If pilots are to assess if their flight is going to be in any way affected by turbulence it is imperative that they can read the signs. They must familiarize themselves with all available meteorological information concerning their flight and be able to read the reports and forecasts.
For a good evaluation of turbulence the pilot needs certain types of weather information. Necessary are observations, forecasts and any advisories and weather warnings like AIRMETs or SIGMETs. In this space we will see what kind kind of turbulence information can be extracted from these information sources.
As said previously, key weather information for the pilot is in observations, forecast and advisories. The pilot must be able to discriminate all weather data for relevant information, sections below gives some hints.
This table shows you which weather report or map can be used to interpret to obtain certain types turbulence.
|Weather Observation Analysis|
|Surface||Surface Analysis Chart, Weather Depiction chart||LLT, TNT, MWT|
|Soundings||Constant Pressure, Tropopause Data, Composite Moisture / Stability, Winds Aloft Charts||LLT, TNT, MWT, CAT|
|Radar||Radar Summary, Coded Radar Weather Reports||LLT, TNT|
|Satellite||Infrared & Visual Images||LLT, TNT, MWT, CAT|
|Pilot Reports||PIREPs (UA)||LLT, TNT, MWT, CAT|
Jeppesen produces a turbulence analysis map which shows any turbulence from FL200 up to FL450 combined with AIRMETs/PIREPs and maximum winds, this is a valuable resource. We have them on site in our weather section.
Most aviation forecasts are valid for a period of 24 hours ahead of present or reported time. Some report even further ahead but detail and accuracy suffer. From these reports the position of fronts, jet streams and macro scale waves can be used to identify possible future turbulence issues.
A number of weather products used are: Area and Terminal Forecast, Winds and Temperature Aloft, Low Level Surface, High Level Significant Weather Prog, Convective / Severe Weather Lookouts. Depending on the altitude of the flight the pilot can use some or all of these charts to assess the possible turbulence.
Available inflight weather advisories and warning are in the table below, note that some may not be available in your country.
|Advisory & Warnings|
|Convective SIGMET (WST)||TNT|
|SIGMET (WS)||LLT, TNT, MWT|
|AIRMET (WA)||LLT, TNT, MWT, CAT|
|Severe Weather Watch (AWW)||TNT|
|Meteorological Impact Statement (MIS)||LLT, TNT, MWT, CAT|
|Center Weather Advisory (CWA)||LLT, TNT, MWT, CAT|
Legend: LLT - Low Level Turbulence; TNT - Thunderstorms, MWT - Mountain Wave; CAT - Clear Air Turbulence
When reading any report make sure that you check its validity time and period and when it was issued. Old data sometimes stays in the system just because an airport closed and no new reports are available.
For preliminary preflight planning common radio station reports may be used. Just keep in mind that these reports are tailored at the non aviation user and usually do not include any turbulence data, let alone cloud bases or visibility.Written by EAI.