YOLO SUN (SUPPLEMENTAL) NEWS REPORT :
This supplemental news report is published to best provide Woodlanders (indeed, Yolo County in general) with what they need to know, regarding the prior article of Yolo Sun, alongside the most conscientious and reliable (long-range) weather forecast interpretation which is presently available for California (please see below).
Some local folk believe (this specific view has come directly from the mouths of high city officials) that an impending El Nino event may serve to solve Woodland’s water woes; while in actuality, this topic is much more complex (as well as, interesting).
Yesterday (June 11), statewide news reports indicated a strengthening of the El Nino phenomenon of Pacific Ocean warming, possibly leading to increased precipitation for California (in general). Here’s a representative snippet from San Jose Mercury News (SJMN):
“Currently, an ocean area that scientists call the “3.4 region” along the equator near South America that is considered a key indictor of El Niño trends is 1.2 degrees Celsius, or 2.1 degrees Fahrenheit, above the historic average. That departure from normal is twice what it was a year ago. And the trend is expected to keep growing.
“Supercomputers at NOAA, NASA and other world-leading scientific institutions are projecting the temperatures in that ocean region to hit 1.6 degrees Celsius, or nearly 3 degrees Fahrenheit, on average by September. The last time temperatures there reached that level in a September was in 1997, when they hit 2.3 degrees Celsius, or 4.1 degrees Fahrenheit, above average. What followed was among the wettest winters in California history, similar to another strong El Niño year, 1982-83, with California receiving twice as much rain as normal.”
What does this potential strengthening of the current El Nino actually mean for Woodland?
Mainstream journalism (such as SJMN) usually tends to vastly generalize around such key, localized (even Northern California type) details.
However, there exists a blog uniquely devoted to these sorts of details: Weather West ( http://weatherwest.com ).
Weather West displays the work of Daniel Swain, alumni of UCD and now at Stanford.
Weather West has provided unique and valuable California weather and climate information, as well as profound discussion of such, since 2006.
Daniel Swain is a PhD candidate in the Department of Environmental Earth System Science at Stanford University. A member of the University’s Climate and Earth Sciences Dynamic Group, Daniel studies the changing character of extreme meteorological events, with a focus on the role of persistent large-scale atmospheric patterns. He holds a B.S. in Atmospheric Science from the University of California, Davis.
June 3 (El Nino) Essay By Weather West
On June 3, Weather West published a lengthy and intriguing essay about El Nino and the continuing (4th year) California drought, reaching a level of intricate weather interpretation not found within the mainstream press.
Some local folk have suggested, for example, that next winter California may experience something akin to what Texas has recently seen.
Says Weather West:
“Given the strengthening El Niño event, do the drought-busting Texas floods suggest that California will be in for the same experience next winter? Not really–well, at least not directly. The kind of weather pattern that led to the Texas floods–persistent, moist deep convection (thunderstorms) with self-organizing characteristics (i.e. mesoscale convective complexes) aren’t really possible in California. We don’t have anywhere near the kind of warm, moist, and unstable conditions made possible in Texas by the proximity of the Gulf of Mexico, and large-scale atmospheric conditions near California are also generally unfavorable for this kind of event.”
“During weak El Niño events, this effect is less profound, and the end result can often be relatively weak versions of both the subtropical and sub-polar jet vying for influence over the East Pacific. The net effect can be quite variable; if California’s lucky, we see moist storms originating from both regions, but if we’re unlucky, we can largely miss out on storm systems taking both trajectories. If we composite the most recent weak El Niño episodes, the average effect in California actually appears to be a slight drying during the winter months–directly contrary to the El Nino mythology that pervades the Golden State.” (Emphasis added.)
Related to strong El Nino influences, Weather West expresses:
“However, things are a quite a bit different during a strong El Niño event. When East Pacific sea surface temperatures become sufficiently warm, large-scale atmospheric temperature differences between the tropics and the mid-latitudes are big enough to strengthen the subtropical jet quite substantially over the portion of the East Pacific that is most relevant for California wintertime precipitation. This enhanced subtropical jet can greatly enhance the strength of low-latitude storms west and even slightly south of California, and also makes it easier for such systems to tap into the rich tropical and subtropical atmospheric moisture reservoir that exists at lower latitudes. Additionally, storms during strong El Niño years have the potential to be more convectively unstable due to increased lower-atmospheric temperature and moisture, leading to an increased likelihood of intense localized downpours. In other words: a strong El Niño event tends to result in a jet stream structure that 1) steers more storms toward Southern California, 2) is favorable for stronger storms at a lower latitude in the East Pacific, and 3) affords pre-existing storms greater potential access to warm, moisture-rich air masses.”
