Unprecedented Atmospheric River Soaks the Pacific Northwest

by Amir Hussein
5 comments
Atmospheric River

Unprecedented Atmospheric River Drenches the Pacific Northwest

Visual Representation of Atmospheric Water Vapor Levels at 1:30 p.m. Pacific Time on December 4, 2023.

In early December 2023, a potent atmospheric river surged towards the Pacific Northwest of the United States, marking an extraordinary meteorological event. This extended current of moisture-laden air transported warm and humid conditions across much of western Washington and Oregon, shattering daily precipitation and temperature records while intensifying the threat of floods and debris flows.

Monitoring Atmospheric Factors

The provided map depicts the total precipitable water vapor in the atmosphere at 1:30 p.m. Pacific Time on December 4. Precipitable water vapor represents the quantity of water present in a vertical column of the atmosphere if all the water vapor were to condense into liquid form. The map highlights the verdant areas denoting the flow of moisture-laden air originating from the tropical Pacific and heading northeastward. This visual data is derived from NASA’s GEOS ADAS (Goddard Earth Observing System, Atmospheric Data Assimilation System), which utilizes satellite data and computational models to discern atmospheric phenomena.

Impacts on Terrain and Meteorological Records

Upon making landfall, the storm propelled water vapor upwards over the terrain, where it cooled, condensed, and primarily precipitated as rain. The majority of precipitation from this weather system occurred in the region situated between the Pacific coast and the crest of the Cascade Mountains. Certain mountainous regions in Washington state were projected to receive between 5 to 9 inches (130 to 230 millimeters) of precipitation over a 36-hour period ending in the afternoon of December 5.

Meanwhile, in low-lying areas, Seattle set a new daily rainfall record for December 4, with a total of 1.51 inches (38.3 millimeters), as reported by news sources. On December 5, heavier rainfall shifted towards northwest Oregon, with forecasts indicating 2 to 6 inches of precipitation in the Coast Range. Consequently, flood watches were issued as river levels surged.

Breaking Temperature and Relief for Water Supplies

During the course of the storm, both Portland and Seattle registered new record-high temperatures. Portland reached a maximum of 65 degrees Fahrenheit (18 degrees Celsius) on December 4, establishing a record for that particular date while equalling the all-time high temperature record for December. In the early hours of December 5, Seattle recorded a temperature of 59°F (15°C), surpassing the previous record of 58°F (14°C) set in 2020 for that date. The warmth experienced across the region compounded the risk of flooding by melting previously accumulated mountain snow.

The substantial rainfall is expected to alleviate the strain on regional water resources. In the Seattle area, an unusually dry summer had raised concerns about the adequacy of water supplies for municipal use and the preservation of fish habitats. Atmospheric rivers are recurring phenomena during the winter months and can contribute up to 50 percent of the total precipitation, including rain and snow, in the western United States.

Image Credit: NASA Earth Observatory, created by Lauren Dauphin, using GEOS-5 data from the Global Modeling and Assimilation Office at NASA GSFC.

Frequently Asked Questions (FAQs) about Atmospheric River

What is an atmospheric river?

An atmospheric river is a meteorological phenomenon characterized by a long, narrow corridor of moisture-laden air, often originating from tropical regions. It carries a substantial amount of water vapor and can result in heavy precipitation when it makes landfall.

How did this atmospheric river impact the Pacific Northwest in December 2023?

In December 2023, an atmospheric river brought warm, wet weather to the Pacific Northwest, particularly western Washington and Oregon. It led to the toppling of daily rainfall and temperature records and increased the risk of floods and debris flows.

What does the map of total precipitable water vapor represent?

The map illustrates the total amount of water vapor present in the atmosphere at a specific time and location. It helps meteorologists monitor and understand the moisture content in the air, which is crucial for forecasting weather events like this atmospheric river.

How did the storm affect temperature records?

During this weather event, both Portland and Seattle experienced record-high temperatures. Portland reached 65°F (18°C) on December 4, while Seattle hit 59°F (15°C) on December 5, breaking previous temperature records for those dates.

What relief did the rainfall provide for water supplies?

The substantial rainfall from this atmospheric river event is expected to alleviate pressure on regional water supplies, particularly in the Seattle area. This relief comes after concerns were raised about water availability following an unusually dry summer.

Are atmospheric rivers common in the Pacific Northwest?

Yes, atmospheric rivers are relatively common in the Pacific Northwest during the winter months. They can account for a significant portion of the region’s total precipitation, including both rain and snowfall.

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5 comments

WaterWatcher22 December 7, 2023 - 9:57 pm

Rain’s a blessin’ for water, after the dry spell. Gud news!

Reply
ClimateNerd456 December 8, 2023 - 1:55 am

gr8 explnations, thx! Luvd the map pic, it’s real cool!

Reply
InfoBuff2023 December 8, 2023 - 4:41 am

Thnx for sharin’ all these helpful links, appreciate it!

Reply
OutdoorAdventurer December 8, 2023 - 3:34 pm

Portland & Seattle, new temp champs! Climate’s wild, man.

Reply
WeatherGeek123 December 8, 2023 - 6:02 pm

wow! This atmosp river thing’s cray-cray! Big water in sky!

Reply

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