The Weather and Circulation of January 1951

The circulation pattern a t the 700-mb. level during January 1951 shown in figure For the first time since this series of articles was initiated a year ago, the monthly mean 700-mb. height anomaly did not exceed 220 feet in absolute magnitude anywhere in the Northern Hemisphere. In the North American region January height anomalies as small as those observed this year have occurred only once previously (1939) in the past 20 years. As a result, the waves in the westerlies were in approximately their normal location, with principal troughs located in the western Pacific and eastern North America, low latitude troughs in the Mediterranean and the Gulf of California, and ridges in western Canada, the eastern Atlantic, and the southeast Pacific. The outstanding abnormalities in the hemispheric circulation were the High in the Bering Sea, the Low in the Gulf of Alaska, the positive height anomaly center'south of Newfoundland, and the negative height anomaly in northern Eurasia. FIOURE 1.-Mean 7I"mb. chart for the 30-day period January 2-31, 1951. Contours at 200-ft. intervals are shown by solid lines, intermediate contours by lines with long dashes. and 700-mb. height departure from normal at 1M)-ft. intervals by lines with short dashes with the zero isopleth heavier. Anomaly centers and contours are labeled in tens of feet, Minimum latitude trough locations are shown by heavy solid linas.