Thus, even in a strong El Nino, odds are that much of Northern California could be left relatively dry.
Weather West further describes relevant matters (emphasis occasionally added):
“Will El Niño end California’s extraordinary, multi-year drought during Winter 2015-2016?
“Almost certainly not. Over the past four years of very low precipitation and record-shattering warmth, truly enormous water deficits have accumulated throughout California. On a statewide basis, the Golden State would need to see substantially more than an entire year’s worth of extra precipitation fall to eliminate the long-term deficit in a single year (in other words, a year with much greater than 200% of average). Since California’s all-time wettest years (typically associated with very strong El Niño events) have historically involved a doubling (200%) or less of annual precipitation, California would probably need to experience its wettest year on record (by a fairly wide margin) to erase ongoing deficits in a single year. While it’s not physically impossible, that would be a very tall order, indeed. And a winter like that would most likely bring a whole host of other problems.
“Could a strong or very strong El Niño in 2015-2016 substantially mitigate the California drought and/or lead to serious flooding?“Absolutely. If the developing El Niño event reaches a strong or very strong intensity and maintains its strength through winter 2015-2016, the odds of experiencing persistently wet conditions next winter will increase. The occurrence of frequent precipitation events during significant El Niño winters increases the probability that antecedent hydrological conditions will be moist if and when heavy precipitation events do occur, increasing the risk of flooding. Also, since the trajectory of Pacific storms during strong El Niño winters tends to be from a much lower (more southerly) latitude, air masses during rain events tend to be warmer and moister overall.
“This can have several effects, including higher snow lines and more rapid runoff, greater precipitation intensity overall, and an increased risk of deep moist convection (which can produce very high rainfall rates even in the absence of mountainous topography). It’s important to note that almost all of California’s major flood events result from land-falling “atmospheric rivers,” which tend to be more frequent (but not necessarily more intense) during El Niño years. Therefore, a major flood can easily occur during any winter, El Niño or not. Still, for upper-tier El Niño events, there is definitely an increased risk of above-average precipitation and flooding during the cool season.
“Since strong El Niño events increase the likelihood of wet California winters, it does stand to reason that a strong El Niño in 2015-2016 could provide at least partial (and perhaps substantial) drought relief. A wet winter would most likely allow most of California’s major reservoirs to fill, though those who operate California’s dams and reservoirs are heavily constrained by flood control mandates. Surface soil moisture would increase, and drought-stressed forests and ecosystems would benefit substantially in the short term. Stress on urban water supplies would be reduced as demand decreases, and supply increases.
“But even a tremendous amount of water falling from the sky won’t completely alleviate all of California’s drought impacts. And if much of this hypothetical precipitation were to fall as rain rather than snow in the Sierra Nevada, longer-term water storage wouldn’t be boosted nearly as much as it would otherwise.
“California is currently witnessing firsthand what happens during its first year in recorded history without a measurable springtime snowpack, and it’s becoming quite clear that warming temperatures aren’t very compatible with the snowmelt-dependent water storage infrastructure currently in place.
“The Pacific Ocean, on the whole, remains extraordinarily warm (even in regions geographically far removed from those used to define El Niño), and is expected to remain so for the foreseeable future. This means that even if heavy precipitation does return to California next winter, temperatures will likely remain well above the long-term average.
“And just to reiterate a key point from above: we still don’t know for sure whether strong or very strong El Niño conditions will ultimately develop (nor whether they will persist until winter, when they are most relevant for California). Confidence is starting to increase in current projections, since we’re now emerging from the Spring Predictability Barrier and most dynamical models are still suggesting the potential for a powerful event. But when we concatenate all the various uncertainties discussed above, there’s still something of an open question regarding what happens in California next winter.
“At this point, it’s fair to state that the likelihood of experiencing a wetter-than-average winter (and, perhaps, flooding) is increasing, but simultaneously that the risk of the California drought continuing into 2016 is nearly 100%. Needless to say: it will probably be a very interesting year to come for weather and climate-watchers in the Golden State. Stay tuned!”
Yolo Sun greatly encourages Woodlanders to stay up to date regarding Northern California’s general weather conditions and drought forecasts, by means of this valuable blog.