Tahoe Weather Discussion.com

If you haven’t noticed July brought real summer and it’s here to stay for a while. Been looking at some long range winter models and they look really interesting. The earth’s temps have been above average since the onset of El Nino last fall but are beginning to come down. Models are showing a huge cool down globally this winter. How does that affect us? Well with the La Nina coming on we could have quite a cold winter here in Northern CA. That cold will be coming down from the colder than normal Arctic, Alaska, & Canada. What is interesting is that the feed back from all of this cold may mean that the Eastern half of the country is warmer than normal, the complete opposite of last winter.

What I have in mind is the Jan-Feb period of 08. Anyone remember how much it snowed that period. I believe I recorded 25 feet in Tahoe Donner in a 6 week period. Then it just shut off March 1st and we came in below average. I’m hoping for a similar winter with no shut off. What is interesting during La Nina winters is that the snowfall can be above average due to it being colder and piling up faster, but the overall water content puts us below average for precip. I’m not sure I have ever seen the amount of cold for the globe that the models are predicting for the winter, so this winter should definitely be an interesting one when we see how that cold affects the pattern. One thing that is fun during La Nina years is that the MJO is much more of a predictor in terms of when the storm train will arrive. For this winter I may put a diagram of the MJO on the home page so that people can track it’s movement. BA

Starting tomorrow, July 5th, summer is locked in, so the weather will be very predictable until the fall, hot & sunny.

I started writing these blogs 2 years ago so that I didn’t have to email my weather research to my friends everyday. The response over the past two years has been overwhelming. After a few months of writing in 2008, Northstar asked to link to my blog in Jan. of 2009. By the end of the season I had 56,500 visits from 12,600 people in 43 countries. Last summer I created this site to keep a general discussion of Tahoe going with the original blog becoming Northstar specific. In the fall Sierra At Tahoe asked for their own blog as well. This past season I had 247,500 visits from 52,000 people in over 70 countries. Many websites have also decided to link to mine.

It blows my mind that that many people care to read my weather research and tracking. I write these blogs as a way to talk about my favorite hobby which is tracking weather. I love writing these blogs, but I want to always be enjoying doing it and not just because there is so much demand now. I became a little burned out after this long and active winter, so i took the month of June off from writing for some much needed rest. Now I am back and ready to start looking at the upcoming season.

First, let’s go over the re-cap for the month of June. After a few very wet months June flipped and we ended up at about 50% of average precip over the entire area. Because June is a dry month normally overall, the year to date average didn’t change much and we are right at 100% so far on the water year. There are 3 months left in the total water year and we are only at 95% on the total year. If we don’t have above average precip July-September then this will be the 4 straight year of below average precip.

Temps for the month of June were below average, which I don’t think is a surprise if you were here in Tahoe. We averaged 3.4 degrees below average for the month of June. That puts us at 2.8 degrees below average over the past 3 years and 1.4 below average now over the past decade in Tahoe. These numbers are available from the Truckee airport NWS reporting station, which is linked on my Forecasting Tools page.

The main reason for the colder temps over the past few years has been the decrease in the Pacific Ocean temps. They came up briefly this winter over the equator with El Nino, but didn’t warm off the CA coast. The entire Pacific is now cooling. The equatorial Pacific has been cooling since El Nino peaked in Jan. We now have La Nina temps as of the end of June, but in order for La Nina to be declared we need a 3 month average of .5 or more below average along the equator. We should have this by the end of August.

What does La Nina mean for us? Well unlike the 50/50 chance of above or below average precip we have during El Nino, La Nina’s lean more towards below average. Strong La Nina’s though can be different with 50% of them coming in at over 120% of average precip for Northern CA. We haven’t seen a strong one since the winter of 88-89, but that was a below average winter. Current forecast models have this La Nina becoming quite strong by Jan. 2011. The two winters with strong La Nina’s that were well above average were 73-74 & 55-56.

Over the summer I will be looking at the 4 strong La Nina winters including these two to see if I can analog where we might be headed. One thing I do feel confident about is that we will have a cold winter. Normally when a La Nina is coming on the summer will last well into the fall and I am expecting that as of right now as well. Stay tuned as I find more good info related to the upcoming winter……….BA