cw3e-web - Center for Western Weather and Water Extremes

CW3E Event Summary: 18-20 February 2024

27 February 2024

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Low-Pressure System and Atmospheric River Produce Heavy Rain and Snow in CA

An atmospheric river (AR) associated with a slow-moving area of low pressure brought widespread precipitation to California during 18–20 Feb.

The AR:

A deepening mid-level trough off the US West Coast interacted with a remnant plume of subtropical moisture, leading to an AR landfall over California on 18 Feb.
AR1–2 conditions (based on the Ralph et al. 2019 AR Scale) were observed in coastal Northern and Central California.
As the eastward progression of the trough stalled and the synoptic-scale flow became more southerly, the AR briefly re-intensified over Southern California, prolonging precipitation over the Transverse Ranges.

Impacts:

The heaviest precipitation occurred in the western Transverse Ranges, with more than 10 inches in some locations.
At least 1–3 feet of snow fell in the Sierra Nevada, with higher amounts in the vicinity of Lassen Peak.
Heavy rain falling on moist soils caused minor riverine flooding in the Sacramento Valley.
Flooding and mudslides closed portions of US-101, SR-1, SR-33, and SR-150 in Ventura and Los Angeles Counties.
Portions of coastal Southern California have received more than 75% of their normal total annual precipitation during the first 3 weeks of February.
Unusually cool and wet conditions during the month of February have facilitated a dramatic improvement in snowpack conditions throughout the state.

Click images to see loops of West-WRF IVT/IWV analyses and forecasts Valid: 0000 UTC 18 February – 0000 UTC 21 February 2024

Summary provided by C. Castellano, S. Bartlett, P. Iniguez, and S. Roj; 27 Feb 2024

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CW3E AR Update: 26 February 2024 Outlook

February 26, 2024

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AR and Low Pressure System Fuel Precipitation Event Over USWC

An atmospheric river (AR) and low pressure system forecast to make landfall over the USWC will help fuel a multi-day precipitation event that is likely to bring heavy snowfall to the Cascades and Sierra Nevada.
The AR makes landfall over the PNW late on Tue 27 Feb and moves down the USWC through Fri 1 Mar.
There is potential for a pulse of IVT from the central Pacific to reach the USWC and extend AR conditions over northern and central CA when it interacts with AR.
Behind this AR, the associated low pressure system and a mid-level trough will help continue this precipitation event over CA through Sun 3 Mar.
The NWS Weather Prediction Center (WPC) is forecasting significant precipitation over the next 7 days along the WA/OR coasts and OR/CA border and over the Cascades and Sierra Nevada.
The National Blend of Models (NBM) showing very high probabilities (>90%) of snowfall exceeding 36+ in. for portions of the Cascades and Sierra Nevada.
West-WRF Ensemble Meteograms are also showing very high probabilities of significant snowfall (totals > 24 in.) in the Sierra Nevada.
The WPC Excessive Rainfall Outlooks include a Marginal Risk (level 1 of 4, or at least 5% chance) for flooding for the WA/OR/N. CA coasts and the N. Sierra Nevada with the the AR as it moves down the coast.
Stay alert to official NWS forecasts, watches, and warnings at weather.gov and follow guidance from local emergency management officials.

Click images to see loops of GFS IVT and IWV forecasts Valid 1200 UTC 26 February 2024 – 0000 UTC 3 March 2024

Summary provided by M. Steen, P. Iniguez, S. Bartlett and G. Lewis; 26 February 2024

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*Outlook products are considered experimental

For any unfamiliar terms, please refer to the American Meteorological Society Glossary.

