La Nina Update….
With the quiet weather I thought we could take another opportunity today to talk about the upcoming winter. The NWS puts out their weekly ENSO discussion every Monday and the link is on the Forecasting Tools page of this site. Let’s take a look at yesterday’s discussion because there are some interesting things going on that will affect our weather.
The chart below shows the latest CFS version 2 forecast for La Nina this Winter. We have only had 4 La Ninas as strong as last years in the past 60+ years and every single one was followed by a weak La Nina the following season. So this would be amazingly rare if this actually happened. We only hit -2 twice, once in 1955-56 & again in 1973-74 and those were fairly big years with 600 and 480 inches respectively on Donner Summit. But I don’t believe we will get that strong, we are currently at -0.2 for the 3 month average (ONI) and this time last year we were at -1.0 already. Region 1+2 did drop to -1.2 however this week.
I am a fan of freak weather events though so of course I’ll be routing for this to happen. But even if it does we still have another factor that shouldn’t let us have a repeat season. The water just of the CA coast continues to warm and it is now finally in positive territory for the first time in a couple of years. That means it will attract ridges and not troughs along the West Coast, so we will need stronger storms to move it out of the way this year. We may also see an end to the long stretches of below average temps we have been seeing the past few years. We’ll have to wait and see if the water remains warm through the Winter.
This all continues to play into my shorter season theory as well. But the middle still looks like it could be good. Long-range forecasts still show a tendency for the Arctic Oscillation to be negative again this season, which could be attributed to some of the great blocks that set up last season giving us the hose.
For now enjoy the warm temps and nice weather. The next chance of a storm looks like possibly the Southern edge of a big storm that hits to our North at the beginning of November. It doesn’t look too promising though. Keep your eyes on the MJO because we may need its help. If it can enter into the Western Pacific in November we may be able to break the odds that Winter doesn’t start until December this year. Stay tuned…..BA
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