▁mes o - alpha ▁to ▁syn opt ic ▁scale ▁when ▁its ▁horizontal ▁extent ▁grows ▁from ▁. ▁ ▁Ext rat rop ical ▁cycl ones ▁ ▁Norwegian ▁cy clone ▁model ▁▁ ▁The ▁Norwegian ▁cy clone ▁model ▁is ▁an ▁ideal ized ▁formation ▁model ▁of ▁cold - core ▁cycl onic ▁storm s ▁developed ▁by ▁Norwegian ▁meteor olog ists ▁during ▁the ▁First ▁World ▁War . ▁ ▁The ▁main ▁concept ▁behind ▁this ▁model , ▁rel ating ▁to ▁cy c log en esis , ▁is ▁that ▁cycl ones ▁progress ▁through ▁a ▁predict able ▁evolution ▁as ▁they ▁move ▁up ▁a ▁front al ▁boundary , ▁with ▁the ▁most ▁m ature ▁cy clone ▁near ▁the ▁n ortheast ▁end ▁of ▁the ▁front ▁and ▁the ▁least ▁m ature ▁near ▁the ▁tail ▁end ▁of ▁the ▁front . ▁ ▁P rec urs ors ▁for ▁development ▁▁ ▁A ▁pre ex isting ▁front al ▁boundary , ▁as ▁defined ▁in ▁surface ▁weather ▁analysis , ▁is ▁required ▁for ▁the ▁development ▁of ▁a ▁mid - lat itude ▁cy clone . ▁The ▁cycl onic ▁flow ▁begins ▁around ▁a ▁dist urbed ▁section ▁of ▁the ▁station ary ▁front ▁due ▁to ▁an ▁upper ▁level ▁disturb ance , ▁such ▁as ▁a ▁short ▁wave ▁or ▁an ▁upper - level ▁tr ough , ▁near ▁a ▁favor able ▁quadr ant ▁of ▁the ▁upper ▁level ▁jet . ▁However , ▁en hanced ▁along - front al ▁stretch ing ▁rates ▁in ▁the ▁lower ▁tro pos phere ▁can ▁suppress ▁the ▁growth ▁of ▁extr at rop ical ▁cycl ones . ▁ ▁Vert ical ▁motion ▁affect ing ▁development ▁▁ ▁Cy c log en esis ▁can ▁only