Weather Map Explanation: Surface Weather Maps

These 6 weather maps focus on the fire location.

Under construction.

3-hour Precipitation Rate (mm) 

What it shows

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How you use it

yyy

(xxx Other applications might be added later. xxx)

Near-surface (z ≈ 2 m) Relative Humidity (%)

What it shows

xxx

How you use it

xxx

(xxx. Chris, how do you use this?? xxx)

Near-surface (z ≈ 2 m) Air Temperature (°C)

What it shows

Air temperature. By animating or looping the image in time, you can see if the fire site will be getting hotter or colder in the near future.

How you use it

Warmer temperatures generally favour fire formation and fire growth, due to the drying of vegetation that becomes the fuel for fires.

(xxx. Chris, how do you use this?? xxx)

Near-surface (z ≈ 10 m) Wind Speed (km/hr) and Direction

What it shows

In the absence of terrain slopes, fires generally spread faster downwind than upwind, as indicated by near-surface winds. Faster winds generally cause more vigorous fires that expand more rapidly.

How you use it

Animate this map by stepping forward or backward in time to see how fire conditions might change in the near future.

(xxx. Chris, how do you use this?? xxx)

Mid PBL (z ≈ 100 m) Wind Speed (km/hr) and Direction

What it shows

These winds are roughly at the hub height of modern wind turbines. At night when a statically stable boundary layer forms, the wind near the ground can become slow or calm, while the winds aloft at z = 100 m can still be very fast. This is known as a low-level jet.

How you use it

If a low-level jet of air existings over the fire site, then there is the threat that these fast winds could be moved down toward the surface by turbulence or convection in the lower atmosphere. If this causes a sudden increase in wind speed at the surface, then fires could suddenly increase in intensity and propagation speed.

(xxx. Chris, how do you use this?? xxx)

Convective Available Potential Energy; CAPE (J/kg)

What it shows

CAPE indicates how much energy could be released if a thunderstorm forms. However, for a thunderstorm to form, it also needs a trigger mechanism to "kick start it", to get the air to rise past a capping inversion. Larger CAPE indicates stronger up- and down-drafts, heavier rain, stronger gust-front winds, chance of hail, and chance of tornadoes. Sadly, it also indicates greater chance of lightning that could spark other wildfires.

How you use it

Meteorologists look at CAPE (how strong a thunderstorm might be if it forms), CIN (Convective Inhibition, which tends to prevent formation of thunderstorms), and trigger mechanisms (cold fronts, gust fronts, forest fires, etc.) that can overpower the CIN to enable the CAPE to be released to form a strong storm. These meteorologist publish convective outlooks that are based on all these factors.

However, if you don't have access to a convective outlook, you can use CAPE along with sounding info on a thermo diagram (see Chapter 5 of Stull's PrMet book) to gauge likelihood of a storm (see thunderstorm indices in Chapter 14 of Stulls PrMet book).

(xxx. Chris, how do you use this?? xxx)