air conditioning bill).
While SoCal is now having heat, and we are running the A/C, we got through
June and July with cool, fresh air coming through open windows. And even
now, the heat is not yet what we normally experience.
Today's map shows the Jetstream giving us a trough deep into CA. This is
just not normal. This time of year, the Jetstream stays well north of us,
giving SoCal, and usually CentCal, "High and dry".
Meanwhile, as Lindsey says, a monsoonal flow of warm, moist air comes from
the Gulf of Mexico, across Mexico, and up into So. and Cent. CA. Only once
or twice this summer has this flow actually made it to L.A. County, and then
only barely.
The border between the cool Jetstream and the warm monsoon sometimes gives
us dry lightning, and results in fires. This happened in a super-big way in
NoCal a couple of Junes ago. We've had a couple of lightning-caused fires
this summer (I'm guessing the current Monte Fire is one--there was lightning
in that area before the fire started), but I note that they've been in the
south and east of the state.
I'm also guessing that the consistency of the Jetstream flow (bringing
onshore breezes and thus moisture rather than dry desert air) is having an
effect on the behavior of the fires that do start. Some have been a lot of
acres, but most have been controlled relatively quickly.
Last week, it started looking like "our luck was running out". A massive
High formed in the Gulf of Alaska, with the standard Jetstream flow around
it to the north. Within 24 hours, though, it was "gobbled up" by several
Lows as the Jetstream broke under it.
Now, even as the predictions for the Los Angeles-area valleys is for high
90s and triple-digits for the next several days, we are coming under a major
trough (touching the LA area as of 1100 Sunday), which means cool, moist for
at least NoCal and CentCal, and maybe for SoCal again. And again today, the
monsoonal flow is only barely reaching into the extreme SE corner of the
state. I'm guessing/hoping that today's predicted 98F will be, as Saturday,
more like 92F. (High of 91 as of 1315.)
Oh, and we'll have to wait and see what effect, if any, TS Frank (formed
this morning off the southern coast of Mexico) will have on our weather
patterns.
It's been a nice respite from our typical fire season. However, November
(traditional end of fire season--although that hasn't held up well the past
couple of years) is still a long way away.
----- Original Message -----
From: "Kim Noyes" <kimnoyes@gmail.com>
To: "CaliforniaDisasters" <californiadisasters@yahoogroups.com>
Sent: Sunday, August 22, 2010 9:40 AM
Subject: [californiadisasters] Wildfire threat could soar if weather warms
Wildfire threat could soar if weather warmsBy John Lindsey - SLO Tribune
Published: Sunday, Aug. 22, 2010
After 30 years of fighting fires throughout California, Cal Fire Battalion
Chief Chad Zrelak keeps keep a wary eye on the sky. So far this year, San
Luis Obispo County has been spared major wildfires, but many people have
vivid memories of years past, including the Highway 41 Fire.
So far this summer a persistent upper-level, low-pressure trough in the
upper reaches of the atmosphere has allowed cool and moist air from the
Pacific to penetrate farther into the coastal valleys and the North County
than normal, producing one of the coolest summers on record in western San
Luis Obispo County.
Many mornings this summer have seen measurable precipitation from the heavy
drizzle along our immediate coastline.
This in turn has produced a quiet fire season with moisture contents of
vegetation higher than average. The National Fuel Moisture Database
indicates black sagebrush, a common shrub in the Irish Hills and throughout
the western United States, had a moisture content of 101 percent this August
compared to about 96 percent in August of 2008 and 2009.
Vegetation or fuel moisture content is the percentage of the total weight of
the plant including its water content divided by its oven-dry weight.
Moisture content is often greater than 100 percent because the water in a
plant may weigh considerably more than the dry weight itself.
The greater the amount of water in the plant, the more heat will be required
to evaporate the moisture before it will burn. The role of vegetation or
fuel moisture, along with meteorological conditions, is critical in
determining potential fire risk.
Another cause of the quiet fire season has been San Luis Obispo County's
near total lack of the North American monsoon, which can bring lightning. On
July 11, subtropical moisture interacting with an upper-level low off our
coastline produced a few scattered rain showers and thunderstorms throughout
San Luis Obispo County. A particularly intense band of thunderstorms moved
through New Cuyama and sparked a fire that was quickly contained.
<SNIP>
Read entire article here:
http://www.sanluisobispo.com/2010/08/21/1259149/wildfire-threat-could-soar-i
f.html
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