CW3E Subseasonal Outlook: 23 February 2024

February 23, 2024

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Summary provided by C. Castellano, J. Wang, Z. Yang, M. DeFlorio, and J. Kalansky; 23 February 2024

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*Outlook products are considered experimental

CW3E Publication Notice: Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar

CW3E Publication Notice

Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar

February 19, 2024

In the recent publication “Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar” in the Bulletin of the American Meteorological Society by CW3E collaborator and University of Arizona professor Xubin Zeng, among co-authors across institutions including CW3E’s Anna Wilson, propose a new satellite mission to address the challenge in accurately characterizing three-dimensional distribution of horizontal wind vectors (3D winds): Vientos. This proposed satellite mission will combine 2 or more passive water vapor sounders with Doppler wind lidar to accurately measure these 3D winds. This work contributes to CW3E’s 2019-2024 Strategic Plan, in particular the Priority Area dedicated to Atmospheric River Research and Applications by suggesting a transformative modernization of atmospheric measurements.

3D winds are integral to the Earth system, and yet, we do not currently have a method of accurately observing 3D winds with requisite space/time coverage. Information on 3D wind structures in and around atmospheric rivers in particular has the potential to be transformational for our understanding of the underlying processes. Further, our reliance on reanalysis data has been proved by recent studies to contain some systematic dynamical biases and errors. Thus, the need for Vientos is clear. The feasibility of the Vientos concept, which would retrieve 3D atmospheric motion vectors through tracking the movement of water vapor, followed by a bias correction using lidar measurements, has been proved doable by recent missions that explore combining active and passive observations as part of the global observing system.

The Vientos mission would be able to address many scientific questions and contribute to a variety of applications. In addition to 3D wind observations, it would also provide 3D water vapor and temperature data while wind lidar provides aerosol measurements of the near storm environment (Figure 1, from the paper). This could provide many benefits to areas including but not limited to: numerical weather predictions, flight route planning in aviation, Forecast Informed Reservoir Operations (FIRO), wind energy, tracking transport of pollutants and aerosols, climate model evaluations, and carbon monitoring for international negotiations and policy making. Lastly, the essay explores different possible architectures of the project, each providing different resolutions and coverage based on budgets available coinciding with currently planned satellite missions.

Vientos emphasizes the synergy between passive sounders and wind lidar in a way that could fill a critical gap in Earth system scientific knowledge. To read more about the Vientos concept, access the entire publication here.

Zeng, X., Su, H., Hristova-Veleva, S., Posselt, D. J., Atlas, R., Brown, S. T., Dixon, R. D., Fetzer, E., Galarneau, T. J., Jr., Hardesty, M., Jiang, J. H., Kangaslahti, P. P., Ouyed, A., Pagano, T. S., Reitebuch, O., Roca, R., Stoffelen, A., Tucker, S., Wilson, A., Wu, L., & Yanovsky, I. (2024). Vientos – A new satellite mission concept for 3D wind measurements by combining passive water vapor sounders with Doppler wind lidar. Bulletin of the American Meteorological Society (published online ahead of print 2024). https://doi.org/10.1175/BAMS-D-22-0283.1

CW3E Subseasonal Outlook: 16 February 2024

February 16, 2024

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Summary provided by J. Wang, C. Castellano, Z. Yang, M. DeFlorio, and J. Kalansky; 16 February 2024

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*Outlook products are considered experimental

CW3E AR Update: 16 February 2024 Outlook

February 16, 2024

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Pair of Storms to Bring Precipitation to California

A pair of storms are forecast to impact the US West Coast during the next several days.
The first storm is an atmospheric river (AR) that makes landfall across the USWC on Fri 16 Feb.
The landfall orientation of the this AR is likely to be suboptimal for orographic precipitation, potentially limiting the precipitation potential of this system.
The second storm is a second AR that is forecast to make landfall alongside a low pressure system into central CA on Sun 18 Feb.
The second system taps into remnant moisture from the first system, which combined with the persistence of the stationary low pressure system off the CA coast, will result in a multi-day precipitation event for the state.
The NWS Weather Prediction Center (WPC) is forecast significant precipitation over the next 7 days along the northern and central CA coasts and in the Sierra Nevada.
The WPC Excessive Rainfall Outlook (ERO) indicates a Slight Risk (level 2 of 4, or at least 15% chance) for flooding over the northern CA coast with the first storm and along the northern and central CA coasts with the second storm.
The WPC ERO also indicates a Marginal Risk (level 1 of 4, or at least 5% chance) for flooding across broader areas.
The second storm is likely to bring heavy snowfall to the Sierra Nevada. The National Blend of Models (NBM) indicates very high probabilities (>90%) of snowfall accumulations exceeding 24”.

Click images to see loops of GFS IVT and IWV forecasts Valid 1200 UTC 16 February 2024 – 1200 UTC 21 February 2024

Summary provided by M. Steen, P. Iniguez, S. Bartlett and C. Castellano; 16 February 2024

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*Outlook products are considered experimental

For any unfamiliar terms, please refer to the American Meteorological Society Glossary.

CW3E Researcher Agniv Sengupta selected for AMS ECLA

February, 15 2024

CW3E scientist, Dr. Agniv Sengupta, was selected as a member of the American Meteorological Society’s Early-Career Leadership Academy Class of 2023. “The American Meteorological Society’s (AMS) Early Career Leadership Academy (ECLA) aims to build and sustain a diverse network of early career leaders in weather, water, and climate science. ECLA will bring together a select group of early career individuals—in particular, women and underrepresented minorities—for an immersion experience in leadership, such as creative problem-solving, conflict resolution, building trust, and enhancing communication skills. We seek early career individuals from a wide range of professions, interests, perspectives, cultures, and experiences.” (from AMS’s website ).

Group photo of the members of the 2023 AMS ECLA Cohort

This professional development program included four virtual leadership webinars and several peer mentoring calls, leading up to a three-day, in-person summit in Phoenix, Arizona. Webinars for the 2023 ECLA program began with participants taking an individual leadership assessment using the CliftonStrengths test. This assessment helped them identify personalized traits in strategic thinking, influencing, relationship building, and executing. The webinars also covered conflict management and resolution, as well as providing comprehensive diversity, equity, and inclusion (DEI) training with dedicated reading and writing exercises.

During the in-person workshop, participants heard from several invited keynote speakers who shared their leadership journeys and how they navigated various societal and professional challenges. The workshop also included sessions on constructing personal leadership styles, research ethics, team building, enhancing communication skills, and bystander practice and intervention using real-life scenarios.

Dr. Sengupta expresses his appreciation to the AMS for developing ECLA and to the Planning Committee for their hard work in creating an immersive experience for the cohort. He found the overall experience enriching as it provided fresh perspectives, insights into unique leadership styles, and a high-quality, diverse network of peers and mentors. Dr. Sengupta highly recommends this career development opportunity to early-career scientists interested in leadership positions in the future.

Photo of the peer-mentor group of Dr. Sengupta from the ECLA workshop

CW3E AR Update: 14 February 2024 Outlook

February 14, 2024

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Trio of Storms to Bring Precipitation to California

A trio of storms are forecast to make landfall over the US West Coast in the next 7 days.
The first storm is driven by a low pressure system that brings a burst of IVT to the USWC on Wed 14 Feb. This low pressure system persists off the PNW coast through Thu 15 Feb as the second AR propagates toward the USWC.
The second storm is an atmospheric river (AR) that makes landfall across the USWC on Fri 16 Feb. The landfall direction of the AR is likely to be suboptimal for precipitation, potentially limiting the precipitation potential of this system.
The ECMWF EPS is forecasting greater probabilities of IVT > 250 kg m-1 s-1 making landfall over the PNW with the second AR than the GEFS.
The third storm is a second AR that is forecast to make landfall alongside a low pressure system into central CA on Sun 18 Feb.
There is uncertainty amongst GEFS and EPS ensemble members regarding the duration and strength of AR conditions with the second and third ARs across CA.
The WPC is forecasting significant 7 day precipitation over the northern and central CA coasts and the Sierra Nevada.
The WPC Excessive Rainfall Outlook indicates a Slight Risk (level 2 of 4, or at least 15% chance) for flash flooding over the northern CA coast for the 24 hour period ending 4 AM PT Sun 18 Feb with the second AR.
The NWS WPC has issued Excessive Rainfall Outlooks highlighting the potential for flash flood conditions in various locations along the coast of California in association with precipitation during each of the three storms during this period.

Click images to see loops of GFS IVT and IWV forecasts Valid 1200 UTC 14 February 2024 – 0000 UTC 22 February 2024

Summary provided by M. Steen, S. Bartlett and P. Iniguez; 14 February 2024

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*Outlook products are considered experimental

For any unfamiliar terms, please refer to the American Meteorological Society Glossary.

Summary: Major CA Winter Storm (4-6 Feb 2024)

CW3E Event Summary: 4-6 February 2024

14 February 2024

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Major CA Winter Storm (4-6 Feb 2024)

Overall summary:

A strong atmospheric river (AR) impacted much of California on 4-6 Feb 2024.
It was an AR3 in the Santa Barbara base on the Ralph (2019) AR scale.

Precipitation impacts:

Widespread precipitation of 1-5” fell across most of California with 5-10” in the coastal mountains and Los Angeles Basin. Some areas of the San Gabriel Mountains received 10-15” of precipitation.
Los Angeles recorded one of its wettest multi-day stretches on record.
Heavy rain resulted in hundreds of mudslides and high flows on area rivers.
Year-to-date percent of normal snowfall increased by 10-20% across the Sierra Nevada mountains.

Wind and power outages:

- Storm produced widespread winds of 60+ mph across northern California with local peak wind gusts around the San Francisco Bay Area of 80-100 mph.
- Strong winds and wet soils felled hundreds of trees.
- A reported 1.4 million customers were without power at various points across the state.

IVT across the northeast Pacific Ocean during this event

Click image for animation (9MB).

IVT near the US West Cost during this event

Click image for animation (8MB).

Peak IVT values for this AR

Click image for video (YouTube).

AR Recon IOP 31 map

CW3E Radiosondes

MSLP analysis of bomb cyclone

Click image for animation (27MB).

Wind gust analysis

Click image for animation (15MB).

Peak wind gusts

Total precipitation and share of annual rainfall

Chance in WYTD percent of normal precipitation

Chance in WYTD percent of normal precipitation LA area

Rainfall statistics for downtown LA

Snowfall analysis

Summary of impacts

Images of trees toppled

Images of landslides

Images of flooding

River gage data for the Los Angeles River

Images of snowfall

Example of FIRO operations

Summary provided by: P. Iniguez, C. Castellano, J. Cordeira, , J. Kalansky, S. Roj, and M. Steen.

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CW3E Event Summary: 26 January – 2 February 2024

13 February 2024

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Atmospheric Rivers Produce Heavy Precipitation from Alaska to Southern CA

A family of atmospheric rivers (ARs) brought heavy precipitation to portions of Alaska, British Columbia, the Pacific Northwest, and California during 26 Jan – 2 Feb.

The ARs:

AR #1 made landfall in Oregon on 26 Jan and produced at least 2–6 inches of precipitation in portions of western Washington and Oregon.
AR #2 made landfall in British Columbia and southeastern Alaska on 28 Jan and produced 6–12 inches of precipitation over Vancouver Island, the Coast Mountains, the Alaska Panhandle, and the St. Elias Mountains.
AR #3 produced AR4 conditions (based on the Ralph et al. 2019 AR Scale) along the southern Oregon coast and AR3 conditions in coastal Northern California.
AR #3 brought widespread precipitation to California, including 4–8 inches of rain in the Northern California Coast Ranges and western Transverse Ranges, and 1–3 feet of snow in the Sierra Nevada.
All three ARs were fed from a tropical moisture source referred to as a Tropical Moisture Export (TME).

Impacts:

Rain falling on moist soils caused minor-to-moderate riverine flooding in western Washington during the first AR.
The greatest hydrologic impacts occurred in British Columbia during the second AR, with significant flooding near Pemberton, BC.
Minor flooding and several landslides were reported in Northern California during the third AR
This family of ARs and nearby essential atmospheric features were sampled by the NOAA and the 53rd Weather Reconnaissance Squadron as part of the AR Recon field campaign.