Solution forecast center

摘要

This issue's puzzle shows a stormy pattern across Alaska and northwest Canada on the evening of September 9, 2015. Here we see a deep low pressure area in the North Pacific Ocean, and once again readers get a chance to practice drawing rich isobar fields with plenty of features to analyze. We also see some of the first deep polar air masses of the season making their way southward from the Arctic pack ice. With our chart analyzed and most of the highs and lows discovered, let's consider the cause of the low pressure areas. Is the low south of Alaska frontal? Absolutely! One clue is the vast size of the low, shaped by the large scale of the air masses. The other clue is the tem­perature differences. They're not par­ticularly large, but considering that the system spans well over 1,000 miles, wid­ening our view of the air masses, we see temperatures ranging from 60s and 70s over the temperate Pacific to 40s across Alaska and pastern Siberia. These cold and warm air masses are inbound into the low pressure system, and they help sustain continued development.