Author: cw3e-web

CW3E Publication Notice: From California’s Extreme Drought to Major Flooding: Evaluating and Synthesizing Experimental Seasonal and Subseasonal Forecasts of Landfalling Atmospheric Rivers and Extreme Precipitation during Winter 2022 – 2023

CW3E Publication Notice

From California’s Extreme Drought to Major Flooding: Evaluating and Synthesizing Experimental Seasonal and Subseasonal Forecasts of Landfalling Atmospheric Rivers and Extreme Precipitation during Winter 2022 – 2023

October 24, 2023

CW3E researcher Mike DeFlorio, along with co-authors from CW3E, the National Institute of Water and Atmospheric Research (NIWA), the University of Arizona, the University of Graz, the International Research Institute for Climate and Society (IRI), the NASA Jet Propulsion Laboratory, the NOAA Climate Prediction Center, and the California Department of Water Resources (CA DWR), recently published a paper entitled “From California’s Extreme Drought to Major Flooding: Evaluating and Synthesizing Experimental Seasonal and Subseasonal Forecasts of Landfalling Atmospheric Rivers and Extreme Precipitation during Winter 2022 – 2023” in the Bulletin of the American Meteorological Society (BAMS). This research contributes to both the S2S (Subseasonal-to-Seasonal) Prediction of Extreme Weather and Atmospheric Rivers (AR) Research and Applications Priority Areas in CW3E’s 2019-2024 Strategic Plan, and represents a substantial cross-institutional collaborative effort to diagnose observations and evaluate S2S forecasts of ARs, circulation regimes, and extreme precipitation during last year’s historic winter over California and the broader western U.S. region.

The key objectives of this paper are to:

  1. Diagnose observations before and after the 3-week active AR period over California during December 2022 – January 2023, and provide context for how AR landfalls during this period substantially alleviated multi-year drought over California
  2. Evaluate experimental seasonal and subseasonal forecasts of ARs, circulation regimes, and precipitation over the western U.S. and North Pacific Ocean during Winter 2022 – 2023
  3. Introduce experimental western U.S. seasonal and subseasonal forecast synthesis products that summarize and aggregate key information across institutions and methods to provide situational awareness guidance to end users

Figure 1 below (Figure 5 from the BAMS article) illustrates the substantial impact of nine landfalling ARs during December 2022 – January 2023 in alleviating multi-year drought conditions across California and Nevada. During the October 2019 – November 2022 period when drought was still widespread, the equivalent of 1-2 normal water years’ worth of precipitation did not fall across much of Northern and Central California, and Southern California was also in a precipitation deficit. However, by the end
of January 2023, many parts of Central California (including the Sierra Mountain Range), as well as coastal Southern California, were no longer in deficit mode, as indicated by the white regions in panel c). Conditions improved dramatically across Northern California, though many areas remain in deficit compared to normal conditions for the 3.5 year period shown in panel c).

Figure 1: Figure 5 from DeFlorio et al. 2023 (BAMS). Deviations from 1981-2010 normal of precipitation accumulated during (a) October 2019 (beginning of recent drought) through November 2022, (b) total precipitation between December 2022 and January 2023, and (c) between October 2019 and January 2023, with missing or extra overall precipitation expressed in terms of normal water-years. White areas in panel (c) are regions where the net 3.5 years of precipitation anomalies were no longer in deficit mode by the end of January 2023. Precipitation amounts illustrated here are the PRISM 4-km resolution monthly datasets.

During the past several winters, CW3E has been developing experimental seasonal and subseasonal forecast synthesis products in close coordination with stakeholders at CA DWR. An example of the CW3E experimental subseasonal forecast synthesis product applied to the period of interest in this study is shown below in Figure 2 (Figure 12 from the BAMS article). These experimental synthesis products will be included in CW3E’s weekly S2S outlooks during the Winter 2023-2024 season.

