February 08, 2012

Weather Cousins In Hawaii

You would think the weather is very different in Hawaii than here in the Northwest, but there are a lot of things we share, and particularly today. This morning an unusually strong front pushed across the islands, with strong southwesterly winds before passage and powerful northwesterly winds and cooler temperatures behind.  And they even had a convergence zone....just like ours!

First the front.   Here is a visible satellite picture around 12:30 PM PST. You can see the clouds associated with the front to the south and southwest of the Big Island, with cooler, unstable air to the Northwest.

After frontal passage, winds gusted to 40-50 mph on the north coasts of Oahu and Kauai, and a band of showers was associated with the front.  The long fetch of strong NW winds behind the front led to substantial waves (up to 20-30 feet) at some northshore locations.  Surfs up!

But the behind the front something happened to the east of the Big Island that should warm the heart of any Northwesteners-- a convergence zone formed... a kissing cousin to our own Puget Sound convergence zone.

Did you ever consider that the Olympic Peninsula and the Big Island are both mountainous and similar in size?  Roughly 60 miles in diameter?  Here is the proof:

When a front goes through our region the winds often turn from the southwest to the northwest and in the lee of the Olympics, a convergence zone forms over Puget Sound.  You know this well.  Typical radar imagery shows a band of precipitation stretching east/southeast away from the Olympics:

Today, as winds turned northwesterly over the Big Island, a nice convergence zone formed in the lee (southeast) of that barrier.  Here it is:

You can also see a line of showers associated with the front...stretching SW to NE.
My colleagues at the University of Hawaii run the MM5 high-resolution model over the Aloha State.  Here is the simulation of the 10-m winds valid 5 AM Hawaii Standard Time.  You can see the general northwesterly winds and the convergence in the lee of the Big Island.  The other islands don't peturb the flow much; the Big Island is not only large, but has two very large mountains--as high as Mt. Rainier.
Of course, we have something else in common--the Pineapple Express--whereby moisture streams northeastward towards the mainland...but that is another story.

Northwest Weather Workshop.   This is major local meeting for weather professionals and enthusiasts.  All are welcome.  March 2-3 in Seattle.  Info here on the meeting and registration. The banquet speaker on Friday night will be Andy Wappler of Puget Sound Energy.

Latest on my lost dog:  There have been several sightings in Brier, to the east of Mountlake Terrace.  If you live or work there, keep an eye out!  The bureaucrats working for the city of Mountlake Terrace are tearing down our signs, even those on private property away from the street--really crippling our effort to get her back.


  1. We lived for four years in Kapoho on the very eastern tip of the Big Island and observed the convergence zone first hand. It was an amazing place to live: on the ocean, in the moderating trade winds, upwind from the volcano and surrounded by warm tide pools. Now we live near Sequim. Yes, we like good weather after many years in the far, far North.

  2. Fascinating comparison Cliff, I would not have guessed that the Big Island and the Olympics were the same size. They are however, from very different geologic origins though; Hawaii being a mantle hot spot derived super volcano and our lovely Olympics created from rather complex subduction processes 13 million years earlier.

  3. the only problem I have with your comparison is that the west coast of our peninsula is rather notorious for being WET.
    Hawaii's west coast is known for being the "dry side" of the Island.

  4. Great article Cliff! I'll have to ask Steven if they got some badly needed rain out of it.

  5. I live in Brier and will keep an eye out for Leah! I do have one question about the sightings - has she been seen with people or just wandering on her own?

  6. Does anybody know if the Hawaii convergence zone have a sun hole like ours does?

  7. I think the comparison looks good with wet northwesterlies swooping around the mountains and colliding in the lee. The prevailing winds on the Big Island are typicially NE trades, which is why the west side is usually dry.

  8. Not to complain....but when is winter coming back...I miss it over here in Ellensburg, that's why i moved over here...we still have snow on the ground, but I'm looking for the fresh stuff :-)

  9. I will begin my pet detective work this coming Saturday. Same as what Mel has said, has she been spotted with someone or solo? Suffice to say she is probably hungry...what are her favorite foods or sounds?

  10. That is certainly hopeful that Leah is still being spotted....now if you could just figure out where she would be next.....Good luck!

  11. Wouldn't the tearing down of signs on private property be destruction of private property and against the law?

  12. Glad to hear there are still sightings of Leah!

    What if you could convince people to put big signs inside their front windows? Then the city of Mountlake Terrace can't get at them :)


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