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How a Pacific typhoon could help extinguish California wildfires

The typhoon will scramble the jet stream, initiating a chain reaction that could bring wet weather to the West and a late-September heat wave to the East

High-altitude weather map simulation on Sunday shows former typhoon near Alaska helping to pump up jet stream to its east. To the east of the jet stream bulge, stormy weather develops near the West Coast. (WeatherBell)

A typhoon churning through the Pacific may be half a world away, but it will set off a chain reaction that will have significant effects on weather in North America — potentially offering welcome rain to the parched and fire-ravaged West next week.

Currently about 2,000 miles east of Japan, Typhoon Merbok is the third in a series of tropical storms and typhoons barreling across the western Pacific. It’s set to slam into the jet stream and reshape it such that next week’s weather pattern in the United States offers unsettled and rainy conditions in the West and hot, dry conditions in the East.

The typhoon will get drawn into the jet stream while tracking northward and transitioning into a powerful nontropical ocean storm. It will aim at Alaska by Friday, bringing hurricane-force winds to the Aleutians.

The storm’s interaction with the jet stream will contort it — making it more amplified or wavy — resulting in a configuration that could support rain in California and intensify a heat wave building east of the Rockies.

First, Merbok will bolt toward Alaska

As of Wednesday, Merbok was over the northwest Pacific moving due north at about 22 mph. Its maximum sustained winds were estimated to be around 75 to 80 mph, making it the equivalent of a minimal Category 1 hurricane.

It’s worth mentioning that two other storms flank Merbok to the west and are helping steer it to the north. Typhoon Muifa is slamming into Shanghai, one of the most populous cities in the world, with damaging to destructive winds, storm surge and as much as a foot of rain. Tropical Storm Nanmadol swirled between Muifa and Merbok, and is projected to intensify into a typhoon and hit Japan over the weekend.

Typhoon Muifa forecast to hit Shanghai at hurricane strength

As it moves over colder waters, Merbok will begin to morph into a large, nontropical storm. Rather than being fueled by ocean heat, it will begin to derive its energy from temperature contrasts and is forecast to rapidly gain strength.

By Friday afternoon, Merbok will be a hurricane-force nontropical low barreling into the Bering Sea, with wave heights potentially topping 40 feet and widespread 80 mph gusts.

The National Weather Service in Anchorage issued a high-wind watch for the Aleutian Islands, advertising the potential for “southwest winds 50 to 70 mph with gusts up to 90 mph possible.” The strongest winds will probably occur between Attu Island and Adak.

“High winds may move loose debris, damage property, and cause power outages,” the Weather Service wrote. “Travel will be difficult.”

Next it will disturb the jet stream

As Merbok sweeps into the northern Bering Sea, it will slam into the jet stream. Picture a victorious marathon runner jogging into the finish line ribbon upon completing their 26.2 miles: The ribbon bends forward and is stretched. Same thing here.

The jet stream will be bowed northward by the massive disruption brought on by post-tropical Merbok. That will induce ridging, or a northerly deviation of the jet stream, in the Gulf of Alaska, allowing for high pressure to become established and warmth to build in from the south over the northeastern Pacific Ocean.

California may turn stormy

While the jet stream bulges over the eastern Pacific, it will take a big dip along the U.S. West Coast, where a zone of low pressure will hover for days. As the jet stream rounds the curve of low pressure, it will truck copious moisture into the California coastline. That will entail an influx of precipitation, cooler-than-average temperatures and windy conditions.

Some computer models indicate a broad 2 to 4 inches of rain falling across Northern California early next week. While it’s too early to pin down exactly who will see rain and how much, that could be welcome news for those dealing with wildfires. The Mosquito Fire, in the mountains about an hour’s drive northeast of Sacramento, has burned 58,544 acres and is only 20 percent contained.

Smoke from Western fires fuels dangerous air quality

Finally, it will get hot in the East

If you toss a stone into a river, you’ll see ripples downwind of the stone. The crests and dips of those ripples, analogous to high- and low-pressure systems in the atmosphere, tend to stay in place for a while even as the fluid in which they’re embedded continues to flow past them. That’s how the atmosphere is responding after the disruptive impact of Merbok.

One of those crests, or ridges, may become established over the Lower 48, specifically over the Plains, Midwest, mid-South and Ohio Valley. That could bring a week or more without any rainfall, and should also keep temperatures on the toasty side.

Through mid- to late September, temperatures over the Eastern United States could rise 10 to 15 degrees above average, setting records in some instances. Denver, Chicago and Washington could all see highs near 90 at times early next week.

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