CW3E Director Featured in the Water Zone Podcast on KCAA San Bernardino

CW3E Director Featured in the Water Zone Podcast on KCAA San Bernardino

April 25, 2018

The Water Zone is a KCAA (Loma Linda, CA) radio show, hosted by Paul McFadden, that explores water issues in agriculture and farming from various perspectives to advance water conservation. The April 19, 2018 episode featured two notable guests: Dr. F. Martin Ralph, CW3E Director, and Dr. Thomas Philp, a Pulitzer Prize winning journalist who is the executive strategist for the Metropolitan Water District of Southern California.

Follow the link to listen: http://podcasts.kcaastreaming.com/water/20180419.html. Information related to western weather and water can be heard during minutes 11-44 of the episode.

CW3E Hosts 3rd Annual Meeting

CW3E Hosts Third Annual Meeting

April 20, 2018

CW3E hosted its third annual meeting this week, April 16-19, 2018. Part of the vision of CW3E is to create a community of collaboratively-oriented scientists, students, engineers and staff, and to generate the support to enable these collaborations. This was the first annual meeting of this scope. Collaborators from all over the U.S., and National Weather Service forecasters from Reno, Monterey/San Francisco, and San Diego attended. The objectives of the meeting were to bring together scientists and engineers to address major science challenges, share ideas, develop collaborative projects, and to provide early career scientists and students opportunities to present their work.

CW3E Postdoctoral Scholar, Forest Cannon, presents on airborne radar observations of oceanic precipitation in atmospheric rivers.

The meeting began on the afternoon of Monday, April 16th and went through Thursday, April 19th. There was a poster session on the afternoon of April 17th, to give more post-docs and graduate students a chance to present their work. Session topics included extreme precipitation climatology and future projections, mesoscale and physical processes, forecasting, subseasonal to seasonal forecasting, AR reconnaissance and data assimilation, and hydrology and snow. There was a strategic planning session in which all attendees brainstormed and shared their thoughts on where CW3E will be in the next 5 years.

Throughout the meeting there were several chances to discuss future scientific collaborations. Attendees reported how valuable the face-to-face meetings between collaborators were, and how productive it was to discuss potential research avenues in person. Although the exact form of the meeting will evolve in response to feedback, the annual in-person scientific meeting will continue to be central to CW3E’s mission to build a community of scientists and engineers working together to solve challenging problems relating to extreme weather and water events in the west.

CW3E Publication Notice: Evaluation of Atmospheric River Predictions by the WRF Model Using Aircraft and Regional Mesonet Observations of Orographic Precipitation and Its Forcing

CW3E Publication Notice

Evaluation of Atmospheric River Predictions by the WRF Model Using Aircraft and Regional Mesonet Observations of Orographic Precipitation and Its Forcing

April 16, 2018

CW3E project scientist Andrew Martin and co-authors have published a study characterizing predictability limits in Atmospheric River (AR) forecasts and apportioning Russian River precipitation forecast errors among vapor transport and orographic precipitation components. The article, titled Evaluation of Atmospheric River Predictions by the WRF Model Using Aircraft and Regional Mesonet Observations of Orographic Precipitation and its Forcing, is now in early online release at the Journal of Hydrometeorology.

This study leveraged airborne dropsonde observations of offshore Atmospheric Rivers completed during the CalWater experiment and the Atmospheric River Observatory at Bodega Bay and Cazadero, CA to verify forecasts of AR properties and their resulting precipitation. Forecasts were created by CW3E’s numerical weather prediction model, West-WRF, and compared to Global Forecast System reforecasts (GFSRe) valid for the same events. Forecast skill in AR properties and precipitation was evaluated at lead times up to 7 days ahead. Notably, the study found that deterministic skill in integrated vapor transport and other related fields degrades (meaning that forecasts created from climatology perform just as well or better) more than 4 days ahead for both models. However, West-WRF improves upon GFSRe skill in IVT at days 1, 2 and 3 ahead (see Fig. 1c).

