Back to main menu  /  d1+09Z  d1+12Z  d1+15Z Help and usage   /  Use the clickable blipmaps on the right to get the name (mouse over) or the aerological profile (click on) of the place indicated by a black small star. Thermal parameters: BL top height / BL depth / BL topvariab / W* / B/S ratio / Convergence   /  Wind parameters  /  sfc parameters  /  clouds parameters Quick help: The BL top height prediction indicates the height to which air mixing will occur but not all mixing is equally useful to glider pilots. Mixing can be produced both by thermals and by (vertical) wind shear, but only thermals produce the relatively large updrafts needed for soaring. To help evaluate the degree to which the day's mixing is convectively driven, the "B/S" parameter represents the ratio between Buoyancy and Shear production of turbulence. A small Buoyancy/Shear Ratio (B/S) value indicates wind shear predominance leading to bad thermal quality. Thus dry thermals may be broken up by vertical wind shear (i.e. wind changing with height) and unworkable if B/S ratio is 5 or less. At a B/S of 10 or above, vertical shear is likely not a significant bad soaring factor. If convective clouds are present, the actual B/S ratio will be larger than calculated here due to the "cloudsuck". This parameter is truncated at 20 for plotting. Aide rapide: Si les vents sont trop variables dans la couche convective (CC), le mlange d'air dans la CC est chaotique et les thermiques sont dsorganiss. Pour quantifier ce phnomne on utilise le rapport flottabilit / cisaillement (buoyancy/shear ratio en anglais). La carte ci-dessus reprsente les B/S ratio dans le domaine de vol. En pratique, si B/S ratio est plus petit que 5 les thermiques sont dsorganiss. Si ce rapport est suprieur 10, les thermiques sont bons. Si de gros cumulus sont prsents (effet de succion et d'augmentation de la flottabilit des ascendances par ces nuages) les thermiques peuvent tre meilleurs que prvus malgr un B/S petit. Les valeurs de B/S sont tronques partir de 20.