Questions -Answers Nijmegen 21 February 2009
Toptherm The toptherm model is totally different from the SkyView model, developed for soaring purposes only. • Thresholds for turbulence and shower sign: • Turbulence: There are three turbulence classes. These classes are related to the windshear accumulated over the whole convective mixing layer (layer between ground and 1000 m) in steps of 100 m • No turbulence: up to 10 kt/1000m • Low turbulence: 10 – 17 kt/1000 m • Medium turbulence: 18 – 30 kt/1000m • Strong: more than 30 kt/1000m
SkyView • Showers and thunderstorms are grid point related. The probability of thunderstorms and shower is calculated by using a parametriza-tion. • Preconditions: • Showers: temperature of tops < -12°C • Thunderstorms: temperature of tops < -25°C • Humidity: If there are dry levels (spread > 10 K), below the minus 10 degree level, no convective precipitation (showers, thund.) will be developed). • A positive vorticity (updraft area) leads to a higher probability. • Thresholds: showers 30%, thunderstorms 40%
SkyView Possibility to refine the shower symbol to an extend that could show how big the risk for showers is The perametrization of showers and thunderstorms is a automatic process. The results of this process are used by all kind of users (public safety, traffic, industry, air transport, maritime transport etc.) Therefore special parametrizations for soaring purposes is’nt possible. The risk for showers and thunderstorms can be assessed by the conditions mentioned in the transparency before.
Convection Forecast • Is there any difference in the Toptherm model and the convection forecast? • Yes, it is. • The convection forecast based on a parametrization • The Toptherm forecast is the result of direct model outputs
General question on pc_met data • Is there any data available for the use of European Gliding Championship in Lituania? • Yes, there are data • SkyView covers the whole European Area • There are forecasted meteograms for eastern Europe • There are some vertical soundings (actual and forecasted)
General question on pc_met data • Why do thermalson some days stop quite abruptly or on other days gradually fade out? • It depends on advection of cold or warm airmass, windshear/turbulence, small inversions/stable layers. • Recognizing with pc_met data: • By using the actual and the forecasted profils of the vertical soundings • By using of convection forecasts or SkyView data
General question on pc_met data • How can you recognize that soread-out and overdevelopment will last during the whole day or that it quickly will dissipear and normal thermal activity will soon start again? • It can be recognized by using: • Toptherm, SkyView, SkyView LMK, convection forecasts • Furthermore by matching of vertical sounding real and forecasted) for different times
General question on pc_met data • 0n some days with rain showers the thermal activity stops near the rain cloud at the moment it starts to rain. On other days with rain showers the thermal remain active near the rain cloud for a long time. What is the difference and how you can recognise this in the pc_met data? • It depends on the stability of the air mass and the intensity of the shower. If there are strong showers, a lot of cold air (often with grain or hail) is breaking down and stops the thermal for a longer time aslo in the surrounding area • In case of small showers, this effect doesn’t work. Recognition by using the forecasted vertical soundings
General question on pc_met data • Is it possible to predict whether he thermals are large and calm or that they are small and turbulent. IfCan you recognize the build up o rain showers structured in lines using pc_met? • Yes, the recognitions is possible by the use of: • SkyView and SkyView LMK
General question on pc_met data • Can you recognize the build up o rain showers structured in lines using pc_met? • Yes, the recognitions is possible by the use of: • SkyView and SkyView LMK
General question on pc_met data • Is it possible to predict whether the thermals are large and calm or they are small and turbulent? If yes, where can you see this in the pc_met data? • This effect depends on the stability (vertical gradient of temperature) and especially of the vertical gradient of the wind. A constant and consistent wind field leads to more calm thermals. A turbulent wind field leads to turbulent thermals (independent of the intensity of the thermals!
General question on pc_met data • How can you recognize worsening local conditions due to for example colder soil that is more moist or air that is Iess instable? • By using convective forecasts, SkyView and vertical soundings (actual or forecasted) • You can overlay 2 or 3 vertical soundings (development during the day or development along a defined route!
Thank you for your attention Any further questions?