Figure 2: Figure 12 from DeFlorio et al. 2023 (BAMS). CW3E experimental subseasonal (weeks 2-4 lead time) synthesis forecast product for December 22, 2022 00Z subseasonal dynamical ensemble forecasts. The regions include Washington/Oregon (WA/OR), Northern California, Central California, and Southern California (each row). Forecast results from three models (NCEP, ECCC, ECMWF) are shown respectively in each column. The superscripts indicate the different types of subseasonal products being considered in the synthesized forecasts. High confidence is determined when there is a ≥75% probability of a pattern conducive to above normal, below normal, or near normal conditions, and if the majority (>50%) of the forecast products agree on the sign of the anomaly. Low confidence is determined when there is a <75% probability of a pattern conducive to above normal, below normal, and near normal conditions, and >50% of the forecast products agree on the sign of the anomaly. If the individual forecast products disagree on the sign of the anomaly, the synthesized forecast is classified as uncertain.

DeFlorio, M.J., A. Sengupta, C.M. Castellano, J. Wang, Z. Zhang, A. Gershunov, K. Guirguis, R. Luna Niño, R.E. Clemesha, M. Pan, M. Xiao, B. Kawzenuk, P.B. Gibson, W. Scheftic, P.D. Broxton, M.B. Switanek, J. Yuan, M.D. Dettinger, C.W. Hecht, D.R. Cayan, B.D. Cornuelle, A.J. Miller, J. Kalansky, L. Delle Monache, F.M. Ralph, D.E. Waliser, A.W. Robertson, X. Zeng, D.G. DeWitt, J. Jones, and M.L. Anderson (2023), From California’s extreme drought to major flooding: Evaluating and synthesizing experimental seasonal and subseasonal forecasts of landfalling atmospheric rivers and extreme precipitation during Winter 2022 – 2023. Bulletin of the American Meteorological Society, in press, doi:10.1175/BAMS-D-22-0208.1.

CW3E AR Update: 13 October 2023 Outlook

CW3E AR Update: 13 October 2023 Outlook

October 13, 2023

Click here for a pdf of this information.

Multiple Atmospheric Rivers Forecast to Impact Pacific Northwest Through the Weekend

  • A series of atmospheric rivers (ARs) are forecast to make landfall over the Pacific Northwest during the next few days
  • The first and second ARs are forecast to bring weak AR conditions (IVT < 500 kg m−1 s−1) to coastal Washington, Oregon, and Northern California today and Saturday
  • The third and strongest AR is forecast to make landfall Sunday into Monday
  • An AR4/AR5 is possible in coastal OR due to IVT magnitudes potentially exceeding 1000 kg m−1 s−1 and AR conditions potentially lasting more than 48 consecutive hours between the second and third ARs
  • There is still considerable forecast uncertainty in the intensity of the third landfalling AR
  • The ECMWF Ensemble Prediction System (EPS) continues to forecast higher IVT magnitudes in coastal OR and WA compared to the NCEP Global Ensemble Forecast System (GEFS)
  • The NWS Weather Prediction Center (WPC) is forecasting at 2–5 inches of precipitation in the Olympic Mountains and North Cascades during the next 5 days
  • Models are still showing some disagreement in forecast precipitation, with the ECMWF/EPS models predicting higher precipitation amounts in the Olympic Peninsula compared to the GFS/GEFS models
  • Despite the high likelihood of strong AR conditions (IVT > 750 kg m−1 s−1) during the third AR, the south-southwesterly orientation of moisture transport will be unfavorable for orographic enhancement of precipitation in most areas, and significant hydrologic impacts are not anticipated

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 13 October – 1200 UTC 20 October 2023


 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, P. Iniguez, J. Kalansky, and S. Roj; 13 October 2023

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

*Outlook products are considered experimental

CW3E Welcomes Jacob Morgan

CW3E Welcomes Jacob Morgan

October 12, 2023

Jacob joined CW3E in October 2023 as a field research engineer. Prior to joining the Center, Jacob earned his BSc and MSc in Earth Sciences from the University of Oxford (2016) and his PhD in Climate Science from Scripps Institution of Oceanography (2023)

