Thursday, July 16, 2015

Why won't a tropical storm EVER hit the Pacific Northwest?

The visible satellite image Thursday afternoon (see below) has a lot of interesting features, but none struck the eye like Hurricane Dolores moving up the Mexican coast (A).  There is also low clouds (stratocumulus/stratus) moving up the coast (B), clear skies where continental air is pushing offshore (D), and ship tracks, where particles from ship exhausts are producing lines of enhanced cloudiness (C).

Hurricane Dolores is prediction to move up Baja California  and reach the offshore waters west of San Diego by Tuesday AM (see graphic), but it will never reach us.

No tropical storm will ever reach our shores (as a tropical system that is).  The reason?  Because the eastern Pacific off our coast is too cold.

Hurricanes, Typhoons, and tropical storms in general require warm sea surface temperatures, specifically, above roughly 80F or 27 C.

Here is a recent sea surface temperature analysis over the eastern Pacific.   The 27C contour is the at the boundary between yellow and yellow/green.  The hurricane will soon enter a region that is too cold for development....and the system should progressively weaken.    No tropical storm can even get close to us.

If you look carefully, you will see cold water off of New England as well.   Rarely, a tropical storm has reached them (e.g., the great 1938 storm) but only because the very warm Gulf Stream gets close, so tropical storms can maintain their strength until the end, after which they start to weaken rapidly.

Will things change under global warming?  No chance.   Remember this year has much warmer than normal water offshore and we are not even in the neighborhood.  Even more important is that our average sea surface temperature (around 50F) is roughly 30F colder than the minimum.  So it won't even be close- sea surface temperatures might become 5-10F warmer in a century---not anywhere close to 80F.

But the water temperatures around Hawaii are on the margin, so they will have to be watchful.


Unknown said...

I see that the waters off the coast of New England are equally cold on your map, and yet tropical storms do reach New England on occasion.

I think it has more to do with the direction of the trade winds than water temperatures.

Sulla said...

Yes, the more interesting question is what about California? They had a near-miss from a landfalling hurricane in the mid 19th century and a few other brushes since.

El Nino years are the years where the low odds of a California hurricane are somewhat raised. The shearing winds lessen and the water temps get closer to sustaining tropical systems off of San Diego.

It'd be interesting to pose this same question for southern California, although that's well beyond the scope of this blog.

I'm more curious to hear how the warmer water temps impact our extratropical cyclones. Does a warmer eastern Pacific tend to weaken them?

Ansel said...

You'll all think I'm crazy, but as a Connecticut native, I do miss tropical storms. I lived there from 1961 to 1972, and we had several hurricane remnants strike the coast, but, as it happened, no major hurricanes. I was in New Hampshire in 1984 when Hurricane Gloria (a Class 5 storm) was bearing down on Connecticut, but it took a right angle turn east at the last minute.

I also experienced a hurricane in Puerto Rico when I was just a tot, but I can barely remember it.

But to this day I miss warm windy rain. The Pineapple Express can hardly hold a candle to what I used to experience nearly every September.

ryamkajr said...

I would assume the warmer water feeds the hurricanes, making them larger. At least that is what happens with Atlantic hurricanes. No reason for it to be different in the Pacific.

Doug Cotton said...

If you want to know why planetary surface temperatures are what they are, then read my three comments starting here and feel free to discuss on that thread.

Cascadian Engineer said...

"I see that the waters off the coast of New England are equally cold on your map, and yet tropical storms do reach New England on occasion."

I'm not an expert but based on 30 years of life in Florida and studying the atmosphere as part of my engineering expertise I've learned the following:

If you look at a temperature gradient of the Atlantic with the gulf stream you'll see that the cold water band is much narrower. Tropical systems lose energy as they travel over cold water but the length of time over that water makes a huge difference.

An Atlantic storm spends relatively short amounts of time over "cold" water before landfall. A Pacific storm would spend a much longer amount of time over "cold" water before landfall. As a result the pacific storms are much more likely to lose energy and as that happens wind speeds drop.

If one does reach the northwest coast it will likely have lost all of its tropical characteristics and become an extratropical low.

The tradewinds (and westerlies) do play a role though which, along with the jet stream, is why a lot of Atlantic tropical systems get "caught" before landfall as they head north and suddenly veer rapidly to the east toward Europe.

John Marshall said...

To Doug Cotton... I spent some time on your linked site, and read through many of the comments. Once I digested the stated "facts" that the IPCC was created by governments to further their agendas, and that people working to reduce CO2 are actually trying to suppress poor people by raising the cost of energy, I'd seen enough.

I should have known. One of the hallmarks of conspiracy advocates and their kin is that they like to shout (caps and/or bold text) a lot. And they use (as the linked site does) as justification for their ideas the number of visitors to their website.
If that was the case, the various Murdock-owned media outlets would be the bastion of 21st century scientific knowledge.

Also seems like Cliff's blog is collecting more and more of such "thinkers"....

Andy Stahl said...

Pacific Northwesterners of a certain age remember the Columbus Day Storm of 1962, which began its peripatetic life as Typhoon Freda. Sure seemed like a tropical storm to me.

maxxtuner said...

never say never cliff perhaps this should have been mentioned.

Cliff Mass said...

Neither the Columbus Day Storm or ANY other was a tropical storm when they hit us. Some storms had their origins as a tropical storms but all had transitioned to midlatitude storms using a very different energy source...horizontal temperature gradients....cliff

NxNWSURF said...

What might be interesting is that with climate change will warmer water in the east pac. allow tropical storms to travel farther north and west, thus putting Washington into the tropical swell train window. I hope so as mo sure is mo better. Nobody ever talks about how epic global warming could be. Frank

jayelldee said...

What about the 9.2 earthquake and subsequent tsunami to follow that is supposed to devastate Seattle and everything west of the Cascades. Reportedly this is overdue and could happen at anytime.