I've had an automated weather station running in my back yard for the past couple of years, but I just now got it “hooked up” to provide nearly live weather information on the web. If you look just below the Day-By-Day cartoon on the sidebar, you'll see the Lawson Valley Weather link, along with a strip chart of temperature and humidity information for the past week. Clicking on either the link or the chart will take you to a page with 16 meters and strip charts with all sorts of information about the current Lawson Valley weather situation. Right now the weather page is functional and ugly; I'll pretty it up over the next few weeks. The information is automatically updated every 10 minutes.
Wednesday, August 15, 2007
Wildfire Information...
It's that time of year again for Jamulians – with the low relative humidity and high temperature, our risk of wildfire is greatly increased. Add some Santa Ana winds to the mix, along with illegal aliens making campfires anywhere and anytime, and we've got a very volatile situation.
When a wildfire is actually underway, everybody in the area hungers for information – good, solid, reliable, up-to-date information. Unfortunately, this information can be amazingly difficult to come by. The usual sources that you might expect to deliver such information are actually rather bad at it. During the Viejas, Pines, Cedar, and Horse fires, we discovered firsthand (by our own on-the-spot surveys and investigations) that much of the information being put out by the media – newspapers, radio, and television – was either flat-out wrong or very badly out-of-date. Wildfires driven by Santa Ana winds evolve very quickly, and the media news cycles just can't seem to keep up.
So where do you go for information? Here is a list of the best resources that I've accumulated over the years, both from my own research and from local residents where were kind enough to share. If you know of other resources, please leave them in the comments. I'll round 'em all up and revise the post. I've made a permanent link at right to point to this list…
619/590-3160 and 619/590-5100: These fire information hotlines are manned by volunteers during an incident. We've had mostly good information from these folks, though the quality has not be consistent. One thing we particularly appreciate is that you can ask specific questions about the risks to your area, and you will usually get an informed answer. We were particularly impressed with this service during the Horse Fire (which burned quite close to our home).
Lyons Peak Cameras (North, East, South, and West): These cameras are a fantastic resource for Jamulians – a 360° view from Lyons Peak, updated every two minutes. I snagged the photo at right from the north camera (which looks toward our home) this morning – no smoke! A local fellow told me about these cameras around the time of the Horse Fire, and I used them to keep track of the fire's progress in nearly real time. The smoke plumes, smoke direction, and weather were all clearly visible on the screen – we knew when the wind shifted to a direction dangerous to us, and when things looked relatively safe. These cameras are part of the High Performance Wireless Research and Education Network (HPWREN), and the same group maintains several other such cameras.
Fire Planning and Mapping Tools: When I first stumbled across this web site a few years ago, I could scarcely believe what I had found – it is so chock-full of good information that it just didn't seem likely. It takes a bit of work to learn how to use this site, but that is time well invested. The image at right is one that I captured this morning. It shows our area; Jamul is roughly in the center of the screen. The shaded red areas show the boundaries of fires that occurred between 2000 and 2007 – you can see pieces of the Cedar, Viejas, Horse, and Otay fires. With this tool you can easily zoom into any part of California and Nevada, and you can turn “layers” on and off (the red-shaded fire boundaries are one example of such a layer). The real power of this tool lies in the rich set of layers that are available: current fuel loads, current incident boundaries, historical fire boundaries, fuel treatment history, risk assessments, and even satellite data from thermal imaging satellites.
In my own experience, the historical information on this site is far more useful than the information on current incidents. You might think the satellite information, in particular, would be highly useful – but it's got several problems that I've observed. First, it's not all that timely – there may be only two or three satellite passes per day; this is useless and even misleading on a fast-moving wildfire. Second, the resolution is low (about 1 kilometer), so it is not possible to accurately pinpoint the active front. Third, the data can be quite misleading – sometimes active fire fronts don't show up at all, and sometimes inactive places (for example, with lots of embers) do show up. On the Horse Fire we were able to directly compare personal observations, Lyons Peak camera observations, and the satellite data – and the satellite data was always wrong.
