( Pileus ( ( ( is ( a ( fleeting ( , ( ephemeral ( cloud ( ( type and ) forms ) ) ) ) ) ) ) ( as ( ( ( convective up-draughts ) ( in ( the cumulus ) ) ) ( ( force ( upper winds ) ) ( ( ( ( over ( the ( rising congestus ) ) ) , ) just ) ( like ( air ( being ( forced ( to ( rise ( over ( a ( mountain range ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Pileus)) (VP (VBZ is) (NP (DT a) (JJ fleeting) (, ,) (JJ ephemeral) (NN cloud) (NN type) (CC and) (NNS forms)) (SBAR (IN as) (S (NP (NP (JJ convective) (NNS up-draughts)) (PP (IN in) (NP (DT the) (NNS cumulus)))) (VP (VBP force) (NP (JJ upper) (NNS winds)) (PP (PP (IN over) (NP (DT the) (VBG rising) (NNS congestus))) (, ,) (RB just) (PP (IN like) (NP (NP (NN air)) (VP (VBG being) (VP (VBN forced) (S (VP (TO to) (VP (VB rise) (PP (IN over) (NP (DT a) (NN mountain) (NN range))))))))))))))) (. .)))
Pileus is a fleeting, ephemeral cloud type and forms as convective up-draughts in the cumulus force upper winds over the rising congestus, just like air being forced to rise over a mountain range.
(ROOT (S (NP (NN Chinook) (NNS winds)) (VP (VBP occur) (SBAR (WHADVP (WRB when)) (S (NP (NN air)) (VP (VBZ is) (VP (VBN forced) (PP (IN over) (NP (DT a) (NN mountain) (NN range)))))))) (. .)))