Figure 1. a) Value added by GFSRe over GFSRe climatology validated against 145 CalWater dropsondes for the variables z500 (blue), IVT (black), IWV (green) and e925 (red). b) as in a, except for West-WRF value added over GFSRe climatology. c) as in b, except reference forecast is GFSRe.

The study also employed a novel forecast error separation technique to apportion precipitation forecast errors among the component caused by vapor transport simulation and orographic precipitation process simulation. Data from the Atmospheric River Observatory was used to demonstrate that West-WRF forecasts of orographic precipitation during landfalling AR are more accurate in simulating both components; but also that West-WRF forecasts of precipitation can be improved by improving the vapor transport component because its orographic precipitation process is accurate. This lends confidence that CW3E’s effort to improve west coast precipitation forecasts by assimilating offshore observations into West-WRF analyses can yield successful results.

Co-authors include Dr. F Martin Ralph, Reuben Demirdjian, Laurel DeHaan, and Dr. Rachel Weihs of CW3E with Dr. David Reynolds of the Cooperative Institute for Research in Environmental Sciences and Dr. Sam Iacobellis of Scripps Institution of Oceanography. The study was funded by the US Army Corps of Engineers, the California Department of Water Resources, and the National Science Foundation XSEDE program.

Odds of Reaching 100% Water Year Precipitation – April Update

Odds of Reaching 100% of Normal Precipitation for Water Year 2018 (April Update)

April 10, 2018

Contribution from Dr. M.D. Dettinger, USGS

Here is how we usually tend to see the water-year precip-drought to-date or last month’s contributions represented:

Figure 1: Total precipitation anomaly (large map) and total precipitation (smaller map) during water 2018 (September 2017-March 2018). Images courtesy PRISM Climate Group.

A somewhat different viewpoint on the development of precipitation drought considers that development to be a matter of both how much precipitation has fallen (or not) already AND how much more is realistically likely to fall in coming months. E.g., March 2018 simultaneously produced helpful additions to this year’s precipitation totals in California AND was disappointingly far from completely undoing the deficits of the preceding months in most of the State. The following are maps of this year’s drought development that explicitly take both of these aspects into account.

Here is how the drought has evolved so far this water year in terms of the odds of reaching 100% of normal precipitation by end of water-year 2018.

Figure 2: Odds of reaching 100% of water-year normal precipitation totals throughout water-year 2018.

  • Notice how drought conditions have developed across the Southwest, as odds of reaching normal have progressively dwindled month by month. Also notice that, although March was wet in California/Nevada, it was—arguably—too little too late to set us up well for reaching 100% of normal this year, in all but a few locales.

The top row in figure 3 shows the current odds of reaching various fractions (including but not limited to 100%) of water-year-total this year.
Also shown are the corresponding odds prior to March (middle row), and the amount that March precip changed the odds (bottom). This approach offers a far different view than the precipitation anomalies of figure 1, emphasizing different “hot spots” of hope & despair.

Figure 3: Odds of water-year 2018 reaching various fractions of water year normal precipitation totals and the change in these odds during March 2018.

Finally, figure 4 is the “flipped” version of the analysis, asking-at each pixel-how large a water-year total precipitation has a 50% (and other exceedances) chance of being equaled or exceeded this year, as of April 1, 2018.

Figure 4: Chance of water-year total precipitation being equaled or exceeded this year.

  • A different color bar is used here to emphasize that the shades now are illustrating something quite different from the previous maps

How the probabilities above were estimated:
At the end of a given month, if we know how much precipitation has fallen to date (in the water year), the amount of precipitation that will be required to close out the water year (on Sept 30) with a water-year total equal to the long-term normal is just that normal amount minus the amount received to date. Thus the odds of reaching normal by the end of the water year are just the odds of precipitation during the remaining of the year equaling or exceeding that remaining amount.

To arrive at the probabilities shown, the precipitation totals for the remaining months of the water year were tabulated in the long-term historical record (WY1948-2017 in these figures) and the number of years in which that precipitation total equaled or exceeded the amount still needed to reach normal were counted. The fraction of years that at least reached that threshold is the probability estimate. The calculation was also made for the probabilities of reaching 75% of normal by end of water year, 125%, etc., for these figures.

