Wind and Fireworks Brings A Fast-Growing Wildfire Near Lake Chelan

 The  Chelan Hills fire, reported to have been started by some irresponsible fireworks Saturday morning, has now spread to over 10,000 acres (see map below).

A high-resolution visible satellite image this morning shows the burnt area (dark color), and the satellite imagery shows some still-active fires (red dots).  Smoke from  another (smaller) fire is apparent to the southwest.

The fire started in grass and range vegetation, not forest.  

Importantly, this vegetation was NOT unusually dry, as shown in the figure below, which provides 100-h fuel moisture levels on the eastern slopes of the Cascades.  Red is observed moisture level, and the shading shows the normal range.  

Current moisture levels were above normal.

So "climate change" can not be blamed.

What can be blamed was strong winds.  

Winds that were skillfully forecast by the UW WRF modeling system and the NOAA models.  To illustrate, below is the wind forecast for Saturday afteroon be the UW WRF weather model....strong winds were predicted around Chelan!

Below are the strongest observed winds yesterday around the fire area.  A 36 mph gust was observed near the fire start.

Winds at this location really revved up during the afternoon and early evening (see below).

At the same time, relative humidity plummeted to less than 20%--the result of drying of air moving downslope on the eastern side of the Cascades.

There is reason that wildfire starts are maximized on July 4th.  

The ignitions are there, the grasses/range vegetation are dry enough to burn, and it is early enough in the summer so that strong onshore flow produces powerful winds.