I got a new set of MODIS data from what appears to be the first of today’s midday passes, even though the second one happened some time ago.
Let’s look at the west side first:
That big move to the south and east is a surprise. Is MODIS off here? We’ll know when we get the VIIRS data.
In the east:
The southern part of the fire continues to move south. The two outliers are probably misplaced. We saw them this morning, and they didn’t show up there on the VIIRS high-resolution images. The three other new hot spots to the north of there are probably back burns. To see the new hotspots, look for the dark red center dots.
Here’s the result of the second pass:
More back burns are evident, but there’s nothing untoward near Cachagua. There is another hot spot on top of the isolated one we saw on the first pass, which, in my mind, anyway, reduces the probability that the placement is a MODIS mistake.
The orange lines are the dozer fire breaks that were in as of 7/30, plus on that I added by hand. The pink lines are the ones that were planned as of that date.
How to read the MODIS/VIIRS heat indications: The size of the square represents the nominal margin of error. The fire could be anywhere in the square, not just at the center. Dark red squares were detected less than six hours before the data set was created. Light red squares were detected less than twelve hours before the data set was created. Orange squares were detected less than 24 hours before the data set was created. Yellow squares were detected less than six days before the data set was created. When the squares overlay other objects, the color of the square changes somewhat, but the color of the dot in the middle does not. So look at the dot if you’re uncertain what color the square should be. Since the fire is now over six days old, some of the early detections have dropped off the map. MODIS makes mistakes, sometimes missing outbreaks, and sometime misplacing them outside the nominal margin of error. It is also a snapshot of the activity at the time the satellite is overhead, and will definitely miss flare ups between passes. MODIS can’t tell the difference between wildfires and intentional back burns.
The outline of the fire in black is the official Cal Fire Google Earth dataset from two AM today.
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