( ( To ( ( the east ) ( of ( the cyclone ) ) ) ) ( , ( ( the ( moist ( air mass ) ) ) ( ( is ( moving ( to ( ( the north ) ( behind ( the ( warm front ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (TO To) (NP (NP (DT the) (JJ east)) (PP (IN of) (NP (DT the) (NN cyclone))))) (, ,) (NP (DT the) (JJ moist) (NN air) (NN mass)) (VP (VBZ is) (VP (VBG moving) (PP (TO to) (NP (NP (DT the) (NN north)) (PP (IN behind) (NP (DT the) (JJ warm) (NN front))))))) (. .)))
To the east of the cyclone, the moist air mass is moving to the north behind the warm front.
(ROOT (S (NP (NP (DT The) (JJS best) (NN explanation)) (PP (IN for) (SBAR (WHADVP (WRB how)) (S (NP (NN air) (NNS masses)) (VP (VBP move) (PP (IN across) (NP (DT the) (VBN united) (NNS states)))))))) (VP (VBZ is) (SBAR (IN that) (S (NP (DT the) (VBG prevailing) (NNS westerlies)) (VP (VP (VBP move) (NP (NN air) (NNS masses)) (PP (IN from) (NP (NN west))) (PP (TO to) (ADJP (JJ east))) (PP (IN across) (NP (DT the) (VBN united) (NNS states)))) (CC but) (VP (MD may) (VP (VB be) (VP (VBN deflected) (PP (IN by) (NP (DT the) (NN jet) (NN stream)))))))))) (. .)))