Jacob’s doctoral research focused on reconstructing past climate using the composition of air bubbles preserved in ancient Antarctic ice cores. By measuring the composition of oxygen in the bubbles trapped in Antarctic ice cores, Jacob reconstructed periodic northward and southward shifts in the position of the ITCZ during the last glacial period, between twenty thousand and seventy thousand years ago. The shifts occurred in sync with Dansgaard-Oeschger events–abrupt climate warmings in the North Atlantic–and were associated with a strengthening and weakening of the Northern Hemisphere tropical monsoon systems and fluctuations in tropical biosphere productivity.

At CW3E, Jacob will be a member of the field team and is excited to get involved with their various projects. He has plenty of experience navigating the complex logistics involved in executing successful fieldwork projects in remote locations and extreme weather–his list of previous field sites includes Antarctica, Greenland, the Pyrenees, and Bermuda. He is eager to now put these skills to use in the Western US.

CW3E Welcomes Emily Slinskey

CW3E Welcomes Emily Slinskey

October 12, 2023

Dr. Emily Slinskey joined CW3E as a Precipitation Scientist in October 2023. Emily earned her B.S. (2013) in Geography at SUNY Geneseo, M.S. (2018) in Geography at Portland State University, and Ph.D. (2021) in the Earth, Environment, and Society program at Portland State University.

As a graduate student at the Portland State Climate Science Lab, under the direction of Dr. Paul Loikith and in collaboration with the Regional Climate Model Evaluation System (RCMES) group at NASA’s Jet Propulsion Laboratory (JPL), Emily applied an extreme precipitation categorization scheme as a target for a dataset intercomparison over the contiguous United States (CONUS). This work further motivated her doctoral research identifying and characterizing ARs and associated precipitation over the seven USNational Climate Assessment (NCA) regions involving an observational analysis, climate model evaluation, and assessment of change under warming. During this time, Emily also contributed to the Forecast Informed Reservoir Operations (FIRO) effort ledby CW3E and the US Army Corps of Engineers. Her research involved the development and application of an approach to quantify the contribution of non-orographic lift during AR-driven precipitation along the US West Coast.

More recently, Emily completed a postdoc at the UCLA Center for Climate Science under the supervision of Dr. Alex Hall. Supported by the HyperFACETS effort, she developed and applied a statistical framework for quantifying temporal clustering amongARs across the Western US. Following a thorough investigation of the climatological characteristics of clustered ARs, she linked these events to the occurrence and distribution of precipitation using a dynamically downscaled reanalysis product driven by a regional climate model.

At CW3E, Emily will contribute to AR research and operations partnerships to gain an improved process-based understanding of extreme hydrometeorological events and associated impacts to support their predictability over the Western US and beyond.

CW3E AR Update: 11 October 2023 Outlook

CW3E AR Update: 11 October 2023 Outlook

October 11, 2023

Click here for a pdf of this information.

Several ARs to Move Across the Pacific Northwest During the Next Week

  • Several Atmospheric Rivers (ARs) will impinge on the Washington, Oregon, and Northern California coasts beginning Friday (Oct 13) and continuing into early next week
  • Weak AR1-2 conditions (based on the Ralph et al. 2019 AR Scale) are likely Friday afternoon through Sunday (Oct 15) along the WA/OR coastal areas with the 1st and 2nd ARs
  • The jet stream will remain very active across the North Pacific Ocean early next week, providing optimal conditions for continued AR activity in the Monday (Oct 16) to Wednesday (Oct 18) timeframe
  • However, there is considerable model uncertainty surrounding the details of the 3rd AR
  • In total, AR1 or stronger conditions are likely (90%) from Point Reyes, CA and northward around Monday. There is a moderate chance (70%) of up to AR3 conditions along the WA and OR coasts during this time and a low (20%) chance for AR5 conditions along the OR coast
  • Through the next seven days, 2-5” of rain are expected along the coastal mountains and Cascades with localized higher amounts possible
  • Snow levels will remain elevated and mostly above 8,000’ through the event
  • While notable rain is forecast and area rivers will rise, currently no rivers are forecast to exceed flood stage
  • With much more uncertainty, there is potential for a 4th AR later next week

