Annual Rainfall Comparisons for All Thurston County Precipitation Sites by Water Year
Seasonal Weather Outlook: Late Fall 2016
Mid- to late October is a time of distinct seasonal transition, when the strength of cool artic air over the northern latitudes begins. Some years it is subtle and gradual and some years there is a sharp transition into autumn. Here’s what’s happening now.
No extended summer
The transition to cooler artic air began earlier than usual this year, which means that we are not going to enjoy any of the extended summer that we sometimes experience, a very sharp contrast with 2015 and 2014. This summer, temperatures were below average and rainfall was slightly above average. This appears to be the trend for autumn as well. Although I do think we will still have some nice weather in late October …. maybe.
First seasonal frost
This year, the first seasonal frost has already come to some of our neighborhoods on October 11 and 12. It was a very light frost, but enough to kill the pumpkin leaves and other tender garden leaves. If it hasn’t hit your area yet, expect it any day now. Interestingly, since 2001 the number of frost-free days in the Olympia area has increased by almost 20 days. In other words, that’s 20 fewer days of freezing weather per year. This year will lower the average a tiny bit.
As I write this article we just missed (mostly) what was predicted to be a weekend of very potent early season wind and rain storms. All the prediction models were in agreement - this was the lowest pressure we’ve experienced in maybe five years. Weather gurus are surprised by what didn’t happen, and I’m baffled too. I can tell you that the storm did not dissipate. Perhaps it swung north – I’m still reviewing the latest data to see what happened. The bottom line is that it wasn’t as fierce as expected.
These types of strong storms actually begin their lives as typhoons or strong storms over the tropical Pacific SW of Hawaii. Some of them get caught in the northern jet stream of fast moving air and they sail right over to the Pacific NW. That might be what happened to the brunt of this one.
This year, the conditions are right for more of these types of storms to hit us since the ocean is very warm. That means the warm ocean water is breeding many late season tropical storms. Also, the jet stream – that narrow band of very strong air currents that encircles the globe several miles above the earth - is pointed directly at us. That gives those storms a free ride across the Pacific at speeds over 180 mph at 30,000 feet.
The strong Jet also gives these types of storms an added kick of energy to get them to generate very low pressures like a whirl pool in the atmosphere (think of water swirling down a drain). That very low pressure causes a “vacuum effect” and creates a very strong pressure differential with the air around it. That differential pressure is what causes wind as the surrounding atmosphere tries to correct the difference between the low pressure and high pressure. This also drags water vapor into the mix and bands of pressure waves swing off of the low pressure center like arms. These arms pick up a lot of water vapor over the warm ocean as they are rotating around the whirlpool center. That’s what weather forecasters call “fronts.”
Climate change effects in Thurston County
I often get asked if climate change is real and if it’s affecting our local weather or environment. Yep. It is. Below I’ve summarized a few effects -- topics that I have not seen much discussion on. That is partly because the data isn’t readily available or published yet.
I touch on it because Thurston County tracks this type of data as part of our groundwater Monitoring Program (through monitored wells and gauges placed in streams and rivers). Here’s what the data indicate:
The earth is changing. Study of geology or the natural world reveals change is nothing new. It seems to be the natural state of the earth. By measuring the environment, we can learn more about the changes. And being informed and educated is a great way to understand a little bit more about what happens all around us every second of every day.
Past Weather Summaries
What's the Weather?
What are the River Conditions?
Thurston County Emergency Management provides timely data on river levels and background information on when to expect flooding.
What are the Groundwater Conditions?
Current Flooding Threat - None
What's Happening With the Tides?
Contact Mark Biever, R.G, L.P.E.G- Thurston County Environmental Monitoring Program Supervisor, by e-mail email@example.com. or
for Lake information contact Janie Civille, Ph.D. by email at Civillj@co.thurston.w.us
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