IFR Weather

Sea Breeze

A sea breeze is a coastal local wind that blows from sea to land and is caused by temperature differences when the sea surface is colder than the adjacent land. day

Land Breeze

A land breeze (see Figure 10-16) is a coastal breeze blowing from land to sea caused by the temperature difference when the sea surface is warmer than the adjacent land. night

valley breeze

A valley breeze (see Figure 10-19) is a wind that ascends a mountain valley during the day. Air in contact with the sloping terrain becomes warmer (less dense) than air above the valley.

mountain breeze

 mountain breeze (see Figure 10-21) is the nightly downslope winds commonly encountered in mountain valleys. Air in contact with the sloping terrain cools faster than air above the valley

Definition of “Known Icing”

• The NTSB has held that known icing conditions exist when a pilot knows or reasonably should know of weather reports in which icing conditions are reported or forecast

• However, the NTSB's decision making reflects the common understanding that the formation of structural ice requires two elements: visible moisture and an aircraft surface temperature at or below zero degrees Celsius

Radiation Fog:

Is a common type of fog, produced over a land area when radiational cooling reduces the air temperature to or below its dewpoint. Thus, radiation fog is generally a nighttime occurrence

Valley fog

Ground heats→ colder air on mountain sinks into valley → colder air leads to reaching dew point

advection fog

forms when moist air moves over a colder surface and the subsequent cooling of that air to below its dewpoint. It is most common along coastal are

upslope

Upslope fog forms as a result of moist, stable air being adiabatically cooled to or below its dewpoint as it moves up sloping terrain

frontal fog

When warm, moist air is lifted over a front, clouds and precipitation may form. If the cold air below is near its dewpoint, evaporation (or sublimation) from the precipitation may saturate the cold air and form fog.

Steam Fog:

When very cold air moves across relatively warm water, enough moisture may evaporate from the water surface to produce saturation.

Freezing Fog:

Freezing fog occurs when the temperature falls to 32 °F (0 °C) or below. Tiny, supercooled liquid water droplets in fog can freeze instantly on exposed surfaces when surface temperatures are at or below freezing.