cw3e-web - Center for Western Weather and Water Extremes

CW3E AR Update: 5 October 2020 Outlook

October 5, 2020

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Update on Atmospheric Rivers Forecast to Bring Precipitation to the US West Coast

A unique large-scale flow regime is forecast to result in the landfall of two separate but concurrent ARs over the USWC
Current forecasts suggest that IVT magnitudes over southern Oregon may reach 500 kg m^–1 s^–1 while AR conditions are forecast to last ~27 hours, resulting in AR 2 conditions
There is currently a large amount of uncertainty in the forecast, which is resulting in a large spread of potential outcomes
The GFS, ECMWF, and NBM are forecasting different precipitation accumulations from Washington to Northern CA
Due to the numerous fires currently burning across California, this precipitation in the forecast may bring much needed relief to extremely dry conditions

Click images to see loops of GFS IVT/IWV analyses and forecasts Valid 0000 UTC 5 October – 1800 UTC 14 October 2020

Summary provided by C. Hecht, C. Castellano, J. Kalansky, and F. M. Ralph; 5 October 2020

*Outlook products are considered experimental

CW3E Event Summary: 23-27 September 2020

September 29, 2020

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Active weather pattern brings first major precipitation event of the season to the Pacific Northwest

A family of landfalling ARs produced heavy rainfall across western North America during 23–27 Sep
Some locations along the northwestern coast of Oregon experienced AR5 conditions [based on the Ralph et al. (2019) AR scale]
Total estimated 7-day precipitation ending 28 Sep exceeded 2 inches across most of western Washington and northwestern Oregon, with more than 5 inches (locally > 10 inches) in the Olympic Mountains and North Cascades

Click images to see loops of GFS IVT/IWV analyses Valid 0000 UTC 22 September – 0000 UTC 28 September 2020

Summary provided by C. Castellano, J. Kalansky, B. Kawzenuk, and F. M. Ralph; 29 September 2020

CW3E Welcomes Linghan Li

September 29, 2020

Linghan Li joined CW3E as a Research Data Analyst in September 2020. Linghan received her PhD in Oceanography from Scripps Institution of Oceanography, University of California, San Diego, under the guidance of Art Miller. She also holds a MS in Space Physics from Chinese Academy of Sciences and a BE in Electrical Engineering from Wuhan University. Linghan’s PhD dissertation focused on sea ice variability in the Bering Sea, including its atmospheric and oceanic dynamic and thermodynamic controls, using global and regional ocean/ice models and satellite observations. After completing her dissertation, she worked on several coastal ocean modeling projects as a Research Associate at University of Washington.

In her new position at CW3E, Linghan will study ocean-atmosphere interactions, particularly relating to the understudied field of local and remote ocean influences on atmospheric river (AR) evolution and predictability. In this regard, her research will also explore the current ability of coupled models to represent AR evolution over the global oceans via satellite remote sensing and field campaign data. Collectively, these efforts target the improved understanding and forecasting of ARs and their impacts in the western US and globally. Beyond her primary research on ocean-atmosphere interactions, Linghan will also support an ongoing assessment of California climate variability and change in collaboration with scientists in California-Nevada Climate Applications Program.

CW3E AR Update: 24 September 2020 Outlook

September 24, 2020

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Update on Active Period of Atmospheric Rivers over the Pacific Northwest

As an AR is currently impacting the Pacific Northwest, two additional ARs are forecast to bring precipitation to the region and British Columbia
Current forecasts suggest that IVT magnitudes over northern Oregon may not drop below 250 kg m^–1 s^–1, which would result in total AR condition duration of ~75 hours
The combination of strong IVT magnitudes and long durations results in an AR 5 on the AR Scale (Ralph et al. 2019)
Since this is an early season AR and soil moisture across the PNW is dry, impacts associated with these ARs may not be as hazardous as an AR of similar strength that makes landfall in the middle of winter
As much as 7 inches of precipitation has already fallen over the Cascade Mountains of northern Washington and an additional 4–5 inches is forecast to fall during the next period of AR activity