CDF Current Incidents Page: The California Department of Forestry (CDF) is the lead firefighting organization in our area. This page (and the links on it) have some information about all the incidents they are currently working. Our own experience with this site is mixed, mainly because of one weakness (from our selfish perspective): the information on it always seems to be at least 24 hours old, and sometimes more. This delay was very evident to us during the Horse Fire, when our our own observations were clearly a day or so ahead of this web site. On the plus side: they publish information that is hard to obtain elsewhere, especially incident maps and photos. The image at right demonstrates both the good and the bad: it's the most current incident map of the still-burning Zaca Fire (in Santa Barbara County) – over two weeks old!
Fire Imagery – Remote Sensing Center: This is a national web site, with many organizations participating. It has many different kinds of information available, and it's well worth exploring. The most useful looking to me are the thermally-enhanced satellite imagery (example of today in southern California at right), and a map of the whole country similar to the California and Nevada Fire Mapping and Planning Tools discussed above, but with fewer layers. The thermally-enhanced satellite imagery shows both the active fire fronts and the smoke plumes – wonderful information to have during an incident.
National Interagency Fire Center: This site has a lot of useful safety and planning information, and links to lots of other information (including on current incidents, such as the sites above). The image at right shows a simple overall wildfire risk assessment for this year; there's a lot of information like this that you can snag on this site.
Wildland Fire Assessment: This site is run by the National Forest Service (NFS), and has several areas with good information on a national scale. For example, they publish a daily map of 10, 100, and 1000-hour fuel moisture like the one at right. These maps are useful guides to the overall risk in your area. The same site has many other “products” that you can view or download as well, from weather forecasts to direct sensor observations to the output of forecasting models especially created to help predict wildfire behavior. The NFS uses this information to help them decide where to deploy and pre-position their fire-fighting assets.
Another example is shown at right – a map of “observed fire potential”. This product is still experimental, which means (I believe) that the NFS is not yet ready to rely on its results. Our area looks surprisingly low risk until you look very closely and discover that Jamul is in a relatively small area of high risk completely surrounded by lower risk areas.
Those are the resources that I rely on the most (along with my own eyeballs, of course. Do you know of others? If so, please leave comments to share them with your fellow Jamulians!
When a wildfire is actually underway, everybody in the area hungers for information – good, solid, reliable, up-to-date information. Unfortunately, this information can be amazingly difficult to come by. The usual sources that you might expect to deliver such information are actually rather bad at it. During the Viejas, Pines, Cedar, and Horse fires, we discovered firsthand (by our own on-the-spot surveys and investigations) that much of the information being put out by the media – newspapers, radio, and television – was either flat-out wrong or very badly out-of-date. Wildfires driven by Santa Ana winds evolve very quickly, and the media news cycles just can't seem to keep up.
So where do you go for information? Here is a list of the best resources that I've accumulated over the years, both from my own research and from local residents where were kind enough to share. If you know of other resources, please leave them in the comments. I'll round 'em all up and revise the post. I've made a permanent link at right to point to this list…
619/590-3160 and 619/590-5100: These fire information hotlines are manned by volunteers during an incident. We've had mostly good information from these folks, though the quality has not be consistent. One thing we particularly appreciate is that you can ask specific questions about the risks to your area, and you will usually get an informed answer. We were particularly impressed with this service during the Horse Fire (which burned quite close to our home).
Lyons Peak Cameras (North, East, South, and West): These cameras are a fantastic resource for Jamulians – a 360° view from Lyons Peak, updated every two minutes. I snagged the photo at right from the north camera (which looks toward our home) this morning – no smoke! A local fellow told me about these cameras around the time of the Horse Fire, and I used them to keep track of the fire's progress in nearly real time. The smoke plumes, smoke direction, and weather were all clearly visible on the screen – we knew when the wind shifted to a direction dangerous to us, and when things looked relatively safe. These cameras are part of the High Performance Wireless Research and Education Network (HPWREN), and the same group maintains several other such cameras.