[One key simplifying assumption goes into estimating the probabilities this way: The assumption that the amount of precipitation that will fall in the remainder of a water year does not depend on the amount that has already fallen in that water year to date. This assumption was tested (across all climate divisions in California, so far) for each month of the year by correlating historical year-to-date amounts with the remainder-of-the-year amounts, and the resulting correlations were never statistically significantly different from zero.]

Contact: Michael Dettinger (USGS)

CW3E AR Update: 04 April 2018 Outlook

CW3E AR Update: 04 April Outlook

April 04, 2018

Click here for a pdf of this information.

Atmospheric river forecast to impact California over the next four days

  • Forecast confidence is increasing for a moderate or strong AR to strike the U.S. West Coast between this Thursday and Saturday
  • This will be the strongest AR of the season for this region, with total water vapor transport greater than approximately 25 Mississippi Rivers worth of water
  • Heavy precipitation is predicted over the CA coast and Sierra Nevada, with accumulation up to 7 inches possible
  • High freezing levels during the heaviest precipitation will result in rain at high altitudes over the Sierra Nevada leading to potential flooding

Click IVT or IWV image to see loop of 0-102 hour GFS forecast

Valid 0600 UTC 04 April – 1200 UTC 08 April 2018

 

 

 

 

 

 

 

Summary provided by B. Kawzenuk, F.M. Ralph, and C. Hecht; 10 AM PT Wednesday 04 April 2018

*Outlook products are considered experimental

CW3E AR Update: 03 April 2018 Outlook

CW3E AR Update: 03 April Outlook

April 03, 2018

Click here for a pdf of this information.

Atmospheric river forecast to impact Northern California later this week

  • GFS Ensemble members are currently forecasting a potentially strong to extreme AR over northern and central California later this week
  • Forecast certainty has increased since yesterday but there is still some uncertainty in the onset, duration, and strength of the AR
  • Up to 7 inches of precipitation is forecasted to fall over the Coastal and Sierra Nevada Mtns in CA, OR, and WA
  • The GEFS is currently suggesting high freezing levels for most of this event, which may lead to most of the precipitation falling as rain

Click IVT or IWV image to see loop of 0-126 hour GFS forecast

Valid 0600 UTC 03 April – 1200 UTC 08 April 2018

 

 

 

 

 

 

 

Summary provided by B. Kawzenuk, F.M. Ralph, and C. Hecht; 11 AM PT Tuesday 03 April 2018

*Outlook products are considered experimental

CW3E co-Hosts Inaugural Southwest Extreme Precipitation Symposium

CW3E co-Hosts Inaugural Southwest Extreme Precipitation Symposium

April 3, 2018

CW3E co-hosted the inaugural Southwest Extreme Precipitation Symposium (SWEPSYM) with the Floodplain Management Association on March 29th at Scripps Institution of Oceanography in La Jolla, CA (Pictured Below)

SWEPSYM was held at the Robert Paine Scripps Forum on the Scripps Institution of Oceanography Campus in La Jolla, CA. photo credit: Wikimedia Commons

SWEPSYM was established to focus attention on precipitation extremes in Southwestern North America, and their impact on regional hydrology and water resource management. Southwestern US water resources are dependent on precipitation that exhibits significant interannual variability, primarily due to the dominant influence of extreme precipitation events on annual precipitation. Adding to the complexity in understanding the role of extreme events in southwestern US flooding and drought development is the region’s bimodal precipitation distribution; featuring significant contributions from both atmospheric rivers during winter and the North American monsoon in summer. SWEPSYM focuses attention on the continued investigation of the origins and impacts of both ARs and monsoon precipitation, as well as their role in flooding and drought development in historical and climate change contexts. A goal of the Symposium is to bring together researchers and stakeholders with a goal of improving communication and collaboration between the two groups for advancing understanding of the hydrologic cycle in the Southwest and improving regional water security.

The theme for the inaugural event was: Southwest U.S. Droughts and Floods: Past Events and Future Changes. The Symposium brought together researchers, engineers, and practitioners to exchange technical and scientific information about the various factors responsible for producing extreme precipitation and the hydrologic processes responsible for generating runoff in semi-arid and arid areas, both in a historical context and with an eye towards projected changes in the coming decades.

Various topics related to flooding and drought in the Southwest were presented by a diverse group of speakers from academic institutions, government agencies and public utilities. Among the speakers was Dr. Marty Ralph, Director of CW3E at Scripps, who presented on recent developments in understanding the meteorological origins of extreme precipitation in Southwestern U.S., and Jeanine Jones, Interstate Resources Manager for the California Department of Water Resources, who discussed the need for improved precipitation forecasting for better Colorado River Basin drought contingency planning.

The Symposium’s agenda additionally included talks featuring both historical perspectives and climate projections, providing insight on how current conditions compare to historical climate, and what changes are to be expected. For example, Dr. Matthew Kirby (pictured below), Professor of Geological Sciences at Cal State Fullerton, delivered a presentation titled Lake Sediments Reveal Southern California’s Long History of Droughts, Pluvials, and Floods, demonstrating the value of taking a historical perspective on understanding the current state and future fate of water resources in the Southwest. His talk was complemented by a presentation by Dr. Alex Hall, Professor of Atmospheric Science at UCLA, who discussed research results indicating robust evidence for increasing precipitation extremes in California based on an ensemble of downscaled climate projections. Dr. Mike Anderson, the California State Climatologist, capped the day’s talks with a presentation on informational needs for long-term water resource management and planning in the Southwest, which synthesized how research can support water management, regionally.

Dr. Matthew Kirby of CSU-Fullerton delivers a presentation on the use of lake sediments to reveal Southern California’s history of droughts and flooding.

Speakers were re-convened in a panel (pictured below) at the end of the morning and afternoon sessions to discuss how to translate novel research that improves understanding of precipitation and hydrology in the Southwest into actionable information that benefits engineering, water management, flood control, and agriculture.

Pictured from left to right: Dr. Matthew Kirby, CSU-Fullerton; Jeanine Jones, DWR; Dr. Michael Dettinger, USGS; Dr. Amanda Sheffield, NOAA-NIDIS; Dr. Marty Ralph, CW3E, Scripps.

Additional Scientific Details

Despite the large body of published work on both atmospheric rivers and the North American monsoon, gaps remain in understanding, observing and predicting these weather phenomena.

CW3E AR Update: 02 April 2018 Outlook

CW3E AR Update: 02 April Outlook

April 02, 2018

Click here for a pdf of this information.

Atmospheric river forecast to impact Northern California later this week

  • GFS Ensemble members are currently forecasting a potentially strong to extreme AR over Northern California later this week
  • There is currently large uncertainty in the onset, duration, and magnitude of AR conditions, creating uncertainties in the potential impacts of this event
  • >5 inches of precipitation could fall during this event over the high elevations of the Coastal and Sierra Nevada Mountains in Northern California
  • The GFS is currently suggesting freezing levels >8,000 feet for most of this event, which may lead to most precipitation over the high Sierra falling as rain

Click IVT or IWV image to see loop of 0-141 hour GFS forecast

Valid 1200 UTC 02 April – 0900 UTC 08 April 2018

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Monday 02 April 2018

*Outlook products are considered experimental

International Atmospheric Rivers Conference 2018

International Atmospheric Rivers Conference 2018 – Abstract Submission and Registration Open Now! Abstracts Due April 2, 2018

The Center for Western Weather and Water Extremes (CW3E), at Scripps Institution of Oceanography (SIO), UC San Diego will be hosting the 2nd International Atmospheric Rivers Conference (IARC) from June 25-28, 2018. The conference is organized by an international committee, with co-chairs from NASA’s Jet Propulsion Laboratory, the US Army Corps of Engineers in Seattle, CW3E, and Instituto Dom Luiz at the University of Lisbon.

