All-time record warmth despite Southern California rain
It has been a relentlessly warm year across essentially all of California. Not only is 2015 California’s warmest year on record to date (beating the previous record set all the way back in 2014), but the details of the persistently elevated temperatures have been particularly oppressive. Heatwaves have been a frequent occurrence throughout the state this summer and now continuing into early autumn, but it’s not just afternoon highs that have been stifling: overnight minimum temperatures, buoyed by the incredible warmth of the nearshore Pacific waters, have been far above their typical levels. This has been especially true in Southern California, where water water temperatures as high as 80 F (!) have essentially shut off the natural ocean “air conditioner.” Extremely warm ocean temperatures have also interacted with an unusually high number of atmospheric disturbances to bring highly anomalous warm season precipitation to Southern California. Some of these disturbances have been tropical in nature (most memorably, the remnants of Hurricane Dolores back in July), but more recently the culprit has been a series of erratic and slow-moving cut-off lows….
….Central Pacific Hurricane Oho is making a virtually unprecedented northward beeline for the Gulf of Alaska. After weakening from a category 2 storm, Oho is expected to slowly transition into an extratropical (non warm-core) system as it accelerates northward in the coming days. Very impressively, it appears likely that Oho will retain some tropical characteristics (and perhaps hurricane strength winds) as far north as San Francisco (but out over the open ocean well to the west of California). While Oho will not bring any noticeable impacts to California (aside from some unusual surf conditions), it may bring very heavy precipitation and powerful near hurricane-force winds to parts of southeastern Alaska and far northern British Columbia, where it will make landfall this weekend…. El Niño already top-3 event in modern history; further strengthening still expected…..everything’s still on track for a very strong event during the coming winter. In fact, the most recently observational data now clearly indicates that the present event is already comparable in magnitude to both the 1982-1983 and 1997-1998 events, which were the strongest in the long-term record. North American and international forecast models continue to project further strengthening of warm topical Pacific Ocean temperature anomalies for another 1-3 months, with peak magnitude arriving sometime during Northern Hemisphere winter. California impacts—in the form of wetter-than-average conditions–are still expected to be greatest during the core rainy season months of January-March (and perhaps also December), which means that we shouldn’t necessarily expect to see wetter than average conditions in October and November. It does, however, look very warm over the next couple of months, which virtually assures that 2015 will become California’s warmest year on record.