Weather

Thermals

• Created by the heat that rises

• Upward currents of warm air that form as a result of uneven heating of earth’s surface

• primary cause of turbulence

Wind Shear

Sudden drastic change in wind speed or direction in a small area

• Can occur with upward or downward drafts at any time

• At lower altitudes wind shear becomes more hazardous

Wind Hazards

• Loss of flight control

  • Strong wind conditions will affect your ability to maintain control of your drone

• Battery life reduction

  • Loss of power or drone no longer has the ability to maintain altitude

• Return to home issues

  • Complications due to wind resistance and flight conditions

• Sudden altitude change

  • The drone is likely to fly beyond the regulation of the class of airspace

Warm Air Rising

Low pressure

Cold Air

High Pressure

Stratus Clouds

• Gray low level clouds that are flat

  • Light rain/steady drizzle

  • Stable weather

  • Effects drone operations by reducing visibility

  • Altitude restrictions due to low shelf

Cumulus Clouds

• White, puffy, fluffy flat base with dome shaped top

  • Clear visibility

  • Can develop into larger storm formations

  • Effect on drone operations

    • Generally don’t pose any restrictions

    • But if it is part of a developing storm turbulence and storm can follow

3 Stages of a Thunderstorm

1. Cumulus

2. Mature

3. Dissipating

Cumulus Stage

• Warm moist air is rising rapidly and begins to cool causing water vapor to condense

• No precipitation

Mature Stage

• Begins when storm reaches full development

• Characteristics: up and down drafts

• Precipitation

• Heavy rain, lighting, thunder, and down bursts

• Sometimes hail

• Strong wind gusts

Dissipating Stage

• Storm is losing its energy source- warm updrafts weaken and disappear

• No more rain

• Clouds will begin to disappear

Density Altitude

• Not a target altitude it describes how the air feels

• Low density altitude

  • air is thick and more efficient for flight

• High density altitude

  • air is thinner; drone propellers work harder

Stable Air

• Drone will have a very smooth flight

• Reduced visibility due to haze or fog

• Safer for smooth flights but make sure you have 3SM of visibility

Unstable Air

• Good visibility

• Air currents that can rise and fall

• Turbulence and unpredictable conditions

• Cumulus clouds, thunderstorms, and strong winds

Dewpoint

The temperature at which air become fully saturated with moisture

• Moisture at maximum

• Forms best on clear calm nights, temperature on the ground cools faster

• Dewpoint formula depends on temp and humidity

Radiation Fog

• Forms at night when the surface cools

• Also known as ground fog

• Found early in the morning

• Conditions for formation

  • Clear sky

  • Calm winds

  • A long night

Advection Fog

• Warm and moist air moves over cool ground or water

• Can form with strong winds and cloud cover

Up Slope Fog

• Moist air moves upward

• Prevalent at higher elevations

• Can exist in high wind conditions

Steam Fog / Evaporation Fog

• Cool air moves over warm body of water

• Wispy tendrils rising from water surface

• Pre fontal equals warm

• Post frontal equals cold