 

The conference will be located at the beautiful Robert Paine Scripps Forum for Science, Society and the Environment on SIO’s campus. The conference will bring together experts across multiple fields to advance the state of the science and explore needs for new information. Traditional oral and poster sessions will be combined with panel discussions. Cutting-edge research with global and regional perspectives on atmospheric river (AR) science will be presented. Topics include: field observations and remote sensing, AR identification and tracking, physical processes, interactions between atmospheric transport and chemistry, forecasting capabilities, ARs and climate change, and emerging directions – as well as many others.

 

In 2016, CW3E hosted the first ever IARC, drawing over 100 participants from all over the globe including Australia, South America, Europe, Asia and Africa (Ralph et al., 2017). Participants came from all different disciplines and perspectives, from applications, engineering, water management, to researchers using modeling, theory, and observed data to investigate these phenomena. ARs have emerged as a hugely useful conceptual model to focus hydrologists and atmospheric scientists on the transport mechanisms and impacts of precipitation extremes caused by AR landfall, and we look forward to hosting an engaging, inspiring, four-day conference.

 

Abstract submission deadline is April 2, 2018. Student scholarships, which waive the registration fee, are available. Students are strongly encouraged to apply. The student scholarship application deadline is also April 2, 2018.

 

For more information regarding this conference, please visit: http://cw3e.ucsd.edu/iarc2018/. If you have further questions, please contact Dr. Anna Wilson or Dr. Alexandre Ramos.

CW3E AR Update: 23 March 2018 Post Event Summary

CW3E AR Update: 23 March Post Event Summary

March 23, 2018

Click here for a pdf of this information.

A strong AR made landfall over southern California this week

  • The atmospheric river made initial landfall over Big Sur around 1800 UTC Wednesday, 20 March 2018
  • AR conditions were present over southern California about ~1200 UTC Friday, 23 March 2018
  • This was an R-Cat 1 event as over 200 mm of precipitation was observed just south of Big Sur and over the northern Sierra Nevada over 72 hours
  • This event produced nearly 7 percent of normal annual precipitation over all of California and the Northern Sierra 8 Station Index

SSMI/SSMIS/AMSR2-derived Integrated Water Vapor (IWV)

Valid 0000 UTC 19 March – 1200 UTC 23 March 2018

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-48 hour GFS forecast

Valid 1200 UTC 22 March – 1200 UTC 24 March 2018

NEXRAD Radar Reflectivity
Valid 00 UTC 20 March – 12 UTC 23 March 2018

  • Precipitation began over central CA early morning on 20 March 2018
  • Moderate to heavy precipitation occurred over central and Southern CA for nearly 72 hours during 20–23 March
  • The highest precipitation amounts occurred over the Coastal Mts. between Santa Barbara and Big Sur and over the southern Sierra Nevada
  • Several thunderstorms also occurred during this event on 22 and 23 March as evident by the highest reflectivity values observed by radar


 

 

 

 

 

 

Summary provided by C. Hecht, B. Kawzenuk, and F.M. Ralph; 3 PM PT Friday 23 March 2018

*Outlook products are considered experimental

CW3E AR Update: 22 March 2018 Outlook

CW3E AR Update: 22 March Outlook

March 22, 2018

Click here for a pdf of this information.

Update on Atmospheric River Currently Impacting California

  • Precipitation continues to fall across portions of California
  • The AR will begin to propagate southward bringing moderate AR conditions to Orange and San Diego Counties
  • As much as 9.5 inches of precipitation has fallen over the Coastal Mountains of California during the last 48 hours
  • ~3.75 inches of precipitation has fallen over the high elevations of Santa Barbara and Ventura Counties and 3.5 more inches could fall during the remainder of the storm
  • AR conditions are expected to end at ~11 pm PDT (+/– 3 hours) tonight over Southern California

SSMI/SSMIS/AMSR2-derived Integrated Water Vapor (IWV)

Valid 0000 UTC 19 March – 1600 UTC 22 March 2018

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-48 hour GFS forecast

Valid 1200 UTC 22 March – 1200 UTC 24 March 2018

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 3 PM PT Thursday 22 March 2018

*Outlook products are considered experimental

CW3E AR Update: 21 March 2018 Outlook

CW3E AR Update: 21 March Outlook

March 21, 2018

Click here for a pdf of this information.