GOES-17 PACUS Domain GeoColor

Valid 0000 UTC 22 September – 1200 UTC 24 September 2020

Click images to see loops of GFS IVT/IWV analyses and forecasts Valid 1200 UTC 24 September – 1200 UTC 04 October 2020 Forecasting an active week of ARs in the PNW

Summary provided by C. Hecht, B. Kawzenuk, J. Kalansky, and F. M. Ralph; 21 September 2020

*Outlook products are considered experimental

Virtual Happy Hour: CW3E Post-Doc Appreciation

CW3E Launches Public Subseasonal-to-Seasonal (S2S) Experimental Forecast Webpage for Winter 2020-2021

September 24, 2020

In honor of National Post Doc Appreciation Week, CW3E got together to appreciate and celebrate all of our post-docs during a virtual happy hour. We are extremely fortunate to have a group of such smart, motivated, and collaborative post-docs. Thank you all for your many valuable contributions to CW3E!

Our current CW3E post-docs are:

William (Ty) Brandt, PhD

Allison Michaelis, PhD

Alison Cobb, PhD

CW3E Event Summary: 14-18 September 2020

September 22, 2020

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Landfalling AR and Cutoff Low bring much-needed rainfall and improved air quality to the Pacific Northwest

A landfalling AR and cutoff low produced light-to-moderate precipitation (0.50–2 inches) over portions of western Washington and Oregon
Weak-to-moderate AR conditions persisted for more than 48 consecutive hours along the Oregon coast [AR3 based on the Ralph et al. (2019) AR Scale]
Precipitation and changes in wind direction and humidity significantly improved the air quality and alleviated the wildfire threat in western Washington and Oregon

Click images to see loops of GFS IVT/IWV analyses Valid 0000 UTC 14 September – 0000 UTC 21 September 2020

Summary provided by C. Castellano, C. Hecht, J. Kalansky, N. Oakley, and F. M. Ralph; 22 September 2020

CW3E AR Update: 21 September 2020 Outlook

September 21, 2020

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Update on potentially strong atmospheric river forecast to impact the Pacific Northwest

Forecast agreement between models and ensemble members has increased in the magnitude, duration, and location of AR conditions in association with the potentially strong AR forecast to make landfall this week
Forecasts of the strongest IVT magnitudes have shifted further south where AR 5 conditions are now forecast to impact Northern Oregon
Although AR 5s are often hazardous later in the season, given early season conditions (dry soils, low streamflow) this AR is unlikely to produce hazardous impacts
Ensemble probabilities of strong AR conditions (IVT magnitudes >750 kg m–1 s–1) have also increased over portions of the PNW
Model forecasts of precipitation accumulations have increased for portions of the Cascade, Olympic, and Coastal Mountains, though there is still some model-to-model disagreement in exact accumulation

Click images to see loops of GFS IVT/IWV analyses and forecasts Valid 0000 UTC 21 September – 0000 UTC 01 October 2020

Summary provided by C. Hecht, C. Castellano, B. Kawzenuk, N. Oakley, J. Kalansky, and F. M. Ralph; 21 September 2020

*Outlook products are considered experimental

CW3E AR Update: 18 September 2020 Outlook

September 18, 2020

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A Potentially Strong Atmospheric River Could Douse the Pacific Northwest Next Week

Model forecasts are currently indicating the potential for a strong AR to make landfall over the PNW next week, but large ensemble spread in IVT forecasts is leading to considerable uncertainty in AR Scale (ranging from no AR to AR 5 in some locations)
Forecasts of maximum IVT magnitude over the Washington Coast range from < 400 kg m^–1 s^–1 to > 1200 kg m^–1 s^–1
While forecast uncertainty is currently high, more than 4 inches of precipitation are possible over the Olympic Peninsula during the next 7 days (Note: the 7-day forecast may not encompass the entirety of this event)

Click images to see loops of GFS IVT/IWV analyses and forecasts Valid 1200 UTC 18 September – 1200 UTC 28 September 2020

Summary provided by C. Hecht, C. Castellano, B. Kawzenuk, J. Kalansky, and F. M. Ralph; 18 September 2020

*Outlook products are considered experimental

CW3E To Launch Second Year of Experimental Seasonal Forecasts of Precipitation

September 15, 2020

CW3E researchers Alexander Gershunov and Tamara Shulgina, along with collaborators Kristen Guirguis, Julie Kalansky, Brian Kawzenuk, Mike DeFlorio, and Luca Delle Monache, are set to launch the second year of an experimental seasonal precipitation prediction system based on canonical correlation analysis (CCA) this fall on the CW3E website. The prediction system utilizes a statistical approach that is based on relationships between Pacific Ocean sea surface temperature and precipitation. This effort, sponsored by the U.S. Bureau of Reclamation, California Department of Water Resources, and the U.S. Geological Survey via the Southwest Climate Adaptation Science Center, is part of a broad effort at CW3E to improve subseasonal-to-seasonal (S2S) prediction of precipitation, atmospheric rivers (ARs), and ridging events to benefit western U.S. water resource management. A 2-pager document describing this effort in detail can be found here.

CW3E Explores Shifting Seasons and Precipitation in the Yampa River Basin Upcoming Webinar

CW3E Explores Shifting Seasons and Precipitation in the Yampa River Basin Upcoming Webinar:

Thursday, September 17, 11-12:30 Mountain Time

September 15, 2020

The Yampa River is one of the wildest remaining major tributaries of the Colorado River, and provides crucial water supplies to local stakeholders and to locations as far removed as Arizona and Southern California. A multitude of environmental and societal factors are expected to be affected by climate change in the Yampa River Basin, and are pertinent to other watersheds around the American West.

This summer, CW3E and our partners at Colorado Mountain College, Friends of the Yampa, Yampa Valley Sustainability Council, Steamboat Ski and Resort Corporation, and Vacasa, among others, have virtually come together for the third annual Yampa Basin Rendezvous (YBR). YBR 2020 is a series of four interactive webinars examining the Yampa River Basin through the lens of climate change and seasonal variability. The webinars include talks by regional experts and lively discussions.

The first webinar was held on June 4, 2020, introducing the series and providing an overview of the past year in the Yampa Basin with an eye to this year’s theme of Seasonal Variability. The panelists included Marty Ralph, CW3E Director; Kent Vertrees, with Friends of the Yampa and Steamboat Powdercats; and Nathan Stewart, Associate Professor of Sustainability Studies at Colorado Mountain College.

The second webinar of YBR 2020 was held on July 9, 2020. Webinar 2 was a panel discussion on Changes in Measurement with a Changing Climate, addressing what our measurement data are currently showing and ways we can adapt our strategies to be more effective. The panelists were Mike Dettinger, Visiting Researcher at Scripps Institution of Oceanography; Jeff Deems, Research Scientist with National Snow and Ice Data Center; and Gannet Hallar, Associate Professor of Atmospheric Science at University of Utah. Both the first and second webinars are now available to view online.

This week, on Thursday, September 17th, 11-12:30 (Mountain Time), we will have the third webinar of YBR 2020, hosted virtually on Zoom. The third webinar will delve into the changes we are seeing from shifting seasons and precipitation and how these changes are impacting our local and statewide watershed and forest health. Our panelists will include Russ Schumacher, Associate Professor of Atmospheric Science at Colorado State University, Director of the Colorado Climate Center, and Colorado’s State Climatologist; David Stahle, Distinguished Professor of Geosciences at University of Arkansas; and Courtney Peterson, Adaptive Silviculture for Climate Change (ASCC) Coordinator for the Northern Institute of Applied Climate Science. Register here!

This event is part of a larger effort to connect graduate students, post-doctoral scholars, researchers, staff, and faculty from CW3E to the local communities of river basins throughout the west, to share knowledge regarding climate variability and change that has impacts on the environment, people and the economy.

The second webinar of Yampa Basin Rendezvous 2020 was held on 7 July, 2020.