Truckee, California remains true to its namesake “everything is alright”. Spending time there in the sun and snow, it’s easy to feel like everything really is alright with the world. From the Paiute word Tro-kay, it was named for the Native American Trojukai who guided John Frémont in 1849 on his expedition looking for a rail route over the mountains. Although for early European settlers, everything didn’t turn out quite according to the optimistic namesake - the Donner Party did not make its name by living happily ever after, it does all point back to one defining factor – snow.
A history defined by snow, this year fit the mold, record breaking snow fall for the month of January, storms that blew up the news, closed post offices, lost power, and brought over 10 feet of snow in just the week we were there for races, one of which was canceled from too much snow. In years more and more defined by abbreviated race courses and venue changes from lack of snow, this was a new one.
As a stubborn Vermonter, I’ve always enjoyed validating eastern weather to my western friends; the ice makes us better skiers, the rain makes us tougher. The perfect days complemented by rainy ones make more resilient, more appreciative of the nice days. Despite my pride, my argument does automatically imply that the nice (snowy, sunny) days are more enjoyable, and that the rainy ones are worth it in their ability to heighten my enjoyment of the nice ones.
That in mind, on face value, Truckee, California fits perfection, with (historically) predictable huge snowfall in the winter, combined with dry sunny summers. I won’t go as far as to admit that that is better than Vermont weather, but the cynic in me wonders how this is possible, to be perfect all the time there. Why doesn’t Anchorage or Houghton or Salt Lake or Craftsbury get this weather, why is it unique? Turns out there’s a lot of science behind it, no surprise there, and after too much research, I now have a lot of respect for meteorologists and climatologists and people who understand weather.
The North Pacific High Pressure System, which resides west of California over the Pacific Ocean, determines the seasonal changes, causing the wet winters and dry summers. The High moves in closer to California over the summer, creating a block against the weather systems coming in from the west (jet stream), redirecting them north to hit western Canada. In the winter, the High sinks south west towards Hawaii, allowing the jet stream to blow right in, dropping snow on the crest of the Sierra Nevada mountains.
The location of the Sierras are a big player, forcing the stormy air upward. As the air cools over the higher terrain, the moisture condenses (adiabatic cooling), dropping precipitation on the crest of the mountains (Truckee, Donner Summit) and leaving a rain shadow to the east (Nevada is mostly desert).
(Quick geology moment side track- 100 million years ago when the Pacific Plate subducted under the North American Plate on the west coast, granite metamorphosed deep in the crust, the hot magma rising and cooling. (At this point also, gold and other minerals crystalized, which then washed up in streams and sparked the California Gold Rush). Then 4 million years ago, faulting and uplift began, building the Sierra Nevada mountains, glaciers eroding down to the granite, a cycle that continues today.)
That too seemed like enough of an explanation, the Pacific High bringing precipitation in the winter and not the summer, dropping the moisture over the Sierras due to adiabatic cooling. But then, why is Truckee the one that’s always in the news for snow records, why not somewhere a couple hours north or south?
La Nina/El Nino (phases of the El Nino- Southern Oscillation, ENSO) play a big role in determining the winter variation and snowfall amounts. ENSO is dictated by the Trade Winds which move NE to SW in the Northern Hemisphere and SE to NW in the Southern Hemisphere, bring cooler upwelling towards the equator. When the winds slacken, the water stays warmer in the Pacific; the cold water does not get pushed north.
El Nino corresponds with a warmer ocean current flowing north in the Pacific, which correlates with a lower pressure system; when El Nino is in effect, the precipitation comes straight in from the west and hits Southern California. La Nina is the yin to El Nino’s yang, corresponding to colder water temperatures than normal, and a high-pressure system. La Nina creates a similar “block” to that of the Pacific High during the summer, forcing weather north, dropping precipitation on the Cascades and Northern California. Truckee is right on the line between these two areas (Southern and Northern California), sometimes getting greater precipitation from La Nina, sometimes from La Nino.
This year we’re currently in La Nina, transitioning to ENSO neutral, which typically is better for Truckee, as demonstrated this past January. ENSO swings every 3-7 years, but we also have to bring into account a greater cycle, the Pacific Decadal Oscillation (PDO) which is like ENSO, but in longer phases, 20-30 years. PDO can intensify or diminish ENSO; when they’re in the same phase (i.e. PDO is warmer and El Nino is happening), El Nino becomes stronger, while when they’re in opposite phases, they can cancel each other out to a degree.
Zeroing in, we’ve established that the location of Truckee between the La Nina and El Nino affected regions can give the extra snowfall boost, and on a greater scale, it’s location near the Sierra Crest brings the precipitation. But still, why does Truckee get 10% more snow than Tahoe City, just 20 miles south, even though its elevation is 400 feet lower than Tahoe City?
This is where Lake Tahoe comes in, as the second deepest lake in the US, at 1645 feet, with proportionally very little surface area to its depth, it does a remarkable job at conserving heat (and cold), making the surrounding area that much warmer in the winter and colder in the summer, holding on to stored heat (or cold) from the previous season. That’s why it never freezes, the stored heat prevents it from ever getting to freezing conditions. So, in the winter Tahoe City, and the other towns directly around Lake Tahoe see temperatures enough warmer than those areas without the lake proximity (Truckee) that the snowfall is less.
All of these patterns make sense, but then of course there are the anomalies. In 2013-2014, “The Blob” (a warm spot in the Pacific), combined with unusual currents, along with the “Ridiculously Resilient Ridge” caused an enormous dry spell, as if the normal block of the North Pacific High was there permanently through winter and summer, causing drought, massive forest fires, and record-low snow winters. It’s unclear whether these two (the blob and the ridge) are causally related, but it is clear that anomalies like this are likely to become more frequent and more intense as climate change heats up.
My conclusion: it is incredible how reliable these patterns have been! Mother nature is really quite amazing. The effect of the Blob and similar anomalies are also quite concerning in the face of climate change. A warming ocean means lower pressures, changing how weather patterns move. Changing temperatures at the poles will change the trade winds, and therefore also the predictability of La Nina/El Nino.
As far as the East vs West argument, I still stand behind my Eastern weather rationale. I like enjoying the highs in context of the lows. But the Truckee weather is pretty awesome, and not just a fluke in the system, and as climate change rears its head, it seems to only makes sense to enjoy these natural phenomena while they last.
This is my best stab at understanding, any and all critique/corrections are welcome!