Wednesday, October 30, 2019

Two Very Different Style Windstorms To Affect Vermont, California

Widespread rainfall of near two inches is expected with the
upcoming windy storm Thursday into Friday.
This is essentially an update to yesterday's post, with more details about a pretty stiff storm about to sock us here in Vermont, and a nearly unprecedented wind event (and possibly fire event coming to southern California today.

Let's start locally.  It's already been breezy in parts of Vermont, especially the Champlain Valley, as I drove through a blizzard of falling leaves amid 30 mph wind gusts.

That's just a foretaste of what's to come.  Yep, we are going to get a lot of rain and wind.  There's a risk of both flooding and damaging winds Thursday night and Friday in and around Vermont.

I suppose way out ahead of the main storm there could be a couple light showers this afternoon, but they're nothing to worry about. 

The main show arrives tomorrow. At first, it'll just be showers, but a steady rain will move in during the afternoon as winds increase.

It's tricky to predict how strong winds will get while it's raining.  There will be strong winds aloft, but  rainfall can sometimes prevent those winds from mixing down to the surface.

There will be locally strong winds.  Meteorologists at the National Weather Service in South Burlington think channeling effects in the Champlain Valley could bring gusts to 45 mph there.

Worse, the southeast flow could bring strong downslope winds to the western slopes of the Green Mountains. There's definitely a risk of gusts in the 60 to 70 mph range, with maybe a couple locally higher gusts along the western slopes of the Green Mountains Thursday night.

That will be Round One of the wind. More on Round Two at the moment.

Between the wind and the rain, it's not going to be a great night for trick or treating. Overnight, this noisy storm will likely produce a lot of rain.  Most of the state should get one to two inches, with locally three inches possible.

We've had a lot of rain lately, so the soils are saturated. This amount of rain is probably enough to cause some flooding. It won't be an Irene-style epic flood, but even minor flooding is something to pay attention to.  People always tend to try to drive across flooded roads and that's such a bad idea.  This should be obvious, but whatever.

It seems the rivers most at risk of some flooding are the Mad and Winooski and Other Creek in Vermont and Ausable in New York.  But any water way could flood, and small streams could wash out dirt roads.

Newly fallen leaves can form little dams in streams. When these dams eventually break, you get rushes of water that can take out culverts or wreck gravel roads.

In urban areas, newly fallen leaves can can clog storm drains, too.  Needless to say, a flood watch is up pretty much region wide.

Friday morning, the storm's sharp cold front will whip through, which will shut off the heavy rain. (Lighter showers will continue here and there.)

This cold front opens the door for more strong winds, this time from the west.  Gusts in favored areas could reach 55 mph. Most of us will gust over 40 mph Friday.

Overall, there's already a high wind watch up in northwestern New York and those wind watches, warnings and advisories will almost certainly spread across most of Vermont.

Obviously, the large upcoming storm won't just affect Vermont.  The entire Northeast is due for a big blast of wind, rain and power outages with this storm. 

Not everybody will lose electricity, but there will be outages.  Make sure your devices are fully charged by Thursday evening, just in case.

CALIFORNIA WIND/FIRES

It seems like we've been talking about the California wildfires for weeks now, though it's only been days.

It also seems like every time we say this will be the worst day, an even worse day comes along. That's today in southern California.

Meteorologists are predicting one of the strongest Santa Ana winds on record in southern California. This will be combined with a relative humidity of well under 10 percent.  Santa Ana winds and fire weather occur every autumn in southern California, but not like this.

Every time there's a real fire risk, something called a red flag warning is issued.  This happens a lot in southern California in the autumn, so the National Weather Service in Los Angeles worried that people would just dismiss it as just another background noise weather alert.

To shake people out of their complacency, they're calling this one an Extreme Red Flag Warning. "Conditions are as dangerous for fire growth and behavior as we have seen in recent memory," the NWS warned. 

Unlike most Santa Ana wind events, the weather won't be particularly hot this time. Normally, the air rushing down the hills in Santa Ana winds compresses, which heats it up. The air mass triggering the winds is so cold that this warming won't be very pronounced.

Unfortunately, that doens't matter.  Between the winds gusting to 80 mph on the ridgelines and in some canyons and 60 to 70 mph elsewhere; and the relative humidity running in the single digits, you can imaging how fast a fire would spread.  I don't think any human could keep up with it.

So, millions of people in southern California are on edge, wondering if they will be the ones who have to flee in a flash because of a fire.

The winds are so strong this time that even outside fire zones, the National Weather Service is saying people should stay out of forested areas and away from trees.  They could topple easily in such strong winds.

I guess we here in Vermont should count ourselves lucky that we're only going to get lowland flooding, a few toppled trees and power failures.

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