Alfred E Nash III

Not to alarm anyone, but to raise awareness and encourage preparedness for what could be an exceptionally stormy winter across California. As the late, great Rea Strange of Pacific Weather Analysis often said, one of the most reliable indicators of a wet weather pattern for California is the development of strong, persistent upper-level westerlies stretching across the North Pacific Ocean. In my more than 35 years of forecasting weather along California's Central Coast, I've learned to pay particular attention when upper-air charts and numerical weather models indicate the development of a powerful, persistent Pacific jet stream. In fact, I consider this one of the most important atmospheric indicators of a potentially wet and stormy winter for California, especially during a very strong El Niño condition. The latest projections from the European Centre for Medium-Range Weather Forecasts (ECMWF) suggest that an exceptionally powerful subtropical jet stream could develop across the Pacific Ocean and extend across much of the United States this winter and into early spring. Remarkably, these projections indicate the potential for record-strength subtropical jet-stream winds extending from California to Florida. If these long-range ECMWF projections verify, we could be looking at a remarkably active winter storm pattern, with the potential for well-above-normal precipitation across portions of California, particularly from late December through January, February, and March. Of course, there is an important distinction between favorable atmospheric conditions and actual rainfall. These are long-range projections, not guarantees. Even during powerful El Niño events, California's precipitation can vary considerably depending on the position of the jet stream/storm tracks and other atmospheric influences. Nevertheless, the potential development of such an unusually strong and persistent Pacific jet stream is a significant atmospheric signal that deserves our attention. My message is not one of alarm, but of awareness and preparedness. Now is an excellent time to clear drainage systems, inspect roofs and gutters, review emergency plans, and prepare for the possibility of an unusually wet and stormy winter. Please visit ReadySLO.org for preparedness, emergency, and recovery information. I'll continue closely monitoring the upper-air patterns and numerical weather models as we approach the heart of California's rainy season. Special thanks to meteorologist Ben Noll for sharing this ECMWF analysis and highlighting the potential significance of this developing atmospheric pattern. – at Los Osos, CA