Aviation Weather Hazards. Weather radar, observing equipment and balloon launching on roof. Mark Sinclair Department of Meteorology Embry-Riddle Aeronautical University Prescott, Arizona. ERAU Academic Complex. Weather center. Talk Overview. Survey of weather related accidents Turbulence
Weather radar, observing equipment and balloon launching on roof
Department of Meteorology
Embry-Riddle Aeronautical University
ERAU Academic Complex
4,159 (21.3%) weather related
Main cause = wind
I’m an eddy
(more stable air above)
up to 20,000’ MSL
Hot, dry, unstable air
Photo by Joe Aldrich
Flight path of plane
45 kt headwind
45 kt tailwindDry microbursts from high based thunderstorms
July 2003—Photo by Phillip Zygmunt
1999—Photo by Jacob Neider
Friction layer during day
Deep turbulent friction layer
Shallow non-turbulent friction layer
Strong turbulence during day means a deep layer is stirred
Mixing means 3,000 ft wind better mixed down to surface
Stronger turbulence, reduced vertical wind shear
Reduced turbulence means only a shallow layer is mixed
Suppressed downward mixing means surface wind falls to near zero at night
Stronger vertical shear
Orographic cloud and possible IMC conditions on upwind side
Strongest wind speed and turbulence on downwind side, also warm and dry
Desired flight path
Actual flight path
Turbulent Layer 2
2kft above to 6kft below trop
Turbulent Layer 1 - SFC-~7kft above peaks
Mountain Wave (> 25kt perpendicular component /stable air are key)
Wave clouds (altocumulus lenticularis)
Lee wave clouds in NZ
Satellite photo of lee waves over Scotland
IFR conditions are a factor in over half of the General Aviation weather related accidents
Evaporation below cloud base raises the dew-point and lowers the temperature
Typically occurs in winter when there is a surface inversion
The precipitation itself can also lower visibility to below IFR criteria in heavy snow or rain conditionsTypes of Fog - Precipitation Fog
1. How close is the temperature to the dew point? Do I expect the temperature-dew point spread to diminish, creating saturation, or to increase?
2. What time of day is it? Will it get colder and form fog, or will it get warmer and move further from saturation?
3. What is the geography? Is this a valley where there will be significant cold air drainage? Will there be upslope winds that might cool and condense?
4. What is the larger scale weather picture? Will it be windy, suppressing radiation fog formation? Is warm, moist air moving over a cold surface?
POD=Probability of Detection
It happened - was it forecast?
FAR=False Alarm Rate
It was forecast but did not occur.
About 75% of the time LIFR was forecast, it did not happen.
Less than half of the observed LIFR conditions were forecast correctly at TUL.
Departmental Rubber Chicken