CALIFORNIA, Sept. 10 (Our California Times) — NOAA’s September forecast gives El Niño a 97% chance of reaching “Super El Niño” strength during the fall and winter and continuing into early spring. For people in California, the practical step is to follow updates from NOAA and the National Weather Service, especially as the wetter portion of the pattern may arrive from December through March.
The forecast does not mean California is under an emergency warning. It describes a seasonal climate pattern that can shift the odds of certain types of weather. No specific California flood watch, coastal statement or local storm forecast was identified in the information available.
What is El Niño?
El Niño occurs when waters in the central and eastern equatorial Pacific become warmer than average. Those warmer waters can alter the jet stream, rainfall patterns and wind conditions across large parts of the world.
Forecasts use different terms for unusually strong events. In the supplied NOAA-related forecasts, “Super El Niño” has been described as water temperatures at least 2 degrees Celsius above average for three consecutive months. The available observations show that temperatures reached 1.4 degrees above average in July, so the information provided does not confirm that the three-month threshold has already been met.
NOAA’s August outlook gave El Niño a 90% chance of ranking among the strongest events on record during fall and winter. A July outlook had put that chance at 81%. The percentages have changed as forecasts were updated, and terms such as “very strong,” “Super El Niño” and “strongest on record” have not been used consistently in the available reports.
Why are the Atlantic and Pacific behaving differently?
El Niño often suppresses Atlantic tropical activity by increasing upper-level winds, also called wind shear. Strong wind shear can tilt or disrupt developing tropical systems.
At the same time, El Niño can support more activity in the eastern and central Pacific. NOAA’s Climate Prediction Center said in a July 28 outlook that tropical-cyclone formation was unlikely over the Caribbean and central Atlantic for the foreseeable future.
By Sept. 10, the climatological peak of the Atlantic hurricane season, the Pacific had produced 16 named storms, including six hurricanes and three major hurricanes, according to figures reported by Fox Weather. The Atlantic had produced five named storms and no hurricanes.
Those totals describe activity through that date, not a guarantee that the rest of the season will remain quiet. As AccuWeather lead hurricane expert Alex DaSilva put it, “The stronger El Niño becomes, the greater the likelihood of a less active end to the season.”
A quiet Atlantic season can still produce a damaging storm. Steven DiMartino, quoted by Yahoo News, noted that “you only need one hurricane to have significant impacts.”
What could California experience?
The strongest reported California signal is a greater chance of above-average precipitation in Southern California, particularly from December onward. January through March has been identified as the prime period for possible effects by experts cited in Los Angeles Times coverage, including Alexander Gershunov, a research meteorologist at Scripps Institution of Oceanography at UC San Diego, and Michelle L’Heureux.
A strong El Niño can also steer more storms toward the southern part of the state. But a seasonal outlook cannot determine how much rain a particular community will receive, when individual storms will arrive or whether flooding will occur.
The pattern may also affect California’s coast. More active eastern Pacific tropical systems can produce hazardous high waves, and the broader weather pattern could increase the risk of coastal flooding through higher sea levels, according to the Los Angeles Times’ report on the experts’ assessment. Those are potential seasonal impacts, not an active coastal warning.
What should Californians watch?
Residents should use short-range forecasts for decisions about rain, wind, surf and flooding. Seasonal El Niño forecasts are useful for understanding broad risks but cannot replace local advisories.
People near the coast should monitor National Weather Service statements for high surf, coastal flooding and storm conditions. Inland residents should watch for rainfall forecasts and any flood or debris-flow warnings issued for their area. The available information does not identify a specific California location, rainfall total, wave height or date for a local hazard.
The central message is that El Niño is strengthening in the forecast, and its effects may become more important during the winter. It is tilting the odds toward a quieter Atlantic and a more active Pacific while raising the possibility of wetter conditions and coastal hazards in California. The timing and severity of those effects will depend on individual storms and future official forecasts.
