July Re-Cap and Beyond….
It’s getting to be that time of year where we can start to speculate on the upcoming season. I have been doing some research and things have not changed too much from my spring speculation for the upcoming season.
First let’s run through the July numbers. July was the driest month since January in the Tahoe Basin, but that isn’t saying much because the average for July is only around .4 inches of liquid. Both the Lake Tahoe and Truckee River basin are sitting around 140% of average on the water year. We have 2 months to go until the end of the water year.
It has been a beautiful summer so far with cool temps. We ran 4.0 degrees below average in July at the Truckee Airport reporting station. There is still a lot of cold water off the coast as we stay in the cold PDO cycle.
What am I looking at going into late summer and the fall? As we continue in the cold PDO I am using that as the base and then stacking the other variables on top. The ENSO region is currently neutral meaning that we have neither El Nino nor La Nina conditions. I think that will help to point us in the right direction.
I was sent an interesting research paper by a reader about the correlation between the PDO and ENSO in late summer-fall as it relates to the upcoming winter. The researcher is Gregory B. Goodrich from the Department of Geography and Geology at Western Kentucky University. He researched what happens along the West Coast in the winters following different ENSO conditions during a cold PDO. Below are two of the graphs showing La Nina conditions during a cold PDO which we had last fall, and Neutral conditions during a cold PDO which we currently have.
As you can see, we tend to get above average precip when there is a La Nina leading up to winter and below average precip when there is Neutral conditions. The forecast for the ENSO region currrently is that we do go back into a La Nina this fall and then into a moderate La Nina in the heart of winter. I think the key is how fast that happens. If Neutral ENSO continues we should expect a good chance of a below average winter.
Last winter we had a borderline moderate/strong La Nina, but officially I think we stayed at Moderate. Looking at history there are no occurences for a Moderate La Nina followed by another Moderate La Nina in the past 62 years. There are two times during the last cold PDO occurence from the 50′s to the 70′s that had a Strong La Nina followed by a Weak La Nina. Those years were 80-85% of average precip and 92% of average snowfall.
That is where I think we will land this season someplace in the 75-95% of average snowfall. If we can somehow get a strong La Nina to develop which is possible, we could be talking 55-56 which would mean another winter similar to this past winter. Stay tuned as we monitor the ENSO region going into the Fall. BA
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