Synoptic analysis of daily and monthly mean circulation patterns indicates that bimodal warm season precipitation distributions are a frequent occurrence in the upper Middle West. Normal seasonal changes in the positions of ridges and troughs comprising the circumpolar westerlies are associated with a June maximum, a mid-summer decline, and a second peak in September. Warm season depressions (WSDs) in the precipitation profile occur most frequently during periods of northwesterly flow or amplified ridging in the mid-continent. Low frequencies of WSDs are associated with southwesterly flow and/or trough conditions. Labeling this phenomenon an “aberration” (Trewartha, 1981) is contrary to the known relationships between mid-latitude precipitation, atmospheric vertical motions, and the modal North American summer season circulation pattern.
No takes yet. Share an insight, caveat, or question.
Harrington et al. (1985) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: