http://www.surfline.com/surf-news/u...rk-sends-waves-precipitation-record-s_146521/
Precipitation Record Set by 1982-83 El Nino Falls
Update: Modest late-season storm pushes Sierra 8-station index over the mark, sends waves
By Schaler Perry
Published:April 13, 2017
Views:16,915
While the surf wasn't all-time for much of the West Coast this winter, there were still certainly some windows.
After years of prolific drought, California was drenched this winter. Spring is here now, but the water year has just surpassed the former wettest year on record - the very strong El Niño of 1982-83.
In a fairly unprecedented way, surf has been the sideshow to snow, or rain depending on elevation, for much of the West Coast this winter. There have been some fine moments of surf, to be sure, but the amount of water making its way into California this winter hasn’t been seen in decades.
The snowpack in the upper elevations of the Sierra has been astronomical, rendering second floor balconies main entries and burying chair lifts. A key 8-station metric used to quantify water in the Sierra recorded a staggering 89.7 inches this morning, out-doing the 88.5 inches recorded during the 1982-83 El Niño. A storm impacting the West Coast last weekend brought us within an inch of the mark, and a modest low pushed us over the finish line this morning. Note that it is only April 13th, and we still have over five months of water year to go. Despite opportunity for more, and potentially potent, storms on the charts through the next month or so, the climatologically strongest months for precipitation have passed.
So, it's been wet. But why is all this precipitation showing up now instead of last year? You know, when the impending, historic El Niño was slated to quench the growing thirst brought on by four years of drought across California.
On a rudimentary level, that's pretty easy. The Golden State has been on the receiving end of a multitude of Atmospheric River (AR) events. In a normal year we see less than five, this year we've had north of ten. Atmospheric River's aren't specific to the Pacific; they are one of the primary vehicles for transferring water from the tropics to the sub-tropics and mid-latitudes. The colloquial Pineapple Express, which taps moisture near Hawaii and unloads it along the West Coast, is paramount to the amount of precipitation California receives in a given year. It has been working overtime this year.
It's interesting to note that despite breaking the long standing precipitation record from the El Niño of 1982-83, the overall snowpack in the Sierra has not been as prolific.
But why now? And why during a weak La Niña? In terms of the surf-end of El Niño, last winter offered an abundance of waves and generally favorable winds/conditions across California. Especially through much of January and February as high pressure settled over the Southern half of the state, blocking any substantial precipitation.
This year has been different. If you are thumbing through this from California, you are surely admiring the vibrancy brought on by seemingly weeks-straight precipitation. Super bloom anyone? Records have been toppled, and it has been shown that brown vegetation (or lack thereof) + water = green. It is a testament to the amount of water transported in these AR events, many of which have originated from a fairly unique pattern.
Newly minted research by scientists at the National Center for Atmospheric Research (NCAR) has shed light on just what has been driving the unique, prolific patterns delivering drought and deluge in California of late. The global pattern is intuitively named “Wavenumber-5”, noting the simultaneous existence of five pairs of high/low pressure around the globe. As one might imagine, the location of these high and low-pressure features is paramount to the local weather patterns brought on. The historic El Niño winter of 2015-16, along with the preceding winter, were characterized by high pressure over the West Coast bringing less than normal precipitation and mild weather.
Through much of the last several months Wavenumber-5 has been expressed by immense, blocking high pressure extending southeastward from the Aleutians. During that time, troughing has been the dominant feature along the U.S. West Coast, the tap to the Pineapple Express being turned on as cut-off Kona lows repeatedly developed near Hawaii and moseyed towards the U.S. mainland. The most potent of these events, and subsequently the largest swells, have come when the Jet Stream has extended unobstructed from Japan to the California coast.
While the first couple weeks of January brought abundant precipitation, the waves weren’t on par for the historically largest surf month of the year as the high extending from the Aleutians shortened the storm track across the North Pacific. A changing of the guard came mid-January with the first extension of the Jet (see Winterlust) and over the following six weeks there was a historical profusion of both waves and precipitation. In terms of surf, conditions were hit or miss (mostly miss), but the hits have been good to epic.
It's interesting to note that despite breaking the long standing precipitation record from the El Niño of 1982-83, the overall snowpack in the Sierra has not been as prolific. Warm AR events have meant that while many resorts are high enough in elevation to still count feet of snow, the overall snowpack in the Sierra has lagged behind the record-setting precipitation. It's still above average, to be fair, but may have damning implications for the state as we move through the dry season if we see a fairly rapid snowmelt.