Click images to see loops of GFS IVT and IWV forecasts

Valid 0000 UTC 11 October – 1200 UTC 17 October 2023


 

 

 

 

 

 

 

 

Summary provided by P. Iniguez, C. Castellano, M. Steen, and S. Bartlett; 11 October 2023

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

*Outlook products are considered experimental

CW3E AR Update: 6 October 2023 Outlook

CW3E AR Update: 6 October 2023 Outlook

October 6, 2023

Click here for a pdf of this information.

Pair of Atmospheric Rivers Forecast to Impact Pacific Northwest and Northern California

  • A pair of atmospheric rivers (AR) are forecast to make landfall in the Pacific Northwest, the first early on Mon 9 Oct and the second on Tues 10 Oct
  • AR1 conditions (based on Ralph et al. scale) are forecast during the first AR, with a ~24 hour period of IVT >500 kg m-1 s-1 forecast for Washington to Northern California
  • AR2 conditions are forecast during the second AR for a more southerly latitude range along the coast of Central Oregon into Northern California, with a ~42 hour period of IVT >250 kg m-1 s-1 forecast in this region
  • The 00Z GFS and 00Z ECMWF are forecasting 1 to 3 inches of precipitation over much of western Washington and Oregon over the next 10 days. Some of the precipitation is forecast to fall after the ARs
  • The NWS Weather Prediction Center (WPC) is forecasting 7-day precipitation totals >3 inches over the Olympic Peninsula and 1-2 inches along the Oregon and Washington coasts and the windward (west) side of the Cascade Range
  • Precipitation associated with these ARs are forecast to be primarily beneficial to the Pacific Northwest where widespread drought conditions are present, with no river levels forecast to rise above action stage within the boundaries of the NWS Northwest River Forecast center

Click images to see loops of GFS IVT and IWV forecasts

Valid 1800 UTC 08 October – 0600 UTC 11 October 2023


 

 

 

 

 

Summary provided by M. Steen, P. Iniguez and S. Bartlett; 6 October 2023

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

*Outlook products are considered experimental

CW3E Welcomes Kevin Lupo

CW3E Welcomes Kevin Lupo

October 6, 2023

Kevin Lupo joined CW3E in October 2023 as an Atmospheric Data Scientist. Prior to joining CW3E, Kevin earned his B.S. in Meteorology and M.S. in Applied Meteorology at Plymouth State University (2014, 2016), and his Ph.D. in Atmospheric Science at SUNY Albany (2021). At SUNY Albany, Kevin’s research focused on the use of stochastic model error schemes in ensemble forecasts of heavy rainfall events, with a particular focus on the physical processes by which these schemes introduce precipitation variability in ensemble forecasts using the Weather Research and Forecasting (WRF) model. This research was supported by an NSF Partnership for International Research and Education (PIRE) grant, which allowed Kevin to collaborate with students and faculty with diverse research interests from universities both in the U.S. and in Taiwan. More recently, Kevin was a postdoc at NCAR in the Mesoscale and Microscale Meteorology (MMM) Lab, where his work focused on objectively evaluating a progressive, or “too fast” bias in GFS forecasts of cutoff lows, with the goal of identifying corresponding model deficiencies and potential improvements to the Unified Forecast System – Medium Range Weather Application (UFS-MRW) which may improve this bias.

At CW3E, Kevin will contribute to operational and research aspects of West-WRF. Specifically, his work will support funded projects with SDG&E and contribute to the development and evaluation of the West-WRF Ensemble.

CW3E Participates in the 2nd Annual Yampa Youth Water Festival

CW3E Participates in the 2nd Annual Yampa Youth Water Festival

September 27, 2023

El Knappe (left) and Jeri Wilcox (right) explain radiosonde launch heights to 5th graders during the grandstands opening ceremony of the event

On the 27th of September, the Upper Yampa Water Conservancy District of Steamboat, Colorado, hosted the 2nd Annual Yampa Youth Water Festival at the Routt County Fairgrounds in Hayden, Colorado. Researchers from CW3E participated in this event as guest speakers during the grandstands opening event as well as by hosting a booth during the rotational part of the event. This festival brought together nearly 400 5th grade students from the surrounding Routt and Moffat counties. The goal of this festival is to introduce students to the importance of our water resources, particularly in northwest Colorado, through interactive and hands-on activities with the kids about the Yampa River Basin.

At this event, the Land-Based Field Operations Manager, El Knappe, and Field Researcher Jeri Wilcox joined the fun by doing a demonstration of launching a weather balloon at the opening event in front of the grandstands packed with cheering 5th graders. During this presentation, the researchers walked the students through what radiosondes are and the data that the balloon will collect. Following this, CW3E hosted a booth during the rotational segment of the event. These students got the unique opportunity to spend the rest of day rotating through 22 stations, learning about topics including meteorology, ecology, hydrology, and water quality, among other topics. These booths were hosted by a diverse group of organizations, ranging from the Colorado Water Conservation Board to the United States Forest Service. At the CW3E booth hosted by Knappe and Wilcox, students learned about the importance of taking observations and data collection for the scientific process, particularly when making weather forecasts that can have major implications for daily life. Students got to play the role of being a meteorologist by collecting their own data on weather conditions and synthesizing their results into a weather report for effective science communication. This activity was followed up by sending a lesson plan to the teachers that participated in the event which utilized their results from the booth activity as well as the data collected from the weather balloon launch done with the students.

The event was covered by local news outlets including the Steamboat Pilot & Today and Steamboat Radio

CW3E hosts a table for rotating groups of 5th graders where students collect weather observations and create a weather report for their peers based on real-time data

Jeri Wilcox (left) describes the balloon launch as Holly Kirkpatrick of the Upper Yampa Water Conservancy District (middle) and El Knappe (right) prepare to release the balloon

CW3E Publication Notice: Large-Scale Circulation Context for North American West Coast Atmospheric Rivers: Influence of the Subseasonal NPO/WP Teleconnection

CW3E Publication Notice

Large-Scale Circulation Context for North American West Coast Atmospheric Rivers: Influence of the Subseasonal NPO/WP Teleconnection

September 27, 2023

A new paper titled “Large-Scale Circulation Context for North American West Coast Atmospheric Rivers: Influence of the Subseasonal NPO/WP Teleconnection” by Justin Hicks (University of Maryland), Bin Guan (UCLA, NASA JPL), Sumant Nigam (University of Maryland), and Alfredo Ruiz-Barradas (University of Maryland) was recently published in the American Geophysical Union’s Journal of Geophysical Research. This study identifies a subseasonal weather pattern that is particularly influential on AR activity in the western US. The North Pacific Oscillation/West Pacific teleconnection pattern (NPO/WP) is more influential than other subseasonal patterns previously linked to AR activity, both in terms of landfall occurrence and inland reach. The results advance prospects of subseasonal prediction of winter AR activity over the western US, from the incipient-phase knowledge of the impactful subseasonal teleconnections operating over the Pacific-North American region, especially the NPO/WP. This prospect of improved long-term forecasts of high-impact precipitation events (i.e. ARs) is of particular interest to those in the water resources community in the western US.

