Staying informed on fire weather conditions
and forecasts is a pretty basic concept.
But, really how easy is it?
You and your crew are bombarded with information
and indicators regarding your current fire environment.
I mean, you definitely need to know what your fire is doing
at all times, but awareness alone is just the beginning.
Your ability to focus on what is important
and filter what is not, will allow you interpret
and convert it into something useful.
Scott Dorval is a news meteorologist in Boise, Idaho.
He will talk to you about some of the most basic elements
of sky watching and the importance
of simply raising your eyes to the sky and making frequent,
thoughtful observations.
When it's 100 degrees in the summertime,
what's causing the air to rise is, the sun comes
up in the morning, it heats the ground;
the sun does not heat the air, the sun heats the ground.
It heats solid objects; and the solid objects touching the air,
the ground touching the air, and that air then gets warm
like a radiator, warms that air and that layer of air rises
and then cool air comes down to replace it.
And that air warms up and it rises and that's the mixing
that occurs during the day that we talked about.
When you talk about a fire weather forecast mixing,
the air's mixing and it continues to rise.
Rising air will then cool as the air pressure drops.
There is no air at the top of the atmosphere so we know
as the air rises the pressure's dropping
and so the temperature drops and...
the air cools and when it cools far enough it hits its dewpoint
and a cloud forms.
If you have more moisture near the ground, you only have
to take the air and bring it up a shorter distance
you'll get a cloud forming.
If it is extremely dry, the temperature
and dewpoint are very very far apart, the humidity is very low
and so you take this air and you have to make it rise higher
and higher and higher as the temperature falls it has
to fall further and further and you have
to make the air go higher and higher before you
can get a cloud to form.
And the reason storms will form over the mountains first is
because it's an elevated heat source.
The sun is heating the ground in a place where its cooler
than the ambient air next to it and so it doesn't take the air,
so it doesn't have to rise as far to get a cloud
to form that's right clouds will form right
over the mountains earlier in the day as opposed to waiting
for the sun to mix that air all the way up to this point
where it can mix it up on the mountain side nearby.
A this particular picture here is a very unstable afternoon.
You can already see the rain falling as your looking north
into the mountains obviously seeing a very dark cloud here,
you can see the lifting condensation level
that flat bottom to the cloud and you're going
to see the rain starting on in right hand side
of the picture there.
About, 4:twenty you'll see the cloud start to ripple
and the moisture just come ringing right out of the cloud,
out of the thunderstorm and will see it right here on the right
and with that you get a big burst of wind
which knocked my camera over which is good indicator
that was a pretty...pretty strong storm system.
Ok, now this is another indicator showing
that the sun is now heating the ground
and you have vertical development to the clouds,
you cans see the puffy nature to the clouds.
The sun heats the ground, the clouds,
the warm air rises makes those clouds,
now the sun is going down, the heat source is disappearing
as the heat source disappears the clouds just disappear
because the only thing that 's causing that moisture
to condense is the lifting of the air and the lifting
of the air has disappeared.
So you might have had a fire weather forecast
that said nothing is going to happen maybe today or tomorrow
but maybe we've got more indications that we're going
to start bringing more moisture in and then one morning you wake
up and you start to see these low, low clouds,
they're not real big and puffy but they have a puffy nature
to them but there smaller and there's little clusters
of puffy clouds and what you're see here is Altocumulus
Castellanus or ACCUS that's the sign
that ok we've got an unstable day here.
This is the day that I really need to be paying attention
in the afternoon watching for the vertical
development of storms.
May not occur right over us, we may have one coming in,
but that's a sign that the atmosphere is ready,
it's got enough moisture and it's unstable
that it could be ready to fire in the afternoon.
One of the things that most important obviously wind is a
huge deal with fire.
Wind is pretty much everything and how is the weather going
to impact the wind and hit the fire behavior.
This particular loop is from a few years ago
but it really shows virga.
Now virga is when rain falls from a cloud
and doesn't reach the ground.
This particular one you can see some drops reaching the our
camera but this is a good indicator showing what virga
looks like and it basically looks like the cloud is,
it doesn't have a flat bottom anymore.
You can see the rain hanging out of the cloud.
It looks like the cloud is being stretched down to the ground.
That is so vital because around these locations you can get very
gusty winds.
What's happening is the air is being cooled
by that rain that's falling and that rain is not reaching
the ground and it's evaporating because the air is so dry and so
that evaporating air then cools and that cool rush of air comes
rushing down to the ground and can shoot out
in all directions.
Pretty much of every thunderstorm is going
to get some type of outflow boundary in the summer.
They may be weak, they may dissipate some
of them will hold together with 40 mph winds for over 100 miles.
Typically, if you're out near a fire, a burned area,
or the open desert there's going to be a very large dust cloud
and you'll see it right along the ground.
The sky will be darkening um...just above the ground
and that's ...that's another thing to look for.
And if you see that, there's wind coming very very soon,
within minutes.
Let's talk a little bit about cold fronts approaching.
This particular that were going to see.....This particular
cold front happened in the winter time, but watch
how everything is coming toward us.
We're looking towards the south and so clouds..clouds
and weather.
coming toward us, but in the distance you can see the lower
level clouds beginning to develop a lots more moisture
and a watch this rapid shift of the wind and that flag showing
up in the Owyhee plaza there, shifting directions
and obviously we now have a strong uh...westerly wind.
This is a quick motion but when you are watching this
in the field, when you see clouds
that are coming toward you and they start to shift directions,
then you know you got a sign of a potential cold
front coming through.
In the summertime, it's either going to be so dry
that you're not going to have any indication
that a cold front is coming through and you're just going
to get a wind shift and that can be very dangerous
because you have no indication at all from a clear blue sky,
then you get a wind shift and usually
from the North or the West.
Sometimes, you'll get thunderstorms forming
on the edge of a cold front and obviously
that is a little more indication that something is coming.
If you here a forecast of a cold front that's supposed to come
through during the afternoon, chances are it's
going to come through.
It's just a matter of when it's going to happen.
You really need to be aware that the sky could
stay completely blue.
If its dry and it's two o'clock in the afternoon
and you don't see any little puffy cumulus clouds developing
on the ridgetops, that means that it's
so dry you're probably not going to get any cloud
cover what-so-ever.
And a front that comes through just for the wind shift
and the wind picking up.
So when I walk outside, I'm always looking up.
Sometimes I'll go to the beach and people laying
out in the sun, and then a cloud will move in front of the sun
and they'll get up and they'll kind of look around like this,
wondering where the sun is.
They don't even look up.
They don't even...people just do not observe the sky.
Everyday, go outside and just observe what's going
on in the sky and you'll just learn and learn and learn.
Because then you'll have ...Oh boy, with this heavy rain,
I notice this morning we've had such and such..
and it will just start to click.
I can't stress enough, as you go out, you get your briefing.
Anytime you get a chance to get more information you'll want
to keep doing it because ....it will just make your make your
forecast just that much more accurate.
Next day's forecast is this good and then the next day, day two ,
and day three, and day four, and day five.
It all drops off in time and so what makes those drop off is
that it's too far away.
You want to get that very latest information
and constantly be looking at the sky to see
if you can get some information yourself.
We will now view some weather loops
and let you consider what they mean
and share them with your group.