Last night’s official fire outline compared to the night before:
We see significant expansion in the west towards the village of Big Sur
Last night aerial infrared map, with legend in upper left corner:
Looking at the western part of the fire. We can see that the fire has actually crossed the fire break. Is this a mapping error with the fire break? The official fire boundary lined up with the fire break above. Is it an aerial IR mapping error? Is it a back burn? With the mandatory evacuation order for Big Sur last night, and the VIIRS data below, there is reason to believe that some or all of it is wild fire.
On the eastern side of the active fire area we see Some filling in and modest enlargement. The enlargement in the surrounded area near the General Store could be back burning:
If I turn yesterday’s fire boundaries on and we look at the southeaster part of the fire, we can get an idea of how fast it’s expanding:
In the southern part, the expansion is significant and it is burning hotly. Nearer to Cachagua, the parts of the expansion that are hot are moving more slowly. In addition, much of the Cachagua expansion is identified as scattered heat. That it dies down so rapidly may mean that it was the result of back burning.
I also have this morning’s VIIRS data:
Looking at the western part:
VIIRS puts some of the heat on the wrong side of the fire line, just like the aerial photography did, and shows a greater extent. We can’t tell from just the images whether it’s back burning or wild fire, but a mandatory evacuation was issued for the village of Big Sur and nearby areas, and there have been reports that the fire is on the wrong side of the fire line, so this looks serious.
Over near Cachagua:
There is quite a lot of activity moving eastward south of the General Store. To me, that is more of a concern than the fire due west of the General Store that is occuring an an area that has been extensively back burned.
This morning’s MODIS data doesn’t show us anything we didn’t see better on the VIIRS images:
In the west, the MODIS data doesn’t look as bad as the VIIRS did, but I trust the VIIRS data more, even setting aside its higher resolution.
The orange lines are the dozer fire breaks that were in as of 7/30, plus one that I added by hand. The pink lines are the ones that were planned as of that date. The fat black lines are the outlines of the fire’s perimeter on the official Cal Fire maps from last night.
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.
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