Wednesday, October 7, 2015

Hurricane Oho is Heading Towards the Northwest U.S.

Hurricane Oho, now located northeast of Hawaii, is now heading towards the northeast, making landfall on the British Columbia Coast on Friday.  The latest track from the NOAA Central Pacific Hurricane Center has it passing offshore of the Washington coast late Thursday (see graphic)


As a result, the probabilities of of winds getting to 58 mph (shown below) are only high offshore. But even here in Washington State there will be some minor impacts (see below).

A visible satellite image from NASA MODIS satellite on Wednesday afternoon shows that Oho no longer possesses a distinct eye and does not have the symmetric look of a strong hurricane.


One impact from Oho will be waves that will propagate to our coast as long period swell.  Here is a prediction from the NOAA Wavewatch III model for early Saturday morning. The yellows are 8 meter waves...around 25 ft.    This swell will reach the WA coast on Saturday possibly causing beach erosion and dangerous breaking waves.

Let's look at the latest forecasts from the UW WRF system.  This and subsequent plots will show heights (or equivalently pressure) and temperature around 5000 ft (850 hPa).  At 5 PM today, the hurricane was still surrounded by warm air (red colors), with a well defined low center in the middle of the storm.  Still tropical.


By tomorrow (Thursda) at 2 PM, the storm moves northeastward, roughly due west of the OR/CA border.  The structure has changed, with the low turning into a trough and cooler air approaching the storm.  Oho is undergoing what is called extratropical transition, transforming from a tropical to midlatitude storm.

Twelve hours late (2 AM Saturday), the storm had reach the waters of the central WA Coast.  Cooler air is getting entrained into the system, which is looking very asymmetric--like most midlatitude cyclones.  During extratropical transition the energy source of the storm changes, from the warmth of the ocean and the latent heat of water vapor, to the energy inherent in horizontal temperature contrasts.


A key reason why Hurricanes such as Oho undergo weakening and extratropical transition is that fact they pass over cooler water as they move northward.  Generally, hurricanes need water of at least 27C to maintain themselves as a tropical storm.  Take a look at the sea surface temperature distribution in the Pacific, with the route of Oho overlaid.  Oho is now over far too cold water (08/1800 is 11 AM Thursday) to remain a tropical storm....in fact, it is now officially a POST-TROPICAL CYCLONE.


How strong might the winds get offshore?  Here is the forecast for the surface wind gusts at 2 AM Saturday.  Lots of gusts above 60 knots over north Vancouver Is and the offshore waters.   It is good this storm is taking an offshore track!


Locally, it could get windy along the coast and over NW Washington, but nothing serious.   If you were thinking of taking a Friday departure for an Alaska cruise, you might rethink your plans.

Carbon Tax Initiative:  I 732

I-732 is now on the final stretch in getting signatures to put a revenue-neutral carbon tax in front of the state legislature.  I strongly support the initiative and I hope you will as well.  CarbonWashington need signatures and financial support.   Places you can go to sign are found here.

11 comments:

  1. When has one of these eastern Pacific storms directly made landfall in the PNW (notice I said eastern to exclude Columbus Day)?

    Any sort of worst case scenario based on historical records?

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  2. So THAT explains the rather sticky dewpoints today...good to know.

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  3. In the first body text in this article, I believe you mean the storm is heading toward the northWEST, not the northEAST.

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  4. Northeast in reference to direction of travel

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  5. Ugh, bad weekend to have an outdoor wedding!!

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  6. In referencing potential legislation that would allow government to enact a revenue-neutral carbon tax, it might behoove us to consider the following link addressing the whole global climate warming / change debate before handing over even more power to confiscate our hard earned money in the name of saving the Earth to the elected few among us:

    http://therightscoop.com/australian-scientist-discovers-errors-in-global-warming-models-that-completely-undermine-climate-theory/

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  7. Wouldn't it be either "heading northeast" or "headed towards the northwest"? Minor point, but heading toward the northeast is a little confusing.

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  8. I heard the Alaska ferry today tooting its horn as it left Bellingham for Alaska and thought, I wouldn't want to be on that boat this week!

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    1. AK ferry passengers should be plenty comfortable. Two short crossings of open water is not that big of deal. Tourist will experience the extrodinary rain forest of the north.

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  9. fullcirclethinker A better title would be australian scientist publishes bogus objections to a strawman of global warming models that no actual global warming models contain.



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  10. Carbon tax? That is not going to have a positive effect on global warming. We will just import everything (instead of just most things) from overseas, from countries who have no environmental regulation. Why? Because no industry here can survive when the competition has no red tape or environmental laws to worry about getting in the way of keeping production costs down.

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