The 500Mb chart is the key that unlocks the three-dimensional nature of the atmosphere and helps answer the mariner’s two most important weather questions: will the system intensify, and where is it headed? In Heavy Weather Avoidance, Chen and Chesneau merge the seamanship of a master mariner and the forecast expertise of a senior meteorologist, providing readers with double-barrel exposure to what actually goes on in the atmosphere and on the seas surface. Many weather texts offer an academic look at weather systems, complete with model algorithm derivations and equations depicting heat transfer. These fundamentals may be the cornerstone of the science, but commercial mariners and recreational sailors are more concerned about the implications of volatile weather rather than its fluid dynamics. From start to finish the authors have cut to the chase, creating a readable text brimming with useful graphics. Its focused on the root cause of how and why bad weather develops and where its likely to go. Theres enough theory provided for a reader to get a feel for how air mass energy transfer works, but just as the theoretical aspect takes on a mission of its own, theres a shift to more practical self-forecasting and storm avoidance wisdom. Captain Ma-Li Chen shares his well-tested routing strategy and describes how it factors in the use of the 500 Mb chart. His game plan includes a sector analysis of short wave troughs, breaking them into four distinct zones and prioritizing the relative safety of navigating through each region.