El Nino Fall/Winter Outlook 2018-2019
With summer coming to an end, and the trees outside already transitioning into their brighter jackets, I've been curious to take a deeper look into our potential El Nino winter. I've compiled some stats and seasonal forecasts for this coming winter's outlook. The NWS Climate Prediction Center works at the heart of all the forecasting and is currently predicting a 60% chance for an El Nino Fall (Sept.-Nov.) and a 70% chance of an El Nino winter. In other words, there is a favorable chance that we see the El Nino weather pattern affecting our winter weather. I'll get to exactly what El Nino winter conditions look like below.
A Quick Science Lesson:
What is El Nino? It's a large-scale weather pattern that is spawned by warmer than normal sea-surface temperatures (SST) along the equator in the Pacific Ocean. Our trade winds start to weaken and allow this warm blob of water to move eastward as the year comes to an end. Below is a GIF of the SST anomaly this summer so far. You can see how the warmer water (reds, oranges) is mostly centered along the western equator but has started to spread eastward. Scientist are carefully watching these SST's and will do so through Fall. There are zones in the Pacific Ocean (El Nino1+2, El Nino3, El Nino4) that are monitored for warming, or how far the warm blob has stretched east. These give a likeliness that the El Nino will occur, as well as its strength. With summer coming to an end, the consensus shows a slowing of the warm blob. We are in an "El Nino-neutral" status with signs that a weak El Nino will ensue. Ensemble forecast models still show signs that an El Nino will develop in the coming months and SST warming/shifting will continue.
El Nino Impacts:
SST is important to monitor because having a warm blob of water in the Eastern Pacific can have major weather influences across the globe. We tend to see these influences in the winter time. In an El Nino year, the PNW typically sees warmer and drier-than normal conditions. Also, PNW mountain snowpack can take a hit during El Nino winters. Skiers tend to hate the term "El Nino Winter."
Much of Oregon is in a severe drought with below-normal rainfall since May.
PDX May-August Normal Rain: 5.49"
PDX May-August Observed Rain: 1.28"
Moving forward into Fall, we may see the drought continuing. Long-term and seasonal models are showing warmer & drier weather continuing into the year. "SON" means Sept-Oct-Nov.
It is smart to remember that these are forecasts for months well in advance. Even if these predictions don't favor our current extreme drought conditions or the eager snowboarder deciding to buy a season pass to The Meadows, we still have a lot of waiting to do to see what the winter season brings. As a skier myself, I'm still saving every penny to purchase my season's pass. I think this winter, our snow pack will fair just fine.
ENSO Prediction Hub: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml#discussion
Current OR drought conditions: https://nwschat.weather.gov/p.php?pid=201808101831-KPQR-AXUS76-DGTPQR