Some Good Signs for the Second Half of December…..
I know you are not liking the timing in the title since it’s only November, but it’s just our reality right now. I have been saying all Fall that this season would be more condensed than last year, closer to the 07/08 La Nina. It started a little sooner in November with several small storms but it is now back on track with the later start idea.
The good news is that once it does start it should come on fast. Just when you you have given up on Winter it will show up and not leave. But really it is showing up on time, right at the true start of Winter on the 22nd, maybe just before.
Looking at the temperatures in the Pacific they are not helping with the current pattern of the ridge in the Northeast Pacific. Earlier this Fall we saw warmer than average temperatures along and just off of the CA coast. But my opinion was that the temperatures would cool again as we head towards Winter. The ocean temps between here and Hawaii are now colder than this time last year.
With the current pattern it just means the water is too cold to support a Southern branch of the jetstream to come underneath of the ridge. But as we go into the Winter the sinking air over the cold water along the subtropical waters will favor troughing off the West Coast. That combined with warmer than average water temps in the Western Pacific strengthening the jetstream should mean the perfect ingredients for lots of snow in the Winter months.
First, we need to get the ridge to retrograde back away from the West Coast. Right now the positive PNA pattern is supporting the ridge off the coast blocking the storms. We need the PNA to go back negative which supports trough along the West Coast. During La Nina conditions the negative phase of the PNA is supported so we should see it more than not going into the Winter. Here is the forecast map showing it possibly going negative around mid-month.
The other thing that can pull the ridge back and bring a period of enhance precip to the West Coast is our friend the MJO. The MJO is actually getting pretty strong in the Indian Ocean as it progresses towards the Maritime Continent. As it moves into the Wester Pacfic over the next couple of week it should begin to help pull back the ridge.
So although we have quiet weather for the next couple of weeks things are definitely lining up for Winter to possibly begin for real later in the month. Meahwhile we will have some shots of cold from Canada coming down into the West with the chance of a little light snow with the cold front. The first being this Wednesday night into Thursday and the next the beginning of the following week.
So until the pattern breaks stay tuned for updates. I’m still sticking to my Winter forecast of 105% of average snowfall. BA
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