July 29, 2013

The Serious Fire Season Has Begun in the Northwest: Meteorological Threats Ahead

During the past week two major wildfires have initiated and spread to thousand of acres here in the Northwest:  the Mile Marker 28 fire near Satus Pass in south central Washington and the Colockum Tarps fire south of Wenatchee.  And meteorological issues threaten to make the fire situation worse at the end of the week.

Sunday morning's visible satellite image (at 8AM) shows lots of smoke in eastern Washington (mainly from the Satus Pass fire.


The Colockum Pass fire increased in size during the day (see satellite image around 7 PM Sunday below).   Some thunderstorms developed over the north Cascades and if you look closely you can see a cumulus cloud in the middle of the Colockum Pass smoke plume.  The heat was sufficient to cause the air to become highly buoyant, producing a tall cumulus cloud-- called pyrocumulus. 

Lori and Don Robbins sent me a picture of the pyrocumlus from a vantage point in Ellensburg.


And amazing picture from"Sooperfly".   The smoke rises to a level at which it is no longer buoyant and spreads downwind.  The cumulus cloud, with extra warmth from the release of latent heat (heat is released as water is condensed) can rise even higher.



A very clear satellite image of the smoke from the fires was available earlier Sunday afternoon from the NASA MODIS satellite:


A big issue for the Colockum fire (and to a lesser degree the Satus Pass fire) has been the strong westerly winds pushing eastward down the Cascade foothills on Sunday, forced by a strong pressure difference across the Cascades.  This strong winds and large pressure difference are associated with the cooler air that has moved into the west side of the mountains.

Here are the maximum winds for the 24h ending 9 PM Sunday.  Lots of locations getting to 20-30 mph, a number reaching 30-40 mph.  Not good for fighting fires.


The UW WRF model predicted the strong winds on Sunday (see graphic for 5 PM), but forecasts a major weakening on Monday...which should be a boon to the firefighters.
But a bigger threat is on the meteorological horizon...lightning caused fires.  Today, there was quite a bit of lightning in the northeast Cascades and the Okanogan--did they initiate any new fires?  But more ominously, the weather situation will be very favorable for thunderstorms during the middle and end of this week.  Such lighting, plus the dry conditions of the "fuels" at the surface, will produce a substantial threat of new wildfires.

Here is the current fire danger map from the USDA Forest Service.  Eastern Washington has a substantial risk, but eastern Oregon and Idaho are even drier.


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1 comment:

  1. AnselJuly 30, 2013 at 12:46 PM

    I was out hiking in the Entiat and I saw this cloud as I drove out Sunday.

    As I said in my other post, there is another side to getting no rain all summer! Say what you will about humidity, but fires don't often happen in the Eastern forests of my old home. I see the smoke is hazing up the sun a bit today.

    I will also mention that the pine beatle is making things much worse. Forests are dying all over the West, due to the outbreak, making the situation all the more ripe for fire. The word is that milder winters (global warming) is probably behind it. I read that it takes several days of 30 below zero F. to kill beatles. Note: Whereas, as a child, I used to recall stories of extreme cold in the Rockies (40 to 60 degrees below zero in mid-winter) hitting the news, I never hear about that anymore. I suspect that there is a connection.

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