Update on Atmospheric River Currently Impacting California

  • Light to moderate precipitation has begun falling over portions of California
  • GFS Ensemble members have continued to converge on coastal IVT forecast for the remainder of the AR
  • Portions of Southern California are forecast to experience Strong AR conditions between 2 and 5 AM on Thursday 22 March
  • ~1–2 inches of precipitation has fallen over the Santa Ynez Mountains over the past 24 hours
  • An additional 10+ inches of precipitation are forecast to fall over the higher elevations of Santa Barbara and Ventura Counties during the remainder of this AR

National Weather Service Composite Radar Reflectivity

Valid 1748-1858 UTC 21 March 2018

Images from weather.gov

Click IVT or IWV image to see loop of 0-72 hour GFS forecast

Valid 1200 UTC 21 March – 1200 UTC 24 March 2018

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Wednesday 21 March 2018

*Outlook products are considered experimental

CW3E AR Update: 20 March 2018 Outlook

CW3E AR Update: 20 March Outlook

March 20, 2018

Click here for a pdf of this information.

Update on Atmospheric River Forecast to Impact California This Week

  • The terminus of the atmospheric river plume is approaching coastal CA and precipitation will begin today
  • Models are suggesting potentially strong (IVT >750 kg m-1 s-1) AR conditions over San Luis Obispo and Santa Barbara Counties
  • Locations further south may experience moderate strength AR conditions (IVT >500 kg m-1 s-1)
  • AR conditions are forecast to peak over portions of SoCal between Midnight and 11 AM PDT on Thursday, 22 March 2018
  • As much as 10 inches of precipitation may fall over the higher elevations of Santa Barbara and Ventura Counties
  • The National Weather Service has issued numerous Flash Flood Watches and Winter Weather Warnings in California

SSMI/SSMIS/AMSR2-derived Integrated Water Vapor (IWV)

Valid 0000 UTC 18 March – 1600 UTC 20 March 2018

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-72 hour GFS forecast

Valid 1200 UTC 20 March – 1200 UTC 23 March 2018

 

 

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, J. Rutz, and B. Kawzenuk; 1 PM PT Tuesday 20 March 2018

*Outlook products are considered experimental

CW3E AR Update: 19 March 2018 Outlook

CW3E AR Update: 19 March Outlook

March 19, 2018

Click here for a pdf of this information.

Update on Atmospheric River Forecast to Impact California Next Week

  • Several changes have occurred in the forecast for the AR that may impact CA this week
  • GFS Ensemble members have continued to converge on Coastal AR conditions
  • While there is more agreement between GFS Ensemble members there are still numerous changes from model run to model run, introducing several uncertainties in the impacts associated with this event

Click IVT or IWV image to see loop of 0-102 hour GFS forecast

Valid 1200 UTC 18 March – 1800 UTC 23 March 2018

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Monday 19 March 2018

*Outlook products are considered experimental

CW3E AR Update: 16 March 2018 Outlook

CW3E AR Update: 16 March Outlook

March 16, 2018

Click here for a pdf of this information.

Update on Atmospheric River Forecast to Impact California Next Week

  • Several changes have occurred in the forecast for the AR that may impact CA later next Week
  • GFS Ensemble members have started to converge on coastal AR conditions
  • While there is more agreement between ensemble members, there is still considerable uncertainty in onset, duration, and magnitude of AR conditions

Click IVT or IWV image to see loop of 18-180 hour GFS forecast

Valid 0600 UTC 17 March – 0000 UTC 24 March 2018

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 3 PM PT Friday 16 March 2018

*Outlook products are considered experimental