1, SYNOPTIC SITUATION An unusual rise in pressure was lrotcd 011 t l r c AI.1.T. Depart8nlent of Meteorology Irricrob:trograph during tlw early morning of April 12, 1961. T h fact. t'hat no st80r1rr;\or squally weather was observed at, the t'irrre aroused the author's curiosity to irlvestigat8e the pl~errotr~cr~on in greater detail. Stud!of t,llc 3-hr. t'erldencies reported by the net'work of h...