So far this year, Seattle has experienced about 6.5 inches of rain. With an additional 2 to 4-inch forecast, the city could receive about 25 percent of annual rainfall on Jan. 15 from the atmospheric river that soaked the region.
“This wet start could propel Seattle to its wettest start of any year. The previous period from Jan. 1 to 15 occurred in January 1956, when it dropped nearly 7 inches during the first half of the month,” he says. CNN meteorologist Pedram Javaheri.
Atmospheric rivers are long, narrow regions of the atmosphere, such as rivers in the sky, that carry water vapor, according to the National Oceanic and Atmospheric Administration.
Check the nationwide forecasti
There is also a lot of heat in the middle levels of the atmosphere during this particular atmospheric river event. This will raise snow levels to elevations above 6,000 feet in much of the waterfalls, with rain falling below that level.
“This will further aggravate flood concerns, as heavy rains fall on heavy snow. The threat of rapid melting, increased runoff and flooding of rivers downstream is something everyone should ‘be alert in Western Oregon and Washington,’ says Javaheri.
Higher altitudes in Washington could see 2 to 4 inches of rain over the next 24 hours, increasing the risk of flooding and landslides.
Rainfall at lower elevations should be between 1 and 2 inches during this time.
In Portland, Oregon, the National Weather Service Office has forecast up to 7 inches of rain on the highest ground and up to 2 inches for the lowlands through Wednesday morning. Along with this, there is a strong wind warning in place.
Wind warnings extend along the entire Oregon coast, where gusts could reach 75 mph. This raises concerns about downed trees, power cuts and possible hazards on Interstate 5.
The impacts of record forest fires are also increasing flood threats for Oregon. According to the Oregon Forest Department, more than a million acres were burned. These burn scars still make the threat of flooding even greater, due to the calcined terrain and no vegetation to absorb rainwater. This increases the possibility of rapid and landslide floods due to loose terrain.
The culprit
The meteorological phenomenon that causes all this rain is called atmospheric river. They are basically rivers of moisture with a lot of atmosphere. They carry abundant moisture from tropical regions and release it in other areas in the form of rain or snow.
According to NOAA: “These steam columns move over time, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River.”
Not all atmospheric rivers are bad. They often bring very beneficial rains to areas that need it. Many areas of the west coast will get 30% -50% of annual rainfall in a few such events.
This particular atmospheric river is 2,700 miles long and has a bull’s eye to the northwest. This equates to the distance from Seattle to Miami in a straight line, and the moisture it carries could put January 2021 on record books.
Hurricane hunters head for the west coast
This atmospheric river event is so significant that hurricane hunters will fly by, dropping buoys.
“To really understand the importance of an atmospheric river event, you need to get closer to it. Hurricane hunters fly inside them and collect valuable data that predictors use to determine how a particular atmospheric river will affect the region. peaceful coastline, “says CNN meteorologist Allison Chinchar.
This is their second flight of the season and they do something regularly.
“Hurricane hunters first began flying into atmospheric rivers in February 2016 and have since sent between 6 and 12 flights from January to March. By itself, it’s not so uncommon for them to be flying this event, although it is a popular misunderstanding that once the winds of the hurricane season die, so does their role, ”says Javaheri.