Fire Planning and Mapping Tools: When I first stumbled across this web site a few years ago, I could scarcely believe what I had found – it is so chock-full of good information that it just didn't seem likely. It takes a bit of work to learn how to use this site, but that is time well invested. The image at right is one that I captured this morning. It shows our area; Jamul is roughly in the center of the screen. The shaded red areas show the boundaries of fires that occurred between 2000 and 2007 – you can see pieces of the Cedar, Viejas, Horse, and Otay fires. With this tool you can easily zoom into any part of California and Nevada, and you can turn “layers” on and off (the red-shaded fire boundaries are one example of such a layer). The real power of this tool lies in the rich set of layers that are available: current fuel loads, current incident boundaries, historical fire boundaries, fuel treatment history, risk assessments, and even satellite data from thermal imaging satellites.In my own experience, the historical information on this site is far more useful than the information on current incidents. You might think the satellite information, in particular, would be highly useful – but it's got several problems that I've observed. First, it's not all that timely – there may be only two or three satellite passes per day; this is useless and even misleading on a fast-moving wildfire. Second, the resolution is low (about 1 kilometer), so it is not possible to accurately pinpoint the active front. Third, the data can be quite misleading – sometimes active fire fronts don't show up at all, and sometimes inactive places (for example, with lots of embers) do show up. On the Horse Fire we were able to directly compare personal observations, Lyons Peak camera observations, and the satellite data – and the satellite data was always wrong.
CDF Current Incidents Page: The California Department of Forestry (CDF) is the lead firefighting organization in our area. This page (and the links on it) have some information about all the incidents they are currently working. Our own experience with this site is mixed, mainly because of one weakness (from our selfish perspective): the information on it always seems to be at least 24 hours old, and sometimes more. This delay was very evident to us during the Horse Fire, when our our own observations were clearly a day or so ahead of this web site. On the plus side: they publish information that is hard to obtain elsewhere, especially incident maps and photos. The image at right demonstrates both the good and the bad: it's the most current incident map of the still-burning Zaca Fire (in Santa Barbara County) – over two weeks old!
Fire Imagery – Remote Sensing Center: This is a national web site, with many organizations participating. It has many different kinds of information available, and it's well worth exploring. The most useful looking to me are the thermally-enhanced satellite imagery (example of today in southern California at right), and a map of the whole country similar to the California and Nevada Fire Mapping and Planning Tools discussed above, but with fewer layers. The thermally-enhanced satellite imagery shows both the active fire fronts and the smoke plumes – wonderful information to have during an incident.
National Interagency Fire Center: This site has a lot of useful safety and planning information, and links to lots of other information (including on current incidents, such as the sites above). The image at right shows a simple overall wildfire risk assessment for this year; there's a lot of information like this that you can snag on this site.
Wildland Fire Assessment: This site is run by the National Forest Service (NFS), and has several areas with good information on a national scale. For example, they publish a daily map of 10, 100, and 1000-hour fuel moisture like the one at right. These maps are useful guides to the overall risk in your area. The same site has many other “products” that you can view or download as well, from weather forecasts to direct sensor observations to the output of forecasting models especially created to help predict wildfire behavior. The NFS uses this information to help them decide where to deploy and pre-position their fire-fighting assets. 
Another example is shown at right – a map of “observed fire potential”. This product is still experimental, which means (I believe) that the NFS is not yet ready to rely on its results. Our area looks surprisingly low risk until you look very closely and discover that Jamul is in a relatively small area of high risk completely surrounded by lower risk areas.Those are the resources that I rely on the most (along with my own eyeballs, of course. Do you know of others? If so, please leave comments to share them with your fellow Jamulians!
