California winters are notoriously mild. Rainfall is minimal, snow is rare, and temperatures barely dip below freezing. Many who face brutal seasons can’t help but look at us with envy.However, the Bay Area’s bright, blue skies this week should inspire concern – not jealousy. This unorthodox weather stems from the “Ridiculously Resilient Ridge,” also known as the “Triple R” or “RRR.” The RRR also appeared in the 2013, 2014, and 2015 winters, intensifying the California drought and sparking record-low precipitation and record-high temperatures throughout the state. This year, Bay Area cities have only experienced 56-75% of their average rainfall, resulting in the driest first 10 days of December since 2011.
What is the RRR?The name may sound silly, but it’s actually quite literal. The “ridge” is a firmly situated mass of atmospheric high pressure along the West Coast, blocking winter storms from making their way across California, Oregon, and Southern Washington. Atmospheric circulation is the result of constantly changing pressure cycles around the globe. Varying geographical surfaces and air temperatures define the jet stream’s pattern, creating fairly consistent weather patterns. However, the current high pressure near the West Coast and low pressure over the Eastern seaboard is creating a new path for the jet stream. Instead of allowing normal flow of the prevailing mid-latitude Weterlies, the RRR is diverting movement up and over the Northwest, down through the Midwest. We can expect the RRR to stick around for another 5+ days, causing up to 10 more days of rain-free weather. If light rain happens to fall, it doesn’t mean the RRR has dissolved. Along the 2,000-mile ridge, some weak spots inevitably allow circulation to filter through, bringing traces of the weather we should be experiencing.
What causes the RRR?It’s hard to say what causes the RRR, a term only coined in 2013 by scientist Daniel Swain. Though the RRR is not officially linked to climate change, it does contribute to an extreme weather pattern Governor Jerry Brown describes as the “new reality” for California. As Swain points out, it’s important to note that these pressure patterns are now occurring more frequently, and warmer temperatures in the lower atmosphere do accelerate ridging. The broader science community continues to investigate potential causes for “RRR.” However, it has identified three strong possibilities:
- A series of random, coincidental variations in the atmosphere.
- “Arctic amplification,” or the rapid melting of Arctic sea ice that has the potential to alter mid-latitude weather.
- Higher-than-average ocean temperatures in the tropical western Pacific Ocean and Gulf of Alaska.