Author: cw3e-web

CW3E Winter Storm Update: 24 February 2023 Outlook

CW3E Winter Storm Update: 24 February 2023 Outlook

February 24, 2023

Click here for a pdf of this information.

Winter Storm to Bring Additional Precipitation to the Pacific Northwest and California

  • A period of unsettled weather will continue for the US West Coast, with a winter storm forecast to bring precipitation to Washington, Oregon, and California starting Sunday
  • A mid-level trough is forecast to move quickly through the Pacific Northwest on Sunday, bringing precipitation primarily to the Olympic Peninsula and Cascades
  • A second, stronger mid-level trough is forecast to develop over the Gulf of Alaska and shift towards the US West Coast late Sunday, bringing precipitation to locations along the Coast Ranges of Washington and Oregon, Northern California, and the Sierra Nevada early next week
  • The National Weather Service (NWS) Weather Prediction Center (WPC) 5-day QPF totals are > 1.5 inch in the Olympic Peninsula and Northern Cascades, > 3 inches along the Coast Ranges of Oregon and Northern California, and > 5 inches for the Sierra Nevada through Wednesday
  • Significant snowfall accumulation is expected in the Cascades and Sierra Nevada as a result of this cold winter storm, with freezing levels dropping below 1,500 meters in the Sierra Nevada during this event
  • This storm will provide an additional boost to the snowpack in the Sierra Nevada, which is already well above normal for the season as a result of a prolonged period of active weather along the US West Coast
  • The 00Z ECMWF is forecasting higher watershed precipitation totals (3-4inches) along the Coast Ranges of Washington and Oregon and in the northern Cascades than the GFS, while the GFS is forecasting higher watershed precipitation totals (4-6 inches) along the Sierra Nevada as compared to the ECMWF

Click images to see loops of GFS Precip and 500 hPa Vorticity forecasts

Valid 0000 UTC 26 February – 0000 UTC 3 March 2023


 

 

 

 

 

 

Summary provided by S. Bartlett, C. Castellano, S. Roj, and F. M. Ralph; 24 February 2023

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*Outlook products are considered experimental

CW3E AR Update: 21 February 2023 Outlook

CW3E AR Update: 21 February 2023 Outlook

February 21, 2023

Click here for a pdf of this information.

Winter Storm and Atmospheric River Forecast to Bring Heavy Rain and Snow to Southern California

  • An amplifying upper-level shortwave trough will continue to produce unsettled weather over much of the western US during the next few days
  • As time progresses, a cutoff low and a weak atmospheric river (AR) are forecast to develop near the California coast and bring a period of heavy precipitation to Southern California
  • The 00Z ECMWF EPS control is predicting AR 1 conditions (based on the Ralph et al. 2019 AR Scale) over coastal San Diego County and AR 2 conditions near the California–Mexico border
  • The NWS CNRFC is forecasting at least 2–5 inches of total precipitation in the Sierra Nevada and coastal Southern California, with higher amounts expected in the eastern Transverse Ranges and Peninsular Ranges
  • The NWS Weather Prediction Center has issued a marginal risk of rainfall exceeding flash flood guidance in coastal Southern California Friday into Sunday
  • Major winter storm impacts are expected over portions of the Sierra Nevada and Transverse Ranges from Thursday through Saturday
  • Low freezing levels will support significant snowfall accumulations in the higher terrain in Southern California
  • Damaging wind gusts are also possible over much of the southwestern US today into Thursday
  • As part of CW3E’s Atmospheric River Reconnaissance Program (AR Recon), the 53rd Weather Reconnaissance Squadron will continue to provide additional weather observations over the North Pacific, sampling the atmosphere upstream of this storm

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 21 February – 0000 UTC 27 February 2023


 

 

 

 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, and J. Cordeira; 21 February 2023

To sign up for email alerts when CW3E post new AR updates click here.

*Outlook products are considered experimental

CW3E AR Update: 17 February 2023 Outlook

CW3E AR Update: 17 February 2023 Outlook

February 17, 2023

Click here for a pdf of this information.