ABSTRACT

Understanding the variability of atmospheric rivers (ARs) on subseasonal time scales is pivotal for efficient water resource management along the west coast of North America. ARs during 1980–2018 based on the Modern-Era Retrospective analysis for Research and Applications, version 2 are analyzed to quantify the modulation of winter (December–February) landfalling ARs in the western US by leading subseasonal teleconnections, focusing on pentad evolution rather than seasonal-mean patterns. The growth phase of the North Pacific Oscillation/West Pacific (NPO/WP) teleconnection—the second leading pattern in 200-hPa geopotential heights in boreal winter—is found to be particularly influential in modulating the number of landfalling ARs in this region. In the positive phase of NPO/WP growth, the presence of anomalous low pressure centered just south of Alaska (i.e., a strengthening of the Aleutian Low) and anomalous high pressure around Hawaii results in moisture convergence in the central and eastern Pacific, bringing southwesterly moisture fluxes to the coast and inland. The modulation by NPO/WP is stronger than by commonly-considered climate variability modes, such as the Pacific/North American (PNA) pattern. Although southwesterly fluxes are stronger over the Pacific Ocean during the positive phase of PNA, they tend to transition to southerly fluxes before extending inland, resulting in smaller overland impacts in the western US. The analysis of temporal evolutions indicates AR activity peaks 5 days after the mature phase of NPO/WP growth, as in the case of PNA. Overall, the study suggests potential subseasonal predictability of US West Coast ARs from incipient-phase knowledge of the leading teleconnection patterns, especially the NPO/WP.

KEY POINTS

  • The modulation of atmospheric rivers (ARs) in the western US by climate variability modes is analyzed, focusing on pentad evolution

  • The North Pacific Oscillation/West Pacific (NPO/WP) pattern is more influential on western US AR activity than commonly-considered modes

  • The finding advances prospects of subseasonal prediction of ARs over the western US from the NPO/WP’s incipient-phase knowledge

    • Figure 1: Figure 3 from Hicks et al. (2023): Left Panels: Characteristic pentad atmospheric river (AR) counts and 850-hPa height anomalies associated with the leading subseasonal teleconnection patterns and El Niño variability from Niño3.4 sea surface temperature (SST) index during the extended winter season (November–March), obtained from linear regressions during 1980–2018 and 1982–2018, respectively. From top to bottom: the North Atlantic Oscillation (NAO), the growth phase of North Pacific Oscillation/West Pacific (NPO/WP) pattern, the decay phase of NPO/WP, the Pacific North American (PNA) pattern, the Scandinavian (SCAND) pattern, and El Niño. Positive/negative AR regressions are shaded red/blue at 0.2 AR/pentad interval; 850-hPa height anomalies are contoured at 10 m interval with continuous/dashed lines for positive/negative anomalies. Right Panels: AR regressions are superposed on the AR climatology in the Pacific–North American region, where climatological AR counts are contoured at 0.4 AR/pentad; the 2.0 ARs/pentad anomaly contour is thickened for emphasis. A 9-point spatial smoother is applied twice to the AR regressions and climatology.

    Figure 1: Figure 4 from Hicks et al. (2023): Inter-reanalysis comparison of climatological atmospheric river (AR) counts and AR-count regressions on winter teleconnections during 1980–2018: Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) (right column) and ERA-Interim (left column). From the top: regressions on the North Atlantic Oscillation (NAO), the growth phase of North Pacific Oscillation/West Pacific (NPO/WP) pattern, the decay phase of NPO/WP, the Pacific North American (PNA) pattern, and the Scandinavian (SCAND) pattern. AR regressions are shaded red/blue for positive/negative values at 0.2 AR/pentad/index interval (see color bar). The climatological AR count per pentad is contoured in black at 0.4 intervals, with the 2.0 ARs/pentad isoline thickened for emphasis. A 9-point spatial smoother is applied twice to AR regressions and climatology.

    Hicks, J., Guan, B., Nigam, S., & Ruiz-Barradas, A. (2023). Large-scale circulation context for North American west coast atmospheric rivers: Influence of the subseasonal NPO/WP teleconnection. Journal of Geophysical Research: Atmospheres, 128, e2023JD038693. https://doi.org/10.1029/2023JD038693