vertical and horizontal )
Windward, strong updrafts
Lee side, downdrafts
Upto 25m/s
Lee will form standing waves, up high
Turbulence down low
Can see rotating clouds down low. AVOID.
Can see lenticularly up high in the standing waves
Mountain cap will hide ridge.
Finally, downlow there will be a stagnent area.
Affects downwind can be upto 100 NM
Common conditions in NZ for Foehn wind
NW wind over Canterbury.
Can happen in NI as well