Fuel Moisture
One of the key factors determining how fast a wildfire moves and spreads in the chaparral is fuel moisture – the amount of water that has been absorbed by the fuel. Here we're talking about “dead moisture” – the moisture that is in dead wood, brush, and grass. “Live moisture” is the moisture present in living plants, and this is largely independent of atmospheric conditions. The notion that high fuel moisture retards fire makes instant sense to everybody – if the fuel is wet or damp, it isn't going to catch fire as quickly as perfectly dry fuel, nor will it burn as intensely. But dig down into the notion of fuel moisture a little more, and there are some complexities that are well worth knowing…
Fuel moisture is determined in the end by atmospheric humidity and precipitation. However, there is a lag time between a change in atmospheric conditions and a change in the moisture of any particular fuel. Light, small fuels (such as dead grass) will very quickly respond to changes in the atmospheric conditions; heavy fuel (such as large downed logs) will change very slowly. This lag time is critical for firefighters, as it is a major determinant of whether fire will spread quickly or slowly through a particular area at a particular time. Here's how they classify fuel moisture lag time:
In a desert climate such as ours, there is a daily cycle of relative humidity: we are typically very dry during daylight hours, and very variable during nighttime (but averaging about 80% RH). That means that fuels with lag times below about 15 hours will dry out every day, and at some point during the day they will become “flashy”, meaning prone to quick ignition, quick fire growth, and will burn intensely. Since we rarely have more than a week of very dry nights, fuels with lag times of more than about a week (roughly 200 hours) will never completely dry out, and those fuels are much less flashy (and therefore much less dangerous).
Firefighters constantly use fuel moisture information when assessing the risks of any particular area during an incident. For example, the morning after a humid night, a field full of tall, dead grass (about 1 hour fuel) may be perfectly safe – but a couple of hours after sunrise, when the air has been dry for an hour, that same place may be very dangerous.
Homeowners can use fuel moisture information as well, when deciding what has to be cleared from near their homes (or other structures). Plants with plenty of live moisture are best of all; plants (or plant materials, such as leaves, needles, and wood chips) with short lag times are the worst.
Fuel moisture is determined in the end by atmospheric humidity and precipitation. However, there is a lag time between a change in atmospheric conditions and a change in the moisture of any particular fuel. Light, small fuels (such as dead grass) will very quickly respond to changes in the atmospheric conditions; heavy fuel (such as large downed logs) will change very slowly. This lag time is critical for firefighters, as it is a major determinant of whether fire will spread quickly or slowly through a particular area at a particular time. Here's how they classify fuel moisture lag time:
When I first saw fuels classified as “1 hour” or “10 hour” fuels, I thought that meant how long the fuel would burn. But that's not it at all – the time is instead a reference to the lag time between a change in relative humidity and the consequent change in fuel moisture.Fuels are classified into four categories by which they respond to changes in moisture. This response time is referred to as time lag. The four categories are:
- 1-hour fuels: up to 1/4 inch in diameter.
- 10-hour fuels: 1/4 inch to 1 inch in diameter.
- 100-hour fuels: 1 inch to 3 inches in diameter.
- 1000-hour fuels: 3 inches to 8 inches in diameter.
Examples of one-hour fuels are grass, leaves, mulch and litter. Fuel moisture in these fuels can change within one hour according to factors such as temperature, rain, humidity and shade. Conversely, larger diameter fuels such as deadfalls, brush piles, etc., take up to 1,000 hours to respond to changes in environmental factors.
Fuel moisture can be determined by clipping and immediately weighing the sample before oven drying it to a constant weight. Then the following formula can be used to determine percent fuel moisture: [(Wet Weight – Dry Weight)/Dry Weight] x 100.
In a desert climate such as ours, there is a daily cycle of relative humidity: we are typically very dry during daylight hours, and very variable during nighttime (but averaging about 80% RH). That means that fuels with lag times below about 15 hours will dry out every day, and at some point during the day they will become “flashy”, meaning prone to quick ignition, quick fire growth, and will burn intensely. Since we rarely have more than a week of very dry nights, fuels with lag times of more than about a week (roughly 200 hours) will never completely dry out, and those fuels are much less flashy (and therefore much less dangerous).
Firefighters constantly use fuel moisture information when assessing the risks of any particular area during an incident. For example, the morning after a humid night, a field full of tall, dead grass (about 1 hour fuel) may be perfectly safe – but a couple of hours after sunrise, when the air has been dry for an hour, that same place may be very dangerous.
Homeowners can use fuel moisture information as well, when deciding what has to be cleared from near their homes (or other structures). Plants with plenty of live moisture are best of all; plants (or plant materials, such as leaves, needles, and wood chips) with short lag times are the worst.