Atmospheric River Forecast to Bring Precipitation to the Pacific Northwest and Northern California

  • An atmospheric river (AR) is forecast to make landfall in the Pacific Northwest on Sunday and bring precipitation to Washington, Oregon, and Northern California through mid-day on Wednesday
  • IVT > 600 kg m-1 s-1 is forecast during landfall along the coast of Washington, bringing AR 2 conditions (based on the Ralph et al. 2019 AR Scale) to coastal locations of the Pacific Northwest
  • This AR is forecast propagate over the ridge positioned in the eastern North Pacific, bringing primarily northwesterly/westerly IVT to the US West Coast, eventually dissipating along the coast of California by late Wednesday
  • A weak mesoscale frontal wave is forecast to occur during the mid-stage of this AR over the Gulf of Alaska, which will have weak secondary cyclogenesis in association with a mid-level shortwave trough
  • The 00Z GFS is forecasting a stronger and longer duration period of AR conditions for points along the coast as compared to the ECWMF, with the GFS bringing AR conditions south to coastal locations in Northern California
  • The 00Z GFS is forecasting greater 7-day watershed precipitation totals throughout northern California, Oregon, and Washington than the 00Z ECMWF, especially within coastal watersheds along the CA/OR border and the Oregon Cascades
  • The 12Z GEFS ensemble is forecasting snow levels to fall dramatically from > 3,000 m to near sea level by 12Z 22 Feb for much of Northern California and the Sierra Nevada Mountains, resulting in the potential for snowfall accumulation at lower elevations than usual elevations

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 18 February – 1800 UTC 22 February 2023


 

 

 

 

 

 

Summary provided by S. Bartlett, S. Roj, C. Castellano, and F. M. Ralph; 17 February 2023

To sign up for email alerts when CW3E post new AR updates click here.

*Outlook products are considered experimental

CW3E Leadership Meets with Dr. Rick Spinrad, Under Secretary of Commerce for Oceans and Atmospheres & NOAA Administrator

CW3E Leadership Meets with Dr. Rick Spinrad, Under Secretary of Commerce for Oceans and Atmospheres & NOAA Administrator

February 16, 2023

CW3E Director, Marty Ralph, and Field Research Manager, Anna Wilson, met with Dr. Rick Spinrad, the Under Secretary of Commerce for Oceans and Atmospheres & NOAA Administrator, on 15 February 2023 at Scripps Institution of Oceanography. Discussion focused on the unique challenges around water in the western US, including conditions that vary more dramatically between wet and dry than elsewhere in the nation. The importance of water to the western environment and economy was highlighted along with the vital role of the west coast states in the US economy. These states represent roughly 20% of the entire US economy, including California, at 15% of US GDP, which is by far the largest contributor of any of the 50 states.

The role of atmospheric rivers as the drivers of both flood and drought was described and efforts to better understand, observe and predict them were summarized. Advances in modeling, with West-WRF and its super-ensemble, machine learning research and other topics were described. The AR Scale was discussed deeply, including its primary role as a situational awareness aid, with the associated need for experienced forecasters to translate that into point forecasts that factor in antecedent conditions on the ground. AR Recon was described as a breakthrough in improving west coast precipitation forecasts through our CW3E Research And Operations Partnership with NWS, OMAO, the Air Force/Weather Reconnaissance Squadron and other agencies and universities. The use of dropsondes, drifting buoys and airborne radio occultation were highlighted. The need for extending the AR Recon operating season to start in November and to expand coverage to the western Pacific were noted. Finally, the Forecast-Informed Reservoir Operations program was summarized, as well as its use of, and need for, accurate AR forecasts.

CW3E is very appreciative of the chance to meet with Dr. Spinrad and his colleagues from the NOAA Corps who accompanied him, to share our work, receive feedback, discuss key topics and consider the future.

CW3E and Yuba Water Agency Bring Science to Life for Students at Browns Valley Elementary School in Yuba County

CW3E and Yuba Water Agency Bring Science to Life for Students at Browns Valley Elementary School in Yuba County

February 14, 2023

Browns Valley Elementary School students in Yuba County recently had the opportunity to learn about weather forecasting and natural resource management first-hand from the Center for Western Weather and Water Extremes and Yuba Water Agency.

In mid-January, researchers Chad Hecht and Anna Wilson spoke with kindergarten and third-grade students about a weather station that CW3E operates at the school with support from Yuba Water, and how that data informs weather forecasting and water management in the region. This was the first time CW3E had a chance to talk with students about the weather station since it was installed in April 2021.

During CW3E’s visit, students explored the variety of instrumentation at the station, including the inside of a tipping bucket rain gauge. Third-grade students learned about how the weather station’s instrumentation works, what they measure, how the observations can be useful to understanding the atmosphere and how this knowledge and research can be used to improve forecasting and water resource management.

Students were also able look at the data coming in from the station in real time using graphs, which aligns with third-grade learning objectives. This was also an opportunity for Chad and Anna to highlight the importance of observations at this specific weather station as a key part of a larger, watershed-wide network.

The students were actively engaged throughout Anna and Chad’s visit, asked numerous questions, and explained with great enthusiasm the rain gauges they had recently designed and collocated with the weather station.

One week after CW3E’s visit, Yuba Water visited the third-grade class to connect how data from the weather station directly supports decisions by Yuba Water and other natural resource management agencies in the region. Yuba Water’s director of resource planning, John James, explained how weather data fits into the agency’s management of the Yuba River watershed and New Bullards Bar Reservoir, which is near the school and is critical to flood risk reduction and water supply reliability in the region. The discussion gave students the opportunity to ask more questions about the watershed and how it is studied and managed, especially during times of flood and drought.

CW3E and Yuba Water Agency are grateful for the opportunity to work with Browns Valley Elementary School students and teachers, and we look forward to our next visit!

CW3E’s Anna Wilson discusses the Browns Valley Elementary School weather station with the 3rd grade class.

Yuba Water Agency’s John James leads a discussion on the Yuba watershed in the Browns Valley Elementary School 3rd grade classroom.

CW3E Publication Notice: Evaluation of Subseasonal Drought Forecast Skill over the Coastal Western U.S.

CW3E Publication Notice

Evaluation of Subseasonal Drought Forecast Skill over the Coastal Western U.S.

February 10, 2023

Lu Su, a Ph.D. student from UCLA, with her advisor and CW3E collaborator, Professor Dennis Lettenmaier, alongside co-authors Qian Cao (CW3E), Shraddhanand Shukla (UCSB), Ming Pan (CW3E) have recently published a paper titled “Evaluation of Subseasonal Drought Forecast Skill over the Coastal Western U.S.” in the Journal of Hydrometeorology (Su et al., 2023; https://journals.ametsoc.org/view/journals/hydr/aop/JHM-D-22-0103.1/JHM-D-22-0103.1.xml). The research aligns with the Subseasonal to Seasonal Prediction of Extreme Weather Area and the Modeling Capabilities for the Western United States Area within CW3E’s 2019-2024 Strategic Plan because it evaluates the subseasonal drought forecast skill using the Noah Multi-parameterization (Noah-MP) model.

Predictions of drought onset and termination at subseasonal (from two weeks to one month) lead times could provide a foundation for more effective and proactive drought management. This study used reforecasts archived in NOAA’s Subseasonal Experiment (SubX) to force the Noah Multi-parameterization (Noah-MP), which produced forecasts of soil moisture from which we identified drought levels D0-D4. It evaluated forecast skill of major and more modest droughts, with leads from one to four weeks, and with particular attention to drought termination and onset. Usable drought termination and onset forecast skill was found at leads one and two weeks for major D0 -D2 droughts; and limited skill at week three for major D0-D1 droughts, with essentially no skill at week four regardless of drought severity (see Figure 1 and Figure 2). Furthermore, for both major and more modest droughts, limited skill or no skill was found for D3 -D4 droughts. Skill is generally higher for drought termination than for onset for all drought events. In addition, drought prediction skill generally decreases from north to south for all drought events. Evaluation of the subseasonal drought forecast skill can better support water resource and emergency management decisions.

This work used the COMET supercomputer, which was made available by the Atmospheric River Program Phase 2 and 3 supported by the California Department of Water Resources (awards 4600013361 and 4600014294 respectively) and the Forecast Informed Reservoir Operations Program supported by the U.S. Army Corps of Engineers Engineer Research and Development Center (award USACE W912HZ-15-2-0019). The research was funded in part by NOAA Regional Integrated Sciences and Assessments (RISA) support through the California–Nevada Applications Program (Grant NA17OAR4310284).

Figure 1: SubX-based debiased Brier skill score (BSS) for lead weeks 1-4 for drought termination. The columns show results for drought levels D0-D4; the rows show leads from week1 to week4. Blank areas denote no drought at this level in this location.

Figure 2: SubX-based debiased Brier skill score (BSS) for lead weeks 1-4 for drought onset. Columns show drought levels D0-D4; rows show leads from week1 to week4.

Su, L., Q. Cao, S. Shukla, M. Pan, and D. P. Lettenmaier, 2023: Evaluation of Subseasonal Drought Forecast Skill over the Coastal Western U.S. J. Hydrometeor., doi: https://doi.org/10.1175/JHM-D-22-0103.1

CW3E Publication Notice: Impacts of Northeastern Pacific Buoy Surface Pressure Observations

CW3E Publication Notice

Impacts of Northeastern Pacific Buoy Surface Pressure Observations

February 8, 2023

A new study using data from the Atmospheric River Reconnaissance program finds potential for improving weather forecasts, particularly errors in short range prediction of atmospheric rivers (ARs), by increasing the number of drifting buoy surface pressure observations over the world oceans. The paper “Impacts of Northeastern Pacific Buoy Surface Pressure Observations” was recently published in Monthly Weather Review by authors Carolyn Reynolds (U.S. Naval Research Laboratory), Rebecca Stone (Science Applications International Corporation), James Doyle (U.S. Naval Research Laboratory), Nancy Baker (U.S. Naval Research Laboratory), Anna Wilson (CW3E), Marty Ralph (CW3E), David Lavers (European Centre for Medium-Range Weather Forecasts), Aneesh Subramanian (University of Colorado Boulder), and Luca Centurioni (University of California San Diego). This work contributes to the goals of CW3E’s 2019-2024 Strategic Plan to lead AR Research and Applications because the paper illustrates how novel observations of ARs improve forecasts.

Atmospheric River Reconnaissance (AR Recon) is a program led by CW3E and guided by an international, interagency Atmospheric River Modeling and Data Assimilation Steering Committee (Ralph et al. 2020; OFCM 2022). Dropsondes released from Air Force Reserve Command and the NOAA Aircraft Operations Center aircraft are the cornerstone of this effort. The effort also includes a partnership with the NOAA-funded Global Drifter Program led by Dr. Centurioni at the Scripps Lagrangian Drifter Laboratory to add barometers to the regular drifters (Centurioni et al. 2017). Those observations are critical in filling observation gaps in and near ARs over the North Pacific Ocean (Zheng et al. 2021). In this study, the authors investigated the impact of drifter-observed sea level pressure in the northeastern Pacific during the AR Recon 2020 season for their impact on the U.S. Navy’s global atmospheric forecasting system. The authors used Forecast Sensitivity Observation Impact (FSOI) to measure the contribution of individual observations and sets of observations on short-term forecast error reduction, and data-denial experiments to quantify forecast error associated with removing observations.

The results of this study find that observational impacts vary with placement, observation value, and timing. Drifters placed in time-averaged low-pressure regions, such as the Gulf of Alaska, and in isolation from other drifters, have the largest average impacts. Observations in the lowest quartile of sea surface pressures are significantly more beneficial to the model than higher pressure quartiles at the 95% level, with 54.5% beneficial impacts from the lowest quartile, and between 47.6% and 51.3% for the higher quartiles. The greatest impacts for individual drifters occur during periods of tight pressure gradients and strong integrated vapor transport (IVT), which are associated with fronts and ARs, respectively. The time when the observations are taken within the data assimilation (DA) window is also important. The lowest quartile of sea surface pressure observations have smaller beneficial impacts during the first half of the DA window and increasingly larger beneficial impacts during the second half of the DA window, whereas the small beneficial impacts of the upper quartile observations early in the DA window become nonbeneficial as the window progresses. Lastly, data-denial experiments show that AR Recon drifters better constrain the analysis of nearby non AR-Recon drifters, help correct for biases in the model, and contribute statistically significant improvements to tropospheric winds and geopotential height forecasts over the Northern Hemisphere at 72- and 96-hour lead times (Fig. 1).

The results of this study have applications for future AR Recon seasons and the Global Drifter Program to expand the density and targeted spatial coverage in the northeastern Pacific. Motivated in part by this investigation, the 2022 AR Recon deployment included drifters in the Gulf of Alaska and additional buoys off southern Greenland.

This research was funded by the Chief of Naval Research through the Naval Research Laboratory Base Program, by the California Department of Water Resources AR program, the U.S. Army Engineer Research and Development Center, and the National Ocean and Atmospheric Association.

Figure 1: (Fig. 10 from Reynolds et al. 2023): Standard scorecard metrics for North America and Northern Hemisphere NAVGEM forecasts as a function of forecast hour as verified against ECMWF operational analyses for forecast start times of 0000 UTC 22 Jan 2020–0000 UTC 13 Mar 2020. Green colors indicate improvements in the metric with the assimilation of the AR-Recon drifter surface pressure observations that are statistically significant at the 95% level. Pink colors indicate degradations at the 95% level.

Centurioni, L., Horaìnyi, A., Cardinali, C., Charpentier, E., & Lumpkin, R. (2017). A global ocean observing system for measuring sea level atmospheric pressure: Effects and impacts on numerical weather prediction. Bulletin of the American Meteorological Society, 98, 231-238. https://doi.org/10.1175/BAMS-D-15-00080.1

ICAMS, 2022: National Winter Season Operations Plan (NWSOP). Interagency Meteorology Coordination Office, 124 pp., https://www.icams-portal.gov/resources/ofcm/nwsop/2022_nwsop.pdf.

Reynolds, C. A., Stone, R. E., Doyle, J. D., Baker, N. L., Wilson, A. M., Ralph, F. M., Lavers, D. A., Subramanian, A. C., & Centurioni, L. (2023). Impacts of Northeastern Pacific Buoy Surface Pressure Observations. Monthly Weather Review, 151, 211-216. https://doi.org/10.1175/MWR-D-22-0124.1

Ralph, F. M., Cannon, F., Tallapragada, V., Davis, C. A., Doyle, J. D., Pappenberger, F., Subramanian, A., Wilson, A. M., Lavers, D. A., Reynolds, C. A., Haase, J., Rutz, J. J., Cordeira, J. M., Zheng, M., Hecht, C. W., Kawzenuk, B., & Delle Monache, L. (2020). West Coast Forecast Challenges and Development of Atmospheric River Reconnaissance. Bulletin of the American Meteorological Society, 101, E1357-E1377. https://doi.org/10.1175/BAMS-D-19-0183.1

Zheng, M., Delle Monache, L., Wu, X., Ralph, F. M., Cornuelle, B., Tallapragada, V., Haase, J. S., Wilson, A. M., Mazloff, M., Subramanian, A., & Cannon, F. (2021). Data Gaps within Atmospheric Rivers over the Northeastern Pacific. Bulletin of the American Meteorological Society, 102, E492-E524. https://doi.org/10.1175/BAMS-D-19-0287.1

Extreme Atmospheric River Incidents are the Subject of Committee Hearing in California State Assembly

Extreme Atmospheric River Incidents are the Subject of Committee Hearing in California State Assembly

February 6, 2023

At a February 1 Joint Hearing of the State Assembly’s Committees on Emergency Management; Water, Parks, and Wildlife; and Utilities and Energy, CW3E Director F. Martin “Marty” Ralph was one of three speakers who briefed committee members on the latest research on predicting and forecasting the impact of atmospheric rivers. Dr. Ralph referenced CW3E’s AR Scale to demonstrate how the catastrophic impact of an atmospheric river incident increases exponentially for the highest ranked (4 and 5) incidents. Knowing when and where torrents of rain will strike can therefore save property and lives. Weather modeling innovations and ongoing research at CW3E, he noted, continue to improve the skill with which atmospheric rivers can be predicted. CW3E’s “West-WRF” forecast model, for example, is tailored to be the best forecast model for atmospheric rivers.

California’s State Climatologist, Dr. Michael Anderson, and Dr. Daniel Swain, a climate scientist at UCLA’s Institute of Climate and Sustainability also addressed the prediction and forecasting of extreme